2) monophagy among the mining microlepidoptera and all sawfly species, and 3) oligophagy among
beetles.

No correlation was found between utilized needle-age and degree of host-plant specialization.

A comparison of the relative numbers of monophagous, oligophagous, and polyphagous insect
species on the three common conifers (i.e. Scots pine, Norway spruce, and juniper) in Sweden showed
that the frequencies of oligophagy are similar for each of the conifer species. However, the proportion
of monophagous species was found to be significantly greater in juniper than in pine and spruce.

These results are discussed with reference to hypotheses concerning patterns of host specificity in
herbivorous insects based on plant characteristics.

ACKNOWLEDGMENTS

We would like to thank Bengt Ehnstrém and Karl-Johan Hedqvist for providing information on
the biology of the insects. We also thank Hubertus H. Eidmann, J. Mark Scriber, Donald Strong, and
David Tilles for helpful comments on the manuscript.

LITERATURE CITED

BENNETT, W.H. 1954. The effect of needle structure upon the susceptibility of hosts to the pine
needle miner (Exoteleia pinifoliella (Chamb.) Lepidoptera: Gelechiidae). Can. Entomol. 86: 49-54.

BERNAYS, E. and GRAHAM, M. 1988. On the evolution of host specificity in phytophagous
arthropods. Ecology 69: 886-892.

BOEVE, J.L. and PASTEELS, J.M. 1985. Modes of defence in nematine sawfly larvae. Efficiency
against ants and birds. J. Chem. Ecol. 11: 1019-1036.

BROWNE, F.G. 1968. Pests and Diseases of Forest Plantation Trees. Clarendon Press, Oxford.

BURATTI, L., ALLAIS, J.P., GERI, C., and BARBIER, M. 1990. Abietane and primarane diterpene
acid evolution in scots pine, Pinus sylvestris, needles in relation to feeding of the pine sawfly,
Diprion pini L. Ann. Sci. For. 47: 161-171.

CATES, R.G. 1980. Feeding patterns of monophagous, oligophagous, and polyphagous insect
herbivores: the effect of resource abundance and plant chemistry. Oecologia 46: 22-31.

CLARIDGE, M.F. and WILSON, M.R. 1982. Insect herbivore guilds and species-area relationships:
leafminers on British trees. Ecol. Entomol. 7: 19-30.

CONNOR, E.F., FAETH, S.H., SIMBERLOFF, D., AND OPLER, P.A. 1980. Taxonomic isolation and
the accumulation of herbivorous insects: a comparison of introduced and native trees.
Ecol. Entomol. 5: 205-211.
CORNELL, H.V. 1989. Endophage-ectophage ratios and plant defence. Evol. Ecol. 3: 64-76.
DETHIER, V.G. 1954. Evolution of feeding preferences in phytophagous insects. Evolution 8: 33-54.

EHRLICH, P.R. and RAVEN, P.H. 1964. Butterflies and plants: a study in coevolution. Evolution
18: 586-608.


B. MODEL! Genetic * tnkar

nce for middle age Ween eg N gutumaaiie

z
5

SAWFLY SURVIVAL,

MODEL! Genet +
Tes Age + normal
Preterence for etd trees

JODEL! Ganetic« linear
Steves linear

SAWFLY SURVIVAL,
SAWFLY SURVIVAL

100, 100
$ 2
5 z
2 a
5 5
3} &

°

a

iy,
Teg
© ugh

anes

Figure 6. Hypothetical response surfaces for the effects of ponderosa pine
genotype, tree age, and stress on the survival of pine sawflies. Response

surfaces assume that the effects of tree age and stress are independent of
genotype.

28


90-5 r 100

g
fay
uw
Ee

804 90
a °
I< a
~ >
oO 3}
w 704 L 80
e 7 3
g a
a 4
3 a
2 L
Oo 604 70 5
w rr
uw
3 rs)
iw
4 0-=0 Eggs Oviposited 6o 5
50 ° 99 r a
@——@ % Total Oviposited ©
wi
a
io} T T T T T T °
f 2 5 to 15 20
TREE AGE

Figure 2. Influence of tree age on the number of eggs laid and the percent of
total female fecundity oviposited for Neodiprion fulviceps on 1-year-old
foliage of six different ages of ponderosa pine.

On the basis of the literature and the preliminary evidence collected, I hypothesize that for any
given sawfly species there is a tree age at which sawfly survival would be optimal. The preferred tree
age could vary among sawfly species on the same host. This could indicate a method by which sawfly
species with similar life cycles partition their food resources to avoid competition. A hypothetical
response function for the relationship between sawfly survival and tree age is presented for three
ponderosa pine-feeding sawflies (Fig. 4). In this case Neodiprion gillettei (Rohwer), which occurs in
nature on seedlings, would probably have optimal survival on young trees. In contrast, Neodiprion
fulviceps, which occurs on much older trees in nature, would probably have optimal survival on older
trees, I assume that both species’ survival response to tree age approximates a normal curve.

The critical point here is that sawfly survival probably depends on tree age independent of other
factors. It is possible that an experimental bioassay of a highly resistant and highly susceptible
ponderosa pine genotype, above or below the acceptable age range for a particular sawfly species might
indicate that there was no genetic effect, whereas the identical bioassay at the optimal age would
indicate a clear difference in performance between genotypes. Any insect-plant interaction experiments
conducted with plant material of an inappropriate age might produce very misleading results.


KING, J.P. 1971. Susceptibility variation in Lake States jack pine seed sources. U.S. For. Serv. Res.
Pap. NC-53. 10 p.

KNERER, G. and ATWOOD, C.E. 1973. Diprionid sawflies: polymorphism and speciation.
Science 179: 1090-1099.

KNIGHT, F.B. and HEIKKENEN, H.J. 1980. Principles of Forest Entomology. Sth ed. McGraw-Hill,
New York. 461 p.

LARSSON, S. 1989. Stressful times for the plant stress-insect performance hypothesis. Oikos
56: 277-283.

LARSSON, S. and TENOW, O. 1984. Utilization of dry matter and bioelements in larvae on
Neodiprion sertifer Geoffr. (Hymenoptera: Diprionidae) feeding on Scots pine (Pinus sylvestris L.).
Oecologia 43: 157-172.

MATTSON, W.J. and HAACK, R.A. 1987a. The role of drought in outbreaks of plant-eating insects.
BioScience 37: 110-118.

MATTSON, W.J. and HAACK, R.A. 1987b. The role of drought stress in provoking outbreaks of
phytophagous insects, pp. 365-407. In Barbosa, P. and Schultz, J.C., eds. Insect Outbreaks.
Academic Press, New York. 578 p.

MATTSON, W.J., LAWRENCE, R.K., HAACK, R.A., HERMS, D.A., and CHARLES, P.-J. 1988.
Defensive strategies in woody plants against different insect feeding guilds in relation to plant
ecological strategies and intimacy of association with insects, p. 3-38. In Mattson, W.J., Levieux,
J., and Bernard-Dagan, C., eds. Mechanisms of Woody Plant Defenses Against Insects. Springer-
Verlag, New York.

McCULLOUGH, D.G. and WAGNER, M.R. 1987. Influence of watering and trenching ponderosa pine
on a pine sawfly. Oecologia 71: 382-387.

McDONALD, G.I. 1979. Resistance of Douglas-fir to western spruce budworm: results of a preliminary
progeny test. U.S. For. Serv. Res. Note INT-264. 7 p.

McDONALD, G.I. 1982. Progeny testing of Douglas-fir seedlings for resistance to western spruce
budworm, p. 460-465. In Heybroek, H.M., Stephens, B.R., and von Weissenberg, K., eds.
Resistance to Diseases and Pests in Forest Trees. Pudoc, Wageningen, The Netherlands.

McLEOD, J.M. 1970. The epidemiology of the swaine jack pine sawfly, Neodiprion swainei Middleton.
For. Chron. 46: 126-133.

MEYERS, J.H. 1988. Can a general hypothesis explain population cycles in forest Lepidoptera?
Adv. Ecol. Res. 18: 179-242.

SCHMIDT, J.M. and FRYE, R.H. 1977. Spruce beetle in the Rockies. U.S. For. Serv. Gen. Tech.
Rep. RM-49.

SMITH, R.H. 1972. Xylem resin in the resistance of the Pinaceae to bark beetles. U.S. For. Serv. Gen.
Tech. Rep. PSW-1. 7 p.

SMITH, R.H. 1975. Formula for describing effect of insect and host tree factors on resistance to
western pine beetle attack. J. Econ. Entomol. 68: 841-844.

33


HOST-PLANT SPECIALIZATION
IN NEEDLE-EATING INSECTS OF SWEDEN

CHRISTER BJORKMAN and STIG LARSSON

Department of Plant and Forest Protection
Swedish University of Agricultural Sciences
P.O. Box 7044, S-750 07 Uppsala, Sweden

INTRODUCTION

It has been suggested that the enormous diversity of phytochemicals within the plant kingdom
makes it impossible for one and the same insect species to exploit all plant species (Dethier 1954,
Fraenkel 1959). Not surprisingly, the number and diversity of host plants utilized by different
phytophagous insects are highly variable, and the specific selective pressures acting on them are still
poorly understood (Bernays and Graham 1988, Strong 1988). Many hypotheses have been proposed to
explain variations in host specificity among phytophagous insects. For example, there are those based
on plant traits: plant defenses (Ehrlich and Raven 1964), plant apparency (Feeny 1976, Rhoades and
Cates 1976), plant abundance (Root 1973), plant nutritional value (Mattson and Scriber 1987); those
based on insect traits: degree of intimacy with the host plant (Mattson et al. 1988), neuronal capacity
of the insect (Levins and MacArthur 1969) and finally those based on natural enemies’ traits, e.g. the
impact of generalist predators (Bernays and Graham 1988).

In this paper we examine the predictions resulting from hypotheses based on plant characteristics
and insect intimacy. We have used the data available in the literature on host ranges of Swedish
needle-eating insects reported to feed on the three major conifer species native to Sweden: Scots pine
(Pinus sylvestris), Norway spruce (Picea abies), and juniper (Juniperus communis). These species account
for almost all of Sweden’s coniferous flora.

HYPOTHESES EXPLAINING HOST-PLANT SPECIALIZATION

According to the plant apparency hypothesis, differences in tissue chemistry exist between long-
lived perennial plants that are easily discovered by insects (apparent) and annual ephemerals that are
more difficult to discover (unapparent) (Feeny 1976, Rhoades and Cates 1976). Supposedly, apparent
plants contain relatively large amounts of unspecific allelochemicals of low toxicity, high in molecular
weight (e.g. tannins), whereas unapparent plants contain small amounts of specific, highly toxic
allelochemicals with a low molecular weight (e.g. glucosinolates). These groups of allelochemicals have
been called quantitative and qualitative, respectively, by Feeny (1976). Owing to these differences,
polyphagous insects are associated mainly with apparent plants and monophagous insects mainly with
unapparent plants. Being long-lived and large, conifers meet all the criteria of apparent plants. Hence
one can predict that a majority of insects feeding on conifers will be polyphagous. However the
apparency hypothesis further predicts that the types of allelochemicals will vary among tissues within a
plant depending on tissue apparency. Analogous to between-species variation, apparent tissue (usually
perennial), containing unspecific allelochemicals, and unapparent tissue (usually short-lived), containing
more specific allelochemicals, should favor polyphagy and monophagy, respectively.

BARANCHIKOV, Y.N., MATTSON, W.J., HAIN, F.P., and PAYNE, T.L., eds. 1991. Forest Insect
Guilds: Patterns of Interaction with Host Trees. U.S. Dep. Agric. For. Serv. Gen. Tech. Rep. NE-153.

1


DIETZ, K.-J. 1989. Leaf and chloroplast development in relation to nutrient availability. J. Plant
Physiol. 134: 544-550.

EIS, S., GARMAN, E.H., and EBELL, L.F. 1965. Relation between cone production and diameter
increment of douglas fir (Pseudotsuga menziesii (Mirb.) Franco), grand fir (Abies grandis (Dougl.)
Lindl.), and western white pine (Pinus monticola Dougl.). Can. J. Bot. 43: 1553-1559.

ELMOVIST, T., ERICSON, L., DANNELL, K., and SALOMONSON, A. 1987. Flowering, shoot
production, and vole bark herbivory in boreal willow. Ecology 68: 1623-1629.

ELMOVIST, T., ERICSON, L., DANNELL, K., and SALOMONSON, A. 1988. Latitudinal sex ration
variation in willows, Salix spp., and gradients in vole herbivory. Oikos 51: 259-266.

ESLER, KJ., COWLING, R.M., WITKOWSKI, E.T.F., and MUSTART, P.J. 1989. Reproductive traits
and accumulation of nitrogen and phosphorous during the development of fruits of Protea
compacta R. Br, (Calcifuge) and Protea obtusifolia Buek. ex Meisn. (Calcicole). New Phytol.
112: 109-115.

FOX, J.F. and BRYANT, J.P. 1984. Instability of the snowshoe hare and woody plant interaction.
Oecologia 63: 128-135.

FOYER, C.H. 1988. Feedback inhibition of photosynthesis through source-sink regulation in leaves.
Plant Physiol. Biochem. 26: 483-492.

FREEMAN, D.C. KLIKOFF, L.G., and HARPER, KT. 1976. Differential resource utilization by the
sexes of dioecious plants. Science 193: 597-599.

FREEMAN, D.C., HARPER, K.T., and CHARNOV, E.L. 1980. Sex change in plants: old and new
observations and new hypotheses. Oecologia 47: 222-232.

GIFFORD, R.M. and EVANS, L.T. 1981. Photosynthesis, carbon partitioning, and yield. Annu. Rev.
Plant Physiol. 32: 485-509,

GIFFORD, R.M., THORPE, J.H., HITZ, W.D., and GIAQUINTA, R.T. 1984. Crop productivity and
photoassimilate partitioning. Science 225: 801-807.

GROSS, H.L. 1972. Crown deterioration and reduced growth associated with excessive seed production
by birch. Can. J. Bot. 50: 2431-2437.

HAACK, R.A. and SLANSKY, F., Jr. 1987. Nutritional ecology of wood-feeding Coleoptera,
Lepidoptera, and Hymenoptera. In Slansky, F., Jr. and Rodriguez, J.G., eds. Nutritional Ecology
of Insects, Mites, Spiders, and Related Invertebrates. John Wiley & Sons, New York.

HARBORNE, J.B. 1990. Constraints on the evolution of biochemical pathways. Biol. J. Linn. Soc.
39: 135-151.

HARPER, J.L. and WHITE, J. 1974. The demography of plants. Annu. Rev. Ecol. Syst. 5: 419-463.
HAWBOLDT, L.S. 1947. Aspects of yellow birch dieback in Nova Scotia. J. For. 45: 414-422.

HAWBOLDT, L.S. and SKOLKO, A.J. 1948. Investigation of yellow birch dicback in Nova Scotia in
1947. J. For. 46: 659-671.

43


LITERATURE CITED

ABRAHAMSON, W.G. and CASWELL, H. 1982. On the comparative allocation of biomass, energy,
and nutrients in plants. Ecology 63: 982-991.

AGREN, G.I. 1988. Ideal nutrient productivities and nutrient proportions in plant growth. Plant, Cell,
Envir. 11: 613-620.

AGREN, J. 1987. Intersexual differences in phenology and damage by herbivores and pathogens in
dioecious Rubus chaemorus L. Oecologia 72: 161-169.

ALLEN, G.A. and ANTOS, J.A. 1988. Relative reproductive effort in males and females of the
dioecious shrub Oemleria cerasiformis. Oecologia 76: 111-118.

ALLIENDE, M.C. 1989. Demographic studies of a dioecious tree. II. The distribution of leaf predation
within and between trees. J. Ecol. 77: 1048-1058.

ALPERT, P., NEWELL, E.A., CHU, C., GLYPHIS, J. GULMON, S.L., HOLLINGER, D.Y.,
JOHNSON, N.D., MOONEY, H.A., and PUTTICK, G. 1985. Allocation to reproduction in the
chaparral shrub, Diplacus aurantiacus. Oecologia 66: 309-316.

ANDERSON, R.F. 1944. The relation between host condition and attacks by the bronzed birch borer.
J. Econ. Entomol. 37: 588-596.

BARTER, G.W. 1957. Studies of the bronze birch borer, Agrilus anxius Gory in New Brunswick.
Can. Entomol. 89: 12-36.

BAWA, KS. 1980. Evolution of dioecy in flowering plants. Annu. Rev. Ecol. Syst. 11: 15-39.

BAWA, KS. and OPLER, P.A. 1978. Why are pistillate inflorescences of Simarouba glauca eaten less
than staminate inflorescences. Evolution 29: 673-676.

BAZZAZ, F.A. and REEKIE, E.G. 1985. The meaning and measurement of reproductive effort in
plants. In White, J., ed. Studies on Plant Demography. Academic Press, London.

BAZZAZ, F.A., CARLSON, R.W., and HARPER, J.L. 1979. Contribution to reproductive effort by
photosynthesis of flowers and fruits. Nature 279: 554-555.

BAZZAZ, F.A., CHIARIELLO, N.R., COLEY, P.D., and PITELKA, L.F. 1987. Allocating resources to
reproduction and defense. BioScience 37: 58-67.

BERRYMAN, A.A. 1987. The theory and classification of outbreaks. In Barbosa, P. and Schultz, J.C.,
eds. Insect Outbreaks. Academic Press, San Diego.

BERRYMAN, A.A. and STARK. R.W. 1985. Assessing the risk of forest insect outbreaks. Z. ang.
Entomol. 99: 199-208.

BIERZYCHUDEK, P. and ECKHART, V. 1988. Spatial segregation of the sexes of dioecious plants.
Am. Nat. 132: 34-43.

BLOOM, A.J., CHAPIN, F. STUART, III, and MOONEY, H.A. 1985. Resource limitation in plants--
an economic analogy. Annu. Rev. Ecol. Syst. 16: 363-392.

41


PLANT REPRODUCTIVE ORGANS
AND THE ORIGIN OF TERRESTRIAL INSECTS

GEORGY V. STADNITSKY

Technological Institute of Pulp and Paper Industry
Leningrad 198092 U.S.S.R.

INTRODUCTION

It is widely believed that plants facilitated the evolution of terrestrial insects (Southwood 1973).
However, the mechanisms by which this evolution occurred are not yet fully understood. I therefore
propose a hypothesis about one possible mode of formation of terrestrial insects and fauna. The soil,
warm shallow lagoons, tidal zones, and accumulations of detritus are assumed by many authors to be
the "bridges" for the transition of aquatic organisms to terrestrial existence.

The linkage of insects to plants has been offered as an explanation for the evolution of
complete metamorphosis and the ability to fly. It has been suggested that holometabolism occurred in
narrow cavities of the substrate, which might be represented by the cavities and ducts in the plant
reproductive organs. It is assumed that wings and the ability to fly evolved owing to its advantages in
finding food and escaping from enemies.

The Transit to Land

The aquatic fauna is known to be extremely diverse; ancestors of the present arthropods were
highly differentiated in the aquatic environment. In the transient water-land zones, the proto-insect’s
migration onto the land seemed inevitable, although this transit took a long time. Thus it could not
have been simultaneous for various insect groups, although some groups evolved concurrently. Each
group probably had its own bridge. Let us imagine those conditions which contributed to an obligatory
and inevitable transition of aquatic organisms to land. The earth at that time (the Lower
Silurian-Upper Devonian) was represented mostly by rocky, dry desert with scanty vegetation, oxygen
deficiency, and unlimited amounts of severe ultraviolet radiation.

Organisms living in water were shielded from UVR and from drying and over-heating. They
could easily move in a water environment which provided them with necessary support. Those
organisms which moved onto land faced formidable ecological difficulties, the most serious being the
lower viscosity and density of the air as compared to those of the water. Their bodies actually lost
support and their free movement became impaired. For such groups of ancestral arthropods, soil
might have been the bridge to terrestrial life. The land was almost devoid of organic life, having
drastic changes of temperature, humidity, and illumination. The chance to survive and have progeny
was probably very small. The vegetation (the plant protocommunities) had not yet contributed to the
process apart from accumulations of detritus and remnants of aquatic plants which served as screens.

Another, later evolutionary branch of aquatic arthropods was associated with the transition of
plants to terrestrial existence. This happened as a result of differentiation of the plant life cycle into

BARANCHIKOV, Y.N., MATTSON, W.J., HAIN, F.P., and PAYNE, T.L., eds. 1991. Forest Insect
Guilds: Patterns of Interaction with Host Trees. U.S. Dep. Agric. For. Serv. Gen. Tech. Rep. NE-153.

47


Table 1, Preferred distribution of 180 phytophagous insect species over
different forest parts

Number of species

Habitats
Total %
Forest borders and their analogues
Isolated trees (A) 3 1.7
A+B 5 2.8
Forest borders (B) 18 10.0
BtCc 46 25.6
Open, low-density stands (C) 49 27.2
AtB+C 11 6.1
Forest thickets and their analogues
Closed, high-density stands (D) 29 16.1
c+D 7 3.9
Uncertain distribution
A+B+C+D 4 2.2
B+tC+D 1 0.5
Uncertain 7

Climatic conditions are different in every natural zone, however, and the insect species areas
may occur over several bioclimatic zones, Therefore dendrophage distribution in relation to forest
borders may be different. Dispersal from one natural zone to another provide ample evidence that
insect species exchange one kind of habitat for another. We should take this principle into account in
our strategies for controlling insect species epidemics, but for our present purposes it is more
interesting to consider dendrophage distribution within different zones, such as forest and steppe
regions.

My data analysis again showed the majority of species to prefer the forest border and its
analogues: 84 percent the forest zone and 71 percent the steppe. So these "border" habitats are
assumed to have an advantage over forest thickets and their analogue for insects.

There is data indicating some abundant species use the forest borders as a refuge between
outbreaks. Moreover, the initial outbreak areas often coincide with these refugia. At the same time,
my analysis showed both outbreak and nonoutbreak insect species (81 percent and 79 percent
Tespectively) to prefer forest borders. We may say, then, forest borders not only function as refuges
for abundant species, but are preferred habitats for the majority of nonoutbreak species as well. The
question is why?

51


Birch trees experiencing traumatic trunk and canopy death frequently maintain sufficient stored
reserves to resprout from the roots. Substantial resprouting often follows above-ground mortality
resulting from fire or snowshoe hare browsing. Higher levels of terpenoid surface resins of the bark of
juvenile growth originating from root-sprouts are toxic to snowshoe hares and may contribute to the
decline of hare population outbreaks (Bryant 1981, Fox and Bryant 1984). Trees killed by bronze birch
borer can resprout, as well, and sprouts may be too small to permit bronze birch borer colonization
for several years. Sprouting following trunk death is obviously an adaptation to catastrophic
disturbances such as fire and herbivore outbreaks, contributing to the continued dominance by birch of
seral sites.

Sexual Variation in Resistance and the Carbon/Nutrient Balance

Dioecious plants frequently exhibit sexual dimorphism in resources allocated to reproductive
effort, with female effort generally greatest because of resources required for seed and fruit maturation
(Lloyd and Webb 1977, Wallace and Rundel 1979, Hoffmann and Alliende 1984, Bullock 1984, Clark
and Clark 1988, Snow and Whigham 1989, Allen and Antos 1988). Several studies have documented
intraspecific sexual variation in the degree of herbivory experienced by dioecious plants (Dannell et al.
1985, Lovett Doust and Lovett Doust 1985, Agren 1987, Elmqvist et al. 1988, Alliende 1989, Boecklen
et al. 1990). The resource-competition hypothesis predicts increased herbivory on female plants
because their typically greater reproductive effort competes for resources with defense mechanisms.
However, data from the few existing studies suggest that the opposite is true. Male plants generally
experience greater herbivory (Bawa and Opler 1978, Dannell et al. 1985, Agren 1987, Alliende 1989,
Boecklen et al. 1990).

Male and female plants may often segregate along environmental gradients (Putwain and Harper
1972, Freeman et al. 1976, Bawa 1980, Cox 1981, Bierzychudek and Eckart 1988). Differential levels of
herbivory, possibly resulting in skewed sex-ratios, may arise from 1) differential frequency of herbivore
encounters in their respective environments, or 2) differential defensive allocations among male and
female plants.

The nutrient capital required for the growth, maintenance, and maturation of flowers, fruits, and
seeds can be substantial and is obtained in full from the rest of the plant (Bazzaz et al. 1979,
Thompson and Stewart 1981). Limiting nutrients may be mobilized in relatively high proportions from
vegetative tissue to reproductive sinks, thereby contributing to the reductions in vegetative growth
associated with reproduction (Mooney 1972, Sinclair and de Wit 1975, 1976, Thompson and Stewart
1981, Bloom et al. 1985, Alpert et al. 1985). The high quantities of nutrients required for fruit and
seed maturation may contribute to nutrient deficiencies and ensuing growth reductions in female
Telative to male plants (Bullock 1984, Allen and Antos 1988).

The reproductive structures of many species are photosynthetic, contributing in varying degrees
to their own economy of energy and biomass (Dickmann and Kozlowski 1970, Bazzaz et al. 1979,
Reekie and Bazzaz 1987a). Furthermore, enhanced sink strength associated with rapidly developing
reproductive structures may stimulate increased photosynthesis in nearby source leaves, through
feedback mediated effects (Neales and Incoll 1968, Watson and Casper 1984, Foyer 1988, Dick et al.
1990). As a result, the diversion of carbon from vegetative to reproductive structures may be
proportionally less than that of nutrients, especially in female plants (Sinclair and de Wit 1975, 1976,
van Andel and Vera 1977, Lovett Doust 1980, Williams and Bell 1981, Abrahamson and Caswell 1982,
Mooney and Gulmon 1982, Bullock 1984, Allen and Antos 1988, Reekie and Bazzaz 1987b, Esler et al.
1989). Biomass alone may not always be a suitable measure of reproductive effort (Thompson and
Stewart 1981, Abrahamson and Caswell 1982, Bazzaz and Reekie 1985, Reekie and Bazzaz 1987b).

Rapidly growing tissues are invariably strong photosynthetic sinks (Wareing and Patrick 1975,
Patrick 1988). However, nutrient limitation slows their growth (Agren 1988, Patrick 1988).

39


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ay


Similarly, tree stress can result in widely different effects depending on the tree genotype. Even
in the simplest case, when the effects of stress and genotype are linear (Fig. 6d), it is still possible to
obtain highly variable responses if either genotype or stress is not carefully controlled. In the most
complicated case, when resistance is linear and stress is a modified cosine function (Fig. 6f), it is
possible to observe an increase or decrease in sawfly survival with increasing stress depending on the
initial level of stress. Finally, it is important to recognize that a wide variety of genotype, age, and
stress levels could produce the same sawfly survival. A resistant genotype that was highly stressed
could produce the same degree of sawfly survival as a susceptible genotype that was not stressed. Thus
examination of response surfaces can greatly facilitate our understanding of these relationships.

RESPONSE SURFACES AS AN EXPLANATION OF CONTRADICTORY RESULTS

One of the assumptions I made in generalizing the hypothetical response surfaces in Fig. 6 was
that the effects of tree age and stress were the same across all genotypes. In other words, I assumed
that a resistant genotype would have the same response curve to tree age and stress as would a
susceptible genotype. In fact there is no reason to assume that is so. For example, sawfly survival
may not increase on a resistant genotype until that genotype is very heavily stressed. Conversely,
sawfly survival might increase quickly with low-level stress on a susceptible genotype, but drop
drastically at moderate to high levels of stress.

I have illustrated the potential effects of variable response functions across genotypes in Fig. 7.
In this case I create slightly different response functions for susceptible and resistant genotypes. It is
possible to observe (Fig. 7, large stress arrow) quite variable effects of an increase in stress at different
specified stress levels. For genotype A, an increase in stress results in a decrease in sawfly survival,
whereas for genotype B, an increase in stress results in an increase in survival. Likewise for a specific
genotype (Fig. 7, large genotype arrow), sawfly survival will decrease with an increase in stress at stress
level A and increase with an increase in stress at stress level B. It becomes obvious with examination
of Fig. 7 that all of the hypothetical response functions presented for the effect of stress in Fig. 5
could be contained in a single complex response surface. The contradictory results reported in the
literature and emerging from our own experimental data could be explained by a complex model such
as that presented in Fig. 7.

UTILITY OF EXAMINING RESPONSE SURFACES

The purpose of the previous discussion on response surfaces was to demonstrate how reasonable,
individual variable response functions could be combined to create very complex response surfaces. I
have discussed only cases involving two factors interacting to influence sawfly survival. We know that
in nature many more factors interact. I am led to conclude that much more carefully controlled
experimental work is required before true response surfaces are likely to emerge for any insect-plant
system and for any two sets of variables. Without a very disciplined approach to the analysis of
individual factors and combinations of factors, we will probably wander for years generating points on a
Tesponse surface without ever fully recognizing the shape of the overall surface.

To improve the probability of our discovering the true response surface of host plant variables
influencing insect survival, I propose the following protocols. 1) Research should focus on single
insect/host models. Only long-term attention to key host plant traits can identify true response
surfaces. 2) Strongly experimental approaches are required which attempt to hold as many factors
constant as possible while testing for the factor of interest. Common garden/field, greenhouse, or
laboratory studies are more productive than natural field studies in which many variables are not
controlled. 3) Experiments on single factors such as stress must test across the full range of that
factor. As Figs. 6 and 7 demonstrate, an increase in stress could lead to quite variable effects on
survival depending on the initial stress level. 4) Multifactor experiments are useful only when the

29


10.

11.

12.

TABLE OF CONTENTS

GENERAL THEORY ON PLANT/PHYTOPHAGE INTERACTIONS

HOST-PLANT SPECIALIZATION IN NEEDLE-EATING INSECTS OF SWEDEN
Christer Bjorkman and Stig Larsson 2... 6. eee eee 1

SAWFLIES AND PONDEROSA PINE: HYPOTHETICAL RESPONSE SURFACES
FOR PINE GENOTYPE, ONTOGENETIC STAGE, AND STRESS LEVEL
Michael R. Wagner . 0.6.6. eee eet eee tne ene 21

DOES REPRODUCTION COMPROMISE DEFENSE IN WOODY PLANTS?
Daniel A. Herms and William J. Mattson... 1.2.2... cece eee eee eee 35

PLANT REPRODUCTIVE ORGANS AND THE ORIGIN OF TERRESTRIAL INSECTS
Georgy V. Stadnitsky 2... 6... ec eee eee tee e eee 47

PREFERENCE OF DENDROPHAGOUS INSECTS FOR FOREST BORDERS
Andrey V. Gurov 2... ee eee eee eee eee nett eee 50

HIGHLY MOBILE, EXTERNAL PHYTOPHAGES

WOODY PLANT GRAZING SYSTEMS: NORTH AMERICAN OUTBREAK
FOLIVORES AND THEIR HOST PLANTS
William J. Mattson, Daniel A. Herms, John A. Witter, and Douglas C. Allen .......... 53

VARIATION IN THE NUTRITIONAL PHYSIOLOGY OF TREE-FEEDING
SWALLOWTAIL CATERPILLARS
Matthew P. Ayres, Janice L. Bossart, and J. Mark Scriber ... 0.2.0.0... c eee eee 85

DO DIFFERENCES IN INDUCIBLE RESISTANCE EXPLAIN THE POPULATION
DYNAMICS OF BIRCH AND PINE DEFOLIATORS?
Seppo Neuvonen and Pekka Niemel4 .... 2.2.2... 2 eee eens 103

REPEATED DAMAGE OF LEAVES BY PHYLLOPHAGOUS INSECTS: IS IT
INFLUENCED BY RAPID INDUCIBLE RESISTANCE?
LA. Bogacheva . 6... 6. cece te ee een eee tenet eens 113

DOUGLAS-FIR NUTRIENTS AND TERPENES AS POTENTIAL FACTORS INFLUENCING
WESTERN SPRUCE BUDWORM DEFOLIATION
Karen M. Clancy «1.0... cece ce eee eee eee tenes 123

PATTERNS OF NUTRIENT UTILIZATION IN THE NEEDLE-FEEDING GUILD
Thomas Secher Jensen «2... 1. eee eects 134

THE FOLIVORE GUILD ON LARCH (LARIX DECIDUA) IN THE ALPS
W. Baltensweiler 2.1... eee teeter eee 145


at any given moment. When we consider multiple factors simultaneously, we can better define those
instances in which a factor will or will not be influential.

In this paper I discuss the general evidence from the literature and my preliminary experimental
evidence that at least three variables (genotype, ontogeny, and stress) influence the population
parameters of Neodiprion spp. (Hymenoptera: Diprionidae), which feed on ponderosa pine, Pinus
ponderosa Dougl. ex Laws. I also present some hypothetical response functions for these single factors.
Then I generate some three-dimensional figures that illustrate how two individual variables could
interact to create a response surface. Finally, I illustrate how it is possible to generate from very
realistic univariate response functions complex response surfaces which could explain otherwise
apparently contradictory results.

ROLE OF GENOTYPE IN SAWFLY-PONDEROSA PINE INTERACTION

For most plants there is a range of natural suitability for insects that appears to be genetically
controlled. Significant genotype variation in forest trees to insects has been identified for bark beetles
(Stark 1965, Callaham 1966, Berryman 1972, Smith 1972, Smith 1975), scales and aphids (Hoff and
McDonald 1977, Mattson et al. 1988), pitch midge (Hoff 1988), pine weevils (Hall 1959, King 1971,
Wilkinson 1979, Harris et al. 1983, Brooks et al. 1987), shoot moths (Hertel and Benjamin 1975,
Charles et al. 1982), cone insects (Askew et al. 1985), defoliators (Tigner and Mason 1973, Genys and
Harman 1976, McDonald 1979, 1982, Fogal et al. 1982), and pine sawflies (Arend et al. 1961, Wilson
1966, Wright et al. 1967, Henson et al. 1970). Interestingly, Mattson et al. (1988) argue that there is
relatively little evidence for genetic resistance to free-feeding defoliators. Part of their data is based on
examination of the susceptibility of trees in range-wide provenance plantations. It may be that the
procedures used for creating the provenances trials resulted in inadvertent selection of only susceptible
genotypes. For example, it may be that the provenance collection sites were areas with relatively low
defoliator pressure and hence a low selection for insect resistance. At any rate, the evidence suggests
that there is some genotypic variation in insect susceptibility for most tree species.

For the past 3 years I have been attempting to identify individual trees that exhibit phenotypic
resistance to pine sawflies. My basic procedure has been to identify unattacked trees within sawfly
outbreak areas. These phenotypically resistant trees have then been paired with nearby phenotypically
susceptible trees. To date 10 pairs of trees have been identified. I have bioassayed the trees by caging
sawflies on them and measuring stage-specific survival. Following Hanover (1975), seed has been
collected from 14 of the 20 trees and half-sib families have been established. The performance of
sawflies on the maternal trees of the 14 half-sib families is presented in Fig. 1. Whether the traits
that influence susceptibility to sawflies in the maternal trees are inherited by the progeny (half-sibs) has
yet to be determined, but it is clear that there is considerable variation in sawfly resistance in the
maternal phenotype (2 to 65 percent sawfly survival), and this is an indication of genetic resistance
(Bingham 1966, McDonald 1979).

On the basis of the previously cited literature and my preliminary findings, I believe that there
is substantive genetic variation in ponderosa pine resistance to herbivores. In other words, when all
other factors are held constant, there can be considerable variation in insect performance based on
plant genotype alone. For example, I observed a thirtyfold variation in sawfly survival among different
ponderosa pine individuals (Fig. 1). As yet it cannot be established that all of this variation is the
result of genetic factors, but it is highly probable that some of the variation is due to genetic factors.
Greater knowledge about the genetic variation of ponderosa pine could greatly clarify our
understanding of how host plants and herbivores interact.

22


EIDMANN, H.H. and KLINGSTROM, A. 1976. Skadegdrare i skogen. LTs férlag, Boras.

EISNER, T., JOHNESSEE, J.S., CARREL, J., HENDRY, L.B., and MEINWALD, J. 1974. Defensive
use by an insect of a plant resin. Science 184: 996-999.

ENGEL, H. 1939. Beitrage zur Biologie des Kiefernspanners (Bupalus piniarius L.). Mitt. Forstw.
Forstwiss. 10: 51-64.

ESCHERICH, K. 1931. Die Forstinsekten Mitteleuropas. Bd. 3. Paul Parey, Hamburg-Berlin.
ESCHERICH, K. 1942. Die Forstinsekten Mitteleuropas. Bd. 5. Paul Parey, Berlin.

FEENY, P. 1970. Seasonal changes in oak leaf tannins and nutrients as a cause of spring feeding by
winter moth caterpillars. Ecology 51: 565-581.

FEENY, P. 1976. Plant apparency and chemical defense. Recent Adv. Phytochem. 10: 1-40.

FORSTER, W. and WOHLFAHRT, T.A. 1971. Die Schmetterlinge Mitteleuropas. Bd. IV. Eulen
(Noctuidae). Franckh’sche Verlagshandlung, Stuttgart.

FOX, L.R. and MORROW, P.A. 1981. Specialization: species property or local phenomenon? Science
211: 887-893.

FRAENKEL, G.S. 1959. The raison d’etre of secondary plant substances. Science 129: 1466-1470.

FUHRER, E. 1967. Untersuchungen iiber die Ursachen der Befallsdisposition der europaischen Fichte
gegeniiber Epiblemma tedella Cl. (Lep.: Tortricidae). Z. ang. Ent. 59: 292-318.

FUTUYMA, D.J. and PETERSON, S.C. 1985. Genetic variation in the use of resources by insects.
Annu. Rev. Entomol. 30: 217-238.

GHENT, A.W. 1959. Row-type oviposition in Neodiprion sawflies as exemplified by the European pine
sawfly N. sertifer (Geoff.). Can. J. Zool. 37: 267-281.

GRONBERG, G. 1903. Tallspinnaren, Lasicampa pini (L.), dess naturhistoria och fiender, samt medel
mot densamma. Tidskr. Skogshushdlin. 31: 195-214.

HANNEMANN, H.-J. 1961. Kleinschmetterlinge oder Microlepidoptera. I. Tierwelt Deutschlands.
vol. 48. VEB Gustav Fischer Verlag, Jena.

HANNEMANN, H.-J. 1964. Kleinschmetterlinge oder Microlepidoptera. II. Tierwelt Deutschlands.
vol 50. VEB Gustav Fischer Verlag, Jena.

HANNEMANN, H.-J. 1977. Kicinschmetterlinge oder Microlepidoptera. I. Tierwelt Deutschlands.
vol 63. VEB Gustav Fischer Verlag, Jena.

HEDOQVIST, K.-J. 1972. Ostlische Kiefern-Buschhornblattwespe (Gilpinia verticalis Guss.), ein fir
Schweden neuer Forstschadling. Entomol. Scand. 3: 244-248.

HELLRIGL, K.G. 1971. Die Bionomie der Europaischen Monochamus-arten (Coleop., Cerambycid.)
und ihre bedeutung fir die Forst- und Holzwirtsschaft. Pubbl. N 154 del Centro di Entomol.
alpina e forestale del Consiglio Nazionale delle Ricerche. Estratto da REDIA, Firenze 52:
367-510.


REFERENCES: 1) Winter (1983), 2) Escherich (1931), 3) Spuler (1913),

4) Schwenke (1978), 5) Schnaider (1976), 6) Traga&rdh (1915), 7) Hannemann
(1977), 8) Hannemann (1961), 9) Hannemann (1964), 10) Browne (1968), 11) Martin
(1959), 12) Patocka (1960), 13) Fuhrer (1967), and 14) Pointing (1963).

14


MORROW, P.A., BELLAS, T.E., and EISNER, T. 1976. Eucalyptus oils in the defensive oral discharge
of Australian sawfly larvae (Hymenoptera: Pergidae). Oecologia 24: 193-206.

NIEMELA, P. 1983. Seasonal patterns in the incidence of specialism: macrolepidopteran larvae on
Finnish deciduous trees. Ann. Zool. Fenn. 20: 199-202.

NIEMELA, P. and NEUVONEN, S. 1983. Species richness of herbivores on hosts: how robust are
patterns revealed by analysing published host plant lists. Ann. Entomol. Fenn. 49: 95-99.

NIEMELA, P., MANNILA, R., and MANTSALA, P. 1982. Deterrent in Scots pine, Pinus sylvestris,
influencing feeding behavior of the larvae of Neodiprion sertifer (Hymenoptera, Diprionidae).
Ann. Entomol. Fenn. 48: 57-59.

NG, D. 1988. A novel level of interactions in plant-insect systems. Nature (Lond.) 334: 611-613.

NORDSTROM, F., WAHLGREN, E., and TULLGREN, A. 1935-41. Svenska fjarilar. Systematisk
bearbetning av Sveriges storfjarilar, Macrolepidoptera. Nordisk familjeboks férlags AB,
Stockholm.

NUNBERG, M. 1939. Das massenhafte Vorkommen des Kiefernschwarmers Sphinx pinastri L. in Polen.
Verh. VII. Inter. Kongr. f. Ent. Bd. 3: 2033-2051.

PATOCKA, J. 1960. Die Tannenschmetterlinge der Slowakei. Verlag der Slowakischen Akademie der
Wissenschaften, Bratislava.

POINTING, P.J. 1963. The biology and behavior of the European pine shoot moth, Rhyacionia
buoliana (Schiff.), in southern Ontario. II. Egg, larva and pupa. Can. Entomol. 95: 844-873.

POWELL, J.A. 1980. Evolution of larval food preferences in microlepidoptera. Annu, Rev. Entomol.
25: 133-159.

PRICE, P.W. 1983. Hypothesis on organization and evolution in herbivorous insect communities,
p. 559-596, In Denno, R.F. and McClure, M.S., eds. Variable Plants and Herbivores in Natural
and Managed Systems. Academic Press, New York.

RHOADES, D.F. and CATES, R.G. 1976. Toward a general theory of plant antiherbivore chemistry.
Recent Adv. Phytochem. 10: 168-213.

ROOT, R.B. 1973. Organization of a plant-arthropod association in simple and diverse habitats: the
fauna of collards (Brassica oleracea). Ecol. Monogr. 43: 94-124.

SCHNAIDER, Z. 1976. Atlas uszkodzen drzew i krzewow. Panstwowe Wydawnictwo Naukowe,
Warzawa.

SCHWENKE, W. 1953. Beitrage zur Bionomie der Kiefernspanner Bupalus piniarius L. und Semiothisa
liturata Cl. auf biondtischer Grundlage. Beitr. Entomol. 3: 168-206.

SCHWENKE, W. 1974. Die Forstschadlinge Europas. Bd. 2. Kafer. Paul Parey, Hamburg-Berlin.

SCHWENKE, W. 1978. Die Forstschidlinge Europas. Bd. 3. Schmetterlinge. Paul Parey,
Hamburg-Berlin.

SCHWENKE, W. 1982. Die Forstschadlinge Europas. Bd. 4. Hautfliigler und Zweifligler. Paul Parey,
Hamburg-Berlin.

10


(%)

100 4
: 80 4
é 20-4 y
| | ol 4 L l

R2 R3 RB RO RE RT RIO RSE SO9 RA SIO S3 S2 Sa

HALF SIB FAMILY

Figure 1. Total generational survival of Neodiprion fulviceps on maternal
ponderosa pine trees from which 14 half-sib families have been established.

ROLE OF ONTOGENY IN SAWFLY-PONDEROSA PINE INTERACTIONS

Many plants show age-related changes in susceptibility to attack by specific insects. Some insect
species attack juvenile trees, such as sawflies on willows (Craig et al. 1986), cynipid wasps on oaks
(Washburn and Cornell 1981, Frankie and Morgan 1984), and a chrysomelid beetle on cottonwood
(Kearsley and Whitham 1989). Other insects attack primarily mature trees: budworms (Blais 1958),
spruce beetles (Schmidt and Frye 1977, Hard 1985), and Pemphigus aphids (Kearsley and Whitham
1989). Pine sawflies commonly show age-related preferences on their pine hosts (Knight and
Heikkenen 1980, Coulson and Witter 1984, Wagner et al. 1986) and generally prefer pole-sized or
smaller trees.

In 1987 we conducted some preliminary tests of the age-related suitability of ponderosa pine to
Neodiprion fulviceps (Cresson). Branches were collected from five trees (similar vigor) of six different
ages (1, 2, 5, 10, 15, and 20 years). One-year-old foliage was bioassayed under laboratory conditions.
We observed patterns of oviposition (Fig. 2) and survival (Fig. 3) that suggested an effect of tree age.
Neodiprion fulviceps had highest survival on 15-year-old trees which is within the usual range of tree
ages where this sawfly species occurs. It is interesting to note that the optimal age for oviposition
(< 10 years) was not the same as for survival. Because the trees used in this study were of unknown
genotype and because the sample size was small, these data are tentative.

23


hypothesis was developed based on free-living Lepidoptera, other groups might be more sensitive to
variation in nutrient concentrations. In the following, therefore, we have broken down our data into
feeding guilds.

Mining Microlepidopterans

The fact that the main defense compounds in conifers (terpenes) are concentrated in clearly
defined resin ducts (Bennett 1954) may have important consequences for mining insects. For example,
one needle-mining microlepidopteran (Exoteleia pinifoliella) utilizes only pine species whose needles
have very few resin ducts, all of which are small. Thus this species appears to be avoiding the resinous
defense of the host (Bennett 1954). Mining insects seem to be very specialized, irrespective of which
food plants they utilize (Hering 1951, Claridge and Wilson 1982, Price 1983). This implies that the
degree of host-plant specialization is determined by selective pressures other than those proposed by
the apparency hypothesis. The intimate relationship between mining insects and their hosts can
probably best explain the narrow host ranges of mining insects. For example, the need to adapt to the
anatomy and phenology of the plant may determine the range of hosts that a miner can potentially
exploit (Hering 1951). However, the high degree of specialization might actually be an artifact
produced as a result of poor investigation of most mining insects (Connor et al. 1980, Powell 1980).

Chewing Insects

Generally, insects feeding externally on leaves and needles come into minimal contact with their
host’s chemical defense. Among the chewing insects in this study, however, the monophagous species
constitute as large a proportion as the polyphagous species when compared over all conifer species
(32 percent and 36 percent, respectively).

However, most of the monophagous species are sawflies (Table 1) and sawflies are
predominantly monophagous, regardless of which type of plants thcy utilize (Hodkinson and Hughes
1982, Shaw 1984). Neither the apparency nor the nutrition hypothesis predicts this monophagy. In
contrast, the intimacy hypothesis does because conifer-feeding sawflies insert their eggs into the needles
of their host, and needle morphology is an important factor in determining oviposition success (Ghent
1959). The ability of females to find needles suitable for oviposition should therefore be strongly
selected for. A behavioral adaptation of this kind could be a major reason for the prevalence of
monophagy among needle-eating sawflies (Futuyma and Peterson 1985). Moreover, several conifer
sawflies have evolved the ability to "detoxify" the defensive compounds produced by their hosts (Eisner
et al. 1974, Larsson et al. 1986) and furthermore to use these substances in their own defense against
natural enemies (Eisner et al. 1974, Morrow et al. 1976, Boevé and Pasteels 1985). This may be
another reason why sawflies on conifers are so specialized. Thus the intimacy hypothesis is partially
supported in the sawfly case.

The predominance of polyphagy among chewing Lepidoptera accords with the predictions of all
three hypotheses. In two other studies including insects feeding on less apparent, more nutritious
plants, the proportion of polyphagous species was reported to be 54 percent and 32 percent (Holloway
and Hebert 1979, Hodkinson and Hughes 1982, respectively), whereas in this study it was 52 percent.
According to both the apparency and the nutrition hypotheses, however, one would expect relatively
more polyphagous insect species on conifers than on plants of lower apparency and higher nutritional
value. Thus one out of two comparisons with other studies supports these hypotheses. In principal, a
species may behave as a generalist either because every individual is generalistic or because the species
consists of specialized individuals or subpopulations (Van Valen and Grant 1970, Jaenike 1978, Singer
1983). For herbivorous insects there are many examples of specialization among individuals and
populations (Knerer and Atwood 1973, Fox and Morrow 1981, Singer 1983, Futuyma and Peterson
1985, Ng 1988). Lasiocampa quercus provides one such example in this study (Appendix B). Until

5


of physiological metabolism (hystolis, histogenesis) in the period of transition from a wingless, sexless
larva to the winged and sexually mature "imago."

The development within the living plant tissues did not require the development of
morphological and physiological adaptation. Exactly the same advantages are available to primary
wingless insects which occur (and still occur) in strongly moisturized soil cavities. (See Gilyarov 1970.)
However, the temporal discreteness of plant organs and tissues forced the insect to exist outside plants
during a certain period of their ontogenesis, which resulted in the forming of new adaptations. The
development of an isolated pupa (where these processes take place), not affected by the environment,
appeared to be an optimal evolutionary trend. In a number of cases the developed ability of retarding
or stopping the development without morphological reconstructions was fixed, i.e. diapause.

On the other hand, those insects who primarily or secondarily were related to non-discrete plant
organs (leaves, branches) and have created not only the chewing feeding mode but also a sucking one
as well (Orthoptera, Heteroptera, Homoptera) did not develop the pupal stage, they are known as
Hemimetabola.

The above presents the main concepts of a theory which is by no means complete. It should be
considered as a preliminary assumption for a future hypothesis.

49


FAETH, STANLEY H. (219), Department of Zoology, Arizona State University, Tempe, AZ 85287
USA.

FEDORENKO, SERGEY L (213), Institute of Forest, Ural Branch of the U.S.S.R. Academy of
Sciences, Sverdlovsk U.S.S.R.

GAVRIKOV, VLADIMIR L. (385), V.N. Sukachev Institute of Forest and Wood, Siberian Branch of
the U.S.S.R. Academy of Sciences, Krasnoyarsk 660036 U.S.S.R.

GIRS, GALINA L (378), V.N. Sukachev Institute of Forest and Wood, Siberian Branch of the U.S.S.R.
Academy of Sciences, Krasnoyarsk 660036 U.S.S.R.

GUROV, ANDREY V. (50), V.N. Sukachev Institute of Forest and Wood, Siberian Branch of the
U.S.S.R. Academy of Sciences, Krasnoyarsk 660036 U.S.S.R.

HAIN, F. P. (271), Department of Entomology, North Carolina State University, Raleigh, NC 27695
US.A.

HERMS, DANIEL A. (35, 53), The Dow Gardens, 1018 W. Main St., Midland, MI 48640 U.S.A., and
Department of Entomology, Pesticide Research Center, Michigan State University, East Lansing,
MI 48824 U.S.A.

HOLLINGSWORTH, R. G. (271), Department of Entomology, North Carolina State University,
Raleigh, NC 27695 U.S.A.

JENSEN, THOMAS SECHER (134), Zoological Laboratory, Institute of Zoology and Zoophysiology,
University of Aarhus, DK-8000 Aarhus, Denmark

KASAHARA, MAKOTO (397), Laboratory of Silviculture, Faculty of Agriculture, Kochi University,
Monobe B200, Nankoku City, Kochi, Japan 783

KHLIMANKOVA, ELENA S. (211), Siberian Institute of Plant Physiology and Biochemistry, Siberian
Branch of the U.S.S.R. Academy of Sciences, Irkutsk 664033 U.S.S.R.

KHOMENTOVSKY, PETR A. (316), Kamtchatka Department of the Environment, Far-Eastern Branch
of the U.S.S.R. Academy of Sciences, Prospect Rybakov, 19-A, Petropaviovsk-Kamtchatky 683024
USSR.

KISELEV, VICTOR V. (389), V.N. Sukachev Institute of Forest and Wood, Siberian Branch of the
U.S.S.R. Academy of Sciences, Krasnoyarsk 660036 U.S.S.R.

KOLTUNOV, EVGENY V. (213), Institute of Forest, Ural Branch of the U.S.S.R. Academy of
Sciences, Sverdlovsk U.S.S.R.

KORICHEVA, YULIA G. (240), All-Union Research Institute of Plant Protection, Pushkin 8,
Leningrad 189620 U.S.S.R.

KOZLOV, MICHAIL V. (240), All-Union Research Institute of Plant Protection, Pushkin 8, Leningrad
189620 U.S.S.R.

KRIVOSHEINA, NINA P. (335), A.N. Severtzov Institute of Evolutionary Animal Morphology and
Ecology, U.S.S.R. Academy of Sciences, Moscow 117071 U.S.S.R.


1 abi = Abies, Lar = Larix, Pic = Picea, Pin - Pinus, and Jun = Juniper; PIN =
several spp. within Pinaceae; D indicates that the insect species utilizes one
or several deciduous trees or bushes; H indicates that it utilizes one or
several herbaceous plant species.

2 Mono = monophagous, Olig = oligophagous, OligJ = feeding on some member of
Pinaceae and Juniper, and Poly = polyphagous.

3 y = young tissue (buds and current-year needles) and 0 = old tissue
(one-year-old or older needles).

4 ¢ = chewing, M = mining in needles, BM = mining in buds (and/or shoots).

Arrows under Tissue-age and Feeding mode indicate that the insect shifts from
x+y when it becomes older.

REFERENCES: 1) Ehnstrém (pers. comm.), 2) Schwenke (1974), 3) Hellrigl (1971),
and 4) Browne (1968).

20


APPENDIX C

Host-plant utilization, host range, utilized tissue-age, and feeding mode of
Hymenoptera, Symphyta feeding on Swedish conifers. Information on the
occurrence of individual species in Sweden was taken from Hedqvist (pers.
comm.) .

Family Host Host Tissue Feeding
Species plants! range? age mode* References
Pamphiliidae
Acantholyda erythrocephala L. Pin Mono (xo c 1,2
A. flaviceps Retz. Pin Mono Y+0 c 2
A. posticalis Mats. Pin Mono Y+O* c 1,2
Cephalcia abietis L. Pic Mono (¥)0 Cc 2
Cc. arvensis Panzer Pic Mono YO Cc 2
C. erythrogastra Htg. Pic Mono Y+0 c 3
Cc. falleni Daln. Pic Mono Y+O c 2
Diprionidae
Diprion butovitschi Hedqv. Pin Mono Y+0O Cc 2,3
D. pini L. Pin Mono YO Cc 1,2,4
D. simile Htg. Pin Mono Y+0 c 1,2,5
Gilpinia frutetorum F. Pin Mono Y+O Cc 1,2,4
G. hercyniae Htg. Pic Mono (xo c 1,2
G. pallida Klug Pin Mono Y¥+0 Cc 1,2
G. verticalis Guss. Pin Mono Y+0 Cc 2,6
G. virens Klug Pin Mono Y+0 ¢c 1,2
Microdiprion pallipes Fall. Pin Mono Y+0 c 1,2,7
Monoctenus juniperi L. Jun Mono Y+O Cc 1,2
M. obscuratus Htg. Jun Mono Y+0 c 2
M. subconstrictus Thoms. Jun Mono Y+0 c 2
Neodiprion sertifer Pin Mono ie) Cc 1,2,4
Tenthredinidae
Pachynematus montanus Zadd. Pic Mono Yoo Cc 1,2
P. scutellatus Htg. Pic Mono Yo Cc 1,2
Pristiphora abietina Christ. Pic Mono. Y¥+0 Cc 1,2
P. ambigua Fall. Pic Mono Y+0 Cc 1,2
P. amphibola Férst. Pic Mono Y+0 Cc 1,2
P. compressa Htg. Pic Mono Yo Cc 1,2
P. saxesenii Htg. Pic Mono Yo Cc 1,2
P. subarctica Forssl. Pic Mono Y+O Cc 1,2
* Two forms, one feeding on young tissue and the other on old tissue

17


27.

29.

31.

32.

33.

35.

37.

39.

ADELGID HOST INTERACTIONS WITH SPECIAL REFERENCE TO THE
BALSAM WOOLLY ADELGID IN NORTH AMERICA
FP. Hain, R.G. Hollingsworth, F.H. Arthur, F. Sanchez, and R.K. Ross ........---- 271

SIGNIFICANCE OF PHYTOHORMONES IN SIBERIAN LARCH-BUD GALL
MIDGE INTERACTION
Rida M. Matrenina . 0.1... eee erent een enee 288

MANIPULATION OF HOST PLANT BIOMASS ALLOCATION AND RESOURCE
REGULATION BY THE LARCH BUD GALL MIDGE
‘Yuri N. Baranchikov . .

GALL MIDGES (DIPTERA: CECIDOMYIIDAE) IN FOREST ECOSYSTEMS
Marcela Skuhrava 6.1... eee eee e ete 293

SEED GALLS OF SEMUDOBIA BETULAE (DIPTERA: CECIDOMYIIDAE) ON
SPECIES OF BIRCH (BETULA SPP.)
Vaclav Skuhravy 6... ee eee eee ee eee e eens 298

STRUCTURE, SPECIFICITY, AND EVOLUTION OF INSECT GUILDS RELATED
TO CONES OF CONIFERS IN WESTERN EUROPE
Alain Roques 2... 1... cee eet t eet e eee e tee 300

SEED PRODUCTION AND CONE-FEEDING INSECTS OF PINUS PUMILA ON
THE KAMTCHATKA PENINSULA: ASPECTS OF COEXISTENCE
Petr A. Khomentovsky and LS. Efremova .. 1.2.0... 0 cee cece eee ee eee eee 316

IPS TYPOGRAPHUS AND OPHIOSTOMA POLONICUM VERSUS NORWAY SPRUCE:
JOINT ATTACK AND HOST DEFENSE
Erik Christiansen 2.0.0... ce eee eee eee eee e ete e eee 321

RELATIONS BETWEEN WOOD-INHABITING INSECTS AND FUNGI
Nina P. Krivosheina .. 6.6... cet teen e ete e eens 335

ON THE ROLE OF THE TREE IN RELATION TO COLONIZATION BY
IPS TYPOGRAPHUS L.
S. Bombosch . 6... eee eee eee tent e eee eee eee nee 347

INTERSPECIFIC OLFACTORY COMMUNICATION IN THE SOUTHERN PINE
BARK BEETLE GUILD
T.L. Payne, M.T. Smith, M.C. Birch, and A. Ascoli... 2.2... ce eee eee eee eee 352

USING PHEROMONES IN THE MANAGEMENT OF BARK BEETLE OUTBREAKS
Alf Bakke 2... cece ee eee tenet eee nee eens 371

EFFECTS OF LARCH DEFENSES ON XYLOPHAGOUS INSECT GUILDS
Galina I. Girs and Victor M. Yanovsky .... 2... 06-0 eee cece eee rece een e eens 378

EFFECTS OF FIR SAWYER BEETLE ON SPATIAL STRUCTURE OF
SIBERIAN FIR STANDS
Vladimir L. Gavrikov and Valentina P. Vetrova ... 1.0.60. cee cette eens 385


13.

14.

15.

16.

7.

18.

19.

20.

21.

22.

24.

OUTBREAK OF ZEIRAPHERA RUFIMITRANA ON SILVER FIR HITHERTO.
UNKNOWN IN SOUTHWEST GERMANY
Hermann Bogenschiitz ... 0.2... eee tte eet eee ene 165

AN INSECT OUT OF CONTROL? THE POTENTIAL FOR SPREAD AND
ESTABLISHMENT OF THE GYPSY MOTH IN NEW FOREST AREAS
IN THE UNITED STATES

Max W. McFadden and Michael E. McManus 172

INTEGRATING HOST, NATURAL ENEMY, AND OTHER PROCESSES IN
POPULATION MODELS OF THE PINE SAWFLY
AA. Sharov oe eee eee teen eee e ene n ene 187

BIOECOLOGY OF THE CONIFER SWIFT MOTH, KORSCHELTELLUS GRACILIS,
A ROOT FEEDER ASSOCIATED WITH SPRUCE-FIR DECLINE
William E. Wallner, David L, Wagner, Bruce L. Parker, and Donald R. Tobi ......... 199

THE RECONSTRUCTION OF LYMANTRIA DISPAR OUTBREAKS BY
DENDROCHRONOLOGICAL METHODS IN THE SOUTH URALS
Sergei Kucherov .. 6... ee eee eee ett e eens 205

IMPACT OF A SPRING DEFOLIATOR ON COMMON OAK
Victor V, Rubtsov and Irina A. Utkina 2... eee 207

TOLERANCE TO INSECT DEFOLIATION: BIOCENOTIC ASPECTS
Andrey A. Pleshanov, Victor I. Voronin, Elena S. Khlimankova,
and Valentina I. Epova ©... 6.6. eee eee eee e eee eee 21

INSECT-PLANT INTERACTIONS IN ANTHROPOGENICALLY
TRANSFORMED ECOSYSTEMS
Evgeny V. Koltunov, Victor I. Ponomarev, and Sergey I. Fedorenko ...........--+- 213

DOES THE PLANT DEFEND ITSELF AGAINST LEAF-FEEDING INSECTS?
Paul M. Rafes 21... ee eee ee ee ete tee teen etna 215

THE ROLE OF PHENOTYPE STRUCTURE IN THE POPULATION DYNAMICS

OF GYPSY MOTH IN THE LOWER DNIEPER REGION

Nikolaj M. Derevyanko «2.1... eee eee eee eee 217
POORLY MOBILE, INTERNAL PHYTOPHAGES

NOVEL ASPECTS OF HOST TREE RESISTANCE TO LEAFMINERS
Stanley H. Facth 2.2... eee ee terete 219

THE WITHIN-TREE DISTRIBUTION OF CATERPILLAR MINES
Michail V. Kozlov and Yulia G. Koricheva ... 22-2... eee cee eee eee eee 240

ADELGID AND SCALE INSECT GUILDS ON HEMLOCK AND PINE
Mark S. McClure 6.1... ee teeter eeee 256


more data have been accumulated on the nature of polyphagy in herbivorous insects, any general
conclusion would seem premature. Nevertheless, it is possible that "true polyphagy” (i.e. generalistic
individuals) is a rare phenomenon. For example, the cost of multiple detoxification systems might be
too great for individual insects (Karowe 1989).

Needle-Age and Degree of Specialization

According to the apparency hypothesis, young tissue should be protected by qualitative defenses
and thus there should be selection for specialization among insects feeding on such tissue. However,
there is no correlation between needle-age utilized and degree of host-plant specialization in our data
(Table 2). Results from studies of insects on deciduous trees support the apparency hypothesis (Cates
1980, Niemel& 1983). This difference between conifers and deciduous trees with respect to degree of
specialization and utilized tissue-age could be due to the fact that young needles develop more slowly
than young deciduous leaves. Hence the absence of a correlation between needle-age and degree of
specialization could be due to small differences in apparency between young and old needles. Still,
there is evidence showing that young needles of jack pine (Pinus banksiana) and Scots pine contain a
resin acid that repels sawflies normally feeding on old needles (Ikeda et al. 1977 and Niemela et al.
1982, respectively). It has yet to be determined whether other needle-eating insects are repelled by the
same substances (Buratti et al. 1990).

CONCLUSIONS

The applicability of the examined hypotheses to Swedish needle-eating insects can be summarized
in the following way. 1) Polyphagy predominates among chewing lepidopterans, thereby supporting all
three hypotheses. However, the many examples of specialized individuals among polyphagous insects
and the comparison of our results with those obtained in studies of macrolepidopterans on other plant
species weaken this support. 2) The absolute monophagy among sawflies supports the intimacy
hypothesis and may be attributable to the oviposition behavior of the female and the detoxification
ability of the larvae. 3) Although data on the mining insects also supports the intimacy hypothesis, the
impact of generalistic predators cannot be ruled out. 4) No correlation was found between utilized
needle-age and host-plant specialization, possibly because small differences in apparency exist between
young and old needles.

The data presented here supply very little support for the apparency and nutrition hypotheses.
In their defense, we readily acknowledge that they were never developed as explanations for host
specialization by phytophagous insects. For this reason, then, they are too general as we have
presented them. They treat herbivorous insects as a uniform group and do not distinguish between
feeding guilds. It has become more and more apparent that insect feeding guilds must be treated
separately if we are adequately to understand plant-insect interactions (Mattson et al. 1988, Cornell
1989, Larsson 1989). The intimacy hypothesis, which distinguishes between insect feeding guilds, is the
hypothesis given most support by the data obtained in our survey of the literature.

SUMMARY
The degree of host-plant specialization in needle-eating butterflies and moths (Lepidoptera),
sawflies (Hymenoptera, Symphyta), and beetles (Coleoptera) occurring in Sweden has been examined

based on data in the literature.

No general trend was found when all insects were considered. However, a closer examination of
certain feeding guilds revealed that 1) polyphagy is predominant among chewing Lepidoptera,


CONTRIBUTORS
Numbers in parentheses indicate the page on which the authors’ contributions begin.

ALLEN, DOUGLAS C. (53), College of Forestry and Environmental Sciences, State University of
New York, Syracuse, New York 13210 U.S.A.

ARTHUR, F. H. (271), USDA Stored Products Insects R & D Lab, Savannah, GA 31403 U.S.A.

ASCOLI, A. (352), Department of Entomology, Virginia Polytechnic Institute and State University,
Blacksburg, VA 24061 U.S.A.

AYRES, MATTHEW P. (85), Department of Entomology, Michigan State University, East Lansing,
MI 48824 U.S.A.

BAKKE, ALF (371), Norwegian Forest Research Institute, Box 61, 1432 As-NLH, Norway

BALTENSWEILER, W. (145), Institute of Plant Sciences, Division of Phytomedicine,
ETH-Zentrum/CLS, CH 8092 Zurich, Switzerland

BARANCHIKOV, YURI N. (291), V.N. Sukachev Institute of Forest and Wood, Siberian Branch of
the U.S.S.R. Academy of Sciences, Krasnoyarsk 660036 U.S.S.R.

BIRCH, M. C. (352), Department of Zoology, South Parks Road, Oxford, OX1 3PS United Kingdom

BJORKMAN, CHRISTER (1), Department of Plant and Forest Protection, Swedish University of
Agricultural Sciences, P.O. Box 7044, S-750 07 Uppsala, Sweden

BOGACHEVA, L A. (113), Institute of Plant and Animal Ecology, Ural Branch of the U.S.S.R.
Academy of Sciences, 8 March Street, 202 Sverdlovsk 620144 U.S.S.R.

BOGENSCHUTZ, HERMANN (165), Forest Research Station, D-7800 Freiburg, Germany

BOMBOSCH, S. (347), Institut fir Forstzoologie der Universitat Géttingen, Bisgenweg 3,
D-3400 Gottingen, Germany

BOSSART, JANICE L. (85), Department of Entomology, Michigan State University, East Lansing,
MI 48824 U.S.A.

CHRISTIANSEN, ERIK (321), Norwegian Forest Research Institute, N-1432 As-NLH, Norway

CLANCY, KAREN M. (123), USDA Forest Service, Rocky Mountain Forest and Range Experiment
Station, 700 S. Knoles Drive, Flagstaff, AZ 86001 U.S.A.

DEREVYANKO, NIKOLAJ M. (217), LI. Shmalgauzen Institute of Zoology, Ukrainian Branch of the
U.S.S.R. Academy of Sciences, Lenin Street, 15, Kiev, U.S.S.R.

EFREMOVA, L. S. (316), Kamtchatka Forest Experiment Station, Far-Eastern Research Institute of
Forestry, Kluchevskaya str., 24-2, Petropaviovsk-Kamtchatsky 683002 U.S.S.R.

EPOVA, VALENTINA L (211), Siberian Institute of Plant Physiology and Biochemistry, Siberian
Branch of the U.S.S.R. Academy of Sciences, Irkutsk 664033 U.S.S.R.

viii


APPENDIX A

Host-plant utilization, host range, utilized tissue-age, and feeding mode of
microlepidoptera feeding on Swedish conifers. Information on the occurrence
of individual species in Sweden was taken from Gustafsson (1979); reference
not provided.

Family Host Host | Tissue Feeding

Species plants range“ age mode’ References
Yponomeutidae

Argyresthia abdominalis Zell. Jun Mono ? M 1,2

A. arceuthina Zell. Jun Mono 2 BM 1,2

A. aurulentella Stt. Jun Mono ? M 1,2

A. dilectella Zell. Jun Mono ? M 1,2

A. fundella F.v. Résl. Pic, (Abi) Olig Y+0 M 2,4,5

A. glabratella Zell. Pic Mono Y M 1,4

Blastotere bergiella Ratz. Pic Mono Y M 4

Cedestis gysseleniella Zell. Pin, (Abi) Olig 0 M 1,4,6

C. subfasciella Steph. Pin Mono ie) M 1,4,6,7

Ocnerostoma friesei Svensson Pin Mono ? M 1,7

O. piniariella Zell. PIN, Jun OligJ ? M 1,4,7,10
Gelechiidae

Dichomeris juniperella L. Jun Mono ? c 1

D. marginella F. Jun Mono 0? Cc 1,3

Exoteleia dodocella L. Pin Mono ¥(0) M 1,4,10,11
Momphidae

Batrachedra pinicolella Zell. Pic,Pin Olig ? M 1,3
Tortricidae

Acleris abietana Hb. PIN Olig Y+0 Cc 1,4,8,12

A. hyemana Haw. PIN,D Poly ? Cc 1,8

Aphelia paleana Hb. Pic,H Poly ? 2 1,8

A. viburnana Den. & Schiff. PIN,D,H Poly Y Cc 1,4,8

Archips oporana L. PIN, Jun Olig Y¥+0 c 1,4,6,12

A. podana Scop. PIN,D Poly Y+0 Cc 1,4,12

A. rosana L, Pic,D,H Poly ? Cc 1,4,5,10

Blastesthia posticana Zett. Pin Mono Y M 1,4,10

B. turionella L. Pin,H Poly Y M 1,4

Clepsis senecionana Hb. PIN,H Poly 2 M 1

Cnephasia incertana Treit. PIN,H Poly ? MPC? 4,8

Epinotia caprana F. Pin,D Poly ? c 1,8

E. fraternana Haw. PIN Olig o) M 1,4,8

£E. nanana Treit. Pic Mono i) M 1,4,10

E. nigricana H.-S. Abi, (Pic) Olig Y BM 1,4

E. pygmaeana Hb. Pic, (Abi) Olig (0) MC 1,4

E. rubiginosana H.-S. Pin Mono ? MC 1,8,10

12


Department of FOREST INSECT GUILDS:
Agriculture

. PATTERNS OF INTERACTION
Forest Service
Northeastern Forest WITH HOST TREES
Experiment Station
General Technical Edited by:

Report NE-153
YURI N. BARANCHIKOV

8 WILLIAM J. MATTSON
FRED P. HAIN

THOMAS L. PAYNE

Abakan, Siberia, U.S.S.R.
August 13-17, 1989



DOES REPRODUCTION COMPROMISE DEFENSE
IN WOODY PLANTS?

DANIEL A. HERMS and WILLIAM J. MATTSON

The Dow Gardens
1018 W. Main St., Midland, MI 48640 U.S.A.
and
Department of Entomology
Pesticide Research Center, Michigan State University
East Lansing, MI 48824 U.S.A.

USDA Forest Service
North Central Forest Experiment Station
1407 S. Harrison Road, East Lansing, MI 48823 U.S.A.
and
Department of Entomology
Pesticide Research Center, Michigan State University
East Lansing, MI 48824 U.S.A.

PRINCIPLES OF RESOURCE ALLOCATION

A general principle of adaptive allocation was proposed by Cody (1966) who hypothesized that
1) all living organisms have finite resources to partition among growth and competing physiological
Processes such as reproduction and defense; and 2) natural selection results in the evolution of unique
Tesource allocation patterns that maximize fitness in different environments. Today, it is well
established that plants have limited resources to allocate among these processes (Bazzaz et al. 1987),
and theories of life-history strategy rests on the assumption that there are fitness trade-offs associated
with varying patterns of resource allocation (Stearns 1976, 1989, Reznick 1985, Bazzaz et al. 1987,
Lovett Doust 1989). Trade-offs occur when an increase in resources allocated to one fitness
component, such as growth, reduces the allocation to another, such as reproduction. Natural selection
(acting within phylogenetic, physiological, and ecological constraints) should shape patterns of resource
allocation, balancing the costs and benefits associated with these trade-offs, resulting in the evolution of
life-history strategies maximizing fitness. There are direct and indirect costs associated with allocation
to “nongrowth" processes such as reproduction. Direct costs are energy and assimilates invested in
reproductive structures. Indirect costs are unrealized growth and future reproduction as a result of this
investment (Bazzaz and Reekie 1985, Bloom et al. 1985, Bazzaz et al. 1987, Reekie and Bazzaz 1987c,
Ronsheim 1988, Lovett Doust 1989).

The physiological cost of reproduction in the form of reduced vegetative growth has been
documented in a number of cases (Gross 1972, Harper and White 1974, Gifford and Evans 1981,
Willson 1983, Luken 1987, Clark and Clark 1988, Snow and Whigham 1989, Dick et al. 1990).
However, this cost may not be universal (Tuomi et al. 1982, Reekie and Bazzaz 1987c, Reznick 1985).
Genetic, ecological, and physiological trade-offs between growth and defensive secondary chemistry are
also well documented (Bryant et al. 1983, Krischik and Denno 1983, Coley et al. 1985, Loehle 1988,
Bazzaz et al. 1987, Pimentel 1988). Resource allocation patterns are the expression of source-sink

BARANCHIKOV, Y.N., MATTSON, W.J., HAIN, F.P., and PAYNE, T.L., eds. 1991. Forest Insect
Guilds: Patterns of Interaction with Host Trees. U.S. Dep. Agric. For. Serv. Gen. Tech. Rep. NE-153.

35


ROQUES, ALAIN (300), Institut National de la Recherche Agronomique, INRA-CRF-Station de
Zoologie Forestigre, Ardon 45160, Olivet, France

ROZHKOV, ALEXANDR 5S. (391), Siberian Institute of Plant Physiology and Biochemistry, Siberian
Branch of the U.S.S.R. Academy of Sciences, Irkutsk 664033 U.S.S.R.

RUBTSOV, VICTOR V. (207), Forest Science Laboratory, Moscow Branch of the U.S.S.R. Academy
of Sciences, Uspenskoe, 143030 U.S.S.R.

SANCHEZ, F. (271), Department of Chemistry, North Carolina State University, Raleigh, NC 27695
USA.

SCHROEDER, LEIF MARTIN (393), Swedish University of Agricultural Sciences, Division of Forest
Entomology, S-750 07 Uppsala, Sweden

SCRIBER, J. MARK (85), Department of Entomology, Michigan State University, East Lansing,
MI 48824 U.S.A.

SHAROV, A. A. (187), Entomology Department, Moscow State University, Lenin Hills, Moscow
119899 U.S.S.R.

SKUHRAVA, MARCELA (293), Institute of Entomology, Czechoslovak Academy of Sciences,
Branisovska 31, 370 05 Ceske Budejovice, Czechoslovakia

SKUHRAVY, VACLAV (298), Institute of Entomology, Czechoslovak Academy of Sciences,
370 0S Ceske Budejovice, Czechoslovakia

SMITH, M. T. (352), USDA-ARS, P.O. Box 87, Byron, GA 31008 U.S.A.

STADNITSKY, GEORGY V. (47), Technological Institute of Pulp and Paper Industry, Leningrad
198092 U.S.S.R.

TOBL, DONALD R. (199), University of Vermont, Department of Plant and Soil Science, Burlington,
VT 05401 U.S.A.

UTKINA, IRINA A. (207), Forest Science Laboratory, Moscow Branch of the U.S.S.R. Academy of
Sciences, Uspenskoe, 143030 U.S.S.R.

VETROVA, VALENTINA P. (385), V.N. Sukachev Institute of Forest and Wood, Siberian Branch of
the U.S.S.R. Academy of Sciences, Krasnoyarsk 660036 U.S.S.R.

VORONIN, VICTOR L. (211), Siberian Institute of Plant Physiology and Biochemistry, Siberian Branch
of the U.S.S.R. Academy of Sciences, Irkutsk 664033 U.S.S.R.

WAGNER, DAVID L. (199), University of Connecticut, Department of Ecology and Evolutionary
Biology, Storrs, CT 06268 U.S.A.

WAGNER, MICHAEL R. (21), School of Forestry, Box 4098, Northern Arizona University, Flagstaff,
AZ 86011 U.S.A.

WALLNER, WILLIAM E. (199), USDA Forest Service, Northeastern Forest Experiment Station,
51 Mill Pond Road, Hamden, CT 06514 U.S.A.


KUCHEROV, SERGEI (205), Institute of Plant and Animal Ecology, Ural Branch of the U.S.S.R.
Academy of Sciences, Sverdlovsk 620008 U.S.S.R.

LARSSON, STIG (1), Department of Plant and Forest Protection, Swedish University of Agricultural
Sciences, P.O. Box 7044, S-750 07 Uppsala, Sweden

MASSEL, GALINA L (391), Siberian Institute of Plant Physiology and Biochemistry, Siberian Branch
of the U.S.S.R. Academy of Sciences, Irkutsk 664033 U.S.S.R.

MATRENINA, RIDA M. (288), V.N. Sukachev Institute of Forest and Wood, Siberian Branch of the
U.S.S.R. Academy of Sciences, Krasnoyarsk 660036 U.S.S.R.

MATTSON, WILLIAM J. (35, 53), USDA Forest Service, North Central Forest Experiment Station,
1407 S. Harrison Road, East Lansing, MI 48823 U.S.A, and Department of Entomology,
Pesticide Research Center, Michigan State University, East Lansing, MI 48824 U.S.A.

McCLURE, MARK S. (256), Connecticut Agricultural Experiment Station, Valley Laboratory,
P.O. Box 248, 153 Cook Hill Road, Windsor, CT 06095 U.S.A.

McFADDEN, MAX W. (172), USDA Forest Service, Northeastern Forest Experiment Station,
100 Matsonford Road, Radnor, PA 19087 U.S.A.

McMANUS, MICHAEL E. (172), USDA Forest Service, Northeastern Forest Experiment Station,
51 Mill Pond Road, Hamden, CT 06514 U.S.A.

NEUVONEN, SEPPO (103) Department of Biology, University of Turku, SF-20500 Turku, Finland

NIEMELA, PEKKA (103), The Finnish Forest Research Institute, Department of Forest Protection,
P.O. Box 18, SF-01301 Vantaa, Finland

OVTCHINNIKOVA, TAMARA M. (389), V.N. Sukachev Institute of Forest and Wood, Siberian
Branch of the U.S.S.R. Academy of Sciences, Krasnoyarsk 660036 U.S.S.R.

PARKER, BRUCE L. (199), University of Vermont, Department of Plant and Soil Science, Burlington,
VT 05401 U.S.A.

PAYNE, T. L. (352), Department of Entomology, Virginia Polytechnic Institute and State University,
Blacksburg, VA 24061 U.S.A.

PLESHANOV, ANDREY A. (211), Siberian Institute of Plant Physiology and Biochemistry, Siberian
Branch of the U.S.S.R. Academy of Sciences, Irkutsk 664033 U.S.S.R.

PONOMAREY, VICTOR L (213), Institute of Forest, Ural Branch of the U.S.S.R. Academy of
Sciences, Sverdlovsk U.S.S.R.

RAFES, PAUL M. (215), Laboratory of Forestry, Uspenskoje Village, Odintzovo Region, Moscow
Territory 143030 U.S.S.R.

ROSS, R. K. (271), Department of Genetics, North Carolina State University, Raleigh, NC 27695
USA.


sexual (gametophyte) and asexual (sporophyte) generations which was accompanied by the formation of
a special reproductive organ “strobilus," which may be regarded as an analogue of modern cones.

Primary-terrestrial plant protocommunities were prostrate creeping plants partly yet connected
with water, and served as optimal habitat for Arthropoda ancestors to be temporarily found outside the
water. The reproductive organs rose above the water surface. If we take into account the fact that
plants in a water environment could have been used as food and shelter by insects, then endophyte
mode of life could be optimal. Plant fibers on land contained moisture and oxygen, and perhaps the
reproductive structures provided for the best isolation from external hostile conditions. Moreover, they
were food substrates rich in nutrients.

Within this hypothesis it is impossible to imagine other more ecologically optimal habitats for
the insect’s ancestors. Thus we can postulate the existence of two likely "bridges" for the transition
onto the land of aquatic ancestors; they moved via the soil and via plant reproductive structures. This
by no means excludes other ways and means. We should emphasize that these two bridges established
the two further directions of evolution of terrestrial Arthropoda. The soil bridge Arthropoda actually
“stopped” their evolution, e.g. the modern Apterygota, Myriapodes, and Arachinoides. Their
environments excluded both the possibility and the necessity of complete metamorphosis and flying
ability. The second group has undergone substantial evolution and has transformed into the modern
Holometabola. We should postulate on the basis of the above that the aquatic ancestors of modern
insects have not experienced any metamorphosis; this conclusion is recognized by many authors.

The Origin of Flight

‘We can suggest that flight and metamorphosis are inherent features of higher insects and have a
common origin. They appeared because the association with plants predisposed their evolution.
Peculiar features of plant reproductive organs, as habitats for endophytes, are their ephemeral, patchy
existence in comparison with the constant character of the plant proper. They formed on the ends of
the branches, being unevenly and irregularly distributed depending on dynamic weather and soil
conditions. In other words, the habitats and food resources of this branch of terrestrial insects
originally appeared to be discrete in space. Evolution in insects could have proceeded in the following
way: a certain group of terrestrial insects under certain favorable conditions could make locally a
morphological and physiological "jump" which can be regarded as aeromorphosis.

Living conditions in strobilus (or other reproductive organs) were such that an insect as a rule
could not complete its ontogenesis in one strobilus, it had to move to another one situated nearby, on
a neighboring branch, or a neighboring plant, the time for migration being extremely limited. Similar
migrations were performed by adult insects to lay eggs and to provide the food for its progeny.
Crawling would not have been optimal. A jump would be more advantageous, but jumping makes it
necessary to Overcome gravity and to move large distances. Insects with elongated bodies would be
favored. The necessity for organs to appear, which would make the insects able to fly first in a passive
mode and then in an active mode, would be accompanied by re-structuring of muscles and formation of
a wing.

Let us now examine a hypothetical fate of an insect grown in the primary plant reproductive
organ. Its life time was determined by the fulfillment of its own reproduction and was quite short,
though this does not mean that the whole period of plant reproduction was so short: strobila (or
other organs) could exist in the tree crowns quite long, new strobilae substituting for old ones. Those
insects which could deposit their eggs faster had a higher probability to survive and have progeny,
laying their eggs in the neighboring reproductive organs or in those which died later. Larvae hatched
from these eggs, that is embryonization of post-embryonal development occurred as postulated by
lezhikov-Berleze theory. Under such conditions larvae had to live through unfavorable nutrition and
development periods (cooling periods, droughts, absence of food and habitats). The development under
these unfavorable conditions became retarded, but it should have been compensated for by faster rates

48


SUMMARY

In this paper I have reviewed the general literature and examined preliminary data that implicate
genotype, ontogeny, and stress as host factors that influence survival of pine sawflies on ponderosa
pine. Data and the literature have been used to generate hypothetical single-factor response functions.
These response functions have been combined to create response surfaces illustrating the potentially
complex nature of response surfaces derived from relatively simple response functions. Finally I
propose some research protocols to ensure efficient methods of generating response surfaces in order
to establish clear relationships between host plants and their insect herbivores.

ACKNOWLEDGMENTS

I would like to thank Zhao-Yi Zhang for assistance in collecting preliminary data on the effect
of tree age on sawfly survival. I would also like to thank Karen M. Clancy, Clarence S. Dunbar, and
Joel D. McMillin for reviewing the manuscript. D.P. Dykstra and T.E. Gross provided valuable
assistance in generating the three-dimensional figures.

LITERATURE CITED

AREND, J.L., SMITH, N.F., SPURR, S.H., and WRIGHT, J.W. 1961. Jack pine geographical variation
--five year results from lower Michigan. Pap. Mich. Acad. Sci. Arts Lett. 46: 219-238.

ASKEW, R.R., HEDDEN, R.L., and DEBARR, G.L. 1985. Clonal variation in susceptibility to
coneworms (Dioryciria spp.) in young loblolly pine seed orchards. For. Sci. 31: 794-798.

AVERILL, R.D. and FOWLER, R.F. 1973. United States Forest Service Northeast Area State Private
Forestry Progress Report--1972. In Mattson, W.J. and Addy, N.D. 1975. Phytophagous insects as
regulators of forest primary production. Science 190: 515-522.

BERRYMAN, A. A. 1972. Resistance of conifers to invasion by bark beetle-fungus associations.
BioScience 22: 598-602.

BINGHAM, R.T. 1966. Breeding blister rust resistant western white pine--comparative performance of
clonal and seedling lines from rust-free selection. Silvae Genet. 15: 160-164.

BLAIS, J.R. 1958. The vulnerability of balsam fir to spruce budworm attack in northwestern Ontario,
with special reference to the physiological age of the tree. For. Chron. 34: 405-422.

BROOKS, J.E., BORDEN, J.H., and PIERCE, H.D. 1987. Foliar and cortical monoterpenes in Sitka
spruce: potential indicator of resistance to the white pine weevil, Pissodes strobi Peck
(Coleoptera: Curculionidae). Can. J. For. Res. 17: 740-745.

CALLAHAM, R.Z. 1966. Nature of resistance of pines to bark beetles, p. 197-201. In Breeding Pest
Resistant Trees. Pergamon Press, New York.

CHARLES, P.-J., DELPLANQUE, A., MARPAU, A., BERNARD-DAGAN, C., and ARBEZ, M. 1982.
Susceptibility of European black pine (Pinus nigra) to the European pine shoot moth
(Rhyacionia buoliana): variations of susceptibility at the provenance and individual level of the
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Weissenberg, K., eds. Resistance to Diseases and Pests in Forest Trees. Pudoc, Wageningen, The
Netherlands.

31


APPENDIX D

Host-plant utilization, host range, utilized tissue-age, and feeding mode of
Coleoptera feeding on Swedish conifers. Information on the occurrence of
individual species in Sweden was taken from Ehnstrém (pers. comm.).

Family Host. Host Tissue Feeding
Species plants range“ age mode* References

SPECIES IN WHICH LARVAE FEED ON NEEDLES AND/OR BUDS

Anobiidae
Dryophilus pusillus Gyll. PIN Olig Y c 1,2
Curculionidae
Anthonomus phyllocola Hrbst. Pin,(Pic)  Olig Y? c 1,2
A. pinivorax Silfverb. Pic, Pin Olig Y Cc 1,2
Brachonyx pineti Payk. Pin Mono ? Cc 1,2
SPECIES IN WHICH IMAGINES FEED ON NEEDLES AND/OR BUDS
Scarabaeidae
Amphimallom solstitiale L. Pin,D Poly 2 Cc 2
Cerambycidae
Monochamus galloprovoncialis Ol. Pin,(Pic) lig ? c 1,2,3
M. sutor L. Pic,Pin Olig ? 1,2
Chrysomelidae
Calomicrus pinicola Duft. Pin, (PIN) Olig ° c 1,2
Cryptocephalus pini L. PIN,(Jun) OligJ ¥? c 1,2
C. quadripustulatus Gyll. PIN Olig ? c 1,2
Syneta betulae F. Pic,D Poly Y c 1,2
Curculionidae
Anthonomus phyllocola Hrbst. Pin,(Pic)  Olig ? c 1,2
A. pinivorax Silfverb. Pic,Pin Olig Y? c 1,2
Brachonyx pineti Payk. Pin Mono ? c 1,2
Brachyderes incanus L. Pin Mono ? Cc 1,2
Otiorrhyncus leoidopterus F. PIN Olig 2 c 1,2
O. nodosus Mull. Pin Mon? 2 Cc 1
0. scaber L. PIN Olig ? c 2
O. singularis L. PIN,D,H Poly Y(0?) Cc 2,4
Philopedon plagiatum Schall. Pin,Pic,D,H Poly 2 c 1
Strophosoma capitatum de G. Pin,Pic,D,H Poly ? Cc 1
S. melanogrammum Forst. Pin,Pic,D,H Poly ? Cc 1

19


interactions within the plant and their control on assimilate partitioning. Complex physiological
changes in patterns of assimilate partitioning are required to bring about the maturation of
inflorescences, fruits, and seeds. Very likely, these changes will affect traits conferring plants with
resistance to herbivores. Few studies, however, have examined the potential interactions between
reproduction and defense.

In this paper we explore two hypotheses suggesting how plant reproduction may directly and
indirectly affect herbivory and review the limited experimental evidence supporting each:
1) reproductive structures as carbon sinks reduce the allocation of resources to defense; 2) reproductive
structures as nutrient sinks increase the carbon/nutrient ratio in nearby vegetative tissues, resulting in
their increased secondary metabolism and consequent increased resistance to herbivores.

TRADE-OFFS BETWEEN REPRODUCTION AND DEFENSE

Plants have limited resources to support their physiological processes, hence all requirements can
not be met simultaneously, and trade-offs occur among growth, maintenance, storage, reproduction, and
defense processes. Consequently, there is sequential growth and maturation of tissues within organs
and organs within plants and/or strong inverse relationships between the allocation of resources to
growth and nongrowth processes, including reproduction and defense (Mooney 1972, Mooney and Chu
1974, Gifford et al. 1984, Bloom et al. 1985, Willson 1983, Krischik and Denno 1983, Coley et al.
1985, Alpert et al. 1985, Loehle 1988, McLaughlin and McConathy 1979, Bazzaz et al. 1987, Patrick
1988).

Though rarely documented, reproductive effort may come at the expense of defense, if resources
are diverted from resistance mechanisms to reproductive structures. This may occur commonly in the
case of nitrogen-based secondary metabolites such as alkaloids and cyanogens, the concentrations of
which often decline in foliage as growth shifts from vegetative to reproductive processes (Mattson 1980,
Krischik and Denno 1983, Harborne 1990).

Resistance of conifers to bark beetles is generally correlated with their growth efficiency,
i.e. stemwood production per unit foliage (Waring et al. 1980, Waring 1983, Mitchell et al. 1983,
Larsson et al. 1983, Waring and Pitman 1985). Susceptible individuals with low growth efficiencies are
characterized by depleted levels of the stored energy necessary to support defensive reactions (Waring
and Schlesinger 1986, Christiansen et al. 1987). Because heavy pollen and cone production can reduce
growth efficiency, episodes of reproduction may increase susceptibility to bark beetles. For example,
cone production has been shown to depress stem-wood growth and leaf area in several species of
conifers (Eis et al. 1965, Owens 1969, Tappeiner 1969, Dick et al. 1990). Carbon allocated to
reproduction at the expense of energy and substrate required for resin synthesis and wound-induced
hypersensitive responses may contribute to increased bark beetle and pathogen susceptibility.
Reproductive effort may interact with environmental stress to suppress conifer resistance to bark
beetles and contribute synergistically to outbreaks.

Birch Reproduction and Resistance to Bronze Birch Borer

The pistillate catkins of Betula are known to be strong photosynthetic sinks, competing with and
reducing resource allocation to vegetative growth (Gross 1972, Tuomi et al. 1982, Caesar and
MacDonald 1983). Frequently trees producing especially heavy seed crops subsequently exhibit severe
dieback symptoms (Gross 1972, Houston 1987).

Our studies into the physiology of birch resistance to bronze birch borer suggest there may be a
direct trade-off between female reproductive effort and resistance to the bronze birch borer (Agrilus
anxius). Bronze birch borer larvae feed under the bark on the xylem-cambium-phloem interface and

36


1 api = Abies, Lar = Larix, Pic = Picea, Pin = Pinus, and Jun = Juniper; PIN =
several spp. within Pinaceae; D indicates that the insect species utilizes one
or several deciduous trees or bushes; H indicates that it utilizes one or
several herbaceous plant species.

2 Mono = monophagous, Olig = oligophagous, OligJ = feeding on some member of
Pinaceae and Juniper, and Poly = polyphagous.

3 y = young tissue (buds and current-year needles) and 0 = old tissue
(one-year-old or older needles).

4 ¢ = chewing, M = mining in needles, BM = mining in buds (and/or shoots).
Arrows under Tissue-age and Feeding mode indicate that the insect shifts from
x+y when it becomes older.

REFERENCES: 1) Winter (1983), 2) Schwenke (1982), 3) Hedqvist (pers. comm.),
4) Escherich (1931, 1942) 5) Monro (1935), 6) Hedqvist (1972), and 7) Eidmann
and Klingstrém (1976).

18


41.

42.

43.

FIR SAWYER BEETLE-SIBERIAN FIR INTERACTION MODELING:
RESISTANCE OF FIR STANDS TO INSECT OUTBREAKS
Tamara M. Ovtchinnikova and Victor V. Kiselev .. 0.6.0.0 es cece ee teen ee eens 389

CONIFER DEFENSES AND XYLOPHAGOUS INSECTS
Alexandr S. Rozhkov and Galina I. Massel

ATTRACTION OF SOME SCOLYTIDS AND ASSOCIATED BEETLES TO THE
HOST VOLATILES a-PINENE AND ETHANOL
Leif Martin Schroeder

INFLUENCE OF PREDATORS AND PARISITOIDS ON BARK BEETLE
PRODUCTIVITY
Jan Weslien

SEASONAL AND SPATIAL CHANGES IN THE STRUCTURE OF THE
SUBCORTICAL INSECT COMMUNITY IN PINE FORESTS
Ken Yoshikawa and Makoto Kasahara ... 1.6.2.6. eee eee eee eee eee eee 397


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WILLSON, M.F. 1983. Plant Reproductive Ecology. John Wiley & Sons, New York.


1005

Neodiprion Neodiprion Neodiprion

gillettei autumnalis fulviceps”
2
4
2
>
ira
=)
a
>
a
re
2
4
ao

°
Seedling Pole Sowtimber Mature
TREE AGE

Figure 4. Hypothetical response functions for the effect of tree age on the
survival of three species of pine sawflies that feed on ponderosa pine.

two-spotted spider mite, Tetranychus urticae Koch, to a range of water-stress levels of its host plant.
The response was a modified cosine function in which, as stress increased, mite performance first
declined, then increased to an optimum, and then declined again.

Considerably more data are required before a complete response function can be presented for
the effect of ponderosa pine stress on pine sawfly performance. However, it is possible to suggest
some shapes that response functions may take (Fig. 5). The three hypothetical response functions
presented in Fig. 5 represent a range of relationships, any one of which might be the real one. The
shape of that function can have profound effects on the interpretation of experimental results, as I will
show in the next section.


Linear

Modified Cosine
(English-Loeb 1989)

SAWFLY SURVIVAL

Normal

Low High
STRESS

Figure 5. Three hypothetical response functions for the relationship between
sawfly survival and the stress level of ponderosa pine.

RESPONSE SURFACES FOR HYPOTHETICAL RESPONSE FUNCTIONS

Up to this point, I have attempted to identify reasonable single-factor response functions for the
effects of genotype, ontogeny, and drought stress on pine sawfly performance. In this section I present
some reasonable response surfaces of two factors in combination and illustrate how they might
influence sawfly survival.

Six hypothetical response surfaces are presented in Fig. 6. In each of the six cases, I have
assumed that resistance is a linear function of genotype as approximated by the slope created by the
bars in Fig. 1. While holding the genetic resistance factor constant, 1 have plotted the effect of tree
age based on the hypothetical response functions presented in Fig. 4 (Fig. 6a, b, c) and the effect of
stress based on the hypothetical response functions presented in Fig. 5 (Fig. 6d, ¢, f).

In examining the effect of tree age across a range of genotypes, one finds several interesting
patterns emerging. First, sawfly survival can vary dramatically for a given tree age and sawfly species
depending on the host genotype. The optimal age of ponderosa pine for N. gillettei on a resistant
genotype would resuit in less than 50 percent survival, for example, whereas on a susceptible genotype,
survival would be 100 percent (Fig. 6a). Likewise for a given genotype and sawfly species, sawfly
survival can vary dramatically as a function of tree age. In the case of N. autumnalis Smith (Fig. 6b),
survival on a susceptible genotype at the preferred age would be 100 percent, but survival on the same
susceptible genotype at the least preferred age would be only about 50 percent. If an experimental
system does not have control over both of these variables, it is possible to generate experimental data
that demonstrate an infinite array of responses for sawfly performance as a function of tree age.

27


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CODY, M.L. 1966. A general theory of clutch size. Evolution 20: 174-184.

COLEY, P.D., BRYANT, J.P., and CHAPIN, FS., III. 1985. Resource availability and plant
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COX, P.A. 1981. Niche partitioning between sexes of dioecious plants. Am. Nat. 117: 295-307.

DANNELL, K., ELMQVIST, T., ERICSON, L., and SALOMONSON, A. 1985. Sexuality in willows
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DICK, J.M., LEAKEY, R.R.B., and JARVIS, P.G. 1990. Influence of female cones on the vegetative
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DICKMANN, D.I. and KOZLOWSKI, T.T. 1970. Photosynthesis by rapidly expanding green strobili of
Pinus resinosa. Life Sci. 9: 549-552.

42


APPENDIX B

Host-plant utilization, host range, utilized tissue-age, and feeding mode of
macrolepidoptera feeding on Swedish conifers. Information on the occurrence of
individual species in Sweden was taken from Elmqvist et al. (1977); reference
not provided.

Family Host. Host. Tissue Feeding
Species plants range“ age mode’ References
Geometridae
Biston betularia L. Lar,Pic,D,H Poly ? Cc 1,2
Bupalus piniarius L. PIN Olig Y+0 c 1,3,4
Deileptenia ribeata Cl. PIN,D Poly ? c 1,3
Ectropis bistortata Goeze PIN,D,H Poly Y? Cc 1,3
Entephria caesiata
Den. & Schiff. Pin,D,H Poly ? c 1,2
Eupithecia conterminata Zell. Pic Mono 0? Cc 2,5
E. indigata Hb. PIN Olig Y c 1,3
E. intricata Zett. Jun Mono 2 Cc 1,2,5
E. lanceata Hb. PIN Olig Y Cc 2,3
E. laricata Fr. Lar,Jun MonoJ Y? Cc 1,2,3
E. nanata Hb. PIN,H Poly 2 c 1,2,6
E. pusillata
Den. & Schiff. PIN Olig Y+0 Cc 2,3,7
Gymnoscelis rufifasciata Haw. Pic,Pin,D,H Poly 2? Cc 1,2
Hydriomena furcata Thnbg. Pic,Pin,D,H Poly ? Cc 1,3
Hylaea fasciaria L. Pin,(Pic),D Poly oO c 1,3,8
Odontopera bidentata Cl. Pin, Abi,H Poly 0 c 1,2,3
Operophtera brumata L. Pic,D Poly Y c 1,2,3
0. fagata Scharf. Pic,D Poly Y c 1,2,3
Peribatodes secundaria Esp. Pic, Pin Olig (y)O ¢ 1,3,7
Perizoma didymata L. Pic,Pin,H Poly 2 Cc 1,2
Semiothisa liturata Cl. PIN, Jun OligJs O Cc 1,9,10
S. signaria Hb. PIN Olig oO Cc 1,3
Thera cognata Thnbg. Jun Mono 2 c 1,2
T. firmata Hb. Pin,Jun MonoJ ie) Cc 1,3,11
T. juniperata L. Pic, Jun MonoJ 2 c 1,3
T. obeliscata Hb. PIN,Jun Oligs ? c 1,3
T. variata
Den. & Schiff. PIN, Jun OligJ Y+0O Cc 2,3,8
Lymantriidae
Lymantria dispar L. Lar,Pin,D,H Pol* Y Cc 1,3,12
L. monacha L. PIN,D Poly  Y+0xe C 1,3,12
Orgyia antiqua L. PIN,D,H Poly (0) ¢ 1,2,3
Noctuidae
Acronicta rumicis L. Pic,D,H Poly ? c 1,2,13

15


MOONEY, H.A., and CHU, C. 1974. Seasonal carbon allocation in Heteromeles arbutifolia, a California
evergreen shrub. Oecologia 14: 295-306.

MOONEY, H.A. and GULMON, S.L. 1982. Constraints on leaf structure and function in reference to
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NEALES, T.F. and INCOLL, L.D. 1968. The control of leaf photosynthesis rate by the level of
assimilate concentration in the leaf: a review of the hypothesis. Bot. Rev. 34: 107-125.

OWENS, J.N. 1969. The relative importance of initiation and early development on cone production in
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PALO, R.T. 1984. Distribution of birch (Betula spp.), willow (Salix spp.), and poplar (Populus spp.)
secondary metabolites and their potential role as chemical defense against herbivores. J. Chem.
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PATRICK, J.W. 1988. Assimilate partitioning in relation to crop productivity. HortScience 23: 33-40.

PIMENTEL, D. 1988. Herbivore population feeding pressure on plant hosts: feedback evolution and
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PUTWAIN, P.D. and HARPER, J.L. 1972. Studies in the dynamics of plant populations. V.
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RAFFA, K.F, and BERRYMAN, A.A. 1983. The role of host plant resistance in the colonization
behavior and ecology of bark beetles (Coleoptera: Scolytidae). Ecol. Monogr. 53: 27-49.

RAFFA, KF, and BERRYMAN, A.A. 1987. Interacting selective pressures in conifer-bark beetle
systems: a basis for reciprocal adaptations? Am. Nat. 129: 234-262.

REDMOND, D.R. 1955. Studies in forest pathology. XV. Rootlets, mycorrhizae, and soil temperatures
in relation to birch dieback. Can. J. Bot. 33: 595-627.

REEKIE, E.G. and BAZZAZ, F.A. 1987a. Reproductive effort in plants. 1. Carbon allocation to
reproduction. Am. Nat. 129: 876-896.

REEKIE, E.G. and BAZZAZ, F.A. 1987b. Reproductive effort in plants. 2. Does carbon reflect the
allocation of other resources. Am. Nat. 129: 897-906.

REEKIE, E.G. and BAZZAZ, F.A. 1987c. Reproductive effort in plants. 3. Effect of reproduction on
vegetative activity. Am. Nat. 129: 907-919.

REZNICK, D. 1985. Costs of reproduction: an evaluation of the empirical evidence. Oikos 44: 257-267.

RONSHEIM, M.L. 1988. Determining the pattern of resource allocation patterns in plants. Trends
Ecol. and Evol. 3: 30-31.

SINCLAIR, T.R. and de WIT, C.T. 1975. Photosynthate and nitrogen requirements for seed production
by various crops. Science 189: 565-567.

SINCLAIR, T.R. and de WIT, C.T. 1976. Analysis of the carbon and nitrogen limitations to soybean
yield. Agron. J. 68: 319-324.

45


PREFACE

This proceedings is the result of a symposium held in Abakan, Siberia, U.S.S.R., August 13-17,
1989. It was organized under the guidelines of the International Union of Forestry Research
Organizations. Five IUFRO Working Parties convened to achieve this exchange: $2.07-01 (Seed and
Cone Insects), $2.07-05 (Bark Beetles), S2.07-06 (Population Dynamics), $2.07-08 (Gall Midges), and
$2.05-06 (Mechanisms of Tree Resistance to Insects).

The papers are arranged in three sections according to their subject matter: 1) general or
theoretical papers, 2) highly mobile, external phytophages, and 3) poorly mobile, internal phytophages.
The breakdown by external and internal feeding strategy was done to recognize that therein lies a
fundamental dichotomy between the kinds of defenses employed by trees against these two broad
classes of feeders. This is not to imply, however, that within each general class there are not still
substantial guild-to-guild differences in plant defenses. There are. This was the subject of the

symposium.

This publication is the result of a joint effort between the Northeastern Forest Experiment
Station and the North Central Forest Experiment Station, USDA Forest Service. It is symbolic of
their strong support for IUFRO goals of facilitating worldwide research on the significant problems
facing forest resource managers.

ACKNOWLEDGEMENTS

We gratefully acknowledge the support of the V.N. Sukachev Institute of Forest and Wood,
Siberian Branch of the U.S.S.R. Academy of Science, and the U.S.S.R. State Committee for Forests.
Without their unflagging commitment this symposium could not have materialized. In particular,
Dr. A. Isaev, Minister of State Forests, provided crucial sponsorship.

We also thank Mrs. Svetlana Pusir for her very significant technical assistance.

Over the course of more than one year, many people helped to bring this printed volume to
fruition. To them, we are especially indebted because they donated substantial time from their busy
schedules. We recognize them in alphabetical order: Bruce A. Birr, Robert A. Haack, Robert K.
Lawrence, and William A. Main. In addition, we thank Marilyn Brouwer and Robin Bolig for their
exacting efforts in the technical editing and computer formatting of the entire volume.

Finally, we thank the INRA Station de Zoologie Forestiere, Ardon-45160 Olivet, France, for
providing work space and support while editorial chores (of WJM) were being executed.

iii


STARK, R.W. 1965. Recent trends in forest entomology. Annu. Rev. Entomol. 10: 303-324.

TIGNER, T.C. and MASON, R.R. 1973. Resistance to needle miner in lodgepole pine varies with
foliage source. Environ. Entomol. 2: 947-949.

WAGNER, M.R. and FRANTZ, D.P. 1990. Influence of induced water stress in ponderosa pine on
pine sawflies. Oecologia 83: 452-457.

WAGNER, M.R., McCULLOUGH, D.G., and DIMATTEO, J.M. 1986. Life history of Neodiprion
fulviceps (Cresson), a ponderosa pine feeding sawfly (Hymenoptera: Diprionidae). Proc. Entomol.
Soc. Wash. 88(2): 221-226.

WASHBURN, J.D. and CORNELL, H.V. 1981. Parasitoids, patches and phenology: their possible role
in the local extinction of a cynipid gall wasp population. Ecology 62: 1597-1607.

WILKINSON, R.C. 1979. Oleoresin crystallization in eastern white pine: relationship with chemical
components of cortical oleoresin and resistance to the white pine weevil. U.S. For. Serv.
Res. Pap. NE-438. 10 p.

WILSON, L.F. 1966. Relative susceptibility of three ponderosa pine sources to European pine sawfly
(Hymenoptera: Diprionidae) attack in Michigan. The Mich. Entomol. 1: 23-25.

WRIGHT, J.W., WILSON, L.F., and RANDALL, W.K. 1967. Differences among Scotch pine varieties
in susceptibility to European pine sawfly. For. Sci. 13: 175-181.


COULSON, R.N. and WITTER, J.A. 1984. Forest Entomology: Ecology and Management. Wiley-
InterScience, New York. 669 p.

CRAIG, T.P., PRICE, P.W., and ITAMI, J.K. 1986. Resource regulation by a stem-galling sawfly on the
arroyo willow. Ecology 67: 419-425.

CRAIG, T.P., WAGNER, M.R., MCCULLOUGH, D.G., and FRANTZ, D.P. 1991. Effects of
experimentally altered plant moisture stress on the performance of Neodiprion sawllies.
For. Ecol. Manage. 39: 247-261.

ENGLISH-LOEB, G.M. 1989. Nonlinear response of spider mites to drought stressed host plants. Ecol.
Entomol. 14: 45-55.

FOGAL, W.H., MORGENSTERN, E.K., VIIDIK, P., and YEATMAN, C.W. 1982. Variation in
susceptibility to native and introduced coniferous trees to some insects in eastern Canada,
p. 472-477. In Heybroek, H.M., Stephens, B.R., and von Weissenberg, K., eds. Resistance to
Diseases and Pests in Forest Trees. Pudoc, Wageningen, The Netherlands.

FRANKIE, G.W. and MORGAN, D.L. 1984. The role of the host plant and parasites in regulating
insect herbivore abundance, with an emphasis on gall-inducing insects. In Price, P.W.,
Gaud, W.S., and Slobodchikoff, C.N. eds. A New Ecology. John Wiley & Sons, New York.

GENYS, J.B. and HARMAN, D.M. 1976. Variation in larch sawfly attack of different species and
geographical strains of larch exhibiting diverse growth rates. J. Econ. Entomol. 69: 573-578.

HALL, R.C. 1959. Field tests of the resistance of hybrid pines to the pine reproduction weevil.
U.S. Dep. Agric. For. Serv. Tech. Pap. 33. 21 p.

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HARD, J.S. 1985. Spruce beetles attack slowly growing spruce. For. Sci. 31: 839-850.

HARRIS, LJ., BORDEN, J.H., PIERCE, H.D., and OEHLSCHLAGER, A.C. 1983. Cortical resin
monoterpenes in Sitka spruce and resistance to the white pine weevil, Pissodes strobi
(Coleoptera: Curculionidae). Can. J. For. Res. 13: 350-352.

HENSON, W.R., O’NIEL, L.C., and MERGEN, F. 1970. Natural variation in susceptibility of Pinus to
Neodiprion sawflies as a basis for the development of a breeding scheme for resistant trees. Yale
Univ. Sch. For. Bull. 78. Yale University, New Haven. 71 p.

HERTEL, G.D. and BENJAMIN, D.M. 1975. Tip moth and webworm attacks in southwide pine seed
source plantations. U.S. For. Serv. Res. Note SE-221. 6 p.

HOFF, R.J. 1988. Resistance of ponderosa pine to the gouty pitch midge (Cecidomyia piniinopis).
U.S. For. Serv. Res. Pap. INT-387. 3 p.

HOFF, R.J. and McDONALD, G.I. 1977. Differential susceptibility of 19 white pine species to wooly
aphid (Pinus coloradensis). U.S. For. Serv. Res. Note INT-225. 6 p.

KAPLER, J.E. and BENJAMIN, D.M. 1960. The biology and ecology of the red pine sawfly in
Wisconsin. For. Sci. 6: 253-268.

KEARSLEY, M.J.C. and WHITHAM, T.G. 1989. Developmental changes in resistance to herbivory:
implications for individuals and populations. Ecology 70: 422-434.

32


According to the nutrition hypothesis, folivores that feed on nutrient-impoverished plants will
have evolved special behavioral adaptations and digestive and metabolic systems that allow them to
sequester nutrients from very dilute mediums (Mattson and Scriber 1987). Such adaptations should not
in principle prevent them from also feeding on nutrient rich diets. Hence they have the capacity to be
polyphagous if other factors are not limiting. Because the conifer species in this study tend to be
adapted to nutrient poor sites, and characteristically have low concentrations of N in their needles
(Tamm 1955), one might predict then that their phytophagous insects should tend to be polyphagous
other things being equal. In fact, Holloway and Hebert (1979) reported that many species of
macrolepidoptera feeding on conifers seem to be less specific in their choice of hosts than species
feeding on Angiosperms.

According to the Host Intimacy Hypothesis, host specialization by insects will be proportional to
the amount of time and body surface area which is spent in direct contact with living tissues of the
host plant (Mattson et al. 1988). The rationale is that high intimacy requires highly elaborate
behavioral, physiological, and temporal adaptations with a host plant and that increasing intimacy will
therefore impose concomitant specialization. Hence the intimacy hypothesis predicts that intimate
species such as leaf miners should tend toward monophagy whereas nonintimate species such as free
feeding Lepidoptera should tend toward polyphagy.

METHOD AND DEFINITIONS

Information about food plants utilized by each insect species was obtained from Escherich
(1931), Nordstrém et al. (1941), Schwenke (1974, 1978, 1982), Winter (1983), and Ehnstrom (pers.
comm.) but the appendices provide further details. Only insects reported to occur on juniper
(Cupressaceae), Scots pine (Pinaceae), and Norway spruce (Pinaceae) have been included. Most of the
literature data concern insect occurrence at the plant species level, but in some cases information at
the genus level has also been included.

Host-plant specialization is defined according to Cates (1980): insects are considered to be
monophagous (Mono) if they utilize one or several plant species within a single genus, oligophagous
(Olig) if they feed on two or more genera within one plant family or closely related families, or
polyphagous (Poly) if they feed on plants from two or more families (i.e. at least one conifer and some
angiosperm). Insect species feeding on one genus within the Pinaceae plus juniper, and insects feeding
on two or more genera within the Pinaceae plus juniper, denoted MonoJ and OligJ respectively in the
appendices, are included in the oligophagous group elsewhere. Chemistry and morphology are more
similar between the two conifer families than between conifers and angiosperms (Thomas 1970),
justifying our inclusion of insects denoted MonoJ and OligJ in the oligophagous group.

With respect to numbers of insect species associated with various host plants, a good
correspondence has been found between faunal lists derived from the literature and data based on
extensive field sampling (Southwood et al. 1982, Niemela and Neuvonen 1983). Thus the coarse
division of host range used in this study probably reflects actual conditions.

Needles were classified as either young or old. The young included buds and current-year
needles; the old group included needles > 1 year of age.


HOFFMANN, AJ. and ALLIENDE, M.C. 1984. Interactions in the patterns of vegetative growth and
reproduction in woody dioecious plants. Oecologia 61: 109-114.

HOUSTON, D.R. 1987. Forest tree declines of past and present: current understanding. Can. J. For.
Pathol. 9: 349-360.

JING, S.W. and COLEY, P.D. 1990. Dioecy and herbivory: the effect of growth rate on plant defense
in Acer negundo. Oikos 58: 369-377.

KRISCHIK, V.A. and DENNO, RF. 1983. Individual, population, and geographic patterns in plant
defense. In Denno, R.F. and McClure, M.S., eds. Variable Plants and Herbivores in Natural and
Managed Systems. Academic Press, New York.

KRISCHIK, V.A. and DENNO, R.F. 1990. Patterns of growth, reproduction, and herbivory in the
dioecious shrub Baccharis halmifolia. Oecologia 83: 182-190.

LARSSON, S., OREN, R., WARING, R.H., and BARRETT, J.W. 1983. Attacks of mountain pine
beetle as related to tree vigor of ponderosa pine. For. Sci. 29: 395-402.

LLOYD, D.G. and WEBB, C.J. 1977. Secondary sex characters in plants. Bot. Rev. 43: 177-216.
LOEHLE, C. 1988. Tree life history strategies: the role of defenses. Can. J. For. Res. 18: 209-222.

LOVETT DOUST, J. 1980. Experimental manipulation of patterns of resource allocation in the growth
cycle reproduction of Smymnium olusatrum L. Biol. J. Linn. Soc. 13: 155-166.

LOVETT DOUST, J. 1989. Plant reproductive strategies and resource allocation. Trends Ecol. Evol.
4: 230-234.

LOVETT DOUST, J. and LOVETT DOUST, L. 1985. Sex ratios, clonal growth and herbivory in
Rumex acetosella. In White, J., ed. Studies on Plant Demography. Academic Press, London.

LUKEN, J.O. 1987. Interactions between seed production and vegetative growth in staghorn sumac,
Rhus typhina L. Bull. Torrey Bot. Club 114: 247-251.

MATTSON, W.J. 1980. Herbivory in relation to plant nitrogen content. Annu. Rev. Ecol. Syst.
11: 119-161.

McLAUGHLIN, S.B. and McCONATHY, R.K. 1979. Temporal and spatial patterns of carbon
allocation in the canopy of white oak. Can. J. Bot. 57: 1407-1413.

MIHALIAK, C.A. and LINCOLN, D.E. 1985. Growth pattern and carbon allocation to volatile leaf
terpenes under nitrate-limiting conditions in Heterotheca subaxillaris (Asteracea). Oecologia
66: 423-426.

MIHALIAK, C.A., COUVET, D., and LINCOLN, D.E. 1987. Inhibition of feeding by a generalist
insect due to increased volatile leaf terpenes under nitrate-limiting conditions. J. Chem. Ecol.
14: 1-21.

MITCHELL, R.G., WARING, R.H., and PITMAN, G.B. 1983. Thinning lodgepole pine increases tree
vigor and resistance to mountain pine beetle. Forest Sci. 29: 204-211.

MOONEY, H.A. 1972. The carbon balance of plants. Annu. Rev. Ecol. Syst. 3: 315-346.

44


PREFERENCE OF DENDROPHAGOUS INSECTS
FOR FOREST BORDERS

ANDREY V. GUROV

V.N. Sukachev Institute of Forest and Wood
Siberian Branch of the U.S.S.R. Academy of Sciences
Krasnoyarsk 660036 U.S.S.R.

INTRODUCTION

Numerous investigations have shown that forest insect outbreaks usually occur in specific
habitats. Frequently these outbreaks do not generally extend to other territories occupied by these
same host trees. Moreover, in every stand subjected to an outbreak, both slightly undamaged plots and
heavily damaged plots are found. Perhaps some plots are initially more resistant to insect attack, and
insect distribution within forest ecosystems may have a mosaic pattern. Therefore investigation of the
relation between dendrophagous insect distributions and initial heterogeneity of ecosystems may help us
to understand the nature of forest stand resistance. This question lends interest to the peculiarities of
dendrophagous insect distribution in relation to forest borders because borders and different glades are
important factors in forest ecosystem heterogeneity.

INSECT DISTRIBUTION WITHIN STANDS

There is no large body of information on this question in the literature. I have used the
available information on different species from several natural zones and considered the distribution of
180 species belonging to 33 families of six insect orders. Insect distribution was analyzed only at the
main feeding stages.

Table 1 shows the majority (73.3 percent) of the species considered to prefer the forest border
and its analogues (single growing trees or low-density stands).

Distribution of insects within a forest stand may depend on two main factors: 1) the presence
of available food; and 2) microclimatic conditions. It is known that availability of food is more
important for xylophagous insects than for phyllophagous ones. On the other hand, microclimatic
conditions are more important for phyllophagous free-living species than for xylophagous ones. Thus it
is necessary to analyze the distribution of both these insect groups separately. My analysis showed the
forest border and its analogues to be preferable for the majority of species from both groups:

59 percent of xylophages and 66 percent of phyllophages. Thus these stations may satisfy different
requirements (food and climate, among others) of the majority of dendrophages.

BARANCHIKOV, Y.N., MATTSON, W.J., HAIN, F.P., and PAYNE, T.L., eds. 1991. Forest Insect
Guilds: Patterns of Interaction with Host Trees. U.S. Dep. Agric. For. Serv. Gen. Tech. Rep. NE-153.

50


No association was found between the degree of host-plant specialization and needle-age
utilization in chewing insect species (Table 2).

The oligophagous group predominates on all three conifers, comprising ca. 45 percent of the
total number of insect species on each of them (Fig. 1). The relative proportions of monophagous and
polyphagous insects differ between the tree species. Juniper, with its high Proportion, of monophages
and low proportion of polyphages, differs significantly from both spruce and pine (x2 = 9.59,

p < 0.01, df = 2, and x? = 6.15, p < 0.05, df = 2, respectively). Although spruce and pine do not
differ significantly, the proportion of monophages is slightly higher on pine.

DISCUSSION

All conifer species studied must be regarded as highly apparent to insects searching for
ovipositional sites and low in nutritive value. According to the apparency and nutrition hypotheses,
insects feeding on these tree species should tend toward polyphagy. Our data show no such trend
when all insect species are considered. On the contrary, less than one third (29 percent) are
polyphagous (Table 1). However, such a crude comparison might be too superficial. A more realistic
assessment might be achieved by comparing our results with the proportion of monophagous and
polyphagous insect species in studies including Jess apparent and more nutritious plants. This is
possible only with specific insect groups (see below). Juniper differs from both spruce and pine,
furthermore, in having relatively more monophagous insect species (Fig. 1). However, differences
between the three conifer species with respect to apparency and nutritional value appear to be small.
Ideally, any attempt to explain host-plant specialization based on plant characteristics should at least
take variation in feeding habits among insect feeding guilds into account. The selection pressure on
the insect varies depending on the plant traits encountered during feeding. Although this fact was
earlier pointed out by Feeny (1976), among others, it has often been ignored. For example, insects
feeding internally, such as mining insects, might be able to avoid some plant allelochemicals that are
compartmentalized in the plant (Feeny 1970, 1976, Cornell 1989). On the other hand, they might
expose themselves more to rapidly inducible defenses, such as phytoalexins. Although the nutrition

Spruce
n=79

Pine
n=72

Juniper
n=17

Figure 1, Relative proportions (%) of mono-ff, oligo-[], and polyphagous #
insect species on each of the three conifer species. Each bar equals 1008.
n = number of insect species.



FOREST INSECT GUILDS:
PATTERNS OF INTERACTION WITH HOST TREES

Edited by:

YURI N. BARANCHIKOV
V.N. Sukachev Institute of Forest and Wood
Siberian Branch of the U.S.S.R. Academy of Sciences
Krasnoyarsk 660036 U.S.S.R.

WILLIAM J. MATTSON
USDA Forest Service
North Central Forest Experiment Station
1407 S. Harrison Road, East Lansing, MI 48823 U.S.A.
and
Department of Entomology

Pesticide Research Center, Michigan State University

East Lansing, MI 48824 U.S.A.

FRED P. HAIN
Department of Entomology
North Carolina State University
Raleigh, NC 27695 U.S.A.

THOMAS L. PAYNE
Department of Entomology
Virginia Polytechnic Institute and State University
Blacksburg, VA 24061 U.S.A.

Proceedings of a Joint IUFRO Working Party Symposium
Abakan, Siberia, U.S.S.R.
August 13-17, 1989

General Technical Report NE-153

U.S. Department of Agriculture, Forest Service
Northeastern Forest Experiment Station
100 Matsonford Rd., Suite 200
Radnor, PA 19087

1991


1.005 am Egg
0.904 @---@ Larval
0.804 Bees @ Total

0.70 4

(%)

0.60 4
0.504

0.404

SURVIVAL

0.304
0.204

0.104

TREE AGE

Figure 3. Influence of tree age on egg, larval, and total survival of
Neodiprion fulviceps.

ROLE OF STRESS IN PINE SAWFLY-PONDEROSA PINE INTERACTIONS

There is yet no clear consensus on the role of environmental stress in provoking insect
outbreaks even for a single-model system. After 5 years of experimentally stressing ponderosa pine
under field conditions, we still have not established a clear pattern of stress effect (McCullough and
‘Wagner 1987, Wagner and Frantz 1990, Craig et al. 1991). Larvae performed more poorly on stressed
trees than on controls for most years. However, we have observed that increasing stress caused
increased, then decreased sawfly performance at some period during the 5-year study. This suggests
that there is some stress level for the plant at which insect performance is optimal and above or below
which performance declines. Because our studies are on wild populations of unknown genotype and
because the environmental conditions are not uniform between years, our data are inconclusive. Only
rigorous, highly controlled experimental testing will reveal the true nature of the response function for
sawfly survival as a result of ponderosa pine stress. In one of the most rigorous studies of water-
stress effects on herbivores, English-Loeb (1989) measured a nonlinear population response by the


APPENDIX A continued

Family Host Host . Tissue Feeding
Species plants range“ age mode’ References
E. subsequana Haw. Abi, Pic Olig Y M 1,4
E. tedella Cl. Pic Mono (Y)0 M 1,4,13
Olethreutus lacunana

Den. & Schiff. Pic,D,H Poly 2 c 1,4,8
Pandemis cinnamomeana Treit. PIN,D,H Poly Y+0 Cc 1,3,4,12
Philedone gerningana

Den. & Schiff. Pic,D,H Poly 2 Cc 1,3,8
Philedomides lunana Thnbg. PIN,D,H Poly ? c 1,8
Ptycholoma lecheana L. Pic,D Poly 2 Cc 1,4
Rhyacionia buoliana

Den. & Schiff. Pin Mono Y(O) M(BM) 1,4,14
R. duplana Hb. Pin Mono Y BM 1,4
R. pinicolana Doubl. Pin Mono Y BM 1,4
R. pinivorana Zell. Pin Mono Y BM 1,4
Spilonota laricana Hein. Lar, (Pic) Olig Y CoM 1,4
Zeiraphera diniana Guen. Pic,Pin ol* Y C(BM) 1,4,10
2. ratzeburgiana Ratz. PIN Olig Y C(BM) 1,4

Cochylidae
Aethes rutilana Hb. Jun Mono ? c 1,9

Pyralidae
Dioryctria abietella

Den. & Schiff. PIN Olig Y BM 4
D. mutatella Fuchs Pin Mono Y BM 1,4
D. schuetzella Fuchs Pic, Abi Olig Y Cc 1,4

* The Picea-Pinus-race that might be a species (two other races exhibit other
host plant preferences)

1 Abi = Abies, Lar = Larix, Pic = Picea, Pin = Pinus, and Jun = Juniper; PIN =
several spp. within Pinaceae; D indicates that the insect species utilizes one
or several deciduous trees or bushes; H indicates that it utilizes one or
several herbaceous plant species.

2 Mono = monophagous, Olig - oligophagous, OligJ ~ feeding on some member of
Pinaceae and Juniper, and Poly = polyphagous.

3 y = young tissue (buds and current-year needles) and 0 = old tissue
(1-year-old or older needles).

4 ¢ = chewing, M = mining in needles, BM ~ mining in buds (and/or shoots).

Arrows under Tissue-age and Feeding mode indicate that the insect shifts from
xy when it becomes older.

13


The use of trade, firm, or corporation names in this publication is for the
information and convenience of the reader. Such use does not constitute an
official endorsement or approval by the U.S. Department of Agriculture of
any product or service to the exclusion of others that may be suitable.
Statements of the contributors from outside the U.S. Department of
Agriculture may not necessarily reflect the policy of the Department.

COVER

The insects on the cover are all European dendrophilous species: Nymphalis polychloros
(Nymphalidae), Cimbex femorata (Cimbicidae), and Dasyneura rozkovi (Cecidomyiiydae). Mr. Victor
Bakhtin (Krasnoyarsk, U.S.S.R.) was the artist.


are restricted to feeding upon living tissue. Feeding girdles the tree, disrupting the downward transport
of photoassimilates. Dieback of roots occur as they are isolated from their energy source, thereby
limiting nutrient and water uptake. As attack intensifies, dieback initiates and spreads within the
canopy. Heavily infested trees are invariably killed (Anderson 1944, Barter 1957, Carlson and Knight
1969).

From 1986 to 1989, we conducted a controlled, factorial, field experiment investigating the
effects of soil moisture, soil fertility, and defoliation on the expression of birch resistance to bronze
birch borer. We found soil moisture to be the most important environmental variable affecting
resistance. Water deficit reduced rates of photosynthesis, growth, and wound-callus formation, as well
as resistance to bronze birch borer (Herms and Mattson, unpubl. data). We found that paper birch
Tesistance to bronze birch may be based largely on generalized trunk responses to wounding, especially
rapid wound-callus formation. Furthermore, we found that the strength of this response is dependent
on an adequate supply of available current photosynthate (Herms and Mattson, unpubl. data).
Feeding-wounds stimulate callus formation, which if rapid enough, may entirely encapsulate small larvae
within suberized tissue containing high concentrations of secondary chemicals and low concentrations of
nutrients. Normally xylem tissue is a poor source of nutrition (Haack and Slansky 1987); callus tissue
may be even worse, preventing larvae from completing development. Larvae may also be physically
crushed as they are overgrown by callus. In effect, larvae may be in a developmental race against the
tree. Larvae move through the tree in essentially two-dimensional space as they feed, their rate of
progress correlated with their rate of consumption. Lesion development characteristic of a
hypersensitive response occurs in phloem and xylem tissue surrounding the wound. A rapid rate of
callus formation, coupled with reduced rates of larval movement through the wood, may result in larval
encapsulation. Implicit in this hypothesis is the prediction that the rate of callus formation necessary
for resistance should be presented by a threshold value approximately equal to the maximum rate of
larval movement through the plant. Our data suggest that birch trees with rates of callus formation
falling below about 0.02 mm/day are highly susceptible to bronze birch borer.

Paper birch (Betula papyrifera) is monoecious, with pistillate (female) and staminate (male)
catkins produced as separate structures. Male catkins are produced at the end of indeterminate long-
shoots in mid- to late-summer following the termination of shoot elongation. They overwinter,
elongating and releasing pollen as vegetative buds open in spring. Female inflorescences emerge from
overwintering-buds on short shoots as buds break in spring. Female catkin maturation commences
upon pollination, and continues throughout the growing season. Seeds mature in late summer and
drop throughout the fall and winter.

The results of our experiments confirm previous reports showing a trade-off between vegetative
growth and female catkin production (Gross 1972, Tuomi et al. 1982, Caesar and MacDonald 1983).
Plants capable of altering the balance of resources allocated between male and female organs generally
allocate proportionally more resources to female functions in high resource environments (Freeman et
al. 1980). This occurs, presumably, because successful female reproduction requires, in general, a
greater commitment of resources than does male reproduction. In our experiment, however, increased
female reproductive output in 1 year was associated with resource-limited growth during the previous
year. Slow growth may stimulate the initiation of female flowers. Female reproduction itself then
further reduces vegetative growth through resource competition. A positive feedback loop may result.
Female reproductive effort stimulated by slow growth further reduces growth, which further stimulates
female reproduction. Because of reduced rates of callus formation associated with increased female
reproductive effort, this positive feedback loop may result in ever-increasing susceptibility to bronze
birch borer and eventual tree death. In fact, stress-triggered seed production may be an adaptation
which maximizes the life-time reproduction of suppressed trees that are competitively doomed and are
likely to be soon killed by bronze birch borer.

37


SAWFLIES AND PONDEROSA PINE:
HYPOTHETICAL RESPONSE SURFACES
FOR PINE GENOTYPE, ONTOGENIC STAGE,
AND STRESS LEVEL

MICHAEL R. WAGNER

School of Forestry
Box 4098, Northern Arizona University
Flagstaff, AZ 86011 U.S.A.

INTRODUCTION

Patterns that occur in nature are the result of a complex set of current and historical factors
that interact with one another and the adaptive plasticity of plants. Scientists are forced to assess such
Processes on the basis of series of "snapshots" over a relatively short time that represent only part of
the grand pattern. In the case of insects interacting with forest trees, there are dozens of
environmental and host plant factors that could be the key factor responsible for the patterns we
observe, Because of the high experimental standards of rescarch and the many potentially important
factors, scientists tend to construct models by which to test specific hypotheses about key factors. This
methodology produces a body of knowledge about a particular factor (c.g. moisture stress) that does
not necessarily integrate well with the body of knowledge about a second factor (e.g. genetic
resistance). These disjoint sets of data encourage scientists to think in terms of components, and that
leads them to draw conclusions about single factors, in isolation from many other important factors.
Such conclusions can be misleading.

Given the single-factor focus of the scientific community, it is not surprising that inconsistencies
and apparent contradictions are abundant. For example, despite considerable research effort, no clear
pattern has emerged to determine the role of environmental stress in creating insect outbreaks (Larsson
1989). Drought or poor site conditions have been correlated with outbreaks of forest insects (Mattson
and Haack 1987a, 1987b). In the specific case of sawflies (Hymenoptera: Diprionidae), many outbreaks
have been correlated with drought conditions (Kapler and Benjamin 1960, McLeod 1970, Averill and
Fowler 1973, Knerer and Atwood 1973, Larsson and Tenow 1984). One hypothesis explaining this
phenomenon is that environmental stress changes the host plants and thereby increases herbivore
performance in some way. Tests of this hypothesis for sawflies have not been consistently supportive
(McCullough and Wagner 1987, Craig et al. 1991, Wagner and Frantz 1990). Meyers (1988) and
Larsson (1989) have suggested that the general hypothesis that host plant stress causes outbreaks is
"still very much open to debate." Careful reviews of the literature which stratify the evidence by insect
feeding guilds clarify the question for some guilds such as bark beetles, but not for others such as
defoliators (Larsson and Tenow 1984, Larsson 1989). The recent studies cited above might lead us to
conclude that there is no relationship between stress and insect outbreaks, but what about all the
previous correlative evidence and the anecdotal evidence that stress is related to insect outbreaks? It
seems reasonable to hypothesize that stress is important under some circumstances and not others.
The critical point is that several factors interact to create the particular insect/tree pattern we observe

BARANCHIKOV, Y.N., MATTSON, W.J., HAIN, F.P., and PAYNE, T.L., eds. 1991. Forest Insect
Guilds: Patterns of Interaction with Host Trees. U.S. Dep. Agric. For. Serv. Gen. Tech. Rep. NE-153.

21


MODEL Genetic = linear
Stress = modified cosine

Stress Level

100
Af | Senotvee A

SAWFLY SURVIVAL

Stress A | Stress B t

Figure 7. Hypothetical response function for the effects of genotype and
stress on sawfly survival. Model assumes the stress response function is
dependent on genotype.

individual factors are thoroughly understood. 5) Insect response variables need to be chosen carefully.
‘The response variable chosen (e.g. total survival) should be one that can have a significant effect on
insect population dynamics. Field data and population dynamics models can be helpful in identifying
which population parameters are most important for a given insect/plant system. 6) We should be very
careful about generalizing across insect and plant systems. What may be a key factor in one system
may be unimportant in another. Observation of natural patterns will suggest which factors are most
likely to be important for a given system and these should be explored first. 7) Finally, response
surfaces must be carefully defined. As this paper has attempted to demonstrate, relatively simple
single-factor response functions, when combined, can produce complicated response surfaces which must
be understood before definitive conclusions can be drawn.


APPENDIX B continued

Family Host. Host Tissue Feeding
Species plants range“ age mode’ References
Blepharita adusta Esp. Pic,Pin,H Poly 0 c 1,13
Ceramica pisi L. Lar, Pic,D,H Poly 2 Cc 1,3,13
Panolis flammea

Den. & Schiff. PIN, (Jun),D Poly Y+0 c 1,3,14
Panthea coenobita Esp. PIN Olig t) c 2,3,7

Lasiocampidae
Dendrolimus pini L. PIN Olig Y+0O Cc 3,15
Lasiocampa quercus L. PIN,D,H Pol* 2 c 1,3
Macrothylacia rubi L. Pic,D,H Poly ? c 1,2
Selenephera lunigera Esp. PIN Olig ? c 2,3

Sphingidae
Hyloicus pinastri L. PIN Olig 2 c 1,3,16

* Possibly ecological races with respect to host plant choice
** If on spruce, feeds as young larvae on young tissue and later as old larvae
on old tissue; if on pine, vice versa

1 abi ~ Abies, Lar = Larix, Pic = Picea, Pin = Pinus, and Jun = Juniper; PIN -
several spp. within Pinaceae; D indicates that the insect species utilizes one
or several deciduous trees or bushes; H indicates that it utilizes one or
several herbaceous plant species.

2 Mono = monophagous, Olig = oligophagous, OligJ - feeding on some member of
Pinaceae and Juniper, and Poly = polyphagous.

3 y = young tissue (buds and current-year needles) and 0 = old tissue
(one-year-old or older needles).

4 c= chewing, M = mining in needles, BM = mining in buds (and/or shoots).
Arrows under Tissue-age and Feeding mode indicate that the insect shifts from
x+y when it becomes older.

REFERENCES: 1) Winter (1983), 2) Nordstrom et al. (1941), 3) Schwenke (1978),
4) Engel (1939), 5) Hoffmeyer (1966), 6) Browne (1968), 7) Patocka (1960),

8) Escherich (1931), 9) Schwenke (1953), 10) Hofmann (1941), 11) Larsson and
Tenow (1980), 12) Tragardh (1939), 13) Forster and Wohlfahrt (1971),

14) Schwerdtfeger (1970), 15) Grénberg (1903), and 16) Nunberg (1939).

16


WESLIEN, JAN (396), Division of Forest Entomology, Swedish University of Agricultural Sciences,
P.O. Box 7044, S-75007 Uppsala, Sweden

WITTER, JOHN A. (53), School of Natural Resources, University of Michigan, Ann Arbor, MI 48104
USA.

YANOVSKY, VICTOR M. (378), V.N. Sukachev Institute of Forest and Wood, Siberian Branch of the
U.S.S.R. Academy of Sciences, Krasnoyarsk 660036 U.S.S.R.

YOSHIKAWA, KEN (397), Laboratory of Silviculture, Faculty of Agriculture, Kochi University,
Monobe B200, Nankoku City, Kochi, Japan 783

xii


EXPLAINING HIGH BORDER PREFERENCE

Let us consider some possible reasons why forest insects prefer forest borders. Forest border
habitats are characterized by a great variety of 1) microsites and 2) tree and shrub species. For these
reasons, rich insect species communities occur in these habitats. The existence of species variety is
impossible within narrow local microclimatic conditions. However, since the forest borders are
characterized by maximal amplitudes of microclimatic parameter fluctuations, they allow for the
coexistence of insect species with different microclimatic requirements.

It might be thought that all these factors relate only to phyllophages because xylophages depend
on microclimatic conditions to a lesser degree and for them the availability of food is more important.
Only the tree borders are subjected to strong winds and other unfavorable influences, however, and
that circumstance makes for constant renewal of the food base by xylophagous insects.

It is necessary, finally, to account for the preference of forest borders by cone and seed insects.
Unlike the trees in forest thickets, border trees such as conifers may produce cones between "yield
years." As a rule, only border and single-growing trees produce cones every year. Consequently,
border habitats become refugia for cone and seed insects. This may also be a factor in the preference
for forest borders by dendrophages.

Thus we may conclude that: 1) forest borders and their analogues are preferable habitats for a
great number of dendrophagous insects; 2) forest borders and their analogues are strategic sites for
control of abundant forest insect species; and 3) forest borders may be used expressly for the analysis
of fauna of dendrophagous species in certain forest ecosystems.

52


Another Look at Birch Dieback: Bronze Birch Borer is Central

Some students of forest decline in North America have been reluctant to assign the bronze birch
borer a central role in the occurrence of widespread birch dieback (Anderson 1944, Hawboldt 1947,
Carlson and Knight 1969, Houston 1987). At best, the bronze birch borer has been credited with a
minor effect on over-all patterns of tree mortality, primarily killing trees already predisposed to death
by other factors, such as disease. We argue that patterns of bronze birch borer outbreaks are in some
ways analogous to those of the mountain pine beetle, Dendroctonus ponderosae, and are sufficient in
themselves to contribute significantly to historical patterns of birch dieback in North America:
1) outbreaks of the bronze birch borer, like those of the mountain pine beetle, can be classified as
“eruptive” (Berryman and Stark 1985), or more specifically "pulse eruptive" (Berryman 1987); 2) much
like the mountain pine beetle (Raffa and Berryman 1983, 1987, Berryman and Stark 1985), we argue
that bronze birch borer populations are usually regulated largely by the availability of host plants
suitable for larval development and survival (e.g. Carlson and Knight 1969). Outbreaks occur at
irregular intervals when biotic and/or abiotic stress factors increase the availability of suitable host
trees. 3) Once populations reach epidemic proportions, the outbreak spreads to adjacent stands as
large numbers of larvae are able to overwhelm the defenses of vigorous, normally resistant trees.

Paper birch frequently forms even-aged, monospecific stands throughout the boreal forest of
North America, Under conditions favoring rapid tree growth, populations of bronze birch borer are
constrained to endemic levels by lack of susceptible host material. In this situation, birch borer
Teproduction is primarily restricted to suppressed trees succumbing to density-dependent competition
during the thinning phase of stand establishment. Intolerant of shade, suppressed trees are
characterized by low net assimilation rates and lack the resources necessary to support a strong wound
Tesponse.

Episodes of birch dieback, and associated out-breaks of bronze birch borer, have corresponded
with periods of above-average temperatures and below-average precipitation (Hawboldt and Skolko
1948, Redmond 1955, Clark and Barter 1958). Combinations of severe stresses such as drought and
defoliation may simultaneously weaken trees over wide geographic areas, resulting in rapid and
substantial increases in host material suitable for the bronze birch borer, thereby releasing them from
this constraint on population growth (Carlson and Knight 1969).

Female reproduction in birch may play a key role in sustaining bronze birch borer outbreaks. If
stress-induced reductions in growth stimulates female reproduction, and female reproductive effort
further compromises resistance to bronze birch borer, the result may be a positive feedback loop which
rapidly increases the number of susceptible hosts, intensifying and sustaining an outbreak.

Under conditions of extremely high attack density, the defense mechanisms of otherwise resistant
trees may be overwhelmed by simultaneous colonization by many larvae. Under these circumstances,
larval-feeding behavior may act to subvert host defense mechanisms, facilitating the success of their own
colonization as well as colonization by other larvae. When feeding in vigorous hosts, larvae display a
zig-zag pattern of gallery formation as they continually double-back against the grain of the wood
(Carlson and Knight 1969). This pattern of feeding may partially girdle the tree, causing localized
reductions in the strength of wound-induced resistance mechanisms. On the other hand, in severely
Stressed host trees, galleries show no consistent pattern, as larvae apparently feed on the freshest
phloem they encounter (Carlson and Knight 1969).

As borers kill susceptible trees, thereby removing them from the pool of suitable hosts, and as
environmental conditions change favoring increased tree growth and stronger wound responses, the
epidemic subsides. The borer population declines to an endemic level as the supply of suitable hosts
dwindles.


Photosynthesis, however, can be maintained in existing cells, at nutrient concentrations below those
limiting to growth (Chapin 1980, Dietz 1989). Under sink-limiting conditions the carbon/nutrient ratio
of the plant increases. Photosynthate assimilated in excess of growth requirements is frequently
allocated to secondary metabolism, frequently increasing the plant’s resistance to herbivores (Mattson
1980, Bryant et al. 1983, 1987a, 1987b, Mihaliak et al. 1985, 1987). Since “excess” photosynthates could
be stored and contribute to future growth rather than be used in defense, enhanced secondary
metabolism in response to sink limitation may represent a selected, adaptive use of resources
minimizing herbivory (micro and macro) when the plant has limited ability to compensate (via growth)
for it.

A nutrient deficiency in vegetative parts female plants relative to male plants resulting from a
disproportionate allocation of nutrients from vegetative sources to reproductive sinks may limit
vegetative growth (Allen and Antos 1988). Photosynthetic stimulation of source leaves by feedback
control exerted by strong reproductive sinks, coupled with direct photosynthetic activity of reproductive
tissues, may contribute to a favorable carbon economy within the plant. Together, these factors may
interact to increase carbon/nutrient ratio in the foliage of female plants relative to males.

Female plants, because of reduced growth due to their greater reproductive effort, may have
limited ability to compensate for herbivory relative to male plants (Agren 1987, Elmqvist et al. 1987,
1988). Limited compensatory ability coupled with the need by female plants to protect their
reproductive investment, may result in females being under stronger selection than males for powerful
defense (Putwain and Harper 1972, Agren 1987, Boecklen et al. 1990). Consequently, patterns of
defense observed in female relative to male individuals of a species may mirror the phenotypic patterns
of defense predicted by Bryant et al. (1983) in nutrient-deficient relative to nutrient-rich plants.
Female plants, like nutrient-deficient plants, should display reduced growth, increased carbon/nutricnt
balance in vegetative structures, and higher concentrations of secondary metabolites. Very limited
evidence supports this pattern. Male plants do seem to receive higher levels of herbivory (Putwain and
Harper 1972, Dannell et al. 1985, Agren 1987, Elmqvist et al. 1988, Alliende 1989, Boecklen et al.
1990, Krischik and Denno 1990, Jing and Coley 1990) and contain lower concentrations of secondary
metabolites or have less tough foliage (Palo 1984, Boecklen et al. 1990).

Reproductive Effort in Monoecious Plants May Enhance Their Resistance to Folivores

The principles discussed above should also apply to monoecious plants if they translocate
proportionally more nutrients than carbon from vegetative sources to reproductive sinks. This
hypothesis predicts that the carbon/nutrient ratio of vegetative tissues will increase with increasing
teproductive effort, resulting in increased concentrations of carbon-based secondary metabolites, and
possibly enhanced resistance to folivores.

SUMMARY

The process of plant reproduction has pervasive effects on virtually all aspects of plant
physiology and should have important effects on plant resistance to herbivores. We hypothesize that
increased susceptibility to stem-invading herbivores could result as a consequence of the substantial cost
of reproductive effort as resources are diverted from defensive structures and reactions to reproduction.
On the other hand, we hypothesize that reproduction can increase plant resistance to folivores.
Reproductive effort may result in an increased carbon/nutrient ratio in foliage, as nutrients are
translocated to developing flowers, fruits, and seeds. Associated with this increased carbon/nutrient
balance may be enhanced allocation to secondary metabolic pathways and increased resistance to some
herbivores. Few data are available with which to test these hypotheses. The potential interactions
between plant reproduction and herbivory are ripe for investigation.

40


RESULTS

Detailed information concerning the host plants utilized by individual insect species as well as
their host ranges, needle-age utilization, and feeding modes are presented in Appendices A-D.

No obvious trend in the degree of host-plant specialization is apparent when all insect species
are considered (Table 1). However, the degree of specialization varies distinctly among feeding and
taxonomic insect groups. Mining microlepidopterans are mainly monophagous (x2 = 13.38, p < 0.01,
df = 2). The absolute monophagy among the sawflies is notable. Chewing micro- and
macrolepidopterans are predominantly polyphagous, the microlepidopterans, however, not significantly
so (X? = 5.76, p > 0.05, df = 2, and X2 = 14.92, p < .001, df = 2, respectively). Beetles are
mainly oligophagous.

Table 1. Numbers of mono-, oligo-, and polyphagous species within different
insect groups on Swedish conifers

Insect group Monophagous Oligophagous Polyphagous
Microlepidoptera

Chewing 2 5 10

Mining 13 6 0

Others 7 4 3
Macrolepidoptera 2 16 21
Hymenoptera

Symphyta 28 0 0
Coleoptera

Larvae 1 3 0

Adults 2 9 6
All chewing spp. 33 33 37
Total 55 43 40

Table 2. Degree of host-plant specialization among chewing insects as related
to their needle-age (young vs. old) utilization on Swedish conifers
(based on 14 Lepidoptera, one sawfly, and four Coleoptera species)

Host range Young needles Old needles
Monophagous 0 1
Oligophagous 5 5
Polyphagous 5 3