bluuebunny/crossref_metadata_2025 huggingface dataset:
Natural Hybrid Populations between Chasmogamous and Cleistogamous Species, Ainsliaea faurieana and A. apiculata (Asteraceae; Mutisiae): Morphology, Cytology, Reproductive Mode and Allozyme Variation
Authors: WATANABE KUNIAKI , YAHARA TETSUKAZU , KADOTA HIROSHI
Published: February 2005

Abstract Ainsliaea apiculata is a cleistogamous perennial. This species occasionally hybridizes with A. faurieana on Yakushima Island, Japan and the hybrids are fertile. A cytological study of these hybrids revealed no irregularity in their male meiosis and the occurrence of genetic segregation through successful reproduction. Allozyme variation provided evidence for segregation through selfing in the hybrids. Observation on pollen grain number showed that these hybrids have cleistogamous flowers in various frequencies. Cleistogamy is dominantly inherited in the hybrids and selfing by cleistogamous flowers is considered to contribute to the formation of hybrid populations.
Plant Demography and Habitat: A Comparative Approach
Authors: SILVERTOWN JONATHAN , FRANCO MIGUEL
Published: February 2005

Abstract Progress in plant demography will depend upon being able to synthesize a large body of data and this requires a means of comparing populations between sites and species. We have employed a comparative technique using elasticity analysis of stage‐projection matrices to partition the contributions of fecundity (F), survival (L) and growth (G) to the finite rate of increase λ. Ordination of populations of 77 perennial herbs and trees in G‐L‐F space has shown that species segregate in this triangular space according to their life history and habitat. In the present paper we use the correspondence between demographic parameters and habitat revealed by this method to predict how succession and a variety of environmental factors such as grazing and fire are likely to alter the demography of populations and ultimately to change the composition of communities.
Mode of Competition and Size‐structure Dynamics in Plant Communities
Authors: HARA TOSHIHIKO
Published: February 2005

Abstract Competition between individual plants is defined as a mathematical function for the mean growth rate of individuals in a vertically mono‐layered crowded stand as compared with growth of an isolated individual of the same size. The degree of competitive asymmetry can be described mathematically by using this definition. A canopy photosynthesis model for individual growth in a mono‐layered stand shows that physiological and environmental variations have little effects on the size‐structure dynamics of plant populations undergoing strongly asymmetric competition. These variations affect greatly the size‐structure dynamics under symmetric competition. It has also been shown that one‐sided competition (the most asymmetric competition) is never realised in a mono‐layered stand. A spatial competition model shows that variation in the spatial distribution pattern of individuals greatly affects the size‐structure dynamics of populations undergoing symmetric competition, whilst it has little effect on populations undergoing strongly asymmetric competition. Therefore, it can be concluded that a population undergoing strongly asymmetric competition is a stable system little affected by variations in various factors and that a population undergoing symmetric competition is an unstable system greatly affected by these variations.

Based on these theoretical results, the relationships between the mode of competition, species diversity and community stability are discussed and a hypothesis on these processes and mechanisms is proposed for grassland and forest plant communities. One‐sided competition is associated with the stability of community structure, and this type of competition works as a structuring force for plant communities. Symmetric competition is associated with species diversity, and this type of competition cannot be a structuring force of plant communities, i.e. symmetric competition is irrelevant to the deterministic community dynamics. Distinctly multi‐layered forests show “apparent” one‐sided competition between layers (i.e. little direct interactions between canopies in different layers, but higher‐layer trees suppress lower‐layer trees one‐sidedly), bringing about structural stability, but trees in each layer undergo symmetric competition, bringing about species diversity. Mono‐layered grassland shows symmetric competition, bringing about small‐scale spatio‐temporal changes in species' abundance and hence species diversity. The real world lies between the two extreme types of competition, one‐sided and completely symmetric, and each plant community has its own position in this continuous spectrum of the competition mode.
Does Physiological Integration Enable Clonal Herbs to Integrate the Effects of Environmental Heterogeneity?
Authors: HUTCHINGS MICHAEL J. , PRICE ELIZABETH A.C.
Published: February 2005

Abstract The effects of physiological integration on clone behaviour are examined at various structural scales, using data from the stoloniferous herb Glechoma hederacea. The consequences for clone expansion of traumatic fragmentation of the connections between clonal ramets are also illustrated. These results, together with information from other species, are used to refute the commonly‐quoted view that physiological integration between the ramets of clonal herbs evens out the effects of variation in environmental quality, and promotes equitable ramet performance. Instead, clonal species are responsive, at a variety of structural scales, to environmental quality. Therefore, in a heterogeneous habitat, within‐clone variation in the performance of ramets and clonal sub‐structures is to be expected. The seminal study which purports to demonstrate environmental averaging in clonal herbs is shown to be both inadequately designed and inappropriately analysed to accomplish its aim.

Physiological and architectural reasons for the local responses to environmental quality seen in the majority of clonal herbs are discussed.
Population Growth, Structure, and Seed Dispersal in the Understory herb Cynoglossum virginianum: a Population and Patch Dynamics Model
Authors: CIPOLLINI M.L. , WHIGHAM D.F. , O'NEILL J.
Published: February 2005

Abstract We use a combined model of forest canopy dynamics and patch‐specific demography to examine the response of a forest understory herb, Cynoglossum virginianum, to changes in rates of forest disturbance, rates of long distance seed dispersal, and patterns of seed dormancy. The matrix modelling approach followed that of Horvitz and Schemske (1986), in which empirically‐determined demographic parameters of a population experiencing open canopy conditions are modified depending upon demographic decay functions describing plant demography in a series of patch‐types undergoing succession toward fully closed canopy. In our analysis, demographic transition elements were estimated from 14 years of long‐term census data on three subpopulations at the Smithsonian Environmental Research Center, Anne Arundel County, Maryland. One of the three subpopulations was subjected to full canopy exposure in the second year of data collection, while the other two subpopulations remained in full understory conditions for the entire census period. Our results suggest small negative effects of a doubling of the rate of canopy disturbance (defined as the rate at which new treefall gaps appear in closed canopy) and only small positive effects of long distance dispersal on population growth rate, which predicts tittle selection for long distance dispersal. However, our analyses predict positive benefits of enhanced seed dormancy in this species, particularly if dormancy is higher in new gaps relative to understory conditions. These results are primarily a product of enhanced reproductive output in the years immediately following gap opening which is counterbalanced by increased seedling mortality in those years and a near complete suppression of reproductive output in later years (closing gaps). The suppression of reproduction in closing gaps may be a manifestation of a delayed effect of high costs of reproduction imposed in prior years. We discuss our results in terms of observed patterns of seed dispersal and in terms of the overall potential influence of forest gap dynamics on the demography of understory herbs similar to C. virginianum, in which demographic responses to changes in canopy conditions differ in strength and direction among life history stages.
Reproductive Systems and Sibling Competition in Plants
Authors: CHEPLICK G.P.
Published: February 2005

Abstract Competition among relatives can modify the genetic structure of plant populations; in turn, competitive outcomes can depend on the genetic relatedness of the individuals competing. The offspring from individual parents exhibit a continuum of genetic relatedness, depending on parental reproductive systems. Competition among relatives may have evolutionary significance as a selection pressure; sibling competition, for example, has been invoked to explain the evolution of sexual systems, seed packaging within fruits, seed dispersal dimorphisms, and germination behavior.

Density‐dependent fitness consequences of sibling competition have been documented in a population of the annual grass Sporobolus vaginiflorus. This species produces seeds matured in cleistogamous spikelets within leaf sheaths along tillers in autumn: when seeds along the tillers of a maternal parent (i.e. a sibship) germinate in situ the following spring in close proximity to one another, sibling competition results in a high‐density zone centered around the original senescent parent. Both intra‐ and intersibship interactions can occur within a population. Although fitness is much reduced for siblings inside the zone of competition, potential seed rain and net primary productivity per unit area are significantly higher relative to outside the zone. This annual is functionally analogous to a perennial ramet producer with a phalanx growth strategy and the unit of selection may be the sibling group. It is not yet known whether sibling competition is a significant selection pressure in other species, but indirect evidence suggests it may be relatively widespread.
Variation in Outcrossing Rates in Eichhornia paniculata: Temporal Changes in Populations of Contrasting Style Morph Structure
Authors: BARRETT SPENCER C.H. , HUSBAND BRIAN C. , COLE WILLIAM W.
Published: February 2005

Abstract Surveys of mating‐system parameters in populations of the annual, self‐compatible, tristylous, emergent aquatic, Eichhornia paniculata (Pontederiaceae) from N.E. Brazil and Jamaica have indicated that the species exhibits a wide range of outcrossing rates. To investigate whether temporal variation in outcrossing rate was also a feature of populations, open‐pollinated families were sampled from five populations of contrasting style morph structure from N.E. Brazil over three consecutive years (1987–1989). Multilocus estimates of outcrossing rate (t) were obtained from assays of isozyme polymorphisms using starch gel electrophoresis. There was significant variation both among populations and between years in the frequency of outcrossing. Outcrossing in three tristylous populations was high (t > 0.80), with relatively small fluctuations occurring over the three‐year sampling period. In contrast, in a dimorphic and monomorphic population considerable self‐fertilization occurred and the frequency of outcrossing declined significantly from 1987 to 1989 in both populations. In the dimorphic population, increased selfing was associated with a marked reduction in population size and an increase in the frequency of selfing variants of the mid‐styled morph. The significance of temporal variation in outcrossing frequency in plant populations is discussed in relation to its effect on population genetic structure and recent models of mating‐system evolution.
Seedling Establishment of a Canopy Tree Species in Malaysian Tropical Rain Forests
Authors: KACHI NAOKI , OKUDA TOSHINORI , YAP S.K.
Published: February 2005

Abstract Unlike many other canopy tree species in tropical rain forests, Dryobalanops aromatica (Dipterocar‐paceae, local name: Kapur) establishes monospecific dominant (monodominant) forests in Peninsular Malaysia. In natural conditions, monodominance of Kapur does not necessarily mean low species diversity of the Kapur forests. While the emergent canopy layer is occupied by Kapur, many other plant species, which are common to lowland dipterocarp primary forests in the same region, are found in lower canopy layer and understory.

To understand the ecological implications of the monodominance of Kapur, we monitored post dispersal survival and seedling establishment in a pure stand of Kapur in a plantation in Kepong, near Kuala Lumpur. Immediately after seed fall, seeds and cotyledon‐stage seedlings suffered high predation by vertebrates such as rodents. The predation pressure was higher in a more general fruiting year (1991) than in a sporadic fruiting year (1992). In contrast to the high mortality of seeds and newly emerged seedlings, seedlings surviving to the six‐leaf stage showed low mortality, which allowed the establishment of a sapling bank.

The occurrence of saplings of Kapur with a wide range of size classes in natural forests indicates that this species is more shade tolerant than other dipterocarp species such as the Shorea group and that it could well respond to enhanced light conditions caused by canopy opening. These characteristics may partly contribute to maintaining monodominance of Kapur.
Temporal Hierarchies of Variation and the Maintenance of Diversity
Authors: CHESSON PETER , HUNTLY NANCY
Published: February 2005

Abstract A general model shows how the long‐term growth rate of a population can be partitioned into components representing various mechanisms of maintenance of species diversity. One component summarises the effects of fluctuation‐independent mechanisms, which include classical resource partitioning and frequency‐dependent herbivory. Two other components represent fluctuation‐dependent mechanisms, the storage effect and relative nonlinearity of competition.

The general model shows how a community will track an equilibrium set by fluctuation‐independent mechanisms and the environmental state when community dynamics are faster than the rate of environmental change. Fluctuation‐dependent mechanisms can be important for diversity maintenance with or without such tracking, but on long timescales their effects are indistinguishable from those of fluctuation‐independent mechanisms.

These considerations lead to a hierarchical view of mechanisms of diversity maintenance where the effects of different timescales are partitioned or merged depending on the timescale of observation. These issues are illustrated with model examples involving various combinations of resource partitioning, fluctuations in recruitment rates, variation in the timing of germination, and seasonality. The very long timescales associated with climate change contain many complexities but nevertheless many ideas applicable to shorter timescales may be useful in a modified form.
Viruses and the Advantage of Sex in Anthoxanthum odoratum: A Review
Authors: KELLEY STEVEN E.
Published: February 2005

Abstract The nature of the selective forces responsible for the maintenance of sexual reproduction in populations remains controversial. Theoreticians have proposed a variety of mechanisms to explain how sex is adaptive, including varying environments, sib competition, mutational damage, and pathogens. In a well‐studied population of the short‐lived, perennial grass Anthoxanthum odoratum in a mown North Carolina field, significant fitness advantages for sexual vs. asexual offspring have been shown. Evidence from two recent experiments implicates barley yellow dwarf luteovirus (BYDV), a single‐stranded RNA virus, as a cause of the short‐term advantage for sex in this population. When planted in sites close to parents, asexual offspring were twice as frequently infected as sexual offspring. In other sites, infection was more frequent among common than rare genotypes. Viruses possess a unique combination of features which make them plausible candidates to favor sexual reproduction in plants. Viruses are pervasive, have subtle but significant fitness effects, have the potential for rapid mutation and evolution, and are spread by vectors whose behaviors are host frequency dependent. The ecological and evolutionary consequences of viruses in plant populations deserve further study.
Genetic Variation in the Endangered Santa Ana River Woolly‐Star, Eriastrum densifolium ssp. sanctorum (Polemoniaceae)
Authors: BRUNELL MARK S. , RIESEBERG LOREN H.
Published: February 2005

Abstract Eriastrum densifolium ssp. sanctorum (Milliken) Mason is a geographically restricted subspecies occurring only in a short stretch of the Santa Ana River Wash, in southern California. This subspecies is considered endangered and has been afforded US federal protection. Enzyme electrophoresis was used to assess its genetic variability and its relationship to other nearby conspecific populations, which are morphologically similar to ssp. sanctorum. Gene diversity is higher than expected for this endemic taxon. Most of the genetic variation in this subspecies resides within the sites comprising the single, large population. Analysis of nearby populations involving other subspecies of Eriastrum densifolium indicate that these entities are very closely related to the Santa Ana River population. The genetic vulnerability of this plant appears to be low, and the relationship to other nearby, morphologically similar populations is uncertain.
Seedling Growth and Morphology of the Deciduous Tree Cornus controversa in Simulated Forest Gap Light Environments in Subtropical China
Authors: CORNELISSEN J.H.C.
Published: February 2005

Abstract Seedling growth and morphology of the deciduous tree Cornus controversa from subtropical China were studied in four simulated forest gap light environments: 100%, 55%, 33% and 18% full sunlight. The best performance was in 33% full sunlight. Overall, Cornus seedlings grew taller than those of five broad‐leaved evergreen species from the same area. In terms of total plant mass only Cinnamomum camphora seedlings grew bigger than Cornus seedlings. Cornus seedlings needed relatively small biomass investments to become tall and to produce a great total length of axes. Growth of Cornus seedlings was probably enhanced by their comparatively ‘cheap’ leaves in terms of weight per area, which resulted in large total leaf area per unit plant weight. The results provide ecophysiological support of Cornus' competitive strength in forest gaps amidst mostly evergreens.
Size‐dependent Resource Allocation Pattern and Gender Variation of Anemone debilis Fisch.
Authors: KUDO GAKU
Published: February 2005

Abstract Size‐specific effects on the resource allocation pattern and gender variation at the flowering stage were studied in a perennial hermaphrodite, Anemone debilis. With an increase of plant size, allocations to inflorescence and roots decreased, while those to leaves and stem were constant; allocations to rhizome increased. A negative correlation between sexual reproduction and survival or vegetative reproduction was suggested. There was a trade‐off in resource allocation between male function (androecium) and female function (gynoecium) within an inflorescence. Gender of A. debilis gradually shifted to femaleness with size increment. This size‐specific sex allocation pattern agrees with the prediction of the theoretical model for entomophilous hermaphroditic plants.
Pollination Ecology ofPedicularis palustrisL. (Scrophulariaceae) in North America
Authors: MACIOR LAZARUS WALTER
Published: February 2005

AbstractField collections and measurements of corolla tubes andBombustongues indicated thatPedicularis palustris, an early summer‐blooming plant on Ile aux Grues and Ile aux Oies in the St. Lawrence River, Canada, is pollinated nototribically by queens of four species of bumblebees foraging for nectar and sternotribically by three species ofBombusworkers scraping pollen from anthers concealed in the galea. Short‐tongued workers ofB. terricolasecured nectar by perforating the base of the corolla tube dorsally or ventrally and, in some cases, pollinated the flower while robbing nectar. The flowers are insect‐dependent for pollination and are almost exclusively bumblebee‐pollinated. Sugar concentration of nectar, determined by refractometry, ranged from 8.0% to 19.5% (mean = 13.9%), and fructose and sucrose components of nectar samples from North America and the Netherlands were detected by thin‐layer chromatography. Excavated roots ofPedicularis palustrisconfirmed its root‐hemiparasitism. Parallel pollination studies were carried out onHypericum perforatumandVicia craccaon the mainland in the same area which bloomed later thanPedicularisand were pollinated primarily byBombusworkers. Predominance of queen pollinators onPedicularisand worker foragers onHypericumandViciaand analysis of corbicular pollen loads of foragers suggest a phenological relationship betweenPedicularis palustrisand the annual reproductive cycle of its bumblebee pollinators previously derived from investigations of other North American and Japanese species.
Afterripening Pattern during Cold Stratification of Achenes of Ten Perennial Asteraceae from Eastern North America, and Evolutionary Implication
Authors: BASKIN CAROL C. , BASKIN JERRY M. , LECK MARY A.
Published: February 2005

Abstract At 0‐ to 12‐week intervals, imbibed achenes of ten perennial Asteraceae from eastern North America were removed from 5°C (cold stratification) and tested for germination over a range of daily thermoperiods. The objective was to determine changes in the temperature requirements for germination as achenes came out of dormancy (after‐ripened). In Eupatorium fistulosum, Helenium autumnale, Kuhnia eupatorioides, Mikania scandens, Ratibida pinnata, Solidago altissima and Verbesina alternifolia, the minimum temperature for germination decreased during afterripening (Type 2 response), and in Aster divaricatus, Echinacea simulata and E. tennesseensis the minimum and maximum temperatures decreased and increased, respectively (Type 3 response). The majority of the 32 species of Asteraceae whose afterripening pattern has been investigated have a Type 2 response, and the family is one of many in eastern North America with species that have Type 2. We hypothesize that the ancestors giving rise to species with Type 2 were species with (1) nondormant seeds that required high temperatures for germination, or (2) dormant seeds that afterripened during warm (dry) winters and germinated only at high temperatures.
Enzyme Electrophoretic Evidence for Diploidy in Japanese Woodwardia japonica (L.f.) Sm. (Blechnaceae, Pteridophyte) with 2n= 68
Authors: TAKAMIYA MASAYUKI , YAMAGUCHI SHUJI , NOKITA HIROYUKI , ONO KANJI
Published: February 2005

Abstract Enzyme‐electrophoretic variation was examined in sporophytes of Woodwardia japonica (2n= 68) and segregation was examined in gametophytes. Despite the high chromosome number, W. japonica displayed disomic segregation of isoenzyme patterns. This and karyotype analyses indicate that W. japonica is a diploid derived from a base number of either x= 17 or x= 34.
Increased Reproductive Allocation of Rumex japonicus Caused by Leaf Clipping
Authors: SUZUKI NOBUHIKO
Published: February 2005

Abstract To elucidate the effects of herbivory by chrysomelid beetles on Rumex japonicus, rosette leaves were clipped and the subsequent fruit production and root growth were observed. The increase of leaf biomass of some clipped plants was greater than that of control plants, although this varied among individual plants. The root growth of clipped plants was less than that of control plants. Fruit production increased with plant size, and there was no difference in fruit production between clipped and control plants. Reproductive allocation (fruit biomass, relative to fruit biomass plus root growth) increased with plant size; it was greater in clipped plants than in control ones. Based on these results, reproductive allocation strategy against herbivory was discussed.
Population Structure and Reproductive Biology of Saururus cernuus L. (Saururaceae)
Authors: THIEN LEONARD B. , ELLGAARD ERIK G. , DEVALL MARGARET S. , ELLGAARD SARA E. , RAMP PAUL F.
Published: February 2005

Abstract The population structure and reproductive biology of Saururus cernuus (Lizard's Tail; Saururaceae; Piperales), is documented in five sites in southern Louisiana (Mississippi Delta). The species is common throughout the southeastern United States in marshes, along streams, edges of lakes, and in the understory of moist forests. The clonal species exhibits sexual and vegetative reproduction. Wind and insects both play important roles in pollination. Pollen may be borne by insects directly. Alternatively, the pollen may be borne by wind after its release is triggered from pendulous floral spikes (the “Lizard's Tail”) by either wind or insect landings (insect‐mediated wind pollination). The plants are self‐incompatible and seed set results from a combination of pollination modes with wind pollination being the primary mode (rare in the Magnoliidae). Inflorescence and floral structure exhibit adaptive features that facilitate the various modes of pollen transfer, viz., numerous, small scented, protogynous flowers with no perianth, ultraviolet patterns produced by stamen filaments, small pollen grains, curved inflorescences, and exerted stamens, etc. Fruit production and seed germination are documented and plant growth and densities are compared in sunny versus forest sites.
Pollinator Restriction in the Narrow‐tube Flower Type of Mertensia ciliata (James) G. Don (Boraginaceae)
Authors: SUZUKI KAZUO
Published: February 2005

Abstract Mertensia ciliata (Boraginaceae) includes two flower types with different corolla tube widths, wide and narrow. The former is pollinated by both queens and worker bumblebees, while the latter type is pollinated exclusively by bumblebee workers. Morphological comparisons between the flowers and the bumblebees showed that the relationship between the width of the corolla tube mouth and the head width of the bumblebee is a primary factor restricting pollinators to workers in the narrow‐tube type. Length of the proboscides and corolla tube are of secondary importance for this restriction, since some queens are not able to reach the bottom of a narrow corolla tube even if their proboscis is extended fully.
Effects of Different Photoperiods and Chilling Treatments on Growth and Reproduction of Cardamine flexuosa With. and Its Ecological Implications
Authors: ISHIGURI YOSHIO , KUDOH HIROSHI , KAWANO SHOICHI
Published: February 2005

Abstract Phenotypic variability of Cardamine flexuosa (Cruciferae) was examined in response to different lengths of exposure to low temperature (5°C) at the juvenile stage, and to two photoperiod regimes (8 and 16 hrs day‐lengths) in the subsequent growth period. The results indicated that this species had a facultative chilling or long‐day requirement for flowering. The long‐day and chilling treatments both caused an earlier onset of stem internode elongation. Longer chilling treatments reduced the number of nodes and increased internode length under both long and short photoperiod regimes. Prolonged chilling treatments followed by long‐day photoperiod remarkably induced more numerous basal branches and inflorescences, as a result producing more siliques. Remarkable rosette leaves Were formed at the base of the main stem when partial chilling and the short‐day treatment suppressed stem internode elongation. The responses to chilling and long‐day treatment closely resembled the synchronized flowering of this species in spring in the field. Delayed flowering under the short‐day treatment resembled size‐ or age‐dependent flowering in late summer to autumn in the field populations.
Bumblebee Pollination of Melampyrum ciliare (Scrophulariaceae)
Authors: KOJIMA JUN‐ICHI , HORI YOSHIMICHI
Published: February 2005

Abstract Melampyrum ciliare has tubular flowers predominantly visited by Bombus diversus. Floral structure (including the positions of anthers and stigma) and structure of the distal part of the corolla indicate cross‐pollination by bumblebees. In M. ciliare, young flowers with white spots on the labium, which disappeared with flower aging, produced larger amounts of nectar than older ones without spots. Bumblebees visited flowers with white spots significantly more frequently than would be expected if they chose flowers randomly. These findings and the high seed production of open‐pollinated flowers suggest effective pollination of M. ciliare by bumblebees.
6‐Phosphogluconate Dehydrogenase (6PGD) Gene Duplication in Kalimeris (Asteraceae)
Authors: NISHINO TAKAKO , MORITA TATSUYOSHI
Published: February 2005

Abstract The genus Kalimeris with a diagnostic character of short or inconspicuous pappus consists of two sections, Asteromoea and Cordifolium. As a result of 6PGD isozyme analysis, sect, Asteromoea, including 2 × and poly‐ploid taxa from 5 × to 8 ×, show similar cytosolic isozyme multiplicity and share a monomorphic locus. The data suggest that gene duplication of polyploid members was derived from a common ancestor. K. miqueliana, belonging to sect. Cordifolium. also possessed a gene duplication in 6PGD, though significant differences were detected in electrophoretic mobility between the sections. The occurrence of gene duplication in East Asian diploid Astereae leaves intact the validity of the allopolyploid‐origin hypothesis of n= 9, which was rejected by Gottlieb (1981a) in American Astereae.
Pollen‐Foraging Dynamics of Subalpine Bumblebees (Bombus Latr.)
Authors: MACIOR LAZARUS WALTER
Published: February 2005

Abstract A 23‐year study on Mount Rainier of nectar‐foraging hummingbirds and pollen‐foraging bumblebees (Bom‐bus Latr.) indicated a constant relative frequency of Bombus species in the area and a wide occurrence of insect species on flowers plus a wide range of flower species pollinated by a single insect. Early‐blooming plants had a high queen/worker pollinator ratio, while workers predominated on later‐blooming plants. No altitudinal difference in distribution of Bombus species occurred. Analysis of 955 corbicular pollen loads from 1158 bumblebees collected yielded 49.5% monolecty for queens and 34.5% for workers with a wider range for queens than for workers. Colors of corollas photographed in visible and ultraviolet light corresponded to the visual spectra of animal pollinators. In the stable plant‐pollinator community investigated, pollinating insect activity appears phenologically controlled by floral anthesis and behaviorally related to floral form and function. Bumblebee tongue length, however. Is not a valid determinant for foraging niche separation except in Castilleja with a deep corolla tube accommodating long tongues of hummingbirds and bumblebees. It is concluded that in a biotic community well‐coordinated with the physical environment, limited flower constancy of pollen‐foraging pollinators appears to contribute a necessary degree of adaptive versatility through sharing of insect and floral resources. Flower constancy is primarily a function of the circumstance in which a pollinator operates and not simply a characteristic of the pollinator itself.
Why are Biennials so Few?: Hart's Results Revisited
Authors: BENDER MARTIN H. , BASKIN JERRY M.
Published: February 2005

Abstract Hart (1977) constructed a model to explain the rarity of biennials in the North American flora. However, Hart's model is inadequate, because: 1) biennials were not compared with annuals, 2) facultative biennials were not included, and 3) the range of general perennial life histories was not considered. Revision of Hart's model shows that strict and facultative biennials are rare, because they compete most successfully against annuals and general perennial life histories only in a narrow range of juvenile and adult survivorship values.
Life History Evolution in Amphicarpic Plants
Authors: CHEPLICK GREGORY P.
Published: February 2005

Abstract Plants with dimorphic flowers or seeds provide excellent material for the study of life history evolution because the dimorphism often involves measurable differences in morphology, size, number, or genetic relatedness. For amphicarpic plants, the proportion of aerial: subterranean morphs produced is highly variable (from 0 to > 100) and related to both environmental and genetic factors. Plants from aerial seeds produce lower ratios of aerial: subterranean morphs than those from subterranean seeds. Despite substantial variation, subterranean seeds are generally heavier than aerial seeds (but fewer) and produce vigorous seedlings with high survivorship and high fitness. Adaptive advantages of subterranean seeds include retention of offspring in favorable parental microhabitats, protection of seeds from herbivory, predation, or fire, and avoidance of desiccating conditions on the soil surface; potential disadvantages include lack of gene exchange, high energy costs, limited dispersal, and sibling competition. For the few species studied, aerial reproduction is more plastic than subterranean reproduction and more likely to be affected by environmental conditions.

Quantitative genetic analyses of a population of the annual grass Amphicarpum purshii have revealed lower heritabilites for subterranean relative to aerial reproductive traits. Subterranean seed number and mass show genetic correlations with shoot mass while aerial seed number and mass do not; seed set percentages of both seed types as well as percentage allocation to both reproductive morphs show negative genetic correlations with shoot mass. In this Amphicarpum population, directional selection on shoot mass may indirectly select for increased subterranean (but not aerial) seed output.
Ecological and Evolutionary Interactions between Wild Crucifers and Their Herbivorous Insects
Authors: YANO SHUICHI
Published: February 2005

Abstract Insects feeding on ten species of wild crucifer were investigated. Differences in host plant range and insect community structure were examined with regard to anti‐herbivore defense mechanisms. Most of the crucifer species deterred insect herbivory by disappearing in the summer or by lowering their intrinsic quality as food for insects. Species with these defense mechanisms were exploited by only a few specialized herbivorous insects that seemed to have counter defenses. The plants without these defense mechanisms were used by many herbivorous insect species. Rorippa indica lacked direct defenses, but supported a low total density of herbivore individuals. This crucifer has an indirect defense mechanism: ants attracted to floral nectar defended the plant from deleterious herbivores. Crucifers that disappeared seasonally lacked other anti‐herbivore defense mechanisms. This suggests that the phonological response is an alternative other responses to herbivore attack.
Endosymbiosis of Aphids with Microorganisms: a Model Case of Dynamic Endosymbiotic Evolution
Authors: FUKATSU TAKEMA
Published: February 2005

Abstract Almost all aphids harbor prokaryotic intracellular symbionts in the cytoplasm of mycetocytes, huge cells in the abdomen specialized for this purpose. The aphids and their intracellular symbionts are in close mutualistic association and unable to live without their partner. The intracellular symbionts of various aphids are of a single origin; they are descendants of a prokaryote that was acquired by the common ancestor of the present aphids. The date of establishment of the symbiotic association is estimated to be 160–280 million years ago using 16S rRNA molecular clock calibrated by aphid fossils. Molecular phylogeny indicates that the intracellular symbiont belongs to a group of gut bacteria, suggesting the possibility that it was derived from a gut microbe of aphids. While the in‐tracellular symbionts are universal and highly conserved amongst aphids, other types of symbiotic microorganisms are also present. In various aphids, bacterial “secondary” intracellular symbionts are found in addition to the standard symbionts. They are thought to be acquired many times in various lineages independently. Some Cerataphidini aphids do not have intracellular symbiotic system but harbor yeast‐like extracellular symbionts in the hemocoel. In a lineage of this group, symbiont replacement from intracellular prokaryote to extracellular yeast must have occurred. The diversity of the endosymbiotic system of aphids illuminates a dynamic aspect of endosymbiotic evolution.
Plant‐Herbivore Interactions and Theory of Coevolution1
Authors: MATSUDA HIROYUKI , ABRAMS PETER
Published: February 2005

Abstract We consider a mathematical model for the coevolution of a plant's defense against herbivores and the herbivore's ability to exploit the plant. The result of coevolution is predicted using the phase portrait of trait value dynamics and contour plots of fitnesses. The following results are derived: (1) The fitnesses of both plant and herbivore are higher at an “armless” state in which both plant and herbivore invest a minimum amount of energy and/or resources in defense and feeding respectively, than at the coevolutionarily stable state (CSS); (2) Perpetual increase in the trait values of both species may occur when the marginal costs of defense and feeding abilities decrease as these abilities increase; (3) If the marginal costs of defense and feeding abilities increase as the abilities increase, there is a coevolutionary equilibrium with finite trait values; (4) There may be more than one coevolutionarily stable state (CSS).
Molecular Phylogeny and Coevolution
Authors: YOKOYAMA JUN
Published: February 2005

AbstractRecent advances in molecular phylogenetic estimation in diverse organisms have improved our understanding of coevolution. From the phylogenies of interacting organisms, we can interpret the evolution of adaptive characters, and the history of interaction. Molecular approaches are generally more informative than these based solely on phenotypic characters. Molecular genetic method can be applied to organisms that have only simple morphological features and can be used for comparisons at any taxonomic level. Estimation of divergence time is also possible but still difficult because evolutionary rates of macromolecules are not always constant and suitable fossil records are often not available for calibrating rates of change. Here I review recent progress in the application of molecular techniques to the interpretation of coevolutionary relationships.
Importance of Queen Bumble Bees as Pollinators Facilitating Inter‐morph Crossing inPrimula sieboldii
Authors: WASHITAN IZUMI , KATO MAKOTO , NISHIHIRO JUN , SUZUKI KAZUO
Published: February 2005

AbstractFlower‐visiting insects, the distribution of pollen on an insect's body, and fruit and seed sets ofPrimula sieboldiiE. Morren were investigated in a maritime deciduous forest habitat of the Hidaka region in Hokkaido. Queens ofBombus diversus tersatusSmith (Hymenoptera: Apidae),Bombus schrencki albidopleuralisSkorikov, andBombus deuteronymus deuteronymusSchulz were observed to visit the flowers of the species. Bumblebee claw marks were found on the flower petals of 68% of the flowering ramets of the species. Scanning‐electronmicroscopy revealed that pin and thrum pollens ofP. sieboldiiwere deposited in different positions along the proboscis of aB. diversus tersatusqueen (n=38400 grains). On the glossa, all the observed pollen was of the pin type, while more than half of the pollen grains observed on the upper part of the proboscis, galea, stipes, and maxillary palpus were of the thrum type. In the field, high fruit and seed sets were recorded for both pin and thrum morphs, indicating the occurrence of sufficient legitimate pollination during the flowering season. In addition to the effectiveness of queen bumblebees as pollinators forP. sieboldiisuggested in this study, phenological and morphological matches, i.e., early spring flowering during the queen bee emergence season and the similar lengths of the corolla tube and the bee proboscis, also support the inference that queen bumble bees play an important role in legitimate pollination ofP. sieboldii.
Morphological Constraints of Shoot Demography of a Clonal Plant: Extra‐ and Intravaginal Tillers of Festuca rubra
Authors: HERBEN TOMÁŠ , KRAHULEC FRANTIŠEK , HADINCOVÁ VĚRA , KOVÁŘOVÁ MARCELA , SKÁLOVÁ HANA
Published: February 2005

Abstract Festuca rubra forms tillers in two different ways: extravaginally and intravaginally. Demography of these two tiller types was observed in seventeen selected tussocks of Festuca rubra s.s. over four growing seasons. Extravaginal tillers were bigger at birth and on the average produced twice as many daughter tillers per tiller. In general, the natality and mortality of extravaginal tillers were less regular than that of intravaginal tillers. Overall tillering rate per tiller was correlated with the density of the surrounding vegetation; mortality, natality and tiller life span were not. High density of the surrounding vegetation did not result in increased formation of extravaginal tillers. The proportion of the extravaginal tillers was not correlated with the density of the F. rubra tussocks. There is no evidence for foraging by extravaginal tillers, but they do act as founders of small clusters of tillers.
Contrasting Demographic Characteristics of Seeds and Vegetative Propagules in an Understory Herb Syneilesis palmata (Compositae)
Authors: NISHITNI SATOMI , KIMURA MAKOTO
Published: February 2005

Abstract Quantitative comparisons between seeds and vegetative propagules of Syneilesis palmata (Compositae) were conducted for size and size‐related demographic parameters mainly in two populations in a plantation forest (forest interior and edge). Seeds were smaller than vegetative propagules and their size range was relatively small (0.8–5.7 mg). The number of vegetative propagules per mother plant was relatively constant (about two) and their size range was relatively large (the range was 0.009–8.95 g). The length of the pre‐reproductive period was size‐dependent. Plants from seeds required about 7 years to become fertile, while large vegetative propagules (> 1.38 g) became fertile in the growing season following their birth. The probability of survival from birth to fertile stage was also dependent on size. More than 85% of vegetative propagules larger than 0.8 g could survive to reproduction. Smaller vegetative propagules suffered higher mortality and only 0.0034% of seeds in the forest interior and 0.41% of those in the forest edge survived to reproduction. The decrease in the survival probability with decreasing offspring size was more conspicuous in smaller size and in the forest interior than in the forest edge. From these demographic characteristics we examined the adaptive significance of resource allocation to seeds and vegetative propagules in S. palmata.
Effects of Light Intensity on the Size Structure and Establishment of Diploids and Triploids of Disporum sessile
Authors: HORI YOSHIMICHI , YOKOI TOMOKO , YOKOI YOTA
Published: February 2005

Abstract The effects of light intensity on population growth rates (λ) of diploid and triploid experimental populations of Disporum sessile were examined by growth experiments varying light intensity and by using a projection matrix model. λ of the diploid population was shown to have greater dependence on light intensity. This parameter under good light conditions was higher than that of the triploid population, but less than that under conditions of shade. This was due to the differences in reproductive traits of both populations. Diploids produce many small daughter plantlets and seedlings, and triploids produce a few daughter plantlets. The difference in λ between the two populations should contribute to enlargement of the habitat of D. sessile.
Evolutionary Biology of Trillium and Related Genera (Trilliaceae) I. Restriction Site Mapping and Variation of Chloroplast DNA and its Systematic Implications
Authors: KATO HIDETOSHI , KAWANO SHOICHI , TERAUCHI RYOHEI , OHARA MASASHI , UTECH FREDERICK H.
Published: February 2005

Abstract A physical map of chloroplast DNA (cpDNA) was constructed for Trillium kamtschaticum using three restriction enzymes, Apal, Pstl and Xhol. The chloroplast genome is 154.5 kbp in size with each portion of the inverted repeat 26.5 kbp in length, separated by large (82.7 kbp) and small (18.8 kbp) single copy regions. The cpDNA of T. kamtschaticum is similar in structure to the cpDNAs of most angiosperms thus far studied. Chloroplast DNA variation in 25 taxa of Trillium was investigated using 14 restriction enzymes, with Paris tetraphylla as an outgroup. Phylogenetic analysis showed that sessile‐flowered species (subgenus Phyllantherum) form a monophyletic group. Pedicellate‐flowered species do not form a monophyletic group, and belong to at least three different groups. T. kamtschaticum, an East Asian diploid species, was found to be most closely related to a group of species from eastern North America.
Characterization and Evolution of a cDNA Encoding the Small Subunit of Ribulose‐ 1,5‐bisphosphate Carboxylase/ oxygenase (rbcS) ofStellaria longipes(Caryophyllaceae)
Authors: ZHANG XING‐HAI , MUHAMMAD NASREEN , CHINNAPPA C.C.
Published: February 2005

AbstractA cDNA clone encoding the small subunit of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (rbcS) of Stellaria longipes (family Caryophyllaceae) was isolated and sequenced. This cDNA was used as a probe to investigate the gene complexity and expression among different genotypes. Southern blot analysis showed that the S. longipes genome contained arbcS gene family. A higher level ofrbcS mRNA was detected in the genotype grown under the long‐day photoperiod and warm condition than under the short‐day photoperiod and cold condition, suggesting the effect of growth condition on the gene expression. Phylogenetic analysis of both the nucleotide and deduced amino acid sequences for both the signal peptide and the mature protein, showed that among ten families of higher plants tested (including four monocot, 14 dicot and one gymnosperm taxa), therbcS ofS. longipes, along with another member of CaryophyllaceaeSilene pratensis, was more closely related to the families Solanaceae, Brassicaceae and Fabaceae than it was to other plant families.
The Importance of Flowering Time and Flower Number in the Relative Fitness of Males and Hermaphrodites in Datisca glomerata (Datiscaceae)
Authors: SPENCER STANLEY C. , RIESEBERG LOREN H.
Published: February 2005

Abstract The persistence of male plants in androdioecious populations of Datisca glomerata requires a large theoretical increase in male fertility of male plants over hermaphrodites. Recent studies have supplied evidence that high outcrossing rates, inbreeding depression, and high male pollen production per flower contribute to increased male fitness in this species. We tested for the contribution of increased flower number and early flowering to a male fitness advantage. Flower number was not found to differ significantly among male and hermaphrodite siblings, but males flowered significantly earlier. Flowering time was influenced also by population and family of origin.