bluuebunny/crossref_metadata_2025 huggingface dataset:
Seeking a sound index of competitive intensity: Application to the study of biomass production under elevated CO2 along a nitrogen gradient
Authors: Navas Marie‐Laure , Garnier Eric , Austin Michael P. , Viaud Agnès , Gifford Roger M.
Published: March 2003

Abstract  The aim of this paper is to evaluate (i) the relevance of currently proposed measures of competitive intensity to elevated CO2 studies by means of an example analysis, hypothesizing that competitive intensity is increased under elevated CO2; and (ii) an alternative method for predicting species performance in mixtures from monocultures. Relative competition intensity (RCI), relative physiological performance and normalized ecological performance were used to characterize the competitive ability of two grasses (Danthonia richardsonii Cashmore, Phalaris aquatica L.) and two legumes (Lotus pedunculatus Cav., Trifolium repens L.) grown in monocultures and mixtures of the four species along a N gradient under conditions of ambient and elevated CO2. Relative competition intensity could not be used to predict competitive outcomes in mixtures under conditions of elevated CO2 because it failed to account for changes in the size of interspecific differences along the N gradient and between CO2 concentrations. Relative physiological performance and relative ecological performance were more useful for investigating biomass production in mixtures and to predict species performance in mixtures from their performance in monocultures. Both indices of relative performance showed an increase in competitive intensity under elevated CO2 conditions. They also showed a decrease in competitive intensity with increasing N supply over most of the range of N supply, but a reversal of that trend at high levels of N supply. The merits and utility of these relative performance indices for elevated CO2 are discussed.
Distribution of Phytophthora cinnamomi at different spatial scales: When can a negative result be considered positively?
Authors: Pryce Josephine , Edwards Will , Gadek Paul A.
Published: March 2003

Abstract  In October 1999, patches of dead and dying trees were identified in rainforest vegetation throughout the Tully Falls area in north Queensland, Australia. Previous incidents of patch death in the region had been attributed to Phytophthora cinnamomi. The distribution of P. cinnamomi was assessed by testing for its presence in seven sites displaying signs of dieback and seven sites that appeared healthy. Each site was a circular quadrat, 20‐m radius (total area = 1256.6 m2). Within each quadrat, two perpendicular line transects were constructed. A single soil sample (250 g) was taken at the centre point and at 1‐m intervals along each transect. All soil samples were tested for the presence of P. cinnamomi using a combination of lupin baiting, subsequent culturing and microscopic identification. Of the 1134 samples, 783 recorded positive responses. The mean number of positive responses was not significantly greater in patch death sites than in control sites, suggesting that at this scale of resolution the distribution of P. cinnamomi was uniform. However, at spatial scales of 1‐m intervals across transects the distribution of P. cinnamomi was random.
Adult aquatic insects: Potential contributors to riparian food webs in Australia's wet–dry tropics
Authors: Lynch Romeny J. , Bunn Stuart E. , Catterall Carla P.
Published: March 2003

Abstract  Changes in the abundance and biomass of aquatic and terrestrial aerial insects with distance (mid‐stream, 0, 10–15 and 160 m) from lowland streams were examined across the dry season landscape in Kakadu National Park, northern Australia. Malaise traps and sticky intercept traps were used to sample the insects at four streams, spaced over an area of 1650 km2. Malaise and intercept catches were dominated by Diptera (flies and midges), both numerically and by biomass. Chironomid midges were the most abundant taxon, making up 43.4 and 51.0% of the malaise and intercept trap catches, respectively. However, most chironomids were small (less than 3 mm body length), contributing 34.9% to intercept trap biomass, but only 5.2% in malaise traps. Ceratopogonid midges and caddisflies (Trichoptera) accounted for most of the remaining adult aquatic insects. Major terrestrial components were Diptera and Hymenoptera in malaise traps and Coleoptera and Diptera in intercept traps. The total abundance and biomass of insects were much greater over streams and along the water's edge than in riparian (10–15 m) and savanna (160 m) habitats primarily because of the presence of large numbers of adult aquatic insects. The abundance and biomass of terrestrial insects in malaise traps showed no relationship with distance, but intercept trap catches suggested slightly greater abundances over the water and at the water's edge. The great abundance of aquatic insects relative to terrestrial insects close to streams suggests that they have the potential to be an important component of the diets of riparian insectivores, and predation may be an important pathway by which aquatic nutrients and energy are moved into terrestrial food webs.
Trophic trickles rather than cascades: Conditional top‐down and bottom‐up dynamics in an Australian chenopod shrubland
Authors: Dawes‐Gromadzki Tracy Z.
Published: March 2003

Abstract Despite continued interest in the relative roles of top‐down (predation) and bottom‐up (productivity) factors in structuring ecological communities, there have been few studies of diverse terrestrial arthropod systems. Top‐down theory predicts that decreased predator populations will result in increased herbivore populations and reduced plant populations. Bottom‐up theory predicts that a positive producer level response to nutrients will support greater herbivore and predator populations. Few studies simultaneously examine both theories. In the present study, the roles of predators and nutrients in structuring an Australian chenopod shrubland community were investigated, by using a complete 2 × 2 factorial design with three replicated plots with and without nutrients (fertilizer) and predators (two wolf spiders and two ants). Producer and major arthropod taxa responses, predator densities and soil nutrient levels were monitored from April 1996 to February 1998. In agreement with bottom‐up theory, the abundances of some plants and herbivores increased with the addition of nutrients, but most effects varied temporally and did not increase the abundances of any predator taxa. The effects of predator removal propagated down the food web to influence some herbivore and producer taxa but, in contrast to top‐down theory, effects were temporally dependent and varied in the direction of response within each trophic level. Predators and nutrients only interacted significantly to determine the abundance of one taxon. The findings suggest that true trophic cascades are not a primary determinant of chenopod community structure, with ‘conditional trophic trickles’ a better descriptor for the effects of predators and nutrients on this community. It is suggested that the expression of top‐down and bottom‐up effects is conditional on appropriate timing and extent of rainfall. The results provide further support for the theory that food webs are more complex in terrestrial than in aquatic systems, with abiotic and biotic heterogeneity, intraguild interactions and non‐consumptive interactions between adjacent trophic levels all confounding the classic consumptive interactions that are required for the expression of top‐down and bottom‐up forces.
Spatial ecology of arboreal snakes (Hoplocephalus stephensii, Elapidae) in an eastern Australian forest
Authors: Fitzgerald M. , Shine R. , Lemckert F.
Published: March 2003

Abstract  Stephens' Banded Snakes (Hoplocephalus stephensii Krefft 1869) are large (to 1 m), highly arboreal elapid snakes, restricted to mesic forested areas along the eastern coast of Australia. Radiotelemetric monitoring of 16 individuals at Whian Whian State Forest in north‐eastern New South Wales over 25 months provided the first data on spatial ecology of this threatened taxon. Two major influences on movements by Stephens' Banded Snakes were identified: the distribution of large hollow‐bearing trees, and the avoidance of conspecifics. Radiotracked snakes were sedentary inside tree hollows for extended periods (mean = 8 days) during their active season, interrupted by occasional long (mean = 124 m) nocturnal movements to another shelter tree. Snakes travelled on the ground rather than within the canopy, and thus were potentially exposed to terrestrial predators. Although the home ranges of the radiotracked snakes overlapped substantially (mean = 27%), simultaneous occupancy of ‘shared’ shelter trees was less common than expected by chance. Hence, we conclude that adult Stephens' Banded Snakes generally avoid the presence of conspecifics. Snakes used from five to 30 shelter trees and home ranges of male snakes were larger than those of females (mean = 20.2 vs 5.4 ha). The large spatial scale of these movements, and limited overlap among individuals, means that a viable population of this taxon requires a large area of contiguous forest. This requirement may explain why the species has not persisted in small forest fragments.
Ecological consequences of altered hydrological regimes in fragmented ecosystems in southern Australia: Impacts and possible management responses
Authors: Cramer Viki A. , Hobbs Richard J.
Published: March 2003

Abstract  Although the potential impacts of rising water tables and secondary salinization on agricultural land in southern Australia have been recognized for some time, it is only recently that the impacts on native vegetation have been considered. Despite the likely extent and severity of the problem, no comprehensive approach to assessing the impact of salinity upon native vegetation has been attempted to date. In the present paper, we discuss the causes and impacts of rising water tables and dryland salinity, assess the levels of risk in different ecosystem types and consider the possibilities for the maintenance of biodiversity and ecosystem function in vegetation at risk. We examine the salinity risk to woodland vegetation in the Western Australian (WA) wheatbelt, and consider both broad‐scale context and finer‐scale variation within individual patches of vegetation. From this information, we develop a set of conceptual models of the potential impacts of shallow saline water tables on ecosystem structure and processes in remnant vegetation in agricultural areas, particularly in the WA wheatbelt. First, we suggest that fine‐scale variability in surface topography and soil characteristics may play an important role in limiting the impacts of rising saline water tables. The outcome will depend on the interaction of the heterogeneity of the impact, species distribution in relation to small‐scale environmental heterogeneity and variation in species response to hydrological change. Second, we suggest that shallow saline water tables can be considered to cause an ‘edge effect’, which moves inwards from the edge of remnants of native vegetation. Finally, we consider how saline surface flows exacerbate the effects of shallow saline water tables and hasten vegetation decline in remnant areas. We put these models forward as hypotheses to be tested in different situations. We contrast the situation of secondary salinization in Australian vegetation with that of naturally saline systems in Australia and elsewhere, and suggest that these systems may provide important signposts toward developing management approaches for vegetation at risk. In conclusion, we consider the need to set priorities for the protection and restoration of natural vegetation at risk from altered hydrology, based on an assessment of relative threat and probability of persistence or recovery. We highlight the urgency for action that protects native vegetation from the increasing risks of rising water tables.
Dispersal for distance? Acacia ligulata seeds and meat ants Iridomyrmex viridiaeneus
Authors: Whitney Kenneth D.
Published: March 2003

Abstract  Ant seed dispersal distances are typically small, averaging less than 1 m in published studies. Here, a new record (180 m) for ant seed dispersal distance is reported, and preliminary observations are made on the interaction between meat ants Iridomyrmex viridiaeneus Viehmeyer (Hymenoptera: Formicidae) and diaspores of the sandhill wattle, Acacia ligulata A. Cunn. ex Benth. (Fabaceae) in Kinchega National Park, New South Wales (NSW), Australia. Iridomyrmex viridiaeneus moved diaspores over distances of 7–180 m (mean 93.9 m) from the source trees to their nests, removed the arils underground and discarded the seeds over a 3000‐m2 area surrounding the nest. A germination trial determined that the viability of discarded seeds was 40%, with 80% of the viable seeds in a dormant condition. Although the cumulative effects of I. viridiaeneus on A. ligulata recruitment require further investigation, this study and others raise the possibility that myrmecochorous systems in the Australian arid zone may be characterized by longer dispersal distances than those in other parts of the world. Long‐distance seed movement by ants lends credence to the hypothesis that distance dispersal (in contrast to directed dispersal) could be of benefit to myrmecochorous plants.
Influence of weather conditions on activity of tropical snakes
Authors: Brown G. P. , Shine R.
Published: March 2003

Abstract  There are many anecdotal reports of massive day‐to‐day variation in activity levels of tropical reptiles and amphibians, and intuition suggests that weather conditions may be responsible for much of that variation. Our analysis of a large data set on the activity levels of tropical snakes and frogs confirms the existence of this short‐term variation in activity levels, reveals strong synchrony between sympatric taxa in this respect, but also shows that standard weather variables (temperature, humidity, precipitation, moonlight, atmospheric pressure) are surprisingly poor at predicting the numbers of individuals and species encountered during standardized surveys. We recorded the numbers of snakes and prey taxa (frogs) encountered on 349 nights over the course of one year on a 1.3‐km transect in the Adelaide River floodplain, in the wet–dry tropics of Australia. Frogs, water pythons (Liasis fuscus), slatey‐grey snakes (Stegonotus cucullatus) and keelbacks (Tropidonophis mairii) all showed strongly seasonal patterns of activity. After adjusting for seasonal differences, encounter rates were related to climatic conditions but different taxa responded to different weather variables. Water python activity was related to amount of moonlight, keelback activity was related to temperature, and frog activity was related to relative humidity, rainfall, temperature and moonlight. However, weather variables explained relatively little of the variation in activity levels. Strong synchrony was evident among encounter rates with various taxa (independent of season and weather conditions), suggesting that activity levels may be determined by other unmeasured factors.
Invasion of exotic plants in nutrient‐enriched urban bushland
Authors: King Scott A. , Buckney Rod T.
Published: March 2003

Abstract  Invasion of exotic plants into vegetation communities on low‐nutrient soils in Sydney is often attributed to increased phosphorus in the soil. However, the composition of native vegetation in nearby national parks has been found to be more closely correlated to combinations of soil nutrients and other environmental variables than phosphorus alone. This study examined whether phosphorus or a range of variables better matched patterns of native and exotic plants in urban bushland. Sites in urban bushland and national parks were sampled, vegetation frequency recorded and soil samples collected. Soil samples were analysed for a range of chemical and physical attributes. A significantly greater number of exotic species were found at the urban sites, and significantly fewer native species than in the national parks. All measured soil nutrients were found to be of a significantly increased concentration in urban soil. Using regression analysis, an index of all measured soil nutrients was found to explain more of the variation in the percentage of exotic species at a site than phosphorus alone. Multivariate analysis showed a gradient of sites from minimal exotic invasion to heavy invasion. However, this gradient also corresponded to changes in native species. The gradient was found to match that of increasing soil nutrient levels. A combination of soil nutrients was found to correlate better with the multivariate species composition than was phosphorus alone. The results suggest that it is the increase of many soil nutrients, not phosphorus alone, that is contributing to the invasion of urban bushland by exotic plants and the alteration of the suite of native species.
Effects of phosphorus on growth and competitive interactions of native and introduced species found in White Box woodlands
Authors: Allcock Kimberly G.
Published: March 2003

Abstract  White Box (Eucalyptus albens Benth.) woodlands are among Australia's most endangered ecosystems and are threatened by exotic species invasion. There is evidence from other Australian communities that phosphorus enrichment can facilitate invasion, and differential growth of native and exotic species under increased phosphorus is a possible mechanism. Two glasshouse experiments were designed to test the following three questions relating to species responses to phosphorus: (i) do exotic and native species have different patterns of growth along a gradient of increasing phosphorus?; (ii) do exotic species have a greater competitive effect on native species than do conspecifics?; (iii) does phosphorus enrichment compound the competitive effect of exotic species on native species? Four native perennial species (Themeda australis (R. Br.) Staph., Bothriochloa macra (Steud.) S. T. Blake, Austrodanthonia racemosa (R. Br.) H. P. Linder and Eucalyptus albens) and two exotic annual species (Vulpia bromoides (L) Gray and Echium plantagineum L) were used. In the first experiment, plants were grown individually under six levels of soil phosphorus ranging from 0 to 60 p.p.m. In the second experiment, individuals of Eucalyptus albens and B. macra were grown alone, with a conspecific competitor, or with an exotic (V. bromoides or Echium plantagineum) competitor under low (10 p.p.m.) and high (100 p.p.m.) phosphorus. Both exotic species showed a greater positive response to increased phosphorus than the native species in experiment 1, and Eucalyptus albens seedlings grown with Echium plantagineum were significantly smaller than individuals grown alone or with Eucalyptus albens in experiment 2. There was no evidence that high phosphorus increased the competitive effect of the exotic species, but the combination of a strong positive response to phosphorus and a strong effect on growth of a native species indicates that phosphorus enrichment could favour exotic species in woodland remnants and that field studies testing the effect of phosphorus in a broader context would be appropriate.
Correlations between leaf constituent levels and the densities of herbivorous insect guilds in an Australian forest
Authors: Peeters Paula J.
Published: March 2003

Abstract  Significant correlations were found between herbivorous insect densities and leaf constituent levels across 18 species of understorey shrub in an Australian forest. In general, insect densities were positively correlated with nitrogen and water and negatively correlated with fibre and its constituents (cellulose and lignin), but not all insect guilds were significantly correlated with all leaf constituents. When mature leaf traits were considered, total herbivore density among plant species was most strongly correlated with levels of nitrogen and water. However, when insects were divided into functional guilds, only densities of sucking insects were significantly correlated with mature leaf nitrogen and water, whereas chewing insect densities were significantly correlated with mature leaf fibre and lignin. Low leaf nitrogen levels were recorded for all plants surveyed (among the lowest reported for woody angiosperms), and many plant species also had high levels of leaf fibre. These features are characteristic of Australian forests and have been linked to the generally nutrient‐poor soils of this continent. Levels of new leaf nitrogen (% fresh weight) were generally less than or equal to levels of mature leaf nitrogen (% fresh weight). Hence the new leaf preference of several herbivore guilds could not be explained by higher levels of leaf nitrogen. However, significant negative correlations were found between chewer densities and levels of leaf fibre, cellulose and lignin for new and mature leaves, suggesting that higher levels of fibre, cellulose and lignin in mature leaves may be contributing more strongly to the new leaf preference of chewers than leaf nitrogen levels. Despite the significant correlations between leaf constituent levels and the densities of individual guilds, multivariate analyses found no significant relationship between leaf constituent levels and the taxonomic or guild composition of herbivorous insect assemblages.
Short and chubby or long and slim? Food intake, growth and body condition in free‐ranging pythons
Authors: Madsen Thomas , Shine Richard
Published: March 2003

Abstract  An animal's sex and body size can influence not only its rate of food consumption, but also the way in which it allocates the resultant energy among the competing demands of maintenance, growth, reproduction and storage. A 13‐year mark–recapture study of pythons (Liasis fuscus) in tropical Australia provides extensive data on these topics. Rates of food intake and growth were highest in small pythons, and decreased more rapidly with body size in males than in females. Allocation to storage (as measured by the snake's mass relative to its body length) showed a more complex pattern. Body condition was high at hatching, but dropped rapidly as energy was allocated to growth rather than storage. Condition then increased through juvenile life, was at a maximum close to maturation, and was higher in females than in conspecific males. Body condition thereafter decreased with increasing body length. These allocation ‘decisions’ reflect the relative advantages of growth versus energy storage at different body sizes. Hatchling snakes grow rapidly (and hence become thin) because greater body size enables the snake to ingest larger prey items. Adult females amass larger energy reserves than males, because they need reserves to produce the clutch. Large snakes become thinner because their feeding rates are low, and they cannot compensate with increased prey size because large‐bodied mammalian prey are rare in our study area.
Of rowing boats, ocean liners and tests of the anova homogeneity of variance assumption
Authors: McGuinness Keith A.
Published: March 2003

Abstract  One of the assumptions of analysis of variance (anova) is that the variances of the groups being compared are approximately equal. This assumption is routinely checked before doing an analysis, although some workers consider anova robust and do not bother and others avoid parametric procedures entirely. Two of the more commonly used heterogeneity tests are Bartlett's and Cochran's, although, as for most of these tests, they may well be more sensitive to violations of the anova assumptions than is anova itself. Simulations were used to examine how well these two tests protected anova against the problems created by variance heterogeneity. Although Cochran's test performed a little better than Bartlett's, both tests performed poorly, frequently disallowing perfectly valid analyses. Recommendations are made about how to proceed, given these results.
Melbourne Vascular Surgical Association audit
Authors: Beiles C. Barry ,   the Melbourne Vascular Surgical Association Audit Committee
Published: March 2003

Background:  The formation of the Melbourne Vascular Surgical Association has led to the establishment of a vascular surgical audit programme that commenced in January 1999. This has allowed establishment of a benchmark for quality assurance in vascular surgery in Australia.

Methods:  A consultative process allowed widespread adoption of the audit across all public hospital vascular units in Melbourne and the two largest regional centres in Victoria. Data were collected at two points during admission: at operation and at discharge. Risk stratification, using logistic regression and risk‐adjusted ratios for adverse events was assessed for comparison of outcomes between units for the first 3 years of data collection. There is regular contact with all participants for data feedback and quality control.

Results:  The standard of vascular surgery across Victoria is consistent, and there has been excellent compliance by all academic vascular units. Private practice data are less complete, and only half of the vascular surgeons have participated.

Conclusions:  A statewide audit process is feasible and viable. Coordination by the Melbourne Vascular Surgical Association is crucial for its continued success.
Predation on the slug Deroceras reticulatum by the carabid beetles Pterostichus madidus and Nebria brevicollis in the presence of alternative prey
Authors: Mair J. , Port G. R.
Published: March 2003

1 Slugs are important pests in many agricultural crops and potential biological control agents are being studied as an alternative to molluscicides. Carabid beetles may be able to reduce slug populations, but their role as control agents may be influenced by the presence of alternative prey.

2 Attacks on the pest slug Deroceras reticulatum (Müller) by the carabid beetles Pterostichus madidus (Fabricius) and Nebria brevicollis (Fabricius) were investigated in the presence of alternative prey (earthworms and Calliphora fly larvae). Consumption of slug eggs and aphids was also investigated.

3 All five prey types were consumed to varying degrees during the experiments. Both beetle species showed a significant preference for Calliphora larvae over slugs. Pterostichus madidus showed a significant preference for earthworms over slugs. No preference was shown between earthworms or Calliphora larvae by P. madidus females or N. brevicollis. However, P. madidus males showed a significant preference for Calliphora larvae over worms. Pterostichus madidus showed no preference between slug eggs and aphids; N. brevicollis showed a significant preference for aphids over slug eggs.

4 The results from this study indicate that generalist beetles will often attack other prey in preferences to adult slugs. Slugs may not be preferred because of their mucus. Other prey items occur frequently in arable soils and generalist carabids may ignore slugs altogether and may only feed on them when slug density is high or other prey are unavailable.
Survival, longevity and fecundity of overwintering Mesoplatys ochroptera Stål (Coleoptera: Chrysomelidae) defoliating Sesbania sesban (Leguminosae) and implications for its management in southern Africa
Authors: Sileshi G. , Kenis M.
Published: March 2003

1 The defoliator beetle, Mesoplatys ochroptera Stål, is a serious pest of the legume tree sesbania (Sesbania sesban (L.) Merrill) in agroforestry systems in southern Africa. The survival of the overwintering stage of M. ochroptera and post‐ emergence longevity and fecundity of adults in sesbania fallows in eastern Zambia were quantified.

2 Only adult M. ochroptera survived during the winter (May–August) and the dry season (September–October) hidden under weeds, plant litter, in soil cracks and under rocks. During these periods, some beetles were occasionally found feeding on S. sesban, particularly in natural stands in humid areas. The adults were parasitized by the braconid Perilitus larvicida van Achterberg at a rate of 8.5–16.4%. The beetles stayed in the winter refuges for up to 210 days and emerged with the first heavy rains in October–November. The effective survival of beetles overwintering in an insectary was 18.1% in 1998 and 37.7% in 1999, and that of beetles overwintering in the field was estimated at 0.4 and 2.8% in 1998 and 1999, respectively.

3 The post‐emergence longevity and oviposition period of females in the insectary was 14–31 days and 5–29 days, respectively. The post‐emergence fecundity varied from 87 to 783.

4 It is concluded that the serious M. ochroptera infestation observed every year following the rains is due to synchronous emergence of overwintered resident adult populations and their high capacity for reproduction on many species of Sesbania. Recommendations for pest management in sesbania planted‐fallows are given.
Response of natural populations of predators and parasitoids to artificially induced volatile emissions in maize plants (Zea mays L.)
Authors: Bernasconi Ockroy Marco L. , Turlings Ted C. J. , Edwards Peter J. , Fritzsche‐Hoballah Maria Elena , Ambrosetti Lara , Bassetti Paolo , Dorn Silvia
Published: March 2003

1 In response to herbivore attack, maize plants (Zea mays L.) emit a specific blend of induced volatiles. Artificial damage and subsequent treatment of the damaged site with caterpillar regurgitant induces the same response. The induced volatile chemicals are known to be highly attractive to several parasitoids of herbivores in laboratory bioassays, but very limited information is available on how the plant odours affect entomophagous insects in the field.

2 Experiments were conducted to determine if induced maize volatiles attract parasitic and predatory insects under field conditions and whether they affect their spatial distribution.

3 In a preliminary field experiment with blue sticky traps near treated (damaged and treated with caterpillar regurgitant) and healthy plants, more entomophagous insects (total number of parasitic Hymenoptera, Anthocoridae and Syrphidae) were trapped near treated plants than near healthy plants.

4 In a second experiment, attraction to the induced volatiles was monitored with sticky traps placed next to treated and healthy maize plants in a regular maize field. No significant differences between the two treatments were found, but significantly more insects (parasitic wasps, thrips and anthocorid bugs) were trapped near to the top of plants than on traps placed near the mid‐stem. Displacement of these insect groups within the field seemed to occur principally over the canopy, but under severe weather conditions they travelled lower in the canopy.

5 In a third experiment, the effect of induced maize odours on the spatial distribution of predators and parasitoids was investigated by placing sticky traps at different distances from healthy and treated plants. The higher catches of parasitoids near treated plants and the increased presence of these insects on the downwind side of treated plants support the notion that herbivore‐induced maize odours attract natural enemies of maize pests in the field.
Response of the pine engraver, Ips pini (Say) (Coleoptera: Scolytidae), to conophthorin and other angiosperm bark volatiles in the avoidance of non‐hosts
Authors: Huber Dezene P. W. , Borden John H. , Stastny Michael
Published: March 2003

1 Seventeen non‐host angiosperm bark volatiles, seven of which are antennally active to Ips pini (Say), the pine engraver (PE), were tested for their ability to disrupt the response of the PE to pheromone‐baited traps.

2 Four green leaf volatiles (GLVs) were tested [1‐hexanol (Z)‐3‐hexen‐1‐ol, hexanal, and (E)‐2‐hexenal]. None had any disruptive effect singly, as a group or in all possible blends based on functional groups, despite the fact that the two aldehydes were antennally active. These compounds may have, in some instances, actually masked the disruptive effect of other compounds. The PE thus differs in its response from other Scolytidae, including other Ips spp.

3 Eight non‐host volatiles that were antennally active to other bark beetles, but not to PEs, had no disruptive effect, validating the use of coupled gas chromatographic‐electroantennographic detection analyses to detect compounds with potential behavioural activity.

4 The bicyclic spiroacetal conophthorin, (E)‐7‐methyl‐1,6‐dioxaspiro[4.5]decane, was disruptive when tested alone. When blends of two aldehydes [salicylaldehyde and nonanal] plus an alcohol and a phenol [benzyl alcohol and guaiacol] were combined with conophthorin, an enhanced disruptive effect was revealed. No single compound, other than conophthorin, disrupted the pheromone‐positive response and no blend that did not contain conophthorin was consistently disruptive to both sexes. Conophthorin seems to be a critical component in the non‐host angiosperm message for I. pini during its host selection phase.

5 Combination of the repellent synomones, verbenone and ipsenol, with the five disruptive non‐host volatiles may provide a potent treatment to protect trees, logs or stands from attack by the PE.
Effects of Elatobium abietinum on nutrient fluxes in Sitka spruce canopies receiving elevated nitrogen and sulphur deposition
Authors: Stadler Bernhard , Müller Thomas , Sheppard Lucy , Crossley Alan
Published: March 2003

1 In a field acid mist simulation experiment, Sitka spruce (Picea sitchensis) was sprayed with different pollutant treatments: N, NH4NO3; S, Na2SO4; NS Acid, NH4NO3 + H2SO4 and control, no spray. Treatment effects on the abundance of the green spruce aphid Elatobium abietinum and honeydew production were assessed. In addition, needles were sampled for phyllosphere micro‐organisms. In a manipulative experiment, shoots were established and maintained as with or without E. abietinum infestation in order to determine the effects of infestation on needle loss and throughfall nutrient fluxes.

2 Aphid numbers were highest during the end of May and early June, with almost twice as many needles infested in the NS Acid treatment compared with the other treatments. Honeydew production was not affected by the treatments.

3 On infested shoots, increasing numbers of yellowing and dead needles were recorded above the throughfall collectors as the season progressed. The numbers of dead needles falling into the collectors were significantly higher beneath infested shoots. There were strong positive correlations between aphid numbers above the throughfall collectors, the number of yellowing and dead needles on the shoots and the number of needles in the funnels of the throughfall collectors. Litter production was more affected by aphid number than by pollutant treatment.

4 Bacteria, yeasts and filamentous fungi were more prolific on infested needles and treatment effects on colony forming units (CFUs) were most pronounced in the NS Acid treatment.

5 Fluxes of inorganic nitrogen beneath infested shoots were generally lower than beneath uninfested shoots. This effect was more pronounced in those treatments that supplied N i.e. N, NS Acid. The combination of aphid infestation and N‐addition exerted the strongest influence on nutrient fluxes. The fluxes of potassium and of organic carbon (DOC) were higher beneath infested shoots in all treatments, through most of the survey period.
Using matrix models to explore the influence of temperature on population growth of arthropod pests
Authors: Bommarco Riccardo
Published: March 2003

1 Population growth of four arthropod pests on agricultural crops, the pea aphid, the bird‐cherry oat aphid, the Mediterranean fruit fly, and the two‐spotted spider mite, was modelled using stage matrix models.

2 Temperature was included as a variable in the model, affecting fecundity, mortality and growth rate. Linear temperature dependence was used to describe fecundity and individual growth rate in the matrix model. Life table data collected at various constant experimental temperatures were used to parameterize the model.

3 Sensitivity analysis identified the most influential demographic parameters determining the growth rate of the population at different temperature regimes. Mortality of young adults and immature stages were found to be the most important parameters in determining population growth for all species presented. However, high temperatures increased the relative impact of individual growth rates and fecundity on the growth of the population.
Mortality of second‐instar larvae of Tuta absoluta produced by the hexane extract of Lycopersicon hirsutum f. glabratum (PI 134417) leaves
Authors: Verçosa de Magalhães Sergio Tinôco , Jham Gulab N. , Picanço Marcelo C. , Magalhães Gouvan
Published: March 2003

1 The mortality resulting from exposure of second‐instar larvae of Tuta absoluta to a hexane extract of Lycopersicon hirsutum f. glabratum (PI 134417) leaves was evaluated in the laboratory.

2 A crude hexane extract was fractionated on a silica gel column to produce 17 fractions. The toxicity of the fractions was evaluated on T. absoluta larvae at 2 and/or 6 mg/10 larvae/Petri dish along with a control.

3 Only two fractions, 4.50 and 10.18% of the total hexane extract, were found to result in very high mortality of second‐instar T. absoluta.

4 All the 17 fractions were analysed by capillary gas chromatography/mass spectrometry (GC/MS). The two most toxic fractions were virtually identical and contained mainly undeca‐2‐one (2‐UD) and trideca‐2‐one (2‐TD).

5 A third major sub‐fraction 13 (50.73% of the total hexane extract) was further fractionated on a silica gel column to obtain five additional sub‐fractions. The toxicity of all the five sub‐fractions was evaluated using second‐instar T. absoluta at 2 mg/10 larvae/Petri dish and also analysed by GC/MS. The most toxic sub‐fractions contained mostly 2‐UD and 2‐TD.

6 The results suggest that 2‐UD and 2‐TD could be related to resistance of L. hirsutum to T. absoluta.
Post hibernation dispersal of three leaf‐eating beetles (Coleoptera: Chrysomelidae) colonising cultivated willows and poplars
Authors: Sage Rufus B. , Fell David , Tucker Kenneth , Sotherton Nicolas W.
Published: March 2003

1 We studied the spring dispersal of three common chrysomelids, from overwintering habitats into cultivated willow and poplar coppices at four sites in southern England over 2 years.

2 Adult Galerucella lineola, Phratora vulgatissima and P. vitellinae overwintered under the bark of mature trees or in other niches that simulated this habitat, within a few hundred metres of the coppice plantation. Relatively few beetles remained in the coppice fields during the winter.

3 Phratora vitellinae at the poplar sites emerged several weeks later than G. lineola and P. vulgatissima at the willow sites, reflecting the later leafing of poplar compared to willow. For all species, dispersal was by flight, with most activity during warm periods. Dispersal continued for several weeks for the willow‐ feeding species but was shorter for P. vitellinae.

4 All three species initially colonized the edge of the coppice field. Typically, 80% or more of the beetles colonising a plantation were within 8 m of the edge. Both Phratora spp. accumulated in the plantation edge zone for several weeks before leaving this area and colonising the crop interior.

5 The patterns of dispersal and colonization identified by this study may facilitate chrysomelid management practices in infested short rotation coppice that avoid the need for insecticide applications over the entire plantation.

Keywords
Chrysomelidae, Galerucella lineola, Phratora vitellinae, Phratora vulgatissima, poplar, short rotation coppice, willow, winter dispersal.
Genetic variation in host susceptibility to attack by the mahogany shoot borer, Hypsipyla grandella (Zeller)
Authors: Newton A. C. , Watt A. D. , Lopez F. , Cornelius J. P. , Mesén J. F. , Corea E. A.
Published: March 2003

1 Attack by shoot borers (Hypsipyla grandella Zeller) is the main factor limiting the cultivation of Cedrela odorata and Swietenia macrophylla, two economically important members of the mahogany family. No viable methods of pest control are currently available. To assess for genetic variation in susceptibility to pest attack, a combined progeny/provenance test of C. odorata and a provenance test of S. macrophylla were established separately at CATIE, Turrialba, Costa Rica, and assessed intensively over an 84‐week period.

2 Variation in height growth between provenances was highly significant in both species, provenance means varying by a factor of 2.7 and 1.2 in C. odorata and S. macrophylla, respectively. Cedrela odorata also displayed provenance variation in foliar phenology, as 94.7% of the trees from a ‘wet zone’ provenance remained foliated, whereas > 35% of trees from three ‘dry zone’ provenances abscised their leaves during the dry season.

3 Both species displayed significant genetic variation in susceptibility to shoot borer attack. At the peak of attack during the second year of growth, the effect of provenance was highly significant in both species, the mean number of attacks per tree varying between 0.8–2.4 and 0.6–1.3 in different provenances of C. odorata and S. macrophylla, respectively. A provenance of C. odorata from San Carlos, Costa Rica, displayed consistently lower susceptibility to pest attack, being subjected to fewer attacks during the first year and demonstrating a higher mean height to first point of damage.

4 The nitrogen, total tannin and proanthocyanidin concentration of foliage varied significantly between C. odorata provenances: nitrogen concentration was significantly lower and tannin and proanthocyanidin contents were significantly higher in trees from the San Carlos provenance, Costa Rica. This study therefore suggests that proanthocyanidins may reduce susceptibility of C. odorata to H. grandella, at least during the early period of growth.

5 These results provide support for the development of plant resistance as a strategy for managing shoot borers. In particular, there may be scope for selecting for high foliar proanthocyanidin content and the ability to tolerate attack by vigorous apical growth.
Effects of previous defoliation on pine looper larval performance
Authors: Šmits Agnis , Larsson Stig
Published: March 2003

1 During outbreaks of the pine looper, Bupalus piniarius, its host, Pinus sylvestris, is severely defoliated. The larvae of this geometrid normally feed on mature needles. However, because trees are totally defoliated during outbreaks, the next generation is forced to feed on current‐year needles.

2 Bupalus piniarius larvae feeding on previously defoliated trees may show lower performance either because of induced resistance or because larvae have to feed on needles not normally fed upon (current instead of mature).

3 These hypotheses were tested in an experiment where larvae were reared on (i) shoots naturally defoliated the previous year, and thus, bearing only current‐year needles, (ii) non‐defoliated shoots where larvae had access only to current‐year needles, and (iii) control shoots with access to both current and mature needles.

4 There was no support for the induction hypothesis. Survival was lower on naturally defoliated shoots than on control shoots (81.3 vs. 90.9%), but survival was lower also on non‐defoliated shoots where larvae had access only to current‐year needles (78.8%). Data on larval feeding distribution showed a strong preference for mature needles.

5 Needle nitrogen concentration of current‐year needles was 38% higher on defoliated trees than on non‐defoliated trees.

6 It is concluded that defoliation affected larval performance primarily through the removal of the preferred type of needles and not because of an induced resistance. Effects of increased concentrations of allelochemicals in defoliated shoots, if present, were probably cancelled out by increased nitrogen concentrations.
What affects the rate of gypsy moth (Lepidoptera: Lymantriidae) spread: winter temperature or forest susceptibility?
Authors: Sharov Alexei A. , Pijanowski Bryan C. , Liebhold Andrew M. , Gage Stuart H.
Published: March 2003

1 The effect of winter temperature and forest susceptibility on the rate of gypsy mothLymantria dispar(L.) range expansion in the lower peninsula of Michigan was analysed using historical data on moth counts in a grid of pheromone‐baited traps collected from 1985 to 1994 by the Michigan Department of Agriculture. The rate of spread was measured by the distance between population boundaries in consecutive years. Boundaries were estimated for population thresholds of 1, 3, 10, 30, and 100 moths per trap using a polar coordinate system.

2 The average rate of spread estimated using all population thresholds was 15.8 km/yr.

3 The rate of spread was higher in the northern part of the lower peninsula than in the southern part, despite lower minimum January temperatures in the north.

4 The rate of spread was positively correlated with forest susceptibility, which was higher in the north than in the south.

KeywordsBiological invasions, forest susceptibility,Lymantria dispar, population spread, temperature.
Predator–prey interactions: olfactory adaptations of generalist and specialist predators
Authors: Dickens Joseph C.
Published: March 2003

1 Olfactory responses of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), a generalist predator, Podisus maculiventris (Say) (Hemiptera, Heteroptera: Pentatomidae) (Pm), and a specialist predator, Perillus bioculatus (F.) (Hemiptera, Heteroptera: Pentatomidae) (Pb) were investigated. Volatiles tested included 20 compounds emitted by undamaged potato plants (Solanum tuberosum), plants that had been artificially damaged, or plants damaged by feeding by CPB larvae.

2 Coupled gas chromatography/electroantennogram detector (GC/EAD) recordings revealed five compounds for which reliable responses were recorded from CPB antennae: (E)‐2‐hexen‐1‐ol, (Z)‐3‐hexen‐1‐ol, (±)‐linalool, nonanal, methyl salicylate, and indole. Both Pm and Pb responded selectively to the same compounds as the CPB with exceptions: (1) (Z)‐3‐hexenyl butyrate elicited reliable responses for both Pm and Pb, and (2) (E)‐2‐hexen‐1‐ol and (Z)‐3‐hexen‐1‐ol were inactive for Pm and Pb under these conditions. Dose–response curves showed that CPB was at least 100 times more sensitive to (E)‐2‐hexen‐1‐ol than were the predators. Both predators were more sensitive to each of the other compounds than were CPB. Both CPB and Pm were attracted to a five component blend comprising (E)‐2‐hexen‐1‐ol, (Z)‐3‐hexen‐1‐ol, (±)‐linalool, nonanal and methyl salicylate. However, attraction of CPB to the blend occurred only with lower doses of (E)‐2‐hexen‐1‐ol and (Z)‐3‐hexen‐1‐ol.

3 These results show that the herbivore (CPB) has olfactory receptors which are more sensitive to constitutive host plant volatiles, e.g. green leaf volatiles, while both generalist (Pm) and specialist (Pb) predators are more sensitive to systemic volatiles produced in response to prey feeding.

Keywords Colorado potato beetle, constitutive compounds, host plant, induced compounds, olfaction, Perillus bioculatus, Podisus maculiventris, predator, prey, tritrophic.
The influence of understory nectar resources on parasitism of the spruce budworm Choristoneura fumiferana in the field
Authors: Cappuccino Naomi , Houle Marie‐José , Stein Jayson
Published: March 2003

1 Nectar provided by flowering plants has been suggested as an important factor enhancing parasitism rates of herbivorous insects. Artificial nectar has been shown to increase parasitoid longevity and fecundity in laboratory studies.

2 We studied the influence of understory nectar on parasitism of the spruce budworm Choristoneura fumiferana in a field experiment in which we either removed understory flowering herbs or sprayed a sucrose solution on the understory vegetation in 0.25 ha quadrats.

3 Cohorts of laboratory‐reared second instars were transferred the field to evaluate parasitism in the quadrats. The larvae were harvested as fifth instars and reared for parasitoids.

4 Parasitoids of early instars caused greater mortality in the supplemental sucrose treatment than in the vegetation‐removal treatment or the control. Parasitoids of older larvae did not respond to the treatments. Larger‐scale treatments may be necessary to elicit a response by the larger parasitoids that attack older larvae.