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ABSTRACT: This paper complements and updates a review of spider ballooning literature by WEYMAN (1993), with expanded discussion of the possible causative factors of ballooning by spiders that inhabit arable farmland. Results relating to other taxonomic groups (especially Acari) are also described, where these help to illuminate the processes underlying the phenomenon of ballooning. Changes in air movement are proposed as an immediate trigger for take-off behaviour, and food deprivation is confirmed as a short-term moderator affecting ballooning frequency. Seasonal changes in ballooning motivation of spiders inhabiting arable farmland have not been found. Within species, ballooning frequency can vary with the growth stage and sex of the spider but variations may also represent a mixed strategy within the population. Differences in ballooning frequency between species are difficult to detect if sample size is low, trapping period is short, or the results are not controlled for the physiological states of the spider populations being compared. Where real inter-specific differences in ballooning frequency occur, they may be related to foraging strategies, physiological adaptations to exploit transient food resources, or dispersal selection pressures in the origin habitats of each species. Ballooning by spiders found on arable farmland is suggested to have evolved primarily as a risk-spreading strategy to maximise survival in unpredictable habitats. In addition to reducing the risk of being confined in deteriorating habitats, ballooning could confer on spiders the opportunity to exploit (in advance of less dispersive predatory invertebrates) ephemeral blooms of prey organisms. Areas for further research are suggested.
Ethology Ecology and Evolution 05/2010; October 2002(Vol. 14):307-326. · 0.74 Impact Factor
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ABSTRACT: Aphid predators are a systematically disparate group of arthropods united on the basis that they consume aphids as part of their diet. In Europe, this group includes Araneae, Opiliones, Heteroptera, chrysopids, Forficulina, syrphid larvae, carabids, staphylinids, cantharids and coccinellids. This functional group has no phylogenetic meaning but was created by ecologists as a way of understanding predation, particularly for conservation biological control. We investigated whether trait-based approaches could bring some cohesion and structure to this predator group. A taxonomic hierarchy-based null model was created from taxonomic distances in which a simple multiplicative relationship described the Linnaean hierarchies (species, genera, etc.) of fifty common aphid predators. Using the same fifty species, a functional groups model was developed using ten behavioural traits (e.g. polyphagy, dispersal, activity, etc.) to describe the way in which aphids were predated in the field. The interrelationships between species were then expressed as dissimilarities within each model and separately analysed using PROXSCAL, a multidimensional scaling (MDS) program. When ordinated using PROXSCAL and then statistically compared using Procrustes analysis, we found that only 17% of information was shared between the two configurations. Polyphagy across kingdoms (i.e. predatory behaviour across animal, plant and fungi kingdoms) and the ability to withstand starvation over days, weeks and months were particularly divisive within the functional groups model. Confirmatory MDS indicated poor prediction of aphid predation rates by the configurations derived from either model. The counterintuitive conclusion was that the inclusion of functional traits, pertinent to the way in which predators fed on aphids, did not lead to a large improvement in the prediction of predation rate when compared to the standard taxonomic approach.
Bulletin of entomological research 08/2008; 98(6):587-97. · 1.58 Impact Factor
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ABSTRACT: Predation by generalist predators is difficult to study in the field because of the complex effects of positive and negative interactions within and between predator species and guilds. Predation can be monitored by molecular means, through identification of prey DNA within predators. However, polymerase chain reaction (PCR) amplification of prey DNA from predators cannot discriminate between primary and secondary predation (hyperpredation), in which one predator feeds on another that has recently eaten the target prey. Here we quantify, for the first time, the potential error caused by detection of prey DNA following secondary predation, using an aphid-spider-carabid model. First, the aphid Sitobion avenae was fed to the spider Tenuiphantes tenuis and the carabid Pterostichus melanarius, and the postconsumption detection periods, for prey DNA within predators, were calculated. Aphids were then fed to spiders and the spiders to carabids. Aphid DNA was detected in the predators using primers that amplified 245- and 110-bp fragments of the mitochondrial cytochrome oxidase I gene. Fragment size and predator sex had no significant effect on detection periods. Secondary predation could be detected for up to 8 h, when carabids fed on spiders immediately after the latter had consumed aphids. Beetles tested positive up to 4 h after eating spiders that had digested their aphid prey for 4 h. Clearly, the extreme sensitivity of PCR makes detection of secondary predation more likely, and the only reliable answer in future may be to use PCR to identify, in parallel, instances of intraguild predation.
Molecular Ecology 01/2006; 14(14):4461-8. · 5.52 Impact Factor
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ABSTRACT: The drive towards a more sustainable and integrated approach to pest management has engendered a renewed interest in conservation biological control, the role of natural enemy communities and their interactions with prey. Monoclonal antibodies have provided significant advances in enhancing our knowledge of trophic interactions and can be employed to help quantify predation on target species. The tetragnathid spider Pachygnatha degeeri Sundevall was collected from fields of winter wheat in the UK and assayed by ELISA for aphid proteins. It was demonstrated that this spider did not simply consume greater quantities of aphids because it was bigger. In addition, P. degeeri contained significantly greater concentrations of aphid in their guts than other spiders, showing that aphids comprised a greater proportion of their diet. Although P. degeeri constituted only 6% of the spider population numerically, females and males respectively contained 16% and 37% of total aphid proteins within all spiders screened, significantly more than their density would predict. These spiders also preyed upon aphids at a disproportionately high rate in June, during the aphid establishment phase, theoretically the best time for limiting growth in the aphid population. Although less abundant than other generalist predators, the capability of these hunting spiders to consume large numbers of aphids highlights them as a more significant component of the predator complex than had previously been realized. Limitation of aphid numbers early in the year by generalist predators provides more time for the specialist aphid predators and parasitoids to move in.
Bulletin of Entomological Research 05/2005; 95(2):161-7. · 1.88 Impact Factor
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ABSTRACT: Collembola comprise a major source of alternative prey to linyphiid spiders in arable fields, helping to sustain and retain these predators as aphid control agents within the crop. Polymerase chain reaction primers were developed for the amplification, from spider gut samples, of DNA from three of the most abundant species of Collembola in wheat crops in Europe, namely Isotoma anglicana, Lepidocyrtus cyaneus and Entomobrya multifasciata. The primers amplified fragments of the mitochondrial cytochrome oxidase subunit I (COI) gene and were designed following alignment of comparable sequences for a range of predator and prey species. Each of the primer pairs proved to be species-specific to a Collembola species, amplifying DNA fragments from 211 to 276 base pairs in length. Following consumption of a single collembolan, prey DNA was detectable in 100% of spiders after 24 h of digestion. We report the first use of DNA-based techniques to detect predation by arthropods on natural populations of prey in the field. All three species of Collembola were consumed by the spiders. By comparing the ratios of the Collembola species in the field with the numbers of spiders that gave positive results for each of those species, it was possible to demonstrate that the spiders were exercising prey choice. Overall, a single target species of Collembola was eaten by 48% of spiders while a further 16% of spiders contained DNA from two different species of Collembola. Preference was particularly evident for I. anglicana, the species most frequently found in spider guts yet the least numerous of the three target species in the field.
Molecular Ecology 01/2004; 12(12):3467-75. · 5.52 Impact Factor
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ABSTRACT: Theoretical developments are helping us to comprehend the basic parameters governing the dynamics of the interactions between generalist predators and their many pest and nonpest prey. In practice, however, inter- and intraspecific interactions between generalist predators, and between the predators and their prey, within multispecies systems under the influence of rapidly changing biotic and abiotic variables are difficult to predict. We discuss trade-offs between the relative merits of specialists and generalists that allow both to be effective, and often complementary, under different circumstances. A review of manipulative field studies showed that in approximately 75% of cases, generalist predators, whether single species or species assemblages, reduced pest numbers significantly. Techniques for manipulating predator numbers to enhance pest control at different scales are discussed. We now need to find ways of disentangling the factors influencing positive and negative interactions within natural enemy communities in order to optimize beneficial synergies leading to pest control.
Annual Review of Entomology 02/2002; 47:561-94. · 11.45 Impact Factor
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Journal of Applied Ecology 12/2001; 38(1):88 - 99. · 5.05 Impact Factor
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ABSTRACT: "Secondary predation" occurs when one predator feeds on a second predator, which has in turn eaten a target prey. Detection of prey remains within predators using monoclonal antibodies cannot distinguish between primary and secondary predation, potentially leading to quantitative and qualitative food chain errors. We report the first fully replicated experiments to measure secondary predation effects, using an aphid-spider-carabid system. Aphids, Sitobion avenae, were fed to spiders, Lepthyphantes tenuis, which were allowed to digest their prey for a range of time intervals. The spiders were then fed to carabids, Poecilus (=Pterostichus) cupreus, which were again allowed to digest their prey for set periods. The anti-aphid monoclonal antibody used to identify S. avenae remains in P. cupreus was one that detected an epitope that increased in availability over the first few hours of digestion, amplifying the signal, extending detection periods and thus increasing the chances of detecting secondary predation. Despite this, and the fact that spiders are known to digest their prey more slowly than many other predators, detection of secondary predation was only possible if the carabids were killed immediately after consuming at least two spiders which were, in turn, eaten immediately after consuming aphids. As this scenario is unlikely to occur frequently in the field it was concluded that secondary predation is unlikely to be a serious source of error during field studies.
Molecular Ecology 09/2001; 10(8):2049-57. · 5.52 Impact Factor
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ABSTRACT: 1. Spiders form a major component of the generalist predator fauna, potentially able to restrict pest population growth, but their populations may be food-limited under current farming regimes. This study aimed to quantify food availability to spiders in winter wheat and to determine whether spider web locations are positively associated with available food resources. 2. Mini-sticky traps (availability rate per 24 h, including prey falling from the crop) and mini-quadrats (instantaneous density on the ground by day) were used, in combination, to monitor the availability of potential prey to web-building species of money spider (Linyphiidae) in fields of winter wheat in Warwickshire, UK, 1997–98. 3. These methods were applied to web sites of individual spiders and to non-web sites located randomly up to 30 cm away from each web. A total of 18 546 invertebrates were captured using these methods. 4. Overall, significantly more potential prey were available in web sites than in non-web sites (both on sticky traps and in quadrats). 5. Prey availability in May and July was about a third of that in June (both on sticky traps and in quadrats) and may have been below that known to be necessary for spiders to realize their maximum population growth rate. 6. The peak rate of capture of linyphiid spiders on mini-sticky traps was 0·6 trap –1 day –1 at web sites, and approximately half this value at non-web sites. Numbers of spiders captured by mini-sticky traps and mini-quadrats increased exponentially as the season progressed. The high capture frequency in relation to population density, and the differential between web and non-web sites, points to a dynamic and aggregated dis-tribution of spiders in winter wheat, which is consistent with what is known about mate-searching and web site abandonment rates by the Linyphiidae. 7. The combination of techniques described here is recommended for monitoring prey availability in prey-enhancement programmes and may prove useful in quantitative studies of both intra-and interspecific interactions between spiders.
Journal of Applied Ecology. 01/2001; 38:88-99.
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ABSTRACT: The ground beetles from the speciose beetle family Carabidae and, since their emergence in the Tertiary, have populated all habitats except deserts. Our knowledge about carabids is biased toward species living in north-temperate regions. Most carabids are predatory, consume a wide range of food types, and experience food shortages in the field. Feeding on both plant and animal material and scavenging are probably more significant than currently acknowledged. The most important mortality sources are abiotic factors and predators; pathogens and parasites can be important for some developmental stages. Although competition among larvae and adults does occur, the importance of competition as a community organization is not proven. Carabids are abundant in agricultural fields all over the world and may be important natural enemies of agricultural pests.
Annual Review of Entomology 02/1996; 41:231-56. · 11.45 Impact Factor
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ABSTRACT: Groups of linyphiid spiders (Erigone spp.) (Araneae, Linyphiidae), collected at intervals from arable land, were tested in laboratory bioassays to determine the proportion of individuals that exhibited ballooning behaviour on each field sampling occasion. There was no significant variation in the proportions of spiders in each test group ballooning in the laboratory over a year. Investigations of ground density and aerial dispersal, in a grass field and a winter-wheat field, confirmed that peaks in numbers of spiders observed ballooning in the field generally coincided with population peaks in the summer and autumn. Significant correlations between ground populations and aerial catches were found for total spiders, immature spiders, and Bathyphantes gracilis (Blackwall) in both fields, adult spiders in the grass field, Erigone spp. in the grass, and Meioneta rurestris (C.L. Koch) in the wheat. The other groups analysed, Lepthyphantes tenuis (Blackwall) in both fields, Erigone spp. in wheat, and M. rurestris in grass, showed similar but non-significant trends. No significant difference was found between overall ground-to-air ratios for males compared to females, but adult spiders were more likely to balloon than immatures.
Oecologia 03/1995; 101(4):487-493. · 3.41 Impact Factor
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ABSTRACT: The diet and reproductive periods of Harpalus affinis (= Harpalus aeneus) and Clivina australasiae, collected by pitfall trapping from graminaceous and legume crops at four sites on the North Island of New Zealand, were determined by dissection. H. affinis was predominantly phytophagous, with a liking for weed seeds; its main animal foods were Aphididae and Diptera. Females were gravid in spring (September-November) and summer (December-February) whilst tenerals were found mainly in autumn (March-May). Diet and phenology were similar in New Zealand, Europe and North America. C. australasiae was a polyphagous carnivore, consuming 11 categories of animal food (the most frequent being Enchytraeidae and Lumbricidae) and six categories of plant food. Females contained eggs from August to March. The food and reproductive period of C. australasiae in New Zealand were similar to those previously reported for Clivina fossor in Europe and North America. Overall, both species are considered likely to play a beneficial role in New Zealand agriculture. Opportunities are identified to study further the biocontrol potential and role in ecosystem function (e.g. community assembly rules) of these species, by means of translocation experiments
Australian Journal of Zoology 01/1995; 43(1):39-50. · 0.72 Impact Factor
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Australian Journal of Zoology 01/1995; 43(1):39-50. · 0.72 Impact Factor
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ABSTRACT: Adult male and femaleErigone spp. (Araneae: Linyphiidae) spiders were kept without food for several days. Groups of spiders were tested for aeronautic dispersal
behaviour (ballooning) in the laboratory. The validity of the assessment method was tested. In comparison with satiated spiders,
the starved group exhibited an increased tendency to engage in aeronautic dispersal behaviour. A consistent trend for increased
dispersal behaviour was detected in three independent experiments. Implications for spiders in agro-ecosystems are discussed
briefly.
Entomologia Experimentalis et Applicata 10/1994; 73(2):121-126. · 1.53 Impact Factor
