Although more consensus is now emerging on the magnitude and frequency of cascading trophic effects in aquatic communities, debate over their terrestrial counterparts continues. We used meta-analysis to analyze field experiments cascades arthropod-dominated food webs evaluate overall conditions affecting occurrence strength. found extensive support for presence communities. In majority experiments, predator removal led increased densities herbivorous insects higher levels plant damage....

Knowing how an increase in the resource base of a food web produces effects that propagate through is central to developing clearer understanding food-web structure and dynamics. In detritus-based terrestrial web, we measured responses predaceous arthropods increases prey occurred response experimentally enhancing web's base. Open 2 × 5 m plots on floor deciduous forest were randomly assigned either Food Enhancement or Control treatment. We supplemented arthropod community leaf litter layer...

Field experiments were performed to determine whether the spider Linyphia marginata C. L. Koch is food limited, and, if so, a shortage of prey acts as density—independent or density—dependent limiting factor. The uncovered effects supply, density, and interaction density upon survival (combined migration mortality), rate increase in weight, fecundity. Replicate, unenclosed populations established at two densities, natural levels supplemented by fruit flies added webs one—half each density....

Theory predicts that allochthonous energy subsidies can modify the strength of trophic cascades in food webs. We tested hypothesis a detrital subsidy would enhance grazing web an agroecosystem which generalist predators, wolf spiders and carabid beetles, feed both on detritivores herbivores. crossed detritus-addition with predator-removal treatments replicated 8 × m open fenced plots cucumbers squash. Collembola, major detritivore, became 2–4 times more abundant than control plots; densities...

We examined whether intraguild predation (IGP) weakens the ability of two taxa generalist predators, carabid beetles and lycosid spiders, to control herbivore densities in gardens cucumber squash. also measured fruit production determine IGP predators impact plants indirectly through trophic cascades. These did densities, but their on different herbivores varied dramatically. As community changed season, so too predators' indirect effect production. In spring gardens, lycosids caused...

The race for reaching mates by the time they are receptive, or sexual selection scramble competition, has received little attention. We argue that smaller males favored in species which male must climb to reach females located high habitat patches. This new explanation we term "gravity hypothesis" of size dimorphism (SSD). show a simple biomechanical model animal movement predicts that: (1) should favor comparatively searching sex when involves climbing; and (2) this effect be stronger...

We conducted field and laboratory experiments to examine the relative contributions of mortality from natural enemies cannibalism population regulation wolf spider Schizocosa ocreata. This cursorial is a common generalist predator in leaf litter forests eastern United States. In our study site Maryland, densities recently dispersed young S. ocreata can reach 60—90 individuals/m 2 , but decline <15 spiders/m by early autumn. investigated cause this rapid spiderling density. first performed...

Changes in rainfall predicted to occur with global climate change will likely alter rates of leaf-litter decomposition through direct effects on primary decomposers. In a field experiment replicated at two sites, we show that altered may also how cascading trophic interactions initiated by arthropod predators the leaf litter indirectly influence decomposition. On drier site there was no interaction between and indirect effect contrast, moister spiders accelerated disappearance rate deciduous...

Abstract Generalist predators contribute to pest suppression in agroecosystems. Spider communities, which form a substantial fraction of the generalist predator fauna arable land, are characterized by two functional groups: web-building and cursorial (non-web-building) species. We investigated relative impact these groups on common ( Sitobion avenae , Aphididae) wheat combining molecular technique that revealed species-specific aphid consumption rates with factorial field experiment analyzed...

The activity and density of generalist predators, such as carabid beetles, rove beetles spiders, may increase in response to: (1) increased availability prey from the belowground subsystem and/or (2) enhanced complexity aboveground vegetation. Organic farming practices support decomposer populations enhance habitat due to an weed density. A by predators below‐ or changes could affect predation rates on herbivores food web. We tested this hypothesis a replicated field experiment conducted...

The effectiveness of generalist predators in biological control may be diminished if increased availability alternative prey causes individual to decrease their consumption crop pests. Farming practices that enhance densities microbi-detritivores the detrital food web can lead feed on pest species. ability predict net biocontrol impact predator depends upon knowing extent which shift and less pests when detritus-based are more abundant. We addressed this question by comparing ratios stable...