Molecular evidence for dietary selectivity and pest suppression potential in an epigeal spider community in winter wheat

Abstract

Determining diet breadth of a predator is crucial to understanding its potential role in biological control. Spiders are often the most abundant group of predators in agricultural fields, thereby having considerable pest suppression potential. In this study, we developed a molecular framework to study the feeding habits of an epigeal spider community in a winter wheat agroecosystem, and correlated these results with prey availability. We found that our assemblage of spiders appear to prefer Collembola over other suitable-sized prey that are also frequently encountered (Brachycera, Platygastridae) which were under-utilized in relation to their abundance. Aphid predation was surprisingly high and was not correlated with web size or prey availability. Considering the scarcity of aphids in this system, non-web foraging was likely responsible for the levels of aphid predation recorded. We conclude that there was sufficient abundance of suitable prey (Collembola) to sustain epigeal spider populations in winter wheat such that they were available to prey on pests during immigration into the crop. Our results show that these spiders are not truly polyphagous, but appear to exhibit specialized feeding habits, feeding on jumping (not flying) prey such as Collembola or slowly-crawling prey such as aphids. Given the extent of feeding on scarce aphids, linyphiid spiders have the potential to play an important role in suppressing early-season aphid populations, thereby delaying the potential exponential increase in aphid populations.