The role of non-prey food resources in generalist predator food webs

The annual shedding of pollen in a corn field represents the influx of a new potential nutrition source. The presence of this resource may affect the composition of the prey community within an agroecosystem. Additionally, generalist predators important in biological control, such as spiders, may supplement their diet by consuming these non-prey food resources. Therefore, to examine the role of non-prey food resources in complex generalist predator food webs, central Kentucky corn fields were manipulated to nearly eliminate the presence of pollen in one half of each field in 2009-2010. Prey abundance and pollen interception were monitored throughout the growing seasons at spider webs and non-web sites using sticky traps and sweep net sampling. Additionally, spiders (Araneae: Linyphiidae, Tetragnathidae, Araneidae) were collected and screened for multiple prey DNA, as well as corn DNA, using molecular gut-content analysis via polymerase chain reaction (PCR), allowing for the delineation of trophic interactions within this complex food web. Results indicated strong linkages to certain prey items (e.g., Collembola DNA was present in the gut-contents of up to 80% of some spider species). The role of corn pollen as a supplemental food resource for these generalist predators and the impact of its presence on their food webs is discussed, including implications for dietary diversification and biological control.