Uptake of Bacillus thuringiensis proteins by a community of generalist predators (Araneae) and their prey

With increases in agricultural acreage planted to transgenic crops, the exposure of the spider community to Bacillus thuringiensis proteins via consumption of Bt-containing prey or plant materials has become an essential aspect of genetically modified crop risk-assessment. Spiders have been an under-studied group of arthropods within the non-target arthropod literature, despite their important role as natural enemies in agroecosystems. It is therefore essential to quantify exposure pathways in spider food webs across a variety of transgenic events. Spiders and their prey were collected from multiple Bt and isoline corn fields and screened for Bt-endotoxins using enzyme-linked immunosorbent assay (ELISA). Significant numbers of spiders and prey organisms screened positive for Bt-endotoxins targeting lepidopteran and/or coleopteran pests from each transgenic field. Spiders exhibiting a diversity of foraging strategies screened positive for uptake of Bt-endotoxins, including ground-based, cursorial hunters (Gnaphosidae, Lycosidae), as well as both aerial (Araneidae, Tetragnathidae) and ground-based web-building spiders (Linyphiidae, Theridiidae). Common prey items, including Hemiptera (Miridae, Rhyparochromidae), Coleoptera (Coccinellidae larvae), and Lepidoptera (Noctuidae larvae) also screened positive for both lepidopteran- and coleopteran-specific Bt toxins. These results suggest that there are multiple pathways to Bt-endotoxin exposure for Araneae in a transgenic corn agroecosystem. The interaction pathways for potential Bt-endotoxin flow through the non-target spider food web are outlined based on the results of this study. Implications for the future of transgenic crop risk-assessment and the compatibility of transgenic crops with biological control by the spider community will be discussed.