Biodiversity and Community Structure of Epedaphic and Euedaphic Springtails (Collembola) in Transgenic Rootworm Bt Corn

Springtails are an integral and beneficial part of the soil community. As part of an extensive study of the effect of rootworm Bt corn (Cry3Bb1) on nontarget invertebrates, we evaluated both the abundance and diversity of surface-active (epedaphic) and subsurface (euedaphic) springtails at Ames, IA, and Monmouth, IL, in 2-yr field trials during 2000–2002. Springtails were collected from pitfall traps and soil cores in plots planted with rootworm Bt corn and its non-Bt isoline. Few differences were observed in the abundance of individual species in Bt and isoline corn. Nor did the estimated species richness or the Shannon or Simpson diversity indices differ significantly between Bt and isoline corn at either location during 2000–2002, indicating no effect of Bt corn on springtail diversity. In soil insecticide-treated plots, however, springtails were consistently more abundant than in check plots, perhaps because of adverse insecticide effects on springtail predators. Soil insecticide also reduced both Shannon and Simpson diversity in the Iowa euedaphic and Illinois epedaphic populations. Such consistent insecticide effects on both abundance and diversity of springtails provide a positive control by which to assess the power of the experimental design to detect a comparable impact of Bt corn on springtails. They also show that insecticide use more strongly impacts springtails and their predators than does the practice of growing transgenic crops to control the same pests.