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Abstract
Genetically modified (GM) crops and invasive species have been extensively studied inthe field of agroecology, particularly for their effects on biodiversity. While studies examiningGM crops have found very little evidence that these crops negatively affect arthropodcommunities, they have not taken into account the various agricultural management strategieswithin which they are nested.Due to the frequent disturbance inherent in agricultural production, invasive species arecommon members of arthropod communities in agroecosystems. Invasives can have bothpositive and negative impacts on arthropod communities within these systems; however, thereare many areas in which their influence has not been adequately assessed.In the chapters that follow I first examine the effects of genetically modified, Bt cotton onnon-target arthropod communities relative to and in combination with the effects of tillage andcover crop identity. While Bt cotton appeared to have subtle effects on a few taxa, they wereminor and inconsistent compared to and in combination with the effects of tillage and cover croptype.Next I assess the impact of the red imported fire ant Solenopsis invicta on arthropodsboth at and below the soil surface. The removal of fire ants significantly altered the abundanceof certain arthropod families. Many of the same trophic groups were affected at two field sites,but the abundance of these groups did not always respond in the same direction. Potentialmechanisms leading to the differences detected between field sites, including weed density andarthropod species-specific responses, are further discussed.Finally, I examine the contribution of the red imported fire ant, Solenopsis invicta on eggpredation rates in a cotton agroecosystem. Fire ants contributed greatly to predation of eggs ofthe beet armyworm, Spodoptera exigua, both on cotton foliage and at the soil surface. While fireants also contributed significantly to predation of eggs of the southern green stink bug, Nezaraviridula, in cotton foliage, they ignored eggs of the redbanded stink bug Piezodorus guildinii.This study also suggests that whitefly densities on cotton foliage may significantly influence eggremoval rates of N. viridula eggs by fire ants.