The scale of landscape fragmentation affects herbivore response to vegetation heterogeneity

Using alternating bands of weeds and broccoli I experimentally manipulated vegetation composition and the spatial scale at which the landscape was fra gmented in a factorial design. This experimental approach allowed me to dis tinguish the effect of spatial scale from that of simple crop heterogeneity on crop herbivores. The importance of scale depended on which insect speci es were examined. Cabbage aphids (Buevicoryne brassicae) were influenced by vegetation composition at all tested scales of fragmentation; cabbage butt erflies (Pieris rapae) were not affected by scale or by composition and fle a beetles (Phyllotreta cruciferae) revealed a striking dependence on scale of fragmentation as well as an interaction between scale and composition. T his approach shows the importance of dissecting out the effects of scale fr om other aspects of landscape manipulation, and emphasizes the challenge of developing a theory that will enable prediction of species-specific respon ses to scale.