Habitat subdivision causes changes in food web structure

Theory suggests that the response of communities to habitat subdivision dep ends on both species' characteristics and the extent to which species inter act. For species with dynamics that are independent of other species, subdi vision is expected to promote regional extinction as populations become sma ll and isolated. By contrast, intermediate levels of subdivision can facili tate persistence of strongly interacting species. Consistent with this pred iction, experimental subdivision lengthened persistence of some species, al tering the extent of food web collapse through extinction. Extended persist ence was associated with immigration rescuing a basal prey species from loc al extinction. As predicted by food web theory, habitat subdivision reduced population density of a top predator. Removal of this top predator from un divided microcosms increased the abundance of two other predator species, a nd these changes paralleled those produced by habitat subdivision. These re sults show that species interactions structured this community, and illustr ate the need for investigations of other communities.