9610159 With Habitat fragmentation is one of the biggest threats to biodiversity. Yet conservation biology has no formal theory to predict at what point landscapes are likely to become fragmented, and thus when populations are at risk of extinction. Neutral landscape models provide quantitative predictions about when habitat fragmentation occurs and how species respond to habitat fragmentation. Neutral landscapes are grid maps in which habitat is generated using a theoretical spatial distribution. These theoretical models predict that habitat fragmentation occurs suddenly across a very small range of habitat loss. As a consequence, species may abruptly go extinct at this critical threshold in habitat loss, even though suitable habitat is still available on the landscape. Exactly where the threshold occurs depends upon the spatial arrangement of habitat and the dispersal abilities of the species. For example, a species with poor dispersal abilities will be affected by habitat fragmentation sooner than a species with good dispersal abilities. The potential for threshold effects in habitat fragmentation and the subsequent extinction of populations have been identified as major unsolved problems facing conservationists. The investigators will test neutral landscape theory by assessing the effects of fragmentation on biodiversity and trophic interactions. Because the principles and predictions of neutral landscape theory should apply at any scale, the investigators will develop an experimental model system consisting of microlandscape plots. These plots will represent a range of habitat abundance and fragmentation severity. The plots will be constructed using the habitat distributions predicted by the theory. The investigators intend to examine the response of insect herbivores and their natural enemies within these experimental landscapes. Specifically, they will explore how species with different life-history strategies and dispersal abilities are affected by f ragmentation. They will also study how habitat fragmentation affects the ability of natural enemies (predators, parasitoids) to control their prey or host species. The application of such "microcosm" experiments has recently led to important insights into the structuring and maintenance of biodiversity in natural ecosystems. The research proposed here may be useful in the conservation and management of native agents of biological control in agricultural systems. G:crb97With.crb
