9424615 Maurer An understanding of how to conserve biological diversity must incorporate a knowledge of how geographic ranges of species change, particularly for those species that may be declining in abundance and are likely to become threatened with extinction. This research is designed to examine complex changes in the structure of geographic ranges of species of neotropical migrant warblers. A number of measures of geographic range structure have been discussed in the literature, but these have yet to be related directly to population level processes such as dispersal. Simulation models will be constructed that relate these measures of geographic range structure to population processes in order to provide a theoretical framework to understand mechanisms that determine patterns in geographic range structure within and among species. In order to establish empirical patterns of changes in abundance across geographic ranges of neotropical migrant warblers, and their non-migratory relatives, maps of abundances of species will be constructed for 5 five-year time periods. Differences between logarithms of these maps between time periods will be used to construct maps of the spatial patterns of population change. Maps of abundance across geographic ranges of these species will be correlated with output from vegetation models that are linked to global climate change models. These correlation models will be used to obtain projections of the structure of geographic ranges of species under various climate change scenarios. Maps of diversity of warblers under current conditions and under a variety of global change scenarios will be constructed by overlaying abundance maps, and counting the number of species with abundances >0 in each map unit. The analysis of geographic range structure and dynamics proposed herein will provide insight into the patterns and processes that determine the spatial distribution of abundances of species, and suggest possible mechanisms that are responsible for these patte rns. Such pattern changes under global change scenarios will provide further insight into the potential loss of species with narrow geographic ranges or small populations.
