Metapopulation dynamics and landscape ecology of the Florida Scrub-Jay, Aphelocoma coerulescens.

摘要

Florida's only endemic bird species, the Florida Scrub-Jay ( Aphelocoma coerulescens), is rapidly disappearing throughout much of its range. A 1992–1993 statewide survey shows that it has effectively gone extinct in 10 of 39 formerly occupied counties in less than two decades. To characterize the spatial structure and vulnerability of the Florida Scrub-Jay throughout the state, I developed and applied a new method to describe the species' metapopulation structure. This method uses GIS-generated buffers based on documented dispersal distances to identify separate metapopulations and highly connected subpopulations called mainlands (extinction resistant), islands (extinction prone), or midlands (vulnerable to extinction). Of the 42 jay metapopulations identified, only five include mainlands; 21 consist only of extinction-prone islands. The resulting classification reveals key subpopulations requiring special attention to maintain the long-term viability of the existing metapopulations.; I developed and applied a technique for measuring habitat features and estimating habitat quality over large areas using image processing and GIS methods. The technique showed that jays in central Florida had a strong preference for open sandy areas, and few or no pine trees. A proximity analysis showed that demographic performance decreased near forests. Measurement of habitat variables using this technique will be a valuable technique for habitat management and conservation.; I developed a spatially explicit, individual-based model to simulate the metapopulation dynamics of Florida Scrub-Jays. Special emphasis was placed on realistically modeling dispersal. I conducted a small radio-tracking study and used data from long-term studies to parameterize and validate the model. Stage-age structure and dispersal distances generated by the model showed good fit to field data.; I used this simulation model to investigate the viability of 21 major Florida Scrub-Jay metapopulations across the state. For each metapopulation I simulated 2 or more hypothetical reserve designs, ranging from a minimal design with only currently protected jays, to a maximal design containing all significant populations as of 1993. All habitat was assumed to be restored and fully occupied. Model results indicated that only 3 of 21 metapopulations would be adequately protected without further habitat acquisition. At least 4 metapopulations appear to be at great risk of extinction.