Small and isolated populations are of interest to biologists because they have the potential to become new species. In the absence of human intervention their evolutionary and ecological fates are determined by their genetic variation, and this in turn is governed by their breeding structure. The proposed research will examine the breeding structure of two small populations of Darwin's Finches on one of the Galapagos Islands. Darwin's Finches are unusually suitable for this investigation because they live in undisturbed environments, and their evolution has been well studied. The two chosen populations are Geospiza fortis and G. scandens. Their residency on the island of Daphne Major and their tameness has allowed the establishment of pedigrees; and by extending these pedigrees and following the fates of known individuals by observation, the PI's will establish the circumstances and frequencies of inbreeding and of hybridization, and the fitness consequences of both. Small populations like these Darwin's Finches are of interest to conservation biologists because they are liable to become extinct. Results of this study will have potential applications to the conservation and management of small and endangered populations of animals elsewhere. Demographic and genetic consequences of small population sizes are increasingly being incorporated into the modeling of extinction-prone populations in order to identify vulnerable components of life histories on the one hand, and long-term, minimum, viable population sizes on the other. The study populations are small and fluctuate in numbers. With this study their genetic structure will be understood. Understanding the dynamics of such populations under natural conditions is essential if we are to reliably assess the future course of other populations which are subjected to disturbances.
