- Ecology and Evolutionary Biology
I am interested in ecology, evolution and behavior. I seek an understanding of the origin of new species, their ecological interactions, their persistence in different communities and their ultimate extinction. In this broad area I chose Darwin's Finches on the Galápagos Islands for intensive investigation more than 40 years ago because some unique features, including the tameness of the finches and the simplicity of their undisturbed habitats, make them unusually suitable for field research into questions of evolution.
The fourteen species evolved from a common ancestor in the last few million years. They display striking patterns of morphological and behavioral variation, and some populations are exceptionally variable. To investigate the reasons for these patterns my students and I have concentrated on four topics, and have demonstrated the following. First, there is much heritable variation in populations, partly as a result of hybridization. Second, this genetic variation is occasionally subject to the forces of both natural and sexual selection, as the climatic environment fluctuates between extreme conditions. These two facts mean that populations are currently labile, evolutionarily, which is fortunate because it has enabled us to estimate the minimal forces of selection involved in the transformation of one species to another. Third, the composition of finch communities is strongly determined by patterns of variation in food supply among islands, and by competition among species for that food supply. Evolution of character displacement caused by interspecific competition has been observed and measured. Fourth, finch species recognize each other by their appearance and by their song, as demonstrated by experiments with models and tape-recorded song. Integrating all this information we can say that the primary driving forces in the adaptive radiation of the finches were ecological, with reproductive isolation between newly formed species being largely an incidental consequence of ecological divergence.
Current goals include identifying the causes, frequency and fitness consequences of hybridization by an analysis of pedigrees, uncovering the molecular genetic control of beak development and the origin of differences between species, and seeking a better understanding of the pattern of Darwin's Finch phylogenetic history through an analysis of microsatellite and mitochondrial DNA variation and whole genome sequences. Achieving these goals should throw light on two generalizations: how complex communities develop from simple ones, and how microevolutionary processes can be used to account for macroevolutionary patterns.
Research activity. Having retired in 2008 I no longer supervise graduate students. I am interested in ecology, behavior, evolution and genetics. Within this area my research remains centered on Darwin’s finches, and I carry it out in several collaborations, with my wife (Rosemary), molecular geneticists (Leif Andersson), and others.