B. Rosemary Grant


University Princeton
Ecology and Evolutionary Biology

Rosemary is interested in the diversity of individuals produced by the interaction between genetics, ecology and behavior. How natural selection acts on this variation; the evolutionary response to natural selection and the bearing this has on the process of speciation. A fundamental problem in the study of evolution is to understand the steps involved in the process of speciation, because the question of how one species splits into two addresses the foundation of the biodiversity we see around us today. Yet there is much controversy about the process of speciation. Debates center around, the extent of the role of genetic variation, past history and geography in lineage divergence and the role of genetic variation, behavior and learning as factors in the formation of reproductive barriers to gene flow between closely related sympatric species, and whether or not speciation can occur in sympatry.
She works closely with Peter Grant. They chose the young adaptive radiation of Darwin’s finches on the remote Galapagos Archipelago as a suitable system for investigating the problem of speciation. This radiation offers unique advantages. It is the only bird radiation to have retained the full complement of species, none having gone extinct as the result of human intervention. Furthermore many islands in the archipelago are uninhabited and several of these have few or no introduced plants or animals, enabling us to examine naturally occurring changes under pristine or nearly pristine conditions. Most importantly, the islands are situated astride the equator and are subject to extreme interannual fluctuations in climate caused by the El Nino-Southern Oscillation. Years of abundant rainfall, which occur unpredictably approximately twice a decade, are interspersed with years of drought, and these changes alter the ecological and food conditions for the finches. Such a situation allows the investigation of the three steps leading to species formation: colonization, divergence, and the formation of a reproductive barrier between species. We have and are examining each in turn.