Dissertation Research: Gene Flow and Mitochondrial DNA Evolution in a Cooperatively Breeding Songbird, the Grey- crowned Babbler (Pomatostomus temporalis)

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Scott V. Edwards, working under Allan C. Wilson in the Department of Biochemistry and James L. Patton in the Museum of Vertebrate Zoology, Department of Integrative Biology, will employ new molecular techniques to study patterns and causes of geographic variation in a social songbird. The species to be studied, the Grey-crowned Babbler (Pomatostomus temporalis), is found throughout the northern portions of Australia and in southern New Guinea. It is well known for its conspicuous social system called "cooperative breeding" in which several, often related, individuals forsake breeding on their own to assist the main breeding pair in building nests, guarding territories and raising young. Evolutionary biologists have been intrigued by such systems because they may result in genetic differences between local populations due to inbreeding within populations; on the other hand, geographic differences among populations may be due more to extrinsic factors such as topographic or environmental barriers that serve to isolate populations from one another. Each scenario predicts different patterns of genetic diversity and relatedness at the family-group, population, and regional levels. The recently devised polymerase chain reaction (PCR) provides a method whereby high resolution genetic data can be obtained simply and rapidly from large numbers of individuals of a species. Edwards will collect blood samples from babbler populations throughout its range with the goal of obtaining adequate numbers of individuals within families, populations, and biogeographic regions. The genetic research will focus on an extremely variable region of a maternally inherited molecule found in the mitochondria of all higher organisms--mitochondrial DNA. The PCR when applied to this region will highlight the genetic differences among individuals within an among family groups as well as geographic populations, and will provide a means whereby the contribution of social and/or historical factors determine genetic structure in the Grey-crowned Babbler.