Using genomic patterns of gene expression and population genetic signatures of selection to understand the evolution of island gigantism Background: In repeated observations, island-colonizing mammalian species evolve highly divergent body size dimensions relative to their mainland counterparts. For example, insular elephants and humans evolve smaller body sizes while island-bound murid (mouse-related) rodents evolve larger sizes. Foster first systematically described this “island rule” in 1964, suggesting that the unique distribution of resources on islands may drive rapid morphological evolution. Remarkably, the genetic mechanisms underlying island dwarfism and gigantism have rarely been addressed and remain poorly understood. One well-documented case of island gigantism is that seen in the Gough Island mice (GI mice). The house mouse (M. musculus) colonized Gough Island, which is located approximately 3,000 kilometers southwest of South Africa, in the last few hundred years after being introduced via whaling boats and possibly shipwrecks. During this short time period, the GI mice have evolved the largest body size of any wild house mouse population in the world; their average weight is double that of their mainland and laboratory counterparts. In addition to the rapid evolution of body size, and perhaps related to it, the GI mice evolved carnivorous dietary habits, communally feeding on dead and live albatross chicks.
Because of the vast genomic and molecular genetic resources available for the house mouse (lab mouse for remainder of proposal), the GI mouse population offers an unprecedented opportunity to explore the genetic mechanisms responsible for the rapid morphological and physiological evolution of island species. Moreover Moreover, it is expected that a genetic understanding of phenotypic alterations associated with island gigantism, such as greater body mass, modified skeletal structure, and changed metabolic requirements and processing will also shed light on the genetic variations that contribute to human diseases such as obesity. Of particular importance to an understanding of body size growth, maintenance and evolution are the biochemical processes carried out in the liver. I will use genome-wide sequence variation in GI mice to determine the GI mouse-specific gene expression changes in the liver relative to mainland/lab mice and to identify candidate genomic loci that have been selected to regulate these gene expression differences.