Megan Phifer-Rixey



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Research Overview

I am broadly interested in population genetics and adaptation. One of the questions I am most interested in is how species adapt to environmental variation. My current postdoctoral research is focused on environmental adaptation in house mice. House mice have spread all over the Americas since the arrival of European settlers. We would like to better understand the population genetics of this invasive species as well as the genetics of environmental adaptation. We have collected mice from all over the Americas and are currently using low coverage whole genome sequencing to characterize genetic variation. We are also starting new inbred lines from more extreme climates.

My graduate work focused on understanding how environmental heterogeneity affects shell color variation in the rocky intertidal snail Littorina obtusata. Organisms residing in the rocky intertidal regions of the northern Atlantic Ocean experience significant and, to some extent, predictable variation in abiotic conditions including temperature, humidity, wind and wave exposure. Across multiple geographical scales, L. obtusata show striking patterns of color variation, suggesting that selection is acting on this trait. Using an inferential and an experimental approach, we investigated the forces contributing to the maintenance of shell color polymorphism in this species. We documented consistent clines in shell color morph frequencies in the Gulf of Maine across multiple spatial scales. In addition, experimental manipulations directly link shell color to fitness under stressful thermal regimes. Characterization of neutral structure in this species contrasts with patterns of shell color variation, further supporting a selective explanation for the clines.

Selected Publications

Phifer-Rixey, M., F. Bonhomme, P. Boursot, G.A. Churchill, J. Pialek, P.K. Tucker, and M.W. Nachman, 2012. Adaptative evoluton and effective population size in wild house mice. Molecular Biology and Evolution 29(10): 2949-2955.

Phifer-Rixey, M., Heckman, M., Trussell, G., and P.S. Schmidt. 2008. Maintenance of clinal variation for shell colour phenotype in the flat periwinkle Littorina obtusata. Journal of Evolutionary Biology 21(4): 966-978.

Schmidt, P.S., M. Phifer-Rixey, G.M. Taylor and J. Christner. 2007. Genetic heterogeneity among intertidal habitats in the flat periwinkle, Littorina obtusata. Molecular Ecology 16(11): 2393-2404.