LEE, Carol Eunmi; University of Wisconsin, Madison: Selection and Physiological Evolution during Biological Invasion Events

Invasive species serve as excellent models for studying rapid evolution in response to new environments. Recent invasions of fresh water have occurred multiple times independently in the copepod species complex Eurytemora affinis, providing replicated tests of physiological adaptation. Work in my lab has shown that the transition from estuarine and saltmarsh habitats to fresh water involves strong selection and a heritable shift in salinity tolerance. Within invading populations, there is considerable genetic variance for salinity tolerance, genotype by environment interaction, and differences in the ability to acclimate, providing substrate for selection. In addition, populations vary in response to selection and in the ability the up-regulate activity of ion uptake proteins, suggesting that populations might vary in their propensity to invade. We are currently investigating types of physiological traits that are under selection during invasion events and whether the same evolutionary and physiological pathways are involved during independent invasion events.