Ecology and genetics of contemporary evolution in a colonizing species

There is a growing appreciation that evolutionary change can occur over timescales of years to decades. The goal of the proposed research is to track such contemporary evolution in a wild species for which extensive historical and genetic information is available. Avena barbata is an annual grass introduced to California from the Mediterranean roughly 200 years ago. It was one of the earliest species to be studied with molecular genetic markers in the 1970's. As a result, it is one of the few species for which we have a record of its past genetic state, not just its past traits. In these early studies, two genetic types were identified associated with moister and drier habitats. My lab has identified the chromosomal regions that are under natural selection in these habitats, but our results suggest that a single genetic type should have broad adaptation across both habitats. This genotype should be spreading, and displacing the less fit genotypes - that is, evolutionary adaptation is happening in the present day. This presents an unsurpassed opportunity to study adaptive evolutionary change in action. I will re-visit the locations studied in the 1970's and compare the present genes to those from the past. This will determine what heritable (ie evolutionary) change has taken place, and whether it matches our results on the genes under selection. I will also use DNA sequence data to infer the how closely related the genes in different locations are to each other and so determine the routes by which genes spread to their current locations. By comparing across multiple genes I can determine whether adaptive change involves the mixing of advantageous genes from different sources into a single well adapted genotype. Finally, I will compare the physical and physiological traits of current populations to those of plants grown from seed collected in the past. This will indicate what phenotypic (physical) changes have contributed to adaptation. Together, these results will give a complete picture of contemporary evolution in a wild species as it adapts to a novel range.