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Refugial Brown Bag

May 5, 2013

The brown bag on 4/24/2013 by Yadeeh Sawyer was titled “Living on the Edge: Testing the Coastal Refugia Hypothesis”. Ms. Sawyer looked at post glacial lineages in Microtus longicaudus and the responses to historic climate, demographic change, and underlying evolutionary processes. She also looked at diversification of northern Peromyscus and tried to determine drivers of diversification in high latitude climates by looking at island size and isolation and changes in diversity. However, Ms. Sawyer focused on the coastal refugia roles in shaping island diversification. She asked how historical climate events and the degree of insularity impacted contemporary mammalian phylogeographic structure. She looked at spatial and temporal species distribution by looking through primary biogeographic forces such as size, isolation, topography, and history (glaciers, sea level, climate). She made sure to note that the effects of all of the first three forces were dynamic, constantly changing systems. The systems were represented as oceanic, continental land/bridge, sky islands, and fragmented habitat. Ms. Sawyer believes that glaciation caused populations to move north south or to coastal refugia but as ice melted they could move away from refugia leading to today’s distributions. She found that beringian sources moved south, mainland sources moved north, and coastal sources increased on the continental shelf. She then hypothesized that genetic signatures will reflect glacier refugia and refugal populations were the source for post glacial colonization. She looked at mitochondrial DNA and found that outgroups were all on the same long branch. She found that non refugial locations had higher diversity but that her hypotheses were opposite for the vole, suggested expansion for the shrew, and were expected for the mouse. The vole and shrew showed strong support for glacial isolation, but the mouse did not. The mouse and shrew were stable in refugia which was opposite of what was expected. She didn’t identify source populations. In the future she would like to test other hypotheses, include nuclear data, species trees, ABC tests, migration rates and direction. This was a very interesting talk though I felt confused by most of it. I wish I had had time to go through her data more slowly because I believe that her research is very interesting and will probably be very important to historical biology.


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