Phylogeography of North American Boreal Birds
Phylogeography of Blackpoll Warblers
Blackpoll Warbler (Setophaga striata ) is a long distance Neotropical migrant with a broad breeding range in North America’s boreal forest that encompasses several possible biogeographic barriers. I found significant genetic structure among western, eastern, and Newfoundland populations, but no structure among isolated mountaintop populations at the southeastern periphery of the breeding range. Using coalescent simulations I rejected all multiple-refugia hypotheses in favor of a single refugium. In contrast to previous studies that have invoked multiple Pleistocene refugia as the cause of genetic structure in North American bird species, our analyses suggest that geographic structure in Blackpoll Warblers results from isolation-by-distance rather than historic isolation. (PDF of research article)
Blackpoll Warbler genetic materials come from birds captured in the field (left, center) and museum specimens (right).
Comparative Phylogeography
I have compared the genetic patterns in Blackpoll Warbler to several codistributed boreal bird species. Using spatially explicit niche models and genetic data I was able to identify cases of pseudo-congruence (species with similar genetic patterns, but that likely survived the Pleistocene in different refugia), and pseudo-incongruence (species with incongruent genetic patterns, but were likely co-distributed during the Last Glacial Maximum). These preliminary results suggest that bird communities may be ephemeral, and different species may have colonized their current boreal distribution along different pathways and at different times.
My Ph.D. adviser Jeremy Kirchman (left) and I continue to collaborate on this project to collect genetic data and analyze phylogeographic patterns in additional boreal bird species. |
Effects of Climate Change on Genetic Diversity in Blackpoll Warbler
Climate change is causing species distributions to shift up in latitude and elevation. This means populations of boreal birds currently breeding at high elevations at the southern periphery of their species ranges might be at risk of extirpation. I used climate models to predict the effects of modern climate change on the distributions of 15 boreal species, and found that many of these species are predicted to disappear from mountaintops in northeastern United States during the current century. To determine the effects of these extirpations on genetic diversity within species, I compared multilocus genetic data from Blackpoll Warblers in populations predicted to be extirpated to populations predicted to persist. I found that gene flow among populations of Blackpoll Warblers is high, such that a non-significant level of genetic diversity is expected to be lost due to climate change. This is good news for the Blackpoll Warbler, but species with low leverls of gene flow, or with ranges limited to high elevations might face a greater risk of loss of diversity due to climate warming. (PDF of research article).
|