Year of Award

2010

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Fish and Wildlife Biology

Department or School/College

College of Forestry and Conservation

Committee Co-chair

L. Scott Mills, Karen E. Hodges

Commitee Members

Jon Graham, Winsor H. Lowe, Michael K. Schwartz

Keywords

genetics, Lepus americanus, phylogeography, population dynamics, synchrony, time series

Abstract

In recent decades, climate change has been invoked in the apparent collapse of some of the best-known examples of cyclic and synchronous population dynamics among boreal species. Simultaneously, some studies have predicted that as species' ranges shift poleward and southern habitats fragment in response to climate change, we will lose the southern glacial refugial populations that have historically harbored species' highest genetic diversity and uniqueness. I investigated how climate change and habitat fragmentation may impact genetic and population dynamic processes for the snowshoe hare (Lepus americanus), a species historically recognized as a key driver of North American boreal community dynamics.

I collected >1000 genetic samples and >300 time series from 175 cooperators in 30 U.S. states and Canadian provinces and territories. Based on analyses of nuclear and mitochondrial DNA, I identified three highly divergent groups of snowshoe hares in the Boreal, Pacific Northwest, and Southern Rockies regions of North America. I found high genetic diversity in mid-range (Boreal) hare populations, and high genetic uniqueness but lower diversity in the species' southern range (Pacific Northwest and Rockies). If southern populations decline due to climate change, snowshoe hares may still retain high genetic diversity, but will lose many alleles currently unique to southern populations.

In a simulation study comparing five synchrony metrics, I found the Kendall metric performed best with short, noisy time series similar to those available for snowshoe hares. I used this metric in partial Mantel tests, modified correlograms, and shifting window analyses of hare synchrony patterns. Confirming long-held but previously untested assumptions, I found northern hare populations are significantly synchronized at distances up to several thousand kilometers, while southern populations are not significantly synchronized at any of the distance classes evaluated. I found that historical patterns of synchrony still persist for snowshoe hares, in contrast to reports for some other synchronous species. Hare synchrony patterns clustered into groups defined according to genetic criteria--but not ecoregions or climatic regions--highlighting the importance of dispersal and population connectivity in snowshoe hare synchrony.

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© Copyright 2010 Ellen Cheng