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

Elizabeth Crone, Lisa Eby

Commitee Members

Scott Mills, Winsor Lowe, P. Stephen Corn

Keywords

amphibian, climate change, Montana, population ecology, population modeling

Abstract

Worldwide extinctions of amphibians are at the forefront of the biodiversity crisis, with climate change figuring prominently as a potential driver of continued amphibian decline. Changes in both the mean and variability of climate conditions may affect amphibian populations in complex, unpredictable ways. However, few studies have evaluated effects of climate change on individual vital rates and subsequent population dynamics of amphibians. I investigated the population dynamics of a high elevation population of the Columbia spotted frog (Rana luteiventris) in relation to climate variation over a ten-year period.

I documented an increase in survival and breeding probability as severity of winter decreased. Therefore, a warming climate with less severe winters is likely to promote population viability in this montane frog population. More generally, amphibians and other ectotherms inhabiting alpine or boreal habitats at or near their thermal ecological limits may benefit from the milder winters provided by a warming climate as long as suitable habitats remain intact.

I then used Bayesian models to demonstrate that changes in mean snowpack had a greater effect on viability than changes in the variance of snowpack. In general, future decreases in mean snowpack increase population viability, and increases in variability have little effect.

Finally, I examined whether heterogeneity in pond hydroperiod on the landscape had the potential to stabilize recruitment and population dynamics. Overall, ponds with different hydroperiods showed contrasting dynamics among years. Variability in recruitment was lowest in the scenario with the greatest pond heterogeneity, suggesting that the presence of a diversity of hydroperiods on the landscape may reduce variability in amphibian recruitment.

Through my research, I have been able to determine relationships between climate variables and vital rates in the Columbia spotted frog, and then use population models to explore how future changes in climate or habitat could affect the viability of this population. These results add to our understanding of how climate variation may influence Rana luteiventris dynamics in montane environments, but also provide a demographic backdrop for determining which factors might affect other amphibian populations and species in diverse mountain environments.

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© Copyright 2010 Rebecca Marie Wahl McCaffery