Date of Award

December 2019

Degree Type

Thesis

Degree Name

Master of Science

Department

Biological Sciences

First Advisor

Emily K. Latch

Committee Members

Jeffrey Karron, Gary Roloff

Keywords

density, genetic diversity, Lepus americanus, non-invasive genetic tagging, population structure, spatially explicit capture-recapture

Abstract

As climate continues to change at a rapid rate, species are increasingly vulnerable to the resulting environmental changes. This is especially true for species whose fitness is closely linked to climate-associated environmental conditions. One of these vulnerable species is snowshoe hare, Lepus americanus, who depends on the timing and duration of snowfall to provide camouflage when they go through seasonal pelage changes from brown in the summer to white in the winter. Whereas snowshoe hare are stable across the core of their range, populations along the southern range edge are experiencing declines due to climate driven environmental changes that cause a mismatch between pelage color and the background environment (e.g., white hare pelage against a brown snowless background), making hare more conspicuous to predators, reducing survival and leading to localized extirpations. My thesis aimed to gather baseline demographic estimates (e.g., density) and to characterize fine-scale patterns of genetic diversity and gene flow of snowshoe hare subpopulations in a portion of their southern range within the Hiawatha National Forest-East (HNFE) in Michigan. I combined the two fields of demography and population genetics through non-invasive genetic tagging, in which snowshoe hare fecal pellets (n=847) representing 160 individuals were used in both spatially explicit capture-recapture and genetic analyses. Snowshoe hare density varied across occupied sites (range=0.02-0.838 hares/ha) and was low overall (>1 hare/ha), but similar to other areas along their southern range edge. Density was positively correlated with horizontal vegetation cover at 50 cm (p=0.007) and 100 cm (p=0.01), and conifer stem density (p<<0.001), habitat features previously found to promote snowshoe hare density. Genetic diversity estimates of heterozygosity and allelic richness were high and similar across sites. I found 3 distinct genetic clusters indicating population structure, but this pattern is weak and genetic differentiation was low. Overall, these results indicate that despite low snowshoe hare population densities, genetic diversity remains high and genetic differentiation weak, contrary to expectations for declining populations. Significant differentiation observed between some sites suggests that these populations are beginning to become isolated and would benefit from management actions to increase connectivity between these sites. The variation we see in density across our sites is likely driven by heterogeneity in the landscape and in order to maintain the adaptive potential of snowshoe hare in the HNFE in the face of climate change, maintaining high densities of snowshoe hare populations and subsequent levels of genetic diversity and gene flow should remain a focus of forest managers. This thesis provides the first assessment of snowshoe hare genetic diversity, population genetics, and localized density in this region and supports the effectiveness of using non-invasive genetic tagging to monitor snowshoe hare populations along the southern edge of their range as they face increased vulnerability to climate change.

Download

Share

COinS