Degree Type

Dissertation

Date of Award

2011

Degree Name

Doctor of Philosophy

Department

Ecology, Evolution, and Organismal Biology

Major

Ecology and Evolutionary Biology

First Advisor

William R. Clark

Second Advisor

Anne M. Bronikowski

Abstract

Population structure, the term used to describe the reproductive and demographic cohesiveness of con-specific individuals, is a fundamental concept in ecology and evolution. Despite the importance, patterns and processes of population structure are poorly understood, particularly for highly mobile species with broad distributions. For these organisms, the ability to disperse across large distances and occupy diverse habitats should promote gene flow and limit intraspecific genetic differentiation. However, significant genetic structure is often detected even in the absence of obvious movement barriers, indicating that the factors influencing population subdivision are not always clear. In this dissertation, I examined the patterns and processes of spatial genetic structure over three spatial scales in a mobile and abundant carnivore, the bobcat (Lynx rufus). At the local scale, I integrated telemetry, landscape, and genetic data to test whether habitat fragmentation influences movement behavior of bobcats, and whether these movement constraints translate into fine-scale genetic structuring of bobcats within an agricultural landscape. Despite observing an influence of habitat heterogeneity on bobcat movement behavior, whereby bobcats preferentially moved through forests surrounded by perennial habitat, I did not detect a signature of a landscape effect in the fine-scale genetic structure. However, much of Iowa's landscape was predicted to pose a high level of resistance to bobcat movement, likely impeding connectivity with bobcat populations in neighboring states. At the regional scale, I characterized spatial genetic structure across 15 Midwestern states to delineate populations and identify landscape characteristics influencing recent expansions of bobcats into areas from which they had been extirpated. I identified 6 genetic populations separated by both physical (large expanses of row cropping and a major waterway) and cryptic (zones of sharp changes in habitat type) boundaries. As predicted by the fine-scale analysis, results indicated that bobcats do not readily disperse through this agriculturally-modified landscape, and the newly-established populations in Iowa and northern Missouri are closely linked with bobcats to the southwest, but have had little genetic input from populations to the north and east. At the continental scale, I analyzed genetic data from across the entire United States to determine whether landscape features or other factors generate deeper, broad-scale genetic divergences that warrant recognition as distinct subspecies. The primary signature involved a longitudinal cline with a transition zone occurring along the Great Plains in the central U.S., distinguishing bobcats in the eastern part of the country from those in the western half. Results implicated historical processes as the primary cause of the observed continental-scale genetic patterns, and demographic evidence supported a scenario of post-glacial expansion from two disjunct Pleistocene refugia, which likely were isolated by the aridification of the Great Plains grasslands during interglacial periods. Although genetic patterns were loosely congruent with most subspecific designations, the data supported only two historically independent units: eastern and western bobcats. Collectively, the data indicate that despite the bobcat's mobility and broad niche, population genetic structure is evident and characterized by complex combinations of clines, clusters, and isolation-by-distance arising from habitat heterogeneity, restricted dispersal, and historical processes.

Copyright Owner

Dawn Marie Reding

Language

en

Date Available

2012-04-28

File Format

application/pdf

File Size

194 pages

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