Electronic Theses and Dissertations

Date

2024

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

Committee Chair

Emily Puckett

Committee Member

Youngsang Kwon

Committee Member

Matthew Parr

Abstract

The landscape along the northwest coast of North America structures species populations in and around Southeast Alaska. Brown bears (Ursus arctos) and American black bears (U. americanus) are sympatric in this region. They are similarly sized omnivores and interspecific competition directly affects the resources available to each species as brown bears are larger, more aggressive, and can competitively exclude; however, black bears can better utilize dispersed food sources. Within this system I asked two questions about brown and black bears in Southeast Alaska. The first question had two parts; how has the environment structured gene flow in both species, and are the observed patterns different. I sequenced the DNA from tissue samples for both species from 2017 to 2021 to answer our questions. I analyzed population structure and found support for seven populations of brown bears and six populations of black bears. I used landscape genetics to address gene flow by regressing genetic distance with nine environmental variables. I found that landcover both facilitated and impeded gene flow the most in both species. The categories that contributed the most to gene flow were different for each species and water served as a barrier to both species. The second question was driven by reports from hunters, guides, and management personnel that brown bears are increasingly seen where black bears had previously been found in greater frequency. I analyzed hunter harvest records from 1995 to 2022 to address the question and restricted our analysis to Game Management Units 1C and 1D where these shifts in species density have predominantly been reported. I estimated population size over time, performed a spatial statistical analysis of harvest patterns, and assessed hunter effort and success. From these analyses I found empirical evidence in support of increased brown bear density in areas of 1C but did not find support in 1D. I demonstrated that gene flow patterns differed between two species with a similar ecological niche across a heterogenous environment. I also illustrated the utility of mortality data in detecting distribution changes within sympatric species.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest.

Notes

Open Access

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