Graduation Date

Spring 2018

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Wildlife

Committee Chair Name

William Bean

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Barbara Clucas

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Jeffrey Dunk

Third Committee Member Affiliation

HSU Faculty or Staff

Fourth Committee Member Name

Matthew Johnson

Fourth Committee Member Affiliation

HSU Faculty or Staff

Subject Categories

Wildlife Management

Abstract

Climate is often considered the single most important factor limiting species’ ranges. Other factors, such as biotic interactions, are often assumed to be included via abiotic proxies. However, differential responses to climate change may decouple these relationships or lead to adaptation to novel environments. Accounting for competition and local adaptation should more accurately describe environmental factors influencing current distributions and increase the predictive accuracy of future distributions. Modeling the endangered giant kangaroo rat (Dipodomys ingens) is an excellent application of these model improvements, as the species range consists of geographically and genetically isolated populations experiencing disparate climatic change. From eight years of trapping data, I used Maxent to model the distributions of two isolated populations of D. ingens. Using local surveys and state-wide data, I also modeled California ground squirrels (Otospermophilus beecheyi), a potential novel competitor. Models included landscape variables (slope and soil composition) and climate variables (temperature, precipitation, and climatic water deficit). Niche overlap between the D. ingens populations was moderate (I = 0.43), suggesting that they already experience different climatic regimes and providing support for population-level modeling. Projecting population models into the future, under a high emission climate change scenario (CCSM4, rcp8.5), resulted in less predicted range contraction than modeling the species as a whole. However, forecasted distributions showed areas of increasing niche overlap between the Panoche population of D. ingens and O. beecheyi (I = 0.63 to 0.74), indicating competition could be a novel range limit. These species distribution models identify range limiting factors and detect potentially important future habitat. However, 27% of modeled suitable habitat is currently in agricultural use, preventing D. ingens occupation. In combination with historical distribution models, we can target key areas to prevent further anthropogenic development and to protect the giant kangaroo rat within an endangered ecosystem.

Citation Style

Journal of Wildlife Management

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