Master's Theses

Date of Award

Spring 2004

Degree Name

Master of Science (MS)

Department

Biology

Advisor

Jerry R. Choate

Abstract

Research on North American pocket gophers has revealed that their geographic ranges tend to be allopatric. Competition and habitat selection presumably are responsible for allopatry of several mammalian species. MOSI of what is know all about the causes of allopatry in pocket gophers is based on research conducted in Colorado and New Mexico. That research concluded that when two or more pocket gopher species occur together, they maintained disjunct distributions and possess different habitat requirements. In Kansas, the distributions of two species of pocket gophers, Geomys bursarius and Cratogeomys castanops overlap. Geomys bursarius reportedly is a habitat specialist that occurs in disturbed areas and sandy soils, whereas C. castanops is a soil generalist that occurs in a wide range of soil texture but is restricted to undisturbed native shortgrass prairies. The objectives of my study were to ascertain the current distribution of C. castanops in Kansas, to determine whether its distribution has diminished since it was last mapped in 1971, to document whether C castanops and G hursarius are sympatric in Kansas, to investigate which factors might be influencing the distributions of these two species, and to evaluate whether competition or habitat selection is more important in determining the geographic relationship between C. castanops and G. bursanius in Kansas. I trapped pocket gophers across west-central Kansas and collected soil texture and land cover data. I used ArcView 3.2 to map pocket gopher distributions as well as soil texture and land cover data in the potential home ranges of the pocket gophers. I also investigated the potential causes of large areas where no pocket gophers occurred. I found that, although the geographic ranges of the two species overlap, there were no instances of sympatry. Therefore, I defined their distributions as parapatric. My results showed differences in soil texture preference both at the capture locality and within the potential home range: however, the presence or absence of disturbance in an area is not a good indicator of pocket gopher occurrence. Unoccupied areas within the study area are characterized by soil texture and land use practices that are not conducive to pocket gopher occurrence. I conclude that G. bursarius and C. castanops currently are not competing because they are not sympatric. However, past competition between G. bursarius and C. castanops might have resulted in the observed differences in habitat selection.

Rights

Copyright 2004 Justin D. Hoffman

Comments

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