Genetic structure of white -footed mice (Peromyscus leucopus) and eastern chipmunks (Tamias striatus) in an agriculturally fragmented ecosystem: A landscape genetics approach

Human alteration of natural ecosystems in the form of habitat fragmentation changes the composition and configuration of the landscape and may shift the distribution of resources essential for survival of individuals or entire species. Habitat patches become separated by a complex system of non-ideal matrix, which can inhibit movement and ultimately lead to genetic substructure among populations. In time, negative consequences of isolation may be loss of genetic diversity or extirpation of local populations. I examined white-footed mice and eastern chipmunks in northern Indiana, a region that has undergone extensive changes in land cover over the last 200 years, at multiple scales to elucidate the effect of landscape features on genetic structure. I found no evidence of genetic structure in white-footed mice at the study area scale, while eastern chipmunks exhibited evidence of at least five large subpopulations across the study area. Small scale analysis revealed extensive genetic structure in eastern chipmunks, and a variable degree of structure in white-footed mice. Many populations of eastern chipmunks were separated by distances well within the species’ dispersal capabilities, indicating that a factor other than distance was hindering gene flow. While setting a limit on the maximum distance between two populations, I evaluated the permeability of eight land cover variables at eight different widths. Forests, grasslands, and non-treed corridors were consistently the greatest facilitators of gene flow, while there was some evidence that treed corridors and roads limited gene flow. Finally, I investigated the possible factors influencing the variability in presence of genetic structure at small scales in white-footed mice using both landscape composition and configuration variables. Unlike eastern chipmunks, treed corridors seem to facilitate gene flow and reduce the probability of observing genetic structure at small scales