Effects of habitat fragmentation on small-mammal movements

Increasing rates of habitat fragmentation requires evaluation of its genetic and demographic impacts on wildlife populations. Understanding genetic impacts of habitat fragmentation is important for managing long-term genetic variability of populations. I explored the genetic consequences of forest fragmentation on the red-backed vole (Clethrionomys gapperi ) at different spatial scales and landscape contexts.; First, I examined the large-scale impacts of forest management on this forest specialist. For three populations in a roughly linear arrangement (15 to 50 km apart) in an area containing >60% closed-canopy forest, I found a significant linear relationship between genetic distance and geographic distance suggesting that populations were not negatively impacted by fragmentation. Changes in population densities may obscure such relationships.; Second, I examined how local landscape features affect vole populations. Populations in three landscape configurations (contiguous—sites located completely within a matrix of closed-canopy forest; corridor—sites connected by a corridor of closed-canopy forest; isolated—sites separated from each other by clearcut or young regeneration stands) differed significantly in genetic structure. Genetic distance increased in the order contiguous, corridor, and isolated. I performed a similar analysis on the deer mouse, Peromyscus maniculatus, a habitat generalist. Peromyscus showed no pattern suggesting that this species does not react to the presence of forest corridors. The results suggest that in a managed forest, corridors between unlogged habitats maintain higher population connectivity for C. gapperi than landscapes without corridors.; Finally, I developed a computer simulation model to examine the effects of local landscape context on genetic patterns between populations. The age-structured population genetic model was coupled to an individual-based modified-random-walk movement model to simulate vole populations. Increased mutation rate and decreased population size increased genetic distance between populations. Isolated populations consistently had the highest genetic distance and contiguous populations had the lowest, which correlated with observed migration rates. Corridor quality also affected migration rate. These results suggest that a very simple model is sufficient to explain genetic patterns seen in previous studies.