The intersection of life history characteristics and anthropogenic barriers: A genetic investigation of six mammal species in Indiana
Abstract
Genetic connectivity is a crucial element of self-sustaining wildlife populations. Anthropogenic barriers, such as interstate highways, can disrupt gene flow by preventing dispersal between groups of individuals. Another gene flow disruptor is isolation by distance (IBD): the principle that population differentiation increases as spatial distance increases, because individuals are more likely to mate with individuals that are geographically proximate rather than distant. Investigating landscape genetics of wildlife populations is an important step towards understanding the landscape features and spatial scales that are relevant to maintaining connectivity. In Chapter 1, I explored the effects of interstate highways on genetic connectivity for six species of mammals in Indiana. These species included raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), fox squirrel (Sciurus niger), eastern gray squirrel (S. carolinensis), eastern chipmunk ( Tamias striatus), and white-footed mouse (Peromyscus leucopus ). These species represent a range of attributes, several of which affect dispersal ability across the interstate highway. Site characteristics, such as culverts and bridges, were included in the analysis. Population clustering was evaluated using Bayesian population assignment software and population genetic metrics. The results of the population genetic analyses indicated that five of the study species experienced a decrease in gene flow in relation to interstate highways. Smaller species exhibited population differentiation at more sites than the larger species; however, interstate highways were not a barrier to genetic connectivity for fox squirrels. My results are concordant with previous road ecology research; the barrier effects of high-traffic roads are variable, depending on the study species and potential crossing points. These findings may be carefully extrapolated to predict how species of concern may be impacted by high-traffic roads. For Chapter 2, I investigated isolation by distance (IBD) for two wide-ranging mesopredators: raccoons and Virginia opossums. Previous research has failed to detect the scale of IBD for these species, due to small sample sizes or research design. I investigated IBD using samples collected from nine sites across north central, west central, south central and southern Indiana. My methods included a Bayesian population assignment test and matrix correlation methods. In the Bayesian model, raccoons were assigned to three populations, whereas Virginia opossums exhibited panmixia. Spatial autocorrelation results showed a significant positive correlation between genetic and geographic distance between raccoons up to 25 km and for Virginia opossums up to 4 km. Interspecific differences in behavior and dispersal are the likely causes for differences in the spatial partitioning of populations. The results from this research provide crucial information regarding the genetic connectivity of these mesopredators, and may guide predictions of disease transmission.
Degree
Ph.D.
Advisors
Rhodes, Purdue University.
Subject Area
Wildlife Conservation|Wildlife Management|Genetics
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