Raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana) are highly abundant, synanthropic mesocarnivores that can transmit epizootic diseases of critical importance to human and livestock health such as rabies and tuberculosis. Individuals of both species can exhibit large dispersal distances and our understanding of population connectivity for both of these species is limited. Data on population connectivity and potential for disease transmission are needed for each of these species for the development of data-informed management, control, and vaccination programs. Genetic connectivity among populations can be estimated by evaluation of metrics such as of isolation by distance (IBD) signatures and population structure. Such metrics are influenced not only by geographic distance and barriers to dispersal but also by the life-history characteristics of the species in question. We investigated the scale at which these species exhibited evidence of connectivity via gene flow, using samples collected from 9 sites spanning 254 km across north-central, west-central, south-central, and southern Indiana, USA. We evaluated genetic connectivity and signatures of IBD using Bayesian clustering analyses and matrix correlation methods. In the Bayesian model, raccoons were assigned to 3 genetic clusters, whereas Virginia opossums exhibited apparent panmixia. Spatial autocorrelation results indicated a significant positive correlation between genetic and geographic distance for raccoons at distances up to 25 km and for Virginia opossums up to 4 km. Interspecific differences in reproductive biology, social behavior, and dispersal are likely the causes for differences between these 2 species in the spatial partitioning of populations across broad ranges. In addition, geographic features and past glaciation events may be affecting the genetic characteristics of present-day raccoon populations. Improved information regarding interpopulation distance for these 2 synanthropic species may contribute to more effective management and disease-control programs. Ó 2014 The Wildlife Society.

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There is a growing body of evidence that habitat fragmentation resulting from anthropogenic land use can alter the transmission dynamics of infectious disease. Baylisascaris procyonis , a parasitic roundworm with the ability to cause fatal central nervous system disease in many mammals, including humans, is a zoonotic threat, and research suggests that parasite recruitment rates by intermediate hosts are highly variable among forest patches in fragmented landscapes. During 2008, we sampled 353 white-footed mice ( Peromyscus leucopus ) from 22 forest patches distributed throughout a fragmented agricultural ecosystem to determine the influence of landscape-level habitat attributes on infection rates of B. procyonis in mice. We characterized each mouse in terms of infection status and intensity of infection, and calculated (on a patch-wide basis) prevalence, mean abundance of B. procyonis , and mean intensity of infection. We used an information-theoretic approach to develop a suite of candidate models characterizing the influence of landscape attributes on each of our measured characteristics of B. procyonis infection in white-footed mice, based on previous knowledge of raccoon ( Procyon lotor ) ecology and B. procyonis distribution in agricultural ecosystems. We observed evidence of B. procyonis infection in mice across all 22 habitat patches sampled. However, parasite recruitment rates and intensity were highly variable among patches, and the results of our analyses suggest that spatial variability in B. procyonis infections was primarily driven by emergent properties of fragmented ecosystems. In particular, prevalence, abundance, and intensity of B. procyonis infections in mice were negatively associated with the size and connectivity of forest patches. These results support previous studies indicating that habitat fragmentation can alter the transmission dynamics of infectious disease, and suggest that factors below the scale of landscape, i.e., fine-scale habitat structure or demographic and behavioral attributes of intermediate and/or definitive hosts, also may be important for predicting patterns of B. procyonis infection in intermediate hosts.

Landscape features that form a barrier for one species may not be a barrier for others, depending on how each species perceives the feature. Barriers may not be equivalent, due to unique characteristics at different locations, which may ameliorate barrier effects. In this study, we employed population genetics techniques to investigate how four Rodentia species with differing life history characteristics (fox squirrels [Sciurus niger], eastern gray squirrels [Sciurus carolinensis], eastern chipmunks [Tamias striatus], and white‐footed mice [Peromyscus leucopus]) responded to interstate highways as barriers to movement at seven locations with differing site‐specific landscape features. For comparative purposes, we included control sites that lacked heavily trafficked roads. We detected genetic differentiation relative to interstate highways among the gray squirrels, chipmunks, and white‐footed mice, but signals for differentiation among those three species varied by site, suggesting that site‐specific features are important considerations for species responses to high‐traffic roads. Chipmunk and gray squirrel populations, two forest specialist species that avoid open areas, exhibited more genetic structure corresponding with highways than either white‐footed mice (a nocturnal generalist) or fox squirrels (a larger‐bodied specialist that traverses open areas more readily than the other species in this study). Fox squirrels did not exhibit genetic differentiation at any site, whereas gray squirrel study populations evinced no population differentiation at sites with bridges spanning the interstate highway. Chipmunks also exhibited population differentiation at two of the control sites, indicating that less obvious barriers in the landscape may be as important as roads for sensitive species. We interpreted variation in genetic differentiation of species across sites in the context of how interstate highway features (i.e., the presence and condition of drainage culverts and bridges near study sites), combined with species‐specific life history characteristics, influence the barrier potential of highways. Culvert presence generally corresponded with a low or nonexistent barrier effect; however, an open, large culvert (>8 m in height) may create a semi‐permeable barrier for species that avoid open areas. Bridge presence appeared to facilitate gray squirrel and chipmunk dispersal across highways.