Connectivity of prairie dog colonies in an altered landscape: inferences from analysis of microsatellite DNA variation
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Connectivity of populations influences the degree to which species maintain genetic diversity and persist despite local extinctions. Natural landscape features are known to influence connectivity, but global anthropogenic landscape change underscores the importance of quantifying how human-modified landscapes disrupt connectivity of natural populations. Grasslands of western North America have experienced extensive habitat alteration, fragmenting populations of species such as black-tailed prairie dogs (Cynomys ludovicianus). Population sizes and the geographic range of prairie dogs have been declining for over a century due to habitat loss, disease, and eradication efforts. In many places, prairie dogs have persisted in the face of emerging urban landscapes that carve habitat into smaller and smaller fragments separated by uninhabitable areas. In extreme cases, prairie dog colonies are completely bounded by urbanization. Connectivity is particularly important for prairie dogs because colonies suffer high probabilities of extirpation by plague, and dispersal permits recolonization. Here we explore connectivity of prairie dog populations using analyses of 11 microsatellite loci for 9 prairie dog colonies spanning the fragmented landscape of Boulder County, Colorado. Isolation-by-resistance modeling suggests that wetlands and high intensity urbanization limit movement of prairie dogs. However, prairie dogs appear to move moderately well through low intensity development (including roads) and freely through cropland and grassland. Additionally, there is a marked decline in gene flow between colonies with increasing geographic distance, indicating isolation by distance even in an altered landscape. Our results suggest that prairie dog colonies retain some connectivity despite fragmentation by urbanization and agricultural development.
KeywordsPrairie dogs Microsatellites Connectivity Fragmentation Landscape Urbanization
We thank the City of Boulder Open Space and Mountain Parks Department, the City of Boulder Parks and Recreation Department, the Boulder County Parks and Open Space Department and the Jefferson County Open Space Department for access to study prairie dog colonies on their properties and the Colorado Division of Wildlife for permission to capture and release prairie dogs. Our sincere thanks to the many field workers who collected tissue samples from prairie dogs, especially Amelia Markeson and David Conlin; to Kimberly Kosmenko for collating records of prairie dog relocation; and to Jory Brinkerhoff and Ken Gage for discussion and insight on plague ecology. This research was supported by grants from the National Center for Environmental Research Science to Achieve Results program of the US-Environmental Protection Agency (R-82909101-0) and the National Science Foundation/National Institutes of Health joint program in Ecology of Infectious Diseases (DEB-0224328).
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