For most animal species, natural or man-made barriers such as waterways, roads, or habitat gaps often constrain the movement of individuals across a landscape, reducing genetic exchange and isolating members into distinct populations. But highly mobile, broadly distributed species may be less susceptible to such barriers and hence genetic subdivision. This study will identify if and how landscape characteristics mediate gene flow over three spatial scales in a mobile carnivore, the bobcat (Lynx rufus). At the local scale, telemetry, genetic, and landscape data will be combined to test whether habitat fragmentation influences movement and fine-scale genetic structuring of bobcats within an agricultural landscape. At the regional scale, genetic patterns will be used to delineate populations and identify landscape characteristics influencing recent expansions of bobcats into areas from which they had been extirpated. At the continental scale, DNA samples will be collected and analyzed from across the United States to determine whether landscape features also generate deeper, broad-scale genetic divergences that warrant recognition as distinct subspecies.
This project will lead to significant improvements in our understanding of how landscape characteristics may influence evolutionary and ecological processes in mobile species like bobcats. Such findings are important for evaluating the potential impact of landscape changes on population dynamics and species persistence, predicting the spread of emerging diseases, and effectively managing wildlife. This work will also foster science education through mentoring and outreach, and by providing a hands-on research experience for a high school biology teacher.
Because of factors such as geographic distance, physical obstacles to movement, or behavioral traits, some members of a species are more likely to interact with one another than with other members. "Populations" refer to such groups of individuals with the potential to interbreed. It is important to understand how and why individuals are structured into populations because it can greatly influence, for example, how a species could evolve, spread disease, or recover from local extinction events. However, the patterns and mechanisms of population structure are less clear for species with high dispersal capabilities and broad distributions because movement barriers are not obvious. We examined the patterns and processes of genetic structure over three spatial extents in a mobile and widespread carnivore, the bobcat. Although this species is generally common and adaptable, it had historically been eliminated from large areas in the agricultural Midwest and is currently expanding back into the region. At the local scale (within Iowa), we analyzed genetic markers from 625 individuals along with tracking data from radio-collared animals to evaluate whether habitat fragmentation influenced fine-scale genetic structuring within this agricultural landscape. The tracking data clearly demonstrated that bobcats prefer forest and grassland perennial habitats while moving across the landscape, but we did not find that these behavioral effects translated into differentiated genetic structure among individuals within Iowa. However, our models predicted that much of Iowa’s landscape poses a high level of resistance to bobcat movement. This prediction was consistent with our regional genetic analyses, which showed limited genetic similarity of Iowa bobcats with populations in many neighboring states. The regional study was based on DNA analysis of 1447 individuals from 15 Midwestern states, through which we identified 6 genetic populations separated by both physical barriers (large expanses of row crop agriculture and the Mackinac Straits) and cryptic boundaries (zones of sharp changes in habitat type). Recently-established populations in Iowa and northern Missouri, regions where 30 years ago bobcats were virtually absent, were closely linked with bobcats to the south and west, but showed little genetic input from populations to the north and east. Thus, habitat fragmentation is influencing how bobcats are recolonizing the Midwest. At the continental scale, we analyzed DNA data for 1704 samples from across the entire United States, including samples from 9 of the 12 recognized subspecies. We found that although genetic patterns were loosely congruent with previously delineated subspecific designations, the genetic data supported only two historically independent groups of descendants (eastern and western groups) which adjoin along the Great Plains in central United States. Population genetic evidence supported a scenario of post-glacial expansion from two distinct Pleistocene refugia. In addition, novel genetic sequences discovered in the few Mexico samples included in this study suggests further variation resides in bobcats from that country and warrants additional sampling to investigate the potential uniqueness of Mexico’s bobcat population. As a carnivore and furbearer, the bobcat is a species of ecological and economic importance, so the understanding of population structure directly contributes to proper conservation of this species. As both the regional and national analyses highlight, the identified genetic units occur across several states, suggesting that management strategies for this species should involve more regional cooperation across political boundaries. Since local populations are highly interconnected, management decisions in one state may strongly influence bobcat populations in surrounding states. This may be especially relevant for states in which bobcats are still absent from portions of the landscape, including Iowa, as expansion may depend largely on the population dynamics in neighboring states. Another relevant finding from our study is that bobcats in eastern and western U.S. have had distinct evolutionary histories, and may be adapted to the particular environments they inhabit. Thus, from an evolutionary standpoint, it is important in the future to maintain healthy populations from both regions. Furthermore, our limited data on Mexico indicate the need for further research into the potential uniqueness of the federally endangered Mexican bobcat, which may be of particular conservation and evolutionary importance. An important goal of this project was to foster science education through mentoring and outreach. In summer 2010, we hosted a high school science teacher for 5 weeks of laboratory research, during which the participant experienced the process of scientific research by starting with a research question, processing and analyzing DNA samples, and interpreting and presenting the research findings. In addition, we involved undergraduate and high school students in the research, delivered public presentations to groups ranging from retirement communities to conservation organizations, and maintained a website detailing our research objectives and findings.
