Bobcats across their geographic range: Combining ecological niche modeling and morphology to assess the population genetic structure of Lynx rufus

Background/Question/Methods

Despite a broad distribution, general habitat requirements, and large dispersal potentials, the bobcat exhibits a distinct genetic segregation that longitudinally transects the central U.S. with limited overlap. In order to understand the evolution and maintenance of this population structure, we must use an integrative approach that incorporates genetic, morphological, and environmental aspects in a historical and contemporary framework. The goals of this study are to determine (1) if the climate of the Last Glacial Maximum (LGM) isolated bobcats into genetic refugia that expanded post glaciation to create the contemporary genetic and geographic distribution observed today, and (2) if strong lineage delineation is manifested in the cranial morphology of L. rufus in addition to general geographic and environmental variability. Ecological niche models were created using varying sets of bioclimatic parameters to evaluate geographic suitability in historical and contemporary climate conditions and to reveal range expansion following the recession of the LGM. Geometric morphometric methods were used to evaluate variations in the cranium and mandible of L. rufus and compared across geographic and genetic variability.

Results/Conclusions

Genetically distinct populations of L. rufus, with a climatic restriction to migration occurring in the central U.S., is supported by both models and morphological analyses. When projected onto historical climate, decreased suitability in the central U.S. remains apparent, feasibly creating refugia for the extent of advanced glaciation. Although climatically suitable conditions exist on either side of this cline, aridification following glacial recession coupled with the contemporary dominant grassland habitat of this region may be restricting migration and gene flow, effectively maintaining disparate genetic populations. Geometric morphometric analyses have revealed strong correlations of shape with geographic and environmental variables. Linear trends across a longitudinal gradient suggest that the morphology of the genetic populations are distinctly different with an apparent zone of convergence and hybridization. A junction of mean shapes and skull angles occur at approximately 38° latitude and -98° longitude (central Kansas) representing a region of morphological divergence. Correlations with the principle components of climate also reveal that variations in precipitation and temperature are significant in the morphological diversity of this species. By using ENMs to simulate the contemporary and LGM geographic distributions, and shape analyses to quantify local adaptations, a robust assessment of the biogeographic considerations for population genetic structure can begin to reveal what causes and maintains the genetic structure of a wide – ranging, generalist species, in the ever – changing climate and ecosystems of our planet.