Examining the population genetic structure of Timber Rattlesnakes in East Texas

Examining the population genetic structure of Timber Rattlesnakes in East Texas

Witkowski, Stephen

Lost Pines Habitat Conservation Plan                                                                                                            

Bastrop, Texas USA

Fortner, Michael                                                                                                                                               

Sirsi, Shashwat                                                                                                                                            

Emerson, James D. (presenting)

 xwz6@txstate.edu

Texas State University                                                                                                                                           

San Marcos, Texas USA

Orlando, Dylan

Raven Environmental Services, Inc.                                                                                                           

Huntsville, Texas USA

Clark, Rulon W.

San Diego State University                                                                                                                             

San Diego, California USA

Timber Rattlesnakes (Crotalus horridus) are terrestrial vipers that are endemic to North America. These snakes had an erstwhile distribution through most of the eastern United States and adjacent Canada, extending southward into northern Florida, and westward into eastern Texas. Research efforts on the species have predominantly focused on northern populations. Particularly, there are gaps in our knowledge of genetic diversity in populations from the southern portion of the species range. Understanding the value of such populations in the face of increasing global change is crucial to inform species management plans. We used 14 microsatellite loci to generate genotypes for 59 individuals that were sampled in southeast Texas. At our focal site in Montgomery County, we observed localized genetic structure with support for two distinct clusters within a maximum linear extent of ~ 9 km. Thus, genetic data supports the notion of southern populations of C. horridus forming local breeding aggregates akin to individuals from northern localities. Additionally, such localized genetic structure at our focal site suggests distinct demographic histories for each genetic cluster. Our site may represent habitat that is occupied by a stable, established population as well as recent immigrants to the site. We recommend the use of several independent nuclear genetic markers to characterize genetic variation across the geographic range of C. horridus. This will enable an evaluation of the utility of range edge populations in managing unique and wide-ranging species.