Discerning invasion history in an ephemerally connected system: landscape genetics of Procambarus clarkii in Ash Meadows, Nevada

The delimitation of dispersal routes used by individuals moving between populations has the potential to direct management efforts aimed at limiting the spread of invasive species. Red swamp crayfish (Procambarus clarkii) have successfully invaded aquatic ecosystems across much of the globe, causing loss of biodiversity and habitat destruction. Our research focuses on a Mojave Desert spring system in Ash Meadows National Wildlife Refuge, where a combination of anthropogenic habitat degradation and the establishment of invasive species have caused extinctions, extirpations, and severe population declines of endangered fishes. To infer the invasion history of hydrologically isolated springs, we tested alternative hypotheses of P. clarkii dispersal routes and colonization events throughout Ash Meadows using a landscape genetics approach that combined analysis of microsatellite and mitochondrial DNA genotypes with geographic information system (GIS) mapping. Modeled historic outflows, in conjunction with waterway mapping based on aerial imagery and LiDAR data, show variable drainage routes across the flat topography of Ash Meadows. Estimates of gene flow between P. clarkii populations revealed the drainages utilized by crayfish to move from central to peripheral springs. Additionally, analyses of mtDNA haplotype diversity and distribution suggest isolated springs were colonized by few individuals, and subsequent emigration has been rare. These results will inform ecological restoration in Ash Meadows by directing the placement of barriers to prevent reinvasion of distal springs after eradication of P. clarkii populations. Finally, this research provides a case study for elucidating the functional connectivity of ephemerally connected landscapes, using the integration of genetic and GIS techniques.