Invasive crayfish in a desert spring system: Using landscape genetics to inform ecological restoration

摘要

The delimitation of dispersal routes utilized by invasive species has the potential to direct management efforts in invaded systems, and may be used to prevent the invasion of native communities. Landscape genetics provides a powerful tool to determine post-invasion movement corridors by integrating inferences of gene flow between populations with landscape connectivity metrics. This technique was used to describe dispersal patterns of invasive red swamp crayfish (Procambarus clarkii) through Ash Meadows, a spring system and endemic hotspot in the Mojave Desert. Red swamp crayfish have successfully invaded aquatic ecosystems across much of the globe, and cause severe ecological damage in the form of biodiversity loss and habitat destruction. In Ash Meadows, a combination of anthropogenic habitat degradation and the establishment of invasive species like P. clarkii has caused the extinction of an endemic poolfish, and extirpations and severe population declines of endangered pupfish. Although many Ash Meadows springs are hydrologically isolated, intermittent connectivity occurs during heavy precipitation events - allowing for dispersal of native and invasive species. We used a landscape genetics approach in combination with Geographic Information System (GIS) mapping of surface hydrology to test alternative hypotheses of P. clarkii invasion routes and colonization events throughout Ash Meadows. Mitochondrial DNA (COI) and microsatellite markers were used to infer colonization events and gene flow for populations at 15 sample sites. Modeled historic outflows, in conjunction with waterway mapping based on aerial imagery and LiDAR data, reveal variable drainage routes across the flat topography of Ash Meadows. Estimates of gene flow between P. clarkii populations highlight the drainages utilized by crayfish to reach distal springs. Additionally, analyses of mtDNA haplotype diversity and distribution suggests that 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.