Watershed Structure and Isolation-By-Distance Drives Genetic Structure of a Dispersal Limited Species, the Rocky Mountain Sculpin (Cottus sp.)

Understanding how dispersal ability and habitat configuration constrains gene flow in threatened species may provide valuable insight for conservation management. Rocky Mountain Sculpin (Cottus sp.) are listed as a threatened species within Canada due to their limited distribution, drought, flow augmentation and land-use change. Here we examine a combination of movement data from Passive Integrated Transponder (PIT) tags (n = 223) and genetic samples (n = 1,017) that were genotyped at nine microsatellite loci to describe movement and spatial population genetic structure. Rocky Mountain Sculpin appear to be extremely sedentary because 50% of individuals moved a maximum distance of 10 meters (upstream or downstream) from the release point over a 5 month period. We also found that watershed structure had a large impact on population genetic structure, where our STRUCTURE model identified four broad scale populations of Rocky Mountain Sculpin in Canada. Finally, genetic structure in Rocky Mountain Sculpin is significantly related to fluvial distance between sample locations (i.e., isolation-by-distance). Our study suggests that the threatened Rocky Mountain Sculpin may be particularly susceptible to environmental stressors as they may not be able to disperse readily to avoid adverse conditions and may require more active conservation management for their long-term survival.