Genetic structure of Greater Sage-Grouse (Centrocercus urophasianus) in a declining, peripheral population

Loss of suitable habitat and subsequent fragmentation of populations are recognized as important factors in the decline and extinction of many species because they result in smaller, more isolated populations with reduced genetic diversity. The Greater Sage-Grouse (Centrocercus urophasianus), having declined in distribution and abundance throughout its range, is a candidate species under the U.S. Endangered Species Act and a species of special concern in California. Because the relationships between dispersal, gene flow, and genetic structure are interrelated and affect the long-term persistence of Greater Sage-Grouse, we assessed the genetic structure and patterns of dispersal among Greater Sage-Grouse in a declining, peripheral population in northeastern California. We genotyped 19 microsatellite loci from 167 individuals from 13 leks and 20 individuals captured off lek. Greater Sage-Grouse in northeastern California appear to maintain gene flow and genetic diversity across the sampled region. Despite population declines and habitat loss, leks were not genetically differentiated. Our results showed significant isolation-by-distance among males, which suggests that male Greater Sage-Grouse are more philopatric than females. Spatial autocorrelation analysis revealed stronger spatial structuring for males than for females. Results from the corrected assignment index also confirmed female-biased dispersal, although differences between sexes were not significant. While more research is needed on the proximate and ultimate causes behind the patterns we observed, our results serve as an important step toward understanding genetic structure and patterns of sex-biased dispersal in Greater Sage-Grouse occupying the periphery of the species' geographic distribution.