• conservation genetics;
  • hybridization;
  • population genetics – empirical;
  • wildlife management

Admixture and introgression have varied effects on population viability and fitness. Admixture might be an important source of new alleles, particularly for small, geographically isolated populations. However, admixture might also cause outbreeding depression if populations are adapted to different ecological or climatic conditions. Because of the emerging use of translocation and admixture as a conservation and wildlife management strategy to reduce genetic load (termed genetic rescue), the possible effects of admixture have practical consequences (Bouzat et al. 2009; Hedrick & Fredrickson 2010). Importantly, genetic load and local adaptation are properties of individual loci and epistatic interactions among loci rather than properties of genomes. Likewise, the outcome and consequences of genetic rescue depend on the fitness effects of individual introduced alleles. In this issue of Molecular Ecology, Miller et al. (2012) use model-based, population genomic analyses to document locus-specific effects of a recent genetic rescue in the bighorn sheep population within the National Bison Range wildlife refuge (NBR; Montana, USA). They find a subset of introduced alleles associated with increased fitness in NBR bighorn sheep, some of which experienced accelerated introgression following their introduction. These loci mark regions of the genome that could constitute the genetic basis of the successful NBR bighorn sheep genetic rescue. Although population genomic analyses are frequently used to study local adaptation and selection (e.g. Hohenlohe et al. 2010; Lawniczak et al. 2010), this study constitutes a novel application of this analytical framework for wildlife management. Moreover, the detailed demographic data available for the NBR bighorn sheep population provide a rare and powerful source of information and allow more robust population genomic inference than is often possible.