Whole-genome evaluation of genetic rescue: the case of a curiously isolated and endangered butterfly
Genetic rescue, the translocation of individuals among populations to enhance gene flow, can mitigate inbreeding depression and the loss of adaptive potential in small, isolated populations. Genetic rescue is currently under consideration for an endangered butterfly species in Canada, the half-moon hairstreak (Satyrium semiluna). A small, unique population persists in Waterton Lakes National Park, Alberta, isolated from other populations by more than 350 km. However, the potential benefits of genetic rescue for this population have not been thoroughly evaluated.In this study, we present the first chromosome-level genome assembly and whole-genome resequencing data for the species. Our findings reveal that the Alberta population exhibits extremely low genetic diversity and is highly divergent from the nearest populations in British Columbia and Montana. Runs of homozygosity indicate a prolonged history of inbreeding, while coalescent analyses suggest that this population has been small, isolated, and stable for up to 40,000 years. Populations that remain viable despite inbreeding and low genetic diversity often undergo purging of deleterious recessive alleles. In such cases, genetic rescue might reintroduce these alleles, posing a risk rather than a benefit. Ecological niche modeling also shows that the Alberta population occupies an environment atypical for the species. These combined findings suggest that population crosses could lead to outbreeding depression in the short term. Nevertheless, the Alberta population's reduced adaptive potential makes future genetic rescue a consideration as climate conditions shift. To address this, proactive experimental population crosses are recommended to assess reproductive compatibility and offspring fitness.
BioProject