Conservation Genomics and Species Distribution Models Motivate Proactive and Collaborative Conservation in an Era of Rapid Change

Abstract

Small, fragmented plant populations with low genetic diversity are susceptible to deterministic and stochastic events that can affect long-term persistence of species. Penstemon lemhiensis Keck (Plantaginaceae) is a rare endemic with small, scattered populations across Idaho and Montana threatened by cumulative impacts of biological invasion, drought, and altered fire regimes. When contextualized by an understanding of rangewide distributions under different environmental change scenarios, conservation genetics can be leveraged to motivate proactive conservation action among collaborating stakeholder groups. We applied a genotypingby- sequencing (GBS) approach across eight populations and 93 individuals of P. lemhiensis. Genetic differentiation among populations followed an isolation-by-distance pattern and ranged from low to moderate (FST = 0.095-0.280). Values of inbreeding were low, and often negative (FIS = -0.039-0.032), indicating outbreeding within populations. Population structure analyses identified six ancestral populations and admixture across all individuals. We contextualized these findings by fitting bioclimatic niche models to past, present, and future climate regime scenarios. Habitat connectivity peaked mid-Holocene and nearly disappeared in the future scenario. Genetic analyses and species distribution models indicated that the species may experience drastic range contraction and accelerated isolation and inbreeding in future. We identified a core area in the Upper Big Hole Valley, Montana most likely to persist as suitable habitat. The National Park Service, Bureau of Land Management, and US Forest Service were identified as key stakeholders in that valley. We outline a proactive collaborative conservation strategy that aim to maintain wild P. lemhiensis populations.