Applying genomic approaches to identify historic population declines in European forest bats

Abstract Anthropogenically driven environmental changes over recent centuries have led to severe declines of wildlife populations. Better tools are needed to assess the magnitude and consequences of these declines. Anecdotal evidence suggests European bat populations have suffered substantial declines in the past centuries. However, there is little empirical evidence of these declines that can be used to put more recent population trends into historic context. This study is a collaboration between academics and conservation practitioners to develop molecular approaches capable of providing evidence of historic population changes that can inform conservation status assessments and management. We generated a genomic dataset of 46,872 SNPs for the Western barbastelle, Barbastella barbastellus , a regionally Vulnerable bat species, including colonies from across the species' British and Iberian ranges. We used a combination of landscape genetics and model‐based inference of demographic history to identify both evidence of population size changes and possible drivers of these changes. Levels of genetic diversity increased and inbreeding decreased with increasing broadleaf woodland cover around the colony. Genetic connectivity was impeded by artificial lights and facilitated by rivers and broadleaf woodland cover. The demographic history analysis showed that both the northern and southern British barbastelle populations have declined by 99% over the past 330–548 years. These declines may be linked to the loss of large oak trees and native woodlands due to shipbuilding during the early colonial period. Synthesis and applications . Genomic approaches can provide a better understanding of the conservation status of threatened species, within historic and contemporary contexts, and inform their conservation management. Our findings of will directly influence the definition of the Favourable Conservation Status of the barbastelle, in turn influencing considerations of the conservation of the species in development plans. Knowledge gained will also help set species recovery targets. Policymakers are interested in using our approach for other species. This study shows how we can bridge the implementation gap between genomic research and direct conservation applications. There is an urgent need to carry out such collaborative studies for other priority species to enable informed species recovery interventions via policy mechanisms and project delivery.