Differential expression and climate adaptation in barbastelle bats

Understanding evolutionary responses to climate change is crucial for species of conservation concern, especially for long-lived species such as bats. In this study on western barbastelle bats (Barbastella barbastellus), we use transcriptomics and genomics to investigate (i) plastic responses to different in situ temperatures, and (ii) genetic adaptations to climate that may have evolved in B. barbastellus. Differential expression analysis revealed a number of upregulated genes in bats from lower temperatures (9.9-11.3oC), UCP2 of which has been reported to be important for non-shivering thermogenesis. This suggests that these temperatures induce a cold stress plastic response and are likely near the thermal minima of active B. barbastellus. In contrast, few genes were differentially expressed in higher temperatures (15.0-16.4oC), which suggests that these temperatures are not near the thermal maxima of active barbastelle bats across the range studied. Climate-associated loci identified by genotype-environment association analysis revealed potential adaptations to maximum summer temperatures (between England and Iberian bats) and to precipitation levels (in Teruel bats). Of the variants located within gene regions, IGF1 and MAPKAPK2 have roles in thermogenesis and inflammatory responses. Genomic offset analysis highlighted an elevated risk of maladaptation to future climates if a global fossil-fueled development scenario is prioritised, but a relatively low risk if a global sustainability pathway is chartered. Our results provide evidence that, during their active months, barbastelle bats have evolved plastic mechanisms for acclimating to lower temperatures outside of their optimum range and genetic adaptations to warmer and more arid climates.