Understanding how environmental factors act as selective pressures and drive local adaptation is of great interest in ecology and evolutionary biology, especially in an era of global change. Theory suggests that species with wide latitudinal distributions may have higher degrees of genetic variation, due to natural selection facilitating adaptation to local conditions. Such large pools of genetic diversity may help buffer species from the effects of climate change, dependent on how any adaptive variation is distributed among populations and across a geographic range. Given projections of warming over the coming century, it is important we understand the degree to which conspecific populations can adapt to their local thermal environment, and the mechanisms by which they do so. Here, we assessed population structure through principal component analysis and STRUCTURE and performed environmental association analyses and outlier tests to investigate the genomic signatures of spatially divergent selection in three populations of yellowtail clownfish, Amphiprion clarkii, that inhabit distinct thermal environments.
Results/Conclusions
Based on an analysis of 5,729 single nucleotide polymorphisms (SNPs), we found little indication of population structure among our three sites. However, we identified 89 adaptively divergent loci in 33 candidate genes under selection, all of which were significantly correlated with sea surface temperature minimum. Several of these candidate genes are known to play a role in protein turnover, metabolism, and translation, functions that are often up-regulated during cold stress. Many of our candidate loci were also found in regulatory regions, suggesting that these populations may be adapting to local thermal conditions via alterations to gene regulation networks and differential gene expression. Our results indicate that A. clarkii populations are experiencing spatially divergent selection likely driven by their experienced thermal environment and provide strong support for incorporating local adaptation into models assessing the ability of species to respond to future climatic conditions.