Advances and limits of using population genetics to understand local adaptation

• Population genetics holds promise to identify traits and ecological variables driving local adaptation.
• These approaches can also be used to uncover the genetic architecture of local adaptation.
• Challenges and limitations related to data quality and statistical analyses should not be overlooked and impose limits on the power of population genetic approaches.

Local adaptation shapes species diversity, can be a stepping stone to ecological speciation, and can facilitate species range expansion. Population genetic analyses, which complement organismal approaches in advancing our understanding of local adaptation, have become widespread in recent years. We focus here on using population genetics to address some key questions in local adaptation: what traits are involved? What environmental variables are the most important? Does local adaptation target the same genes in related species? Do loci responsible for local adaptation exhibit trade-offs across environments? After discussing these questions we highlight important limitations to population genetic analyses including challenges with obtaining high-quality data, deciding which loci are targets of selection, and limits to identifying the genetic basis of local adaptation.