Genetic adaptation to climate change in wild populations: a systematic literature review identifies opportunities to strengthen our evidence base

Natalie E. van Dis 

To understand to what extent evolution can contribute to bending the curve of ongoing biodiversity losses, we urgently need to characterize the adaptive potential of populations. This systematic literature review comprehensively gathers existing examples of genetic adaptation to climate change to (1) guide efforts to assess genetic adaptation to climate change in a wider variety of species and ecosystems, and (2) allow the field to capitalize on these existing examples to advance our knowledge on the drivers and constraints underlying climate change adaptation. I identified 51 case studies of 49 species for which genetic change over time in response to climate change has been strongly inferred in wild populations. I furthermore assessed the strength of evidence for each study on five criteria that together robustly demonstrate that these genetic changes are adaptive and in response to climate change: in addition to (1) demonstrating genetic change over time, I determined whether strong inference methods were used to show that (2) a phenotypic change over time occurred, (3) the fitness of the phenotype depends on a climatic variable, (4) climate change-induced selection occurred across generations, and (5) the relative contribution of adaptive and neutral evolutionary processes was assessed. While taxonomic and ecosystem representation need to be improved in the future, patterns emerging from the resulting overview indicate that genetic responses to climate change are happening in many of the species tested and are often population specific, with selection affecting populations both directly and indirectly. However, to further validate and elucidate the frequency of genetic adaptation under climate change and its underlying drivers and constraints, more studies are needed. I identify three key opportunities for the field to strengthen and supplement our evidence base: (1) harness the power of temporal genomics approaches to gain important information about the process and rate of evolution and to allow for assessing genetic change in species and populations that might otherwise be hard to sample, (2) perform follow-up phenotypic characterization and experimentation for 44 of the existing and an additional 84 suggestive examples of genetic adaptation to climate change such that they can contribute to improving the prediction of population responses, and (3) improve spatial and temporal replication to allow for the exciting opportunity to start empirically testing drivers and constraints that determine the likelihood and rate of genetic adaptation to climate change.