Genetic adaptation to climate change: a systematic literature review identifies opportunities to strengthen empirical studies of wild populations

To understand to what extent evolution can contribute to bending the curve of ongoing biodiversity losses, we urgently need to characterize what determines the adaptive potential of populations. We argue that capitalising on existing examples of genetic adaptation to climate change provides the opportunities to fill this major knowledge gap. We performed a systematic literature review and obtained 40 empirical examples of species with direct evidence of wild populations undergoing genetic adaptation in response to climate change selection. Only two of these examples (crustacean Daphnia magna and plant Brassica rapa) presented robust evidence for genetic adaptation driven by climate change, using strong inference methods to show that (1) a phenotypic change over time occurred, (2) the phenotype has a genetic basis, (3) the fitness of the phenotype depends on a climatic variable, (4) climate change-induced selection occurred across generations, and (5) it was assessed to what extent the genetic change involved a response to selection compared to the contribution of other evolutionary processes. There thus are ample opportunities to strengthen the evidence base for these existing examples such that they can contribute to understanding when and how genetic adaptation to climate change can take place. Moreover, improving the spatial and temporal replication of these existing studies is highly needed to identify general principles across species and populations. Especially genomics studies using high-resolution temporal sampling provide important information about the process and rate of evolution, but the field currently lacks such high-resolution temporal genomics studies. We urge the field to capitalize on and strengthen these existing examples of genetic adaptation so that we can identify which drivers and constraints determine the likelihood and rate of evolutionary responses to climate change.