Abstract
Convergent adaptation is the independent evolution of similar traits conferring a fitness advantage in two or more lineages. Cases of convergent adaptation inform our ideas about the ecological and molecular basis of adaptation. In judging the degree to which putative cases of convergent adaptation provide an independent replication of the process of adaptation, it is necessary to establish the degree to which the evolutionary change is unexpected under null models and to show that selection has repeatedly, independently driven these changes. Here, we discuss the issues that arise from these questions particularly for closely related populations, where gene flow and standing variation add additional layers of complexity. We outline a conceptual framework to guide intuition as to the extent to which evolutionary change represents the independent gain of information owing to selection and show that this is a measure of how surprised we should be by convergence. Additionally, we summarize the ways population and quantitative genetics and genomics may help us address questions related to convergent adaptation, as well as open new questions and avenues of research. This article is part of the theme issue 'Convergent evolution in the genomics era: new insights and directions'.
Highlights
Convergence is the independent evolution of similar features in two or more lineages [1]
When convergence is the result of natural selection producing the same solution in response to repeatedly encountered biotic and abiotic pressures, we treat these as natural replicates of a similar process to understand the ecological and phenotypic bases of convergence [2] and the molecular basis of evolution [3,4,5,6]
Throughout this article, we focus on how population-level genomic data both forces us to grapple with the issues that arise in identifying convergent adaptation among closely related taxa and provides novel ways to approach these and related questions
Summary
Convergence is the independent evolution of similar features in two or more lineages [1]. The main insight, that we want to see repeated large allele frequency changes from initially rare alleles, is clear from just the two population cases This framework may be useful in aiding our intuition about the degrees to which selective events have been independent and so can be considered to be convergent. A number of authors have explored the idea of statistical information as a measure of work done by selection and more broadly the role of selection in decreasing the entropy of states including in the presence of different forms of epistasis [40,41,42,43,44] These ideas extend naturally to quantitative traits [40,41,45] as well as substitution models from molecular evolution [41]. Convergent adaptation, at the genetic or phenotypic level, can potentially be conceptualized in this way as the independent gain of information owing to selection
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