Population genomics of parallel adaptation.

Parallel evolution is one of the striking patterns in nature. The presence of repeated evolution of the same phenotypes, suites of traits, and adaptations suggests a strong role for natural selection in shaping biological diversity. The reasoning is straightforward: each instance of repeated evolution makes it less likely that these features evolved neutrally or due to stochastic forces in each population or species. With the growing sequencing capability, we are now poised to examine the genetic basis of parallel evolution in model and nonmodel systems. On pages 4102-4117 of this issue of Molecular Ecology, van Boheemen and Hodgins (2020) provide an exemplar study of this kind, using common ragweed (Ambrosia artemisiifolia; Figure 1a). Their study is noteworthy and ambitious in many respects, and we think will serve as a model for studying parallel adaptation, even in nonmodel species.