Population genomics of rapid evolution in natural populations: polygenic selection in response to power station thermal effluents

Background: Examples of rapid evolution are common in nature but difficult to account for with the standard population genetic model of adaptation. Instead, selection from the standing genetic variation permits rapid adaptation via soft sweeps or polygenic adaptation. Empirical evidence of this process in nature is currently limited but accumulating.

Results: We provide genome-wide analyses of rapid evolution in two Fundulus heteroclitus populations subjected to recently elevated temperatures due to coastal power station thermal effluents. Bayesian and multivariate analyses of population genomic structure reveal a substantial portion of genetic variation that is most parsimoniously explained by selection at the site of thermal effluents. An FST outlier approach in conjunction with additional conservative requirements identify significant allele frequency differentiation that exceeds neutral expectations among exposed and closely related reference populations. Genomic variation patter...