Gene-flow between niches facilitates local adaptation in sexual populations

In sexual populations, gene‐flow between niches is predicted to have differential consequences on local adaptation contingent upon the nature of trade‐offs underlying local adaptation. Sex retards local adaptation if antagonistic pleiotropy underlies trade‐offs, but facilitates adaptation if mutation accumulation underlies trade‐offs. We evaluate the effect of sex in heterogeneous environments by manipulating gene‐flow between two niches in sexual and asexual populations using steady‐state microcosm experiments with yeast. We find that only sex in the presence of gene‐flow promotes simultaneous local adaptation to different niches, presumably as this exposes mutations neutrally accrued in alternate niches to selection. This finding aligns with work showing mutation accumulation underlies trade‐offs to local adaptation in asexual microbes, and with inferences of divergence in the presence of gene‐flow in natural sexual populations. This experiment shows that sex may be of benefit in heterogeneous environments, and thus helps explain why sex has been maintained more generally.