Experimental rewilding of stickleback drives phenotypic shifts that oppose long-term evolutionary trajectories in Daphnia in Alaskan lakes

Trophic rewilding restores top-down interactions and may, in turn, drive novel patterns of evolutionary change. Predatory Northern pike invaded lakes in Alaska and eliminated native fish fauna. In 2018, pike were extirpated to reset these ecosystems. Contrasting trophic ecomorphs (benthic vs. limnetic) of three-spine stickleback were then re-introduced as part of whole-lake rewilding experiments. We examined the top-down effects of stickleback on phenotypic change in Daphnia over three years in lakes that naturally contained sticklebacks and compared such trends with the experimental lakes. We observed consistent phenotypic differences between lakes with naturally occurring populations of benthic vs. limnetic stickleback. The patterns of phenotypic divergence indicate that predatory selection is stronger on Daphnia in lakes with benthic stickleback. The trends in the experimental lakes were temporally variable and opposed the trends observed in natural lakes. Rewilding provides insights into the inconsistencies that can manifest between short- and long-term influences of natural selection.