Upslope diversification and gene flow among congeneric Andean trees

Abstract

SUMMARY The exceptional biodiversity of tropical Andean forests is characterized by rapid turnover of many closely related species across elevation and other environmental gradients. The eco-evolutionary relationships among these congeneric species are often poorly understood—specifically, how they diversify, sort into their elevational niches, and the extent to which species boundaries are maintained through time. In this study, we examined the phylogenetic relationships and patterns of ancient and ongoing gene flow among sympatric Prunus species occurring along elevation gradients in Peru and Bolivia to explore the evolutionary processes underlying this turnover. Phylogenetic relationships reconstructed a pattern of upslope adaptive diversification concurrent with Andean orogeny during the Miocene. Despite deep divergence times, species show evidence of widespread and persistent gene flow, with little constraint imposed by ecological or evolutionary distance. Together, these findings show that during adaptive radiations, observable ecological and morphological differences may emerge despite ongoing gene flow and long before reproductive isolation is complete.