Comparative phylogeography of reef fishes indicates seamounts as stepping stones for dispersal and diversification

Studies on oceanic island biodiversity have been the foundation for much theoretical work. However, seamounts are mostly underexplored, and little information is available about their potential as stepping stones for oceanic dispersal and their role in diversification. Here we used a genetic approach to test different models of marine dispersal between the continental coast and a volcanic ridge composed of seamounts and oceanic islands. We observed that the stepping stone model best fits our results, with one reef fish species displaying ongoing gene flow and another showing endemic lineages restricted to the islands and most isolated seamounts. The data also suggest that connectivity among remote regions could be influenced by Pleistocene sea level fluctuations and that a widespread genetic lineage was originated from an island endemic. Recent findings on island endemic species showed a similar pattern of both origin and export of genetic lineages, indicating that this process occurred multiple times in the Pleistocene. This study highlights the role of seamounts in supporting subpopulations that, in turn, allow island colonization, diversification, and a biodiversity feedback process that nourishes source populations with evolutionary novelty from peripheral regions.