Data from: Does migration promote or inhibit diversification? A case study involving the dominant radiation of temperate Southern Hemisphere freshwater fishes

While theory predicts that dispersal is a pivotal influence on speciation and extinction rates, it can have contradictory effects on each, such that empirical studies are needed to quantify its role. In many studies, dispersal reduction appears to promote diversification, although some analyses of migratory species suggest otherwise. Here we test for a relationship between migratory status and diversification rate within the dominant radiation of temperate Southern Hemisphere freshwater fishes, the Galaxiidae. We reconstructed a molecular phylogeny for the group, comprising >95% of extant lineages, and applied State-dependent Speciation Extinction models to estimate speciation, extinction, and diversification rates. In contrast to some previous studies, we revealed higher diversification rates in non-migratory lineages. The reduced gene flow experienced by non-migratory galaxiids appears to have increased diversification under conditions of allopatry or local adaptation. Migratory galaxiid lineages, by contrast, are genetically homogeneous within landmasses, but may also be rarely able to colonise other landmasses in the temperate Southern Hemisphere. The life history state exhibiting higher diversification likely reflects the spatial context of the study system relative to species dispersal abilities, by means of the intermediate dispersal model; the accurate quantification of dispersal abilities will aid in our understanding of these likely interactions.