Patterns of species range evolution in Indo-Pacific reef assemblages reveal the Coral Triangle as a net source of transoceanic diversity

The Coral Triangle in the Indo-Pacific is a region renowned for exceptional marine biodiversity. The area could have acted as a “centre of origin” where speciation has been prolific, or a “centre of survival” by providing refuge during major environmental shifts such as sea level changes. The region could also have acted as a “centre of accumulation” for species with origins outside of the Coral Triangle, due it a central position between the Indian and Pacific oceans. Here we investigated support for these hypotheses using population-level DNA sequence-based reconstructions of the range evolution of 45 species (314 populations) of Indo-Pacific reef-associated organisms. Our results show that populations undergoing the most ancient population establishment were significantly more likely to be closer to the centre of the Coral Triangle than in peripheral locations. The data are consistent with the Coral Triangle being a net source of coral reef biodiversity for the Indo-Pacific region, suggesting the region has acted primarily as a centre of survival, a centre of origin, or both. These results provide evidence of how a key location can influence the large-scale distributions of biodiversity over evolutionary timescales.