Searching for heat in a marine biodiversity hotspot

Coral reefs exhibit highly congruent patterns of biodiversity, with a prominent hotspot in the Indo-Australian Archipelago (IAA). Unlike many terrestrial systems, the IAA hotspot exhibits extensive latitudinal and longitudinal biodiversity gradients. Conflicting hypotheses have highlighted the importance of the area as a centre of origin, overlap or accumulation, with the location of endemics being used as the primary criterion for testing these hypotheses, by identifying the presumed geographical origins of species. We evaluate the utility of marine endemics for resolving these hypotheses, and examine recent molecular phylogenetic evidence for coral reef species that has revealed the antiquity of the endemics and the other species that make up this hotspot. These analyses emphasize the importance of the IAA in the survival rather than the origins of species.