Indo-Pacific coral biogeography: a case study from the Acropora selago group

We develop species-level biogeographic hypotheses for Acropora, the largest extant coral genus and the dominant scleractinian coral of Indo-Pacific reefs, based on morphometric and phylogenetic analyses of the Acropora selago group. Fourteen morphometric characters differentiated species from this group with an accuracy of 95%. When the Tukey test was administered, 11 of these characters displayed nonoverlapping subsets. The most resolved phylogenetic tree resulted from an analysis based on both morphometric and qualitative characters. Cladistic-biogeographic analysis using this tree and areas derived from species-distribution patterns showed that species with the greatest degree of endemism within the A. selago group possess the most derived character states, while the most primitive species (A. yongei) is the most widespread. Within the range of the group, four areas are recognised: (1) the Red Sea, (2) western to central Indian Ocean, (3) eastern Indian Ocean and (4) western to central Pacific Ocean. Species ranges overlap in a stepwise fashion from west to east. Areas adjacent to one another are biogeographically more closely related than non-adjacent areas. Whilst we offer a scenario for the history of distribution patterns of the A. selago group, we propose that biogeographical hypotheses based on Acropora be tested using a number of different species-groups. Similar distributional ranges for other Acropora species-groups, as well as separate distributional ranges for further groups, suggest that Acropora will provide an appropriate taxon to examine the biogeography of the tropical marine realm.