Wallace's line and marine organisms: the distribution of staghom corals (Acropora) in Indonesia

Historical vicariance factors affect marine distributions differently from terrestrial distributions, land being a barrier to marine dispersal and the water column being a transport medium for larvae. This paper examines distribution patterns of species of the coral genus Acropora, which is found to reach its highest worldwide diversity in the Wallacea region. A morphology-based phylogeny and data from the fossil record indicate an origin of the genus around Africa/Southern Europe with the most recent diversification in Indonesia/West Pacific Ocean. This recent diversification includes forms specialised for deep, calm habitats. It is hypothesised that continuity of reef sites through time and the impact of late-Cenozoic eustatic fluctuations in shaping relictual and endemic faunas have contributed to the high diversity found in Wallacea. Indian Ocean and Pacific Ocean Acropora faunas overlap within the region, however the Pacific Ocean influence is stronger, possibly due to access of larvae through the Pacific through-flow current.