Diversity and biogeography of the scleractinian coral fauna of Easter Island (Rapa Nui)

摘要

Three surveys at Easter Island (Rapa Nui) spanning the period 19992005, and examination of private and museum collections, have revealed a depauperate zooxanthellate scleractinian fauna. Collections were all made off island shelf exposures, from tide pools to 70 m with scuba, And by dredging to 100 m. With synonymies, reassignments, and two new records in the families Pocilloporidae and Faviidae, the Easter Island coral fauna now comprises 13 species. Pocilloporid and poritid coral abundances were generally high on all island shelves protected from southern swells. A cluster analysis of the coral fauna relationships of 19 south, central, and far-eastern Pacific sites indicates a strong affinity between those of Easter Island and the far-eastern Pacific equatorial region (e.g., Colombia, Ecuador, Panama, and the Galapagos Islands). The precipitous drop in coral species richness from the Pitcairn Island group (61 species) to Easter Island suggests the presence of a dispersal barrier between these two remote southeastern Pacific areas, separated by similar to 1,800 km of deep ocean waters. Consideration of the surface circulation based on satellite-tracked surface drifters confirms this conclusion. Surface currents are from cast to west along the topography on which Easter and Sala-y-Gomez Islands sit, suggesting a substantial barrier to recruitment from the west.