THE CORALS ACROPORA-PALIFERA AND ACROPORA-CUNEATA ARE GENETICALLY AND ECOLOGICALLY DISTINCT

Two of the most abundant corals of the Great Barrier Reef Acropora cuneata and Acropora palifera, can be distinguished reliably by conventional taxonomic methods only if large specimens of both species are collected from the same uniform biotope. In this study gross and microscopic examination of the corallite structures of large coralla, collected from a reef crest biotope, were used to confirm the assignment of these specific names to two electrophoretically distinct groups of corals. Identifications based on genetic and morphological data gathered from small fragments of coralla collected from five different sites were in agreement for two sites within which skeletal data were adequate for taxonomic purposes (i.e. one reef crest and one outer lagoon site). However, specimens collected from the other three sites could be identified reliably only by using the electrophoretic data. These results confirm that small fragments from diverse habitats may not be adequate for morphologically based identification. The application of electrophoretic identifications to the results of an earlier electrophoretic survey of 76 sites on 11 reefs revealed that, although A. palifera and A. cuneata frequently co-occur, they have significantly different habitat distributions. Acropora cuneata is more commonly associated with high energy environments such as the reef crest, whereas A. palifera occurs most commonly in the sheltered reef lagoons and on the deeper reef slopes.