MORPHOLOGICAL VARIATION IN THE CORAL GENUS PLATYGYRA - ENVIRONMENTAL-INFLUENCES AND TAXONOMIC IMPLICATIONS

Scleractinian corals are notoriously variable and the high degrees of morphological variation displayed by some species, particularly in res ponse to environmental influences, confound our understanding of speci es boundaries. In order to fully understand the ranges of variation an d the influence of habitat on colonies within the genus Platygyra, lev els of intra- and interspecific morphological variation were quantifie d and colony morphology was examined relative to environmental gradien ts. Measurements of 9 skeletal characters of colonies of Platygyra wer e analysed by multivariate analysis of variance and canonical discrimi nant analysis to examine morphological species boundaries. While the t axonomic literature suggests the existence of 5 morphological species of Platygyra, results from this study suggest there may be 7 present o n the Great Barrier Reef, Australia. A comparison of skeletal characte rs of 2 species, P. daedalea and P. pini, across 4 different habitats indicates that the environment does not influence skeletal characteris tics in these species. Similarly, a detailed survey of distribution pa tterns of Platygyra spp. indicates that all species occur sympatricall y across 6 reef habitats and that colony morphology does not change pr edictably along environmental gradients. The absence of any associatio n between morphology and habitat in Platygyra suggests environment has little influence on morphology in these species. Numerical techniques are likely to be useful for defining species boundaries in highly var iable groups of corals and similarly for understanding ranges of intra specific morphological variation.