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 response to environmental influences, confound our understanding of species boundaries. In order to fully understand the ranges of variation and the influence of habitat on colonies within the genus Platygyra, levels of intra- and interspecific morphological variation were quantified and colony morphology was examined relative to environmental gradients. Measurements of 9 skeletal characters of colonies of Platygyra were analysed by multivariate analysis of variance and canonical discriminant analysis to examine morphological species boundaries. While the taxonomic literature suggests the existence of 5 morphological species of Platygyra, results from this study suggest there may be 7 present on the Great Barrier Reef, Australia. A comparison of skeletal characters of 2 species, P. daedalea and P. pini, across 4 different habitats indicates that the environment does not influence skeletal characteristics in these species. Similarly, a detailed survey of distribution patterns of Platygyra spp. indicates that all species occur sympatrically across 6 reef habitats and that colony morphology does not change predictably along environmental gradients. The absence of any association 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 variable groups of corals and similarly for understanding ranges of intraspecific morphological variation.