Phylogenetic analysis and quantitative assessment of micromorphology and microstructure in the coral family Mussidae (scleractinia)

Coral morphology is highly homoplastic, and reconstructing coral phylogeny based on morphological characters has long been problematic. Coral skeletal micromorphology and skeletal microstructure may be less homoplastic than traditional skeletal macromorphology. Micromorphology includes characteristics of septal teeth and associated features, such as granules. Microstructure is the internal structure of septa, walls and dissepiments. These micro-features can be visualized using light and scanning electron microscopy, and transverse thin sections, respectively. Although coral micro-features have been of interest to coral workers for decades, few have attempted using micro features for phylogenetic analyses. A phylogenetic analysis of the coral family Mussidae using micro-features as characters found that, in this family, phylogenies based on a combination of macromorphology and micro-features are more consistent with molecular phylogenies than phylogenetic analyses based on traditional macromorphological characters alone. Further exploration of micro-features using a quantitative method to assess septal dentition also supports the potential utility of micro-features in coral taxonomy. An elliptic Fourier analysis of septal tooth curvature within the coral family Mussidae reveals that there is quantifiable inter-specific variation in septal tooth shape. Although differences in septal tooth shape have long been described qualitatively, a quantitative assessment of this particular micro-feature confirms the objectivity of septal tooth shape variation. This outline analysis represents an important step toward novel approaches to exploring coral micro-features.