FROM COSTAE TO COI AND SPECIES TO TREES: PROGRESS AND CHALLENGES

Corals present unusual challenges for those wishing to discriminate among species or determine evolutionary relationships. Slow rates of evolution in mitochondrial genes, limited numbers of informative morphological characters, plasticity of skeletal morphology in response to environmental conditions, and in some cases hybridization have all slowed progress.

Nevertheless, progress has been made, particularly when multiple approaches have been brought to bear. Our understanding of evolutionary relationships is very different today than it was twenty years ago, and this has necessitated wholesale taxonomic revisions, with many still ongoing. Solving the coral “species problem” has to be done group by group, a time-consuming process, and many problem areas remain.

High-throughput sequencing approaches are increasingly being used on corals, but typically not for systematic questions. More genetic data will undoubtedly help, but is unlikely to be a magic bullet, especially considering the extensive fossil record that corals possess. Fortunately, sophisticated morphological analyses often yield results that are concordant with molecular results, offering hope for those wishing to reconstruct the evolutionary history of corals with no close living relatives.