The evolutionary history of the order Antipatharia (Cnidaria: Anthozoa: Hexacorallia) as inferred from mitochondrial and nuclear DNA: implications for black coral taxonomy and systematics

Although black corals inhabit all the world's oceans, they have been relatively understudied as approximate to 185 of 247 species occur at depths >50m. Antipatharians have been included in several phylogenetic studies; however, sample sizes are small and taxonomic coverage minimal. Low levels of mitochondrial (mt) sequence divergence within Scleractinia and Octocorallia are assumed to apply to all anthozoans, although no formal study has been conducted on the order Antipatharia. To quantify genetic variation in the black coral mitogenome, we analysed DNA sequences of the two longest intergenic regions (IGRs) and cox3-cox1 for 26 of 41 genera, representing all families and subfamilies. We also quantified divergence at the intraspecific level using six mtIGRs and their flanking protein-coding genes and rRNA for 100+ colonies of Antipathes griggi. Utilizing sequence data from the two mtIGRs, cox3-cox1, as well as nuclear 18S and 28S, we constructed the first multi-locus phylogenies of the Antipatharia. Reconstructions revealed that species in the genus Stichopathes are split across two families, Sibopathes macrospina groups among North Atlantic Parantipathes (suggesting the actinopharynx and mesenteries were secondarily lost), and three families are polyphyletic. These and other results provide novel, independent insights into the evolutionary history of antipatharians and support placement of species into higher-level groupings based on microscopic skeletal features rather than gross colony morphology. An illustrated key to the seven currently recognized families is also provided.(c) 2013 The Linnean Society of London