Morphological and molecular characterization of the problematic whip black coral genus Stichopathes (Hexacorallia: Antipatharia) from Indonesia (North Sulawesi, Celebes Sea)

This study represents a preliminary systematic reorganization of the critical whip black coral genus Stichopathes from Indonesia, and a validation test of its principal morphological features as suitable taxonomic characters. A phylogenetic analysis based on rDNA internal transcribed spacer sequences ITS1 and ITS2 was performed on several specimens coming from different areas of the Indonesian Archipelago. Within the family Antipathidae, these analyses confirmed the separation of the three traditional genera of whip black corals (Stichopathes, Cirrhipathes, and Pseudocirrhipathes). Additionally, the analyses identified five clades for the studied Stichopathes specimens. In each clade, the wire specimens were well characterized by a distinctive set of morphological features, including: the shape of the corallum, the size and arrangement of the polyps, and the shape of the spines. The molecular data obtained, combined with other sequences available in the literature, indicate that the traditional genus Stichopathes is a polyphyletic taxon. In three clades, unbranched Stichopathes-like specimens group together with branched specimens morphologically belonging to the genus Antipathes. This evidence suggests caution when using the corallum branching pattern in the taxonomy of the order, as this character may have evolved separately in different taxa, thus suggesting that an extensive taxonomic revision of the whip black coral genera is required.