Christmas tree worms of Indo-Pacific coral reefs: untangling the Spirobranchus corniculatus (Grube, 1862) complex
Christmas tree worm is the common name of a group of colorful serpulid polychaetes from the genus Spirobranchus that are symbionts of hermatypic corals. As is increasingly common with reef-associated organisms, Spirobranchus is arranged as a complex of species with overlapping geographic ranges. Current species delimitations based largely on opercular morphology are problematic because of high intraspecific variation. Here, a multi-gene phylogeny of the Spirobranchus corniculatus complex, which tentatively includes S. corniculatus, S. cruciger, and S. gaymardi, sampled from the Coral Triangle, Australia, and Fiji, was reconstructed to test whether the complex includes three genetically distinct lineages identifiable by their opercula. Maximum-likelihood analyses of nuclear and mitochondrial markers revealed a single, monophyletic clade for the S. corniculatus complex. Furthermore, the genetic and morphological variation observed is not geographically based, indicating that the former S. corniculatus complex of three morphospecies is a single, morphologically variable species across the Central Indo-Pacific. Resolving the taxonomy of S. corniculatus presents novel opportunities to utilize this tentative bio-indicator species for monitoring reef health.
KeywordsAnnelida Mitochondrial DNA Nuclear DNA Polychaeta
We thank the governments and people of Australia, Fiji, Indonesia, and the Philippines for providing research permission. Funding for the collection of samples was provided by NSF Grant OISE-0730256 to Kent Carpenter and Paul Barber, and a Conservation International support to Paul Barber. We thank Joshua Drew of Columbia University for sample collection in Fiji and Mudjie Santos, Kent Carpenter, Rachel Ravago-Gotanco, and the National Fisheries Research and Development Institute for logistics and laboratory support in the Philippines, and Harry A. ten Hove for assistance in specimen identification. We thank O. Paderanga, A. Semenov, and E. Wong for their photos.
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