Meeting Abstract
S8.4 Wednesday, Jan. 6 On the evolution of deep-sea octocorals and antipatharians: Patterns revealed from molecular phylogenies FRANCE, S.C.**; PANTE, E.; BRUGLER, M.R.; VAN DER HAM, J.L.; University of Louisiana at Lafayette; University of Louisiana at Lafayette; University of Louisiana at Lafayette; University of Louisiana at Lafayette france@louisiana.edu
The discovery of high species diversity in the bathyal benthos has focused questions on the origin of deep-sea species and the processes that lead to speciation in this comparatively monotonous environment. We are exploring these questions using deep-sea corals as a model system, specifically three families of “gorgonians” (Anthozoa: Octocorallia) – Chrysogorgiidae, Isididae, and Primnoidae – and black corals (Anthozoa: Hexacorallia: Antipatharia), whose taxonomic diversity and abundance reach a maximum at depths >200 meters, although shallow-water representatives are known from each group. Phylogenetic analyses of DNA sequences reveal both the Chrysogorgiidae and Isididae are polyphyletic, but it is the inclusion of shallow-water taxa in these families that appear to be the cause: the strictly deep-sea genera cluster on robust monophyletic clades. The Primnoidae are monophyletic (except for the genus Acanthoprimnoa, whose placement on the tree may be affected by very long branch lengths), with shallow-water emergence at high latitudes for some species. The relationships among the deep-water clades from the different families remain unresolved due to short internal branch lengths in the phylogeny, an indication of a relatively-rapid radiation in the past coupled with the low substitution rate observed among octocorals. Among the black corals, the two families whose species are restricted to bathyal depths group as a monophyletic clade, distinct from families dominated by shelf-dwelling species. Our dataset still suffers from incomplete taxon sampling – a reflection of the difficulty of obtaining rare deep-sea specimens – but provides support that evolutionary radiations from deep-sea ancestors are common among these corals.
