Phylogenetic relationships within the Octocorallia (Cnidaria: Anthozoa) based on nuclear 18S rRNA sequences

We determined the nuclear 18S rRNA sequences for 41 species of octocorals and used these to address the validity of the historical ordinal divisions and the current subordinal divisions within the subclass Octocorallia. We also explored the phylogenetic affinities of the species Dendrobrachia paucis...

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Bibliographic Details
Published in:Marine biology 2001-02, Vol.138 (2), p.235-246
Main Authors: BERNTSON, E. A, BAYER, F. M, MCARTHUR, A. G, FRANCE, S. C
Format: Article
Language:English
Subjects:
Anthozoa
Aquatic life
Biological and medical sciences
Chrysogorgia
Classification
Cnidaria. Ctenaria
Corallium
Dendrobrachia paucispina
Fundamental and applied biological sciences. Psychology
Gorgonacea
Invertebrates
Marine
Marine biology
Octocorallia
Paragorgia
Ribonucleic acid
RNA
rRNA 18S
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Summary:We determined the nuclear 18S rRNA sequences for 41 species of octocorals and used these to address the validity of the historical ordinal divisions and the current subordinal divisions within the subclass Octocorallia. We also explored the phylogenetic affinities of the species Dendrobrachia paucispina, which was originally classified in the order Antipatharia (subclass Ceriantipatharia) although polyp structure indicates it belongs in the subclass Octocorallia. Trees constructed using maximum likelihood techniques are incongruent with the current and historical taxonomy of the Octocorallia. There appeared to be three major clades of octocorals. The first clade included most, but not all, pennatulaceans as a monophyletic group. The second clade contained 21 species, representing all major octocoral groups other than pennatulaceans. The third clade contained members from three suborders of the Alcyonacea and one member of the Pennatulacea. These data could not be used to distinguish the branching order of the three major clades. The species D. paucispina had a close affinity with the genera Corallium and Paragorgia (Alcyonacea: Scleraxonia), although its morphology suggests it is more similar to the genus Chrysogorgia (Alcyonacea: Calcaxonia). The morphological character of dimorphism (the presence of both autozooids and siphonozooids within a single colony) corresponded loosely with the topology of the most likely trees, and a single origin of dimorphism could not be rejected. Despite sampling from the majority of families within the Octocorallia, many of the relationships within this group remain ambiguous.
ISSN:0025-3162
1432-1793
DOI:10.1007/s002270000457