Molecular Phylogeny of Coral-Reef Sea Cucumbers (Holothuriidae: Aspidochirotida) Based on 16S Mitochondrial Ribosomal DNA Sequence |
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Authors: | Alexander M. Kerr Daniel A. Janies Ronald M. Clouse Yves Samyn Jeni Kuszak Junhyong Kim |
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Affiliation: | (1) Department of Ecology and Evolutionary Biology, Osborn Zoölogical Laboratories, Yale University, New Haven, CT, 06520, U.S.A.;(2) Department of Invertebrate Zoology, American Museum of Natural History, New York, NY, 10024, U.S.A.;(3) Global Taxonomy Initiative, Royal Belgian Institute of Natural Sciences, Vaurierstraat 29, Brussels, B-1000, Belgium;(4) Present address: Centre for Coral Reef Biodiversity, Department of Marine Biology, James Cook University, Townsville, QL, 8411, Australia;(5) Present address: Department of Biomedical Informatics, The Ohio State University, Columbus, OH, 43210, U.S.A.;(6) Present address: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, U.S.A.;(7) Present address: Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104-6018, U.S.A. |
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Abstract: | Members of the Holothuriidae, found globally at low to middle latitudes, are often a dominant component of Indo–West Pacific coral reefs. We present the first phylogeny of the group, using 8 species from the 5 currently recognized genera and based on approximately 540 nucleotides from a polymerase chain reaction–amplified and conserved 3′ section of 16S mitochondrial ribosomal DNA. Parsimony and likelihood analyses returned identical topologies, permitting several robust inferences to be drawn. Several points corroborated the Linnean classification. Actinopyga and Bohadschia each appear monophyletic and Pearsonothuria is sister to Bohadschia. Other aspects of our phylogeny, however, were not in accord with the taxonomy of Holothuriidae or previous speculations about the group’s evolutionary history. Most notably, the genus Holothuria appears paraphyletic. Actinopyga and Bohadschia, sometimes held to be closely related to one another because of certain morphologic similarities, are only distantly related. The morphologically distinct Labidodemas, even thought to warrant separation at the family level, is nested well within Holothuria. A maximum parsimony reconstruction of ancestral ossicle form on the phylogeny indicated that, in addition to a probable bout of elaboration in ossicle form (the modification of rods or rosettes to holothuriid-type buttons), at least 2 rounds of ossicle simplification also transpired in which buttons reverted to rods or rosettes. Cuvierian tubules, defensive organs unique to numerous members of Holothuriidae, were probably present before the initial radiation of the family, but the reconstruction is ambiguous as to their ancestral function. |
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Keywords: | phylogeny 16S rDNA mtDNA Holothuriidae Isostichopus Stichopus |
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