CSIRO PUBLISHING
www.publish.csiro.au/journals/is
Invertebrate Systematics, 2010, 24, 23–31
Molecules match morphology: mitochondrial DNA supports Bayer’s Lytreia–Bebryce–Heterogorgia (Alcyonacea : Octocorallia) clade hypothesis Sergio Vargas A,B,C,G, Michael Eitel B, Odalisca Breedy A,D,E and Bernd Schierwater B,F A
Museo de Zoología, Escuela de Biología, Universidad de Costa Rica, PO Box 1962-2100, San José, Costa Rica. B ITZ, Ecology & Evolution, TiHo, Hannover, Bünteweg 17d, D-30559 Hannover, Germany. C Present address: Molecular Geo- and Palaeobiology Lab., Department of Earth & Environmental Sciences, Ludwig-Maximilians Universität, Richard-Wagner Str. 10, 80333 Munich, Germany. D Smithsonian Tropical Research Institute, Unit 0948, APO AA, 34002, USA. E Centro de Investigación en Ciencias del Mar y Limnología and Centro de Investigación en Estructuras Microscópicas, Universidad de Costa Rica, San Pedro, Costa Rica. F American Museum of Natural History, New York, Division of Invertebrate Zoology, 79 St at Central Park West, New York, NY 10024, USA. G Corresponding author. Emails:
[email protected],
[email protected]
Abstract. Several studies attempting to clarify the taxonomy and systematics of Octocorallia have highlighted the important role of molecular characters in corroborating or rejecting previous hypotheses based on morphological variation. One such hypothesis is that of a close phylogenetic relationship between the genera Lytreia, Bebryce and Heterogorgia proposed by Bayer based on morphological studies of the genera. Herein, we tested Bayer’s hypothesis using the mitochondrial marker mshI. We deduced a molecular phylogeny including members of the families Gorgoniidae and ‘Paramuriceidae’ that corroborated the existence of Bayer’s Lytreia–Bebryce–Heterogorgia clade. In addition, we provide a morphological assessment of the three genera as well as diagnoses for each of them. We also discuss, based on the phylogenetic results obtained, the evolution of sclerite morphology within Bayer’s Lytreia–Bebyce–Heterogorgia clade. Finally, we propose a Tethyan origin for the Lytreia–Bebryce–Heterogorgia clade. Additional keywords: Bebryce, Heterogorgia, Lytreia, molecular phylogenetics, Octocorallia, sclerite evolution.
Introduction The subclass Octocorallia comprises ~3000 species (~44 families) of sessile, colonial cnidarians that inhabit a wide range of marine environments, from shallow to deep waters across the globe (Fabricius and Alderslade 2000; McFadden et al. 2006a). Octocorals can be consistently identified by several synapomorphies: the presence of eight (generally pinnated) tentacles, eight mesenteries, and characteristic nematocyst morphology defines the group (Berntson et al. 1999; Wirshing et al. 2005). A radically different scenario appears below the subclass level. Traditionally, recognised orders and suborders are defined using highly variable or polymorphic characters, and have been found to be artificial groups by both morphological and molecular studies (Bayer 1981; Sánchez et al. 2003a, 2003b; McFadden et al. 2006a, 2006b). Despite the great deal of confusion in octocoral taxonomy at ordinal, subordinal and family levels, genera are somewhat CSIRO 2010
clearly delineated. Taxonomic revisionary studies of several octocoral genera have added clarity to octocoral classification (e.g. Sánchez 2001, 2005; Breedy and Guzman 2002, 2007; McFadden et al. 2006b; van Ofwegen and Groenenberg 2007), and have also resulted in hypotheses of generic relations that need to be tested. One of these hypotheses is that of a Lytreia–Bebryce–Heterogorgia clade proposed by Bayer (1994) based exclusively on the study of morphological characters of these genera. Interestingly, recent molecular phylogenetic studies of Plexauridae (cf. Wirshing et al. 2005) have found a close relationship between the genus Lytreia and Bebryce, partially corroborating Bayer’s hypothesis; the phylogenetic position of Heterogorgia, the third member of Bayer’s clade, was not determined. In this study we evaluate Bayer’s foreseen Lytreia– Bebryce–Heterogorgia clade. For this purpose, we extend available octocoral mitochondrial mshI sequence datasets to include representatives of the genus Heterogorgia and assess 10.1071/IS09033
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Invertebrate Systematics
the phylogenetic position of these genera within Octocorallia. Heterogorgia Verrill, 1868; Bebryce Philippi, 1841; and Lytreia (Deichmann, 1936) group a small number of finger-like octocorals occurring in tropical waters. Aside from Bebryce, the other two genera have been barely studied since their original designation and several taxonomic problems remain to be addressed. Herein, we provide a morphological characterisation of these genera and discuss on sclerite evolution within Bayer’s clade.
S. Vargas et al.
purpose, we used the primers ND42599F: 50 -GCCATTATGGT TAACTATTAC-30 (France and Hoover 2002) and Mut-3458R: 50 -TSGAGCAAAAGCCACTCC-30 (Sánchez et al. 2003b). The amplified product was sequenced in both directions (i.e. forward and reverse) on a MegaBACE 1000 sequencer using the DYEnamic ET Terminator Cycle Sequencing Kit (Amersham Biosciences) according to manufacturer’s recommendations. The resulting sequences were assembled and edited using the DNA Star Software Package (LaserGene) and further used for phylogenetic analyses.
Materials and methods Tissue preparation In order to obtain the tissue necessary for DNA isolation, we dissected small pieces of alcohol-preserved colonies of H. tortuosa Verrill, 1868, H. verrucosa Verrill, 1868, H. hickmani Breedy & Guzman, 2005 and H. uatumani Castro, 1990 using a scalpel, and removed one to three polyps for subsequent DNA isolation. Specimens were obtained on loan from Smithsonian Natural History Museum (formerly United States National Museum, USMN), Museo de Zoología, UCR (UCR), and Charles Darwin Research Station, Galápagos, Ecuador (CDRS), or collected using SCUBA diving in shallow waters (
