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Antedon Petasus (Fig The genus Antedon (Crinoidea, Echinodermata): an example of evolution through vicariance Hemery Lenaïg 1, Eléaume Marc 1, Chevaldonné Pierre 2, Dettaï Agnès 3, Améziane Nadia 1 1. Muséum national d'Histoire naturelle, Département des Milieux et Peuplements Aquatiques Introduction UMR 5178 - BOME, CP26, 57 rue Cuvier 75005 Paris, France 2. Centre d’Océanologie de Marseille, Station Marine d’Endoume, CNRS-UMR 6540 DIMAR Chemin de la batterie des Lions 13007 Marseille, France 3. Muséum national d'Histoire naturelle, Département Systématique et Evolution The crinoid genus Antedon is polyphyletic and assigned to the polyphyletic family UMR 7138, CP 26, 57 rue Cuvier 75005 Paris, France Antedonidae (Hemery et al., 2009). This genus includes about sixteen species separated into two distinct groups (Clark & Clark, 1967). One group is distributed in the north-eastern Atlantic and the Mediterranean Sea, the other in the western Pacific. Species from the western Pacific group are more closely related to other non-Antedon species (e.g. Dorometra clymene) from their area than to Antedon species from the Atlantic - Mediterranean zone (Hemery et al., 2009). The morphological identification of Antedon species from the Atlantic - Mediterranean zone is based on skeletal characters (Fig. 1) that are known to display an important phenotypic plasticity which may obscure morphological discontinuities and prevent correct identification of species (Eléaume, 2006). Species from this zone show a geographical structuration probably linked to the events that followed the Messinian salinity crisis, ~ 5 Mya (Krijgsman Discussion et al., 1999). To test this hypothesis, a phylogenetic study of the Antedon species from the Atlantic - The molecular analysis and morphological identifications provide divergent Mediterranean group was conducted using a mitochondrial gene. It should allow to come to assignment of the specimens to six species in the genus Antedon. For a better understanding of the relationships among these species. In addition, Antedon example, the specimens from Senegal have been identified as A. bifida but appears to be a good model organism to study the recolonization in the Mediterranean after molecular comparison shows that A. bifida from Senegal and Europe are the Messinian salinity crisis. different. They most probably belong to A. hupferi which occurs in the area and whose morphological description is rather vague. Specimens from the Pinnule b Mediterranean were attributed to different species (A. moroccana, A. a Arm mediterranea and A. adriatica) but seem to belong to a single species Brachial displaying a high phenotypic plasticity. Antedon adriatica may however represent a valid taxon (with two proteic synapomorphies, Fig. 2a) but this Fig. 1a. An Antedon mediter- ranea in situ (© T. Vignaud). needs to be further investigated. These results suggest that the diagnostic 1b. Lateral view of an Cirrus characters used to distinguish species in the genus Antedon are highly unstalked crinoid showing Cirral variable and misleading. New diagnostic characters as well as additional centrodorsal, two cirri, and genes are necessary to better delineate species limits in the genus Antedon. bases of three arms (Modified from Messing & Dearborn, Antedon bifida is distributed in the Atlantic Ocean and the Alboran Sea 1990). (western Mediterranean) while A. mediterranea is distributed in the rest of the Mediterranean (Fig. 2b and Fig. 3). The Alboran Sea is characterized, at its Centrodorsal eastern edge, by an oceanographical barrier: the Almeria - Oran Front (Tintoré et al., 1991 ; Fig. 3). Between this front and the Strait of Gibraltar, two gyres Results line the Spanish and Moroccan coasts. The onset of these oceanographical features dates back to the end of the Messinian salinity crisis. Our results suggest that the divergence between A. bifida (Fig. 3, in The first phylogenetic reconstruction of the genus Antedon (Fig. 2a) was based on the orange) and A. mediterranea (Fig. 3, in violet) migth have occurred by mitochondrial gene of the cytochrome b (cytb). Sequences were obtained for twenty vicariance after the eustatic re-equilibration between the Atlantic and the specimens from fourteen sampling stations (Fig. 2b), representing five nominal species. Mediterranean ~3 Mya (Krijgsman et al. 1999) and could have since been Phylogenetic hypotheses were inferred using maximum parsimony (MP) on nucleic acid maintained by the two gyres, acting as an ecological barrier to larval dispersal sequences (not shown here) and amino acid sequences (Fig. 2a), and using maximum in the Alboran Sea. likelihood (not shown here). Two species of Heliometrinae, a subfamily of Antedonidae, were used as outgroups. ML and MP on nucleic acid analyses give the same results as MP 8°O 7°O 6°O 5°O 4°O 3°O 2°O 1°O 0° Fig. 3. Oceanographic particulari- analyses on amino acid sequences, except for the node A which is not resoluted in the two Almeria 37°N Malaga ties in the Alboran Sea: Western not shown trees. Almeria-Oran Front and Eastern gyres and the Almeria - Antedon petasus (Fig. 2a, framed in blue) is a sister group to all other species in the Oran Front. Antedon sampling 36°N stations are pointed: Malaga and genus. Specimens identified as A. bifida are found in two distinct clades, one clade Western gyre Ceuta Eastern gyre Oran îles Ceuta in orange for A. bifida, and composed of specimens collected off Europe (Fig. 2a, framed in orange), and a second Habibas Habibas islands in violet for A. clade comprising specimens collected off Senegal (Fig. 2a, framed in pink). Specimens 35°N mediterranea. identified as two distinct species (A. moroccana and A. mediterranea, Fig. 2a, framed in violet) show no differences. Two specimens from Croatia (Fig. 2a, framed in red), one identified as A. mediterranea, the other as A. adriatica, are found in the same clade, as a sister group to all others from the Mediterranean. References Florometra serratissima a Promachocrinus kerguelensis CLARK A.H., CLARK A.M. ; 1967. A monograph of the existing crinoids. Volume 1 - The comatulids. Part 5 Sue1-1 - Suborders Oligophreata (concluded) and Macrophreata. Bull. US Nat. Mus. 82: 1-795 100 Sue2-1 ELEAUME M. ; 2006. Approche morphométrique de la variabilité phénotypique : consequences 10 Antedon petasus 100 systématiques et évolutives. Application aux crinoïdes actuels (Crinoidea : Echinodermata). Thèse du Muséum JFS1-1 Sweden National d’Histoire Naturelle, inédit, Paris : 1-402 JFS1-3 Scotland HEMERY L., ELEAUME M., CHEVALDONNE P., DETTAI A., AMEZIANE N. ; 2009. The genus Antedon SBR1-20 (Crinoidea, Echinodermata): discontinuous distribution or problem of definition ? 13th International Echinoderm SBR1-32 Conference, Hobart 64 296-3 KRIJGSMAN W., HILGEN F.J., RAFFI I., SIERRO F.J., WILSON D.S. ; 1999. Chronology, causes and 1 Antedon bifida Lanvéoc 77 298-2 progression of the Messinian salinity crisis. Nature 400: 652-655 Monaco Gripacola 99 SG1-1 MESSING C.G., DEARBORN J.H. ; 1990. Marine flora and fauna of the northeastern United States 100 Marseille Saint Stipan Echinodermata: Crinoidea. NOAA Technical Report NMFS 91: 1-30 SG1-2 Naples Malaga TINTORE J., GOMIS D., ALONSO S. ; 1991. Mesoscale dynamics and vertical motion in the Alboran Sea. JG10-2 80 J. Phys. Ocean. 21: 811-823 2 Antedon moroccana Ceuta Habibas 86 JG10-8 TP8b-2 50 1 63 262-1 A 79 LH159 Antedon mediterranea Acknowledgements 2 78 2 78 89 LH160 MH1-3 Senegal Antedon specimens were sampled in scuba-diving by Pierre Chevaldonné, Patrice Petit de Voize, Jo 1 64 JT1-1 Antedon adriatica Harmelin, Thierry Pérez, Serge Gofas, Helmut Zibrowius, Martina Hervat, Josip Tomisin, Sabine Stöhr, George L = 65 Sevastopulo, Jason Hall-Spencer, Judy Foster-Smith, Mike Thorndyke and the Biological Station of Roscoff. 100 HZ11-3 IC = 0,9077 7 100 Antedon bifida The other crinoids came from the collections of the Muséum national d’Histoire naturelle (Paris, France) and the IR = 0,9562 PPdV1-5 b Victoria Museum (Melbourne, Australie). The molecular handlings were conducted in the Service de Systématique Moléculaire (SSM) of the Muséum Fig. 2a. Phylogenetic relationships among Antedon inferred from the mitochondrial gene cytb translated into national d'Histoire naturelle, with the great help of Céline Bonillo. The sequencing was carried out by protein. Bootstrap values, jackknife values and Decay index are, respectively, given under, above the branches and Genoscope (Evry, France) with Corinne Cruaud and Arnaud Couloux. at nodes. 2b. Geographical distribution of the five Antedon species which are considered as valid. Areas are This study was financed by the support of the white ANR ANTFLOCKS (Antarctic Species Flocks), colored using Clark & Clark (1967) and our data. Sampling stations are figured by red spots. 2007-2010..
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