title: Phylogenetic relationships elucidate colonization patterns in the intertidal grazers Osilinus Philippi, 1847 and Phorcus Risso, 1826 (Gastropoda: Trochidae) in the northeastern Atlantic Ocean and Mediterranean Sea.
abstract: Snails in the closely related trochid genera Phorcus Risso, 1826 and Osilinus Philippi, 1847 are ecologically important algal grazers in the intertidal zone of the northeastern Atlantic Ocean and Mediterranean Sea. Here we present the first complete molecular phylogeny for these genera, based on the nuclear 28S rRNA gene and the mitochondrial 16S rRNA and COI genes, and show that the current classification is erroneous. We recognize nine species in a single genus, Phorcus: estimated by BEAST analysis, this arose 30 (± 10) Ma; it consists of two subgenera, Phorcus and Osilinus, which we estimate diverged 14 (± 4.5) Ma. Osilinus kotschyi, from the Arabian and Red Seas, is not closely related and is tentatively referred to Priotrochus Fischer, 1879. Our phylogeny allows us to address biogeographical questions concerning the origins of the Mediterranean and Macaronesian species of this group. The former appear to have evolved from Atlantic ancestors that invaded the Mediterranean on several occasions after the Zanclean Flood, which ended the Messinian Salinity Crisis 5.3 Ma; whereas the latter arose from several colonizations of mainland Atlantic ancestors within the last 3 (± 1.5) Ma.
authors.affiliation: Allan Wilson Centre for Molecular Ecology and Evolution, Department of Zoology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand. kirsten.donald@otago.ac.nz
authors.forename: Kirsten M
authors.initials: KM
authors.lastname: Donald
authors.forename: Joanne
authors.initials: J
authors.lastname: Preston
authors.forename: Suzanne T
authors.initials: ST
authors.lastname: Williams
authors.forename: David G
authors.initials: DG
authors.lastname: Reid
authors.forename: David
authors.initials: D
authors.lastname: Winter
authors.forename: Raquel
authors.initials: R
authors.lastname: Alvarez
authors.forename: Barbara
authors.initials: B
authors.lastname: Buge
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Hawkins
authors.forename: Jose
authors.initials: J
authors.lastname: Templado
authors.forename: Hamish G
authors.initials: HG
authors.lastname: Spencer
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D001499:Bayes Theorem; D003576:Electron Transport Complex IV / Q000235:genetics; D049851:Gastropoda / Q000145:classification / Q000235:genetics*; D049810:Genetic Speciation; D014644:Genetic Variation; D008522:Mediterranean Sea; D008969:Molecular Sequence Data; D010802:Phylogeny; D058974:Phylogeography; D012335:RNA, Ribosomal / Q000235:genetics; D017422:Sequence Analysis, DNA; D014872:Water Movements
chemical_list: D012335:RNA, Ribosomal; D003576:Electron Transport Complex IV