title: Antitropical distributions and species delimitation in a group of ophiocomid brittle stars (Echinodermata: Ophiuroidea: Ophiocomidae).
abstract: In this paper we examine the phylogeny and biogeography of the temperate genera of the Ophiocomidae (Echinodermata: Ophiuroidea) which have an interesting asymmetrical anti-tropical distribution, with two genera (Ophiocomina and Ophiopteris) previously considered to have a separate species in both the North and South hemispheres, and the third (Clarkcoma) diversifying in the southern Australian/New Zealand region. Our phylogeny, generated from one mitochondrial and two nuclear markers, revealed that Ophiopteris is sister to a mixed Ophiocomina/Clarkcoma clade. Ophiocomina was polyphyletic, with O. nigra and an undescribed species from the South Atlantic Ocean sister to a clade including Clarkcoma species and O. australis. The phylogeny also revealed a number of recently diverged lineages occurring within Clarkcoma, some of which are considered to be cryptic species due to the similarity in morphology combined with the apparent absence of interbreeding in a sympatric distribution, while the status of others is less certain. The phylogeny provides support for two transequatorial events in the group under study. A molecular clock analysis places both events in the middle to late Miocene. The analysis excludes a tectonic vicariance hypothesis for the antitropical distribution associated with the breakup of Pangaea and also excludes the hypothesis of more recent gene flow associated with Plio/Pleistocene glacial cycling.
authors.affiliation: Marine Invertebrates, Sciences, Museum Victoria, GPO Box 666, Melbourne, Victoria 3000, Australia; Department of Genetics, Faculty of Science, University of Melbourne, Parkville, Victoria 3010, Australia. Electronic address: kmnaughton@gmail.com.
authors.forename: K M
authors.initials: KM
authors.lastname: Naughton
authors.affiliation: Marine Invertebrates, Sciences, Museum Victoria, GPO Box 666, Melbourne, Victoria 3000, Australia.
authors.forename: T D
authors.initials: TD
authors.lastname: O'Hara
authors.affiliation: Department of Genetics, Faculty of Science, University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: B
authors.initials: B
authors.lastname: Appleton
authors.affiliation: Discipline of Anatomy and Histology, School of Medicine, University of Sydney, New South Wales 2006, Australia.
authors.forename: P A
authors.initials: PA
authors.lastname: Cisternas
mesh_terms: D000818:Animals; D004447:Echinodermata / Q000145:classification* / Q000235:genetics; D051456:Gene Flow; D018895:Microsatellite Repeats; D010802:Phylogeny; D058974:Phylogeography
keywords: Antitropical; Cryptic species; Molecular; Ophiuroid; Phylogeny