title: Geographic structure in the Southern Ocean circumpolar brittle starOphionotus victoriae(Ophiuridae) revealed from mtDNA and single-nucleotide polymorphism data.
abstract: Marine systems have traditionally been thought of as "open" with few barriers to gene flow. In particular, many marine organisms in the Southern Ocean purportedly possess circumpolar distributions that have rarely been well verified. Here, we use the highly abundant and endemic Southern Ocean brittle starOphionotus victoriaeto examine genetic structure and determine whether barriers to gene flow have existed around the Antarctic continent.Ophionotus victoriaepossesses feeding planktotrophic larvae with presumed high dispersal capability, but a previous study revealed genetic structure along the Antarctic Peninsula. To test the extent of genetic differentiation withinO. victoriae, we sampled from the Ross Sea through the eastern Weddell Sea. Whereas two mitochondrial DNA markers (16S rDNA and COI) were employed to allow comparison to earlier work, a 2b-RAD single-nucleotide polymorphism (SNP) approach allowed sampling of loci across the genome. Mitochondrial data from 414 individuals suggested three major lineages, but 2b-RAD data generated 1,999 biallelic loci that identified four geographically distinct groups from 89 samples. Given the greater resolution by SNP data,O. victoriaecan be divided into geographically distinct populations likely representing multiple species. Specific historical scenarios that explain current population structure were examined with approximate Bayesian computation (ABC) analyses. Although the Bransfield Strait region shows high diversity possibly due to mixing, our results suggest that within the recent past, dispersal processes due to strong currents such as the Antarctic Circumpolar Current have not overcome genetic subdivision presumably due to historical isolation, questioning the idea of large open circumpolar populations in the Southern Ocean.
authors.affiliation: Department of Biological Sciences Auburn University Auburn AL USA.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Galaska
authors.affiliation: Natural Environment Research Council British Antarctic Survey Cambridge UK.
authors.forename: Chester J
authors.initials: CJ
authors.lastname: Sands
authors.affiliation: Department of Biological Sciences Auburn University Auburn AL USA.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Santos
authors.affiliation: Department of Biology Central Michigan University Mount Pleasant MI USA.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Mahon
authors.affiliation: Department of Biological Sciences Auburn University Auburn AL USA.
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Halanych
keywords: Antarctica; cytochrome c oxidase subunit I; ophiuroid; phylogeography; population genetics; restriction‐associated DNA; single‐nucleotide polymorphism