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Marine Ecology Progress Series

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MEPS 405:221-230 (2010)  -  DOI:

Circumpolar dispersal by rafting in two subantarctic kelp-dwelling crustaceans

R. Nikula*, C. I. Fraser, H. G. Spencer, J. M. Waters

Allan Wilson Centre for Molecular Ecology and Evolution, Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand

ABSTRACT: Long-distance oceanic rafting is frequently invoked as an explanation for broad geographic distributions of sedentary marine taxa, but evidence for this ecological process remains elusive. We explored empirically the potential of rafting as a dispersal mechanism by comparing circumpolar mtDNA variability in 3 codistributed subantarctic taxa: 2 direct-developing epifaunal crustacean species (Limnoria stephenseni, Parawaldeckia kidderi) and their macroalgal host (Durvillaea antarctica). A previous study of D. antarctica suggests that its subantarctic populations were established only postglacially, and we predict that the epifaunal invertebrates associated with it experienced a parallel island-colonization episode, facilitated by kelp-rafting. We generated and analysed mtDNA sequence data (cytochrome oxidase subunit I [COI] gene, >900 base pairs) from 89 L. stephenseni and 62 P. kidderi specimens and reanalysed previously published comparable data for D. antarctica. Both epifaunal species exhibited wide-scale circumpolar distributions of a single haplotype. Little sequence diversity was found within island samples, with the exception of P. kidderi in the Falkland Islands. The phylogeographic diversity and structuring of the invertebrates was very similar to that of their kelp host and consistent with a scenario of subantarctic recolonization and population expansion. The dependence of these otherwise non-dispersive crustaceans on macroalgal holdfasts for food and habitat, as well as the great abundance of D. antarctica adrift in the Antarctic Circumpolar Current (ACC), support rafting as their most plausible recolonization mechanism. We suggest that macroalgal rafting may explain similarities in the species composition of intertidal marine communities across the subantarctic.

KEY WORDS: Rafting · Long-distance dispersal · Marine biogeography · Phylogeography · Macroalga · mtDNA · Peracarida · Durvillaea antarctica

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Cite this article as: Nikula R, Fraser CI, Spencer HG, Waters JM (2010) Circumpolar dispersal by rafting in two subantarctic kelp-dwelling crustaceans. Mar Ecol Prog Ser 405:221-230.

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