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Evolutionary innovations in Antarctic brittle stars linked to glacial refugia
Lau, S.C.Y.; Strugnell, J.M.; Sands, C.J.; Silva, C.N.S.; Wilson, N.G. (2021). Evolutionary innovations in Antarctic brittle stars linked to glacial refugia. Ecol. Evol. 11(23): 17428-17446. https://dx.doi.org/10.1002/ece3.8376
In: Ecology and Evolution. John Wiley & Sons: Chichester. ISSN 2045-7758; e-ISSN 2045-7758, more
Peer reviewed article  

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Keyword
    Marine/Coastal

Authors  Top 
  • Lau, S.C.Y.
  • Strugnell, J.M.
  • Sands, C.J.
  • Silva, C.N.S.
  • Wilson, N.G., more

Abstract
    The drivers behind evolutionary innovations such as contrasting life histories and morphological change are central questions of evolutionary biology. However, the environmental and ecological contexts linked to evolutionary innovations are generally unclear. During the Pleistocene glacial cycles, grounded ice sheets expanded across the Southern Ocean continental shelf. Limited ice-free areas remained, and fauna were isolated from other refugial populations. Survival in Southern Ocean refugia could present opportunities for ecological adaptation and evolutionary innovation. Here, we reconstructed the phylogeographic patterns of circum-Antarctic brittle stars Ophionotus victoriae and Ohexactis with contrasting life histories (broadcasting vs brooding) and morphology (5 vs 6 arms). We examined the evolutionary relationship between the two species using cytochrome c oxidase subunit I (COI) data. COI data suggested that Ovictoriae is a single species (rather than a species complex) and is closely related to Ohexactis (a separate species). Since their recent divergence in the mid-Pleistocene, Ovictoriae and Ohexactis likely persisted differently throughout glacial maxima, in deep-sea and Antarctic island refugia, respectively. Genetic connectivity, within and between the Antarctic continental shelf and islands, was also observed and could be linked to the Antarctic Circumpolar Current and local oceanographic regimes. Signatures of a probable seascape corridor linking connectivity between the Scotia Sea and Prydz Bay are also highlighted. We suggest that survival in Antarctic island refugia was associated with increase in arm number and a switch from broadcast spawning to brooding in Ohexactis, and propose that it could be linked to environmental changes (such as salinity) associated with intensified interglacial-glacial cycles.

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