Evolutionary innovations in Antarctic brittle stars linked to glacial refugia
journal contributionposted on 2022-01-17, 03:45 authored by SCY Lau, Jan StrugnellJan Strugnell, CJ Sands, CNS Silva, NG Wilson
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 O. hexactis 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 O. victoriae is a single species (rather than a species complex) and is closely related to O. hexactis (a separate species). Since their recent divergence in the mid-Pleistocene, O. victoriae and O. hexactis 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 O. hexactis, and propose that it could be linked to environmental changes (such as salinity) associated with intensified interglacial-glacial cycles.
Antarctic Circumnavigation Expedition (carried out by the Swiss Polar Institute, supported by the ACE Foundation and Ferring Pharmaceuticals); Australian Research Council Discovery grant, Grant/Award Number: DP190101347; Antarctic PhD student support grant (Antarctic Science Foundation); David Pearse bequest; National Science Foundation (USA) Office of Polar Programs, Grant/Award Number: 1043749; Thomas Davies Research grant (Australian Academy of Science); ARC SRIEAS Grant Securing Antarctica's Environmental Future, Grant/Award Number: SR200100005
JournalEcology and Evolution
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Science & TechnologyLife Sciences & BiomedicineEcologyEvolutionary BiologyEnvironmental Sciences & Ecologycontrasting life historiesevolutionary innovationglacial refugiamorphological innovationpopulation geneticsSOUTHERN-OCEANECHINODERMATA-OPHIUROIDEAGENETIC-STRUCTUREMITOCHONDRIAL LINEAGESSPECIES DELIMITATIONPOPULATION-GENETICSCIRCUMPOLAR CURRENTCRYPTIC SPECIATIONSEABIODIVERSITY