Hesis that C. megalonyx sensu lato survived the glaciations ex situ

Hesis that C. megalonyx sensu lato survived the glaciations ex situ in refugia in the Subantarctic shelf regions, as no sequences from Antarctic specimens nest within the Subantarctic clades. However, we lack samples from several non-Antarctic areas where C. megalonyx has been found, such as South Africa, Kerguelen and the New Zealand Subantarctic islands. There is good evidence that South Georgia acted as a refugium for clade A, as shown by the much greater haplotype diversity arguing against a recent expansion, in contrast to the more southern Scotia Arc islands. A similar pattern was recently found by Gonz ez-Wevar et al. [73] for the limpet Nacella concinna. As the geological evidence suggests that South Georgia was not fully glaciated during the Last Glacial Maximum (LGM) [74], the South Georgia shelf could plausibly have been a refugium for shelf-inhabiting taxa, which is in good agreement with the results of a purchase 3′-Methylquercetin pioneering species distribution modelling study on Southern Ocean shrimps [75]. The hypothesis that the shelf was recolonized from the deep sea after the LGM cannot be rejected by our data, as we have only few samples from deeper than 1000 m. However, we consider it unlikely, as circumpolar survival in the deep sea would lead to greater genetic homogeneity across regions and lack of signatures for recent expansion. Such a pattern is found in the shrimp Nematocarcinus Sulfatinib manufacturer lanceopes [76], but not in our data for C. megalonyx. The hypothesis most consistent with our data is the in situ survival in ice-free refugia, which were probably located at polynyas (temporary ice-free ocean regions) as suggested by Thatje et al. [19]. Because of the strong intraclade regional differentiation in C. megalonyx, seen e.g. within clades D1 and E1, it seems likely that these clades survived in more than one refugium during the LGM, spreading from there and in some cases (clade I) coming into secondary contact. Molecular evidence for in situ survival on the Antarctic shelf has recently been reported for the broadly distributed sea spider Austropallene cornigera [77] and other invertebrates [78]. Our data support dispersal via the Antarctic Circumpolar Current (ACC) at least in the case of clade E1, which may have colonized Bouvet from the South Sandwich Islands, indicating a relatively recent (only one haplotype known from Bouvet) eastward dispersal in latitudes dominated by the ACC. However, the same haplotype also occur in the deep Weddell Sea, which suggests that Bouvet could also have been colonized from the south via the deep sea. Survival in multiple refugia would indicate that interclade splits precede the LGM, and probably occurred during earlier Pleistocene glaciations or even earlier. In a few cases, we observe the same haplotype in geographically widely separated regions, such as a clade E1 haplotype (E1?) that occurs both in the Antarctic Peninsula and Terre Ad ie. This has also been observed in other invertebrates without a planktonic stage [9,20,79] and might be explained by rafting on floating material carried by currents, including ice. Pycnogonids have also been observed swimming [80].The strong regional differentiation, which apparently persisted since the LGM, is typical of benthic brooding organisms with limited dispersal capability. Adult pycnogonids are almost exclusively benthic, the reproduction mode of colossendeids is unknown and no larvae have been recorded from plankton samples. The distribution of C. megalonyx contrasts.Hesis that C. megalonyx sensu lato survived the glaciations ex situ in refugia in the Subantarctic shelf regions, as no sequences from Antarctic specimens nest within the Subantarctic clades. However, we lack samples from several non-Antarctic areas where C. megalonyx has been found, such as South Africa, Kerguelen and the New Zealand Subantarctic islands. There is good evidence that South Georgia acted as a refugium for clade A, as shown by the much greater haplotype diversity arguing against a recent expansion, in contrast to the more southern Scotia Arc islands. A similar pattern was recently found by Gonz ez-Wevar et al. [73] for the limpet Nacella concinna. As the geological evidence suggests that South Georgia was not fully glaciated during the Last Glacial Maximum (LGM) [74], the South Georgia shelf could plausibly have been a refugium for shelf-inhabiting taxa, which is in good agreement with the results of a pioneering species distribution modelling study on Southern Ocean shrimps [75]. The hypothesis that the shelf was recolonized from the deep sea after the LGM cannot be rejected by our data, as we have only few samples from deeper than 1000 m. However, we consider it unlikely, as circumpolar survival in the deep sea would lead to greater genetic homogeneity across regions and lack of signatures for recent expansion. Such a pattern is found in the shrimp Nematocarcinus lanceopes [76], but not in our data for C. megalonyx. The hypothesis most consistent with our data is the in situ survival in ice-free refugia, which were probably located at polynyas (temporary ice-free ocean regions) as suggested by Thatje et al. [19]. Because of the strong intraclade regional differentiation in C. megalonyx, seen e.g. within clades D1 and E1, it seems likely that these clades survived in more than one refugium during the LGM, spreading from there and in some cases (clade I) coming into secondary contact. Molecular evidence for in situ survival on the Antarctic shelf has recently been reported for the broadly distributed sea spider Austropallene cornigera [77] and other invertebrates [78]. Our data support dispersal via the Antarctic Circumpolar Current (ACC) at least in the case of clade E1, which may have colonized Bouvet from the South Sandwich Islands, indicating a relatively recent (only one haplotype known from Bouvet) eastward dispersal in latitudes dominated by the ACC. However, the same haplotype also occur in the deep Weddell Sea, which suggests that Bouvet could also have been colonized from the south via the deep sea. Survival in multiple refugia would indicate that interclade splits precede the LGM, and probably occurred during earlier Pleistocene glaciations or even earlier. In a few cases, we observe the same haplotype in geographically widely separated regions, such as a clade E1 haplotype (E1?) that occurs both in the Antarctic Peninsula and Terre Ad ie. This has also been observed in other invertebrates without a planktonic stage [9,20,79] and might be explained by rafting on floating material carried by currents, including ice. Pycnogonids have also been observed swimming [80].The strong regional differentiation, which apparently persisted since the LGM, is typical of benthic brooding organisms with limited dispersal capability. Adult pycnogonids are almost exclusively benthic, the reproduction mode of colossendeids is unknown and no larvae have been recorded from plankton samples. The distribution of C. megalonyx contrasts.

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