Molecular Data Suggest Long-Term in Situ Antarctic Persistence Within Antarctica's Most Speciose Plant Genus, Schistidium

• Published in: Frontiers in Ecology and Evolution
• Main Authors: Elisabeth M. Biersma, Jennifer A. Jackson, Michael Stech, Howard Griffiths, Katrin Linse, Peter Convey
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media S.A. 2018
• Subjects: bryophyte; polar; biogeography; biodiversity; survival; Antarctic; Evolution; QH359-425; Ecology; QH540-549.5; The Antarctic; Antarctic Peninsula; Antarc*; Antarctica; Schistidium antarctici
• Online Access: https://doi.org/10.3389/fevo.2018.00077; https://doaj.org/article/4022ca6bf4cc4684af9fe856c4ec6159

From glacial reconstructions it is clear that Antarctic terrestrial life must have been extremely limited throughout Quaternary glacial periods. In contrast, recent biological studies provide clear evidence for long-term in situ persistence throughout glacial times within most extant Antarctic faunal and several microbial groups. However, even now, the evolutionary history of the Antarctic flora—despite playing major role in Antarctic ecosystems—remains poorly studied. We assessed the diversity, richness and relative age divergences within Schistidium (Grimmiaceae, Bryophyta), the most species-rich plant genus in the Antarctic, as well as the plant genus containing most Antarctic endemic species. We applied phylogenetic and molecular dating methods based on nuclear ribosomal Internal Transcribed Spacer sequences, including all known Antarctic Schistidium species with available sample material. We additionally investigated the continent-wide genetic diversity within the most common Antarctic representative of the genus—the endemic species Schistidium antarctici—and performed preliminary phylogeographic analyses of the bipolar species Schistidium rivulare. Most previously described Antarctic Schistidium species were genetically distinct, confirming their specific status. Interspecific divergences of all species took place at least ~1 Mya, suggesting a likely in situ persistence in Antarctica for (at least) all endemic Schistidium species. The widespread endemic species, Schistidium antarctici, diverged from other Antarctic congeners in the late Miocene, thereby revealing the oldest extant plant species currently known in Antarctica, and providing increasing support for the hypothesis of vegetation survival through multiple glacial periods. Within S. antarctici we identified several distinct clades dividing the eastern Antarctic Peninsula and Scotia Arc islands from the western Antarctic Peninsula and all continental locations. This suggests that the mountainous spine on the Antarctic Peninsula forms a strong ...