The Evolutionary History of the Antarctic Flora


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Authors
Biersma, Elisabeth Machteld  ORCID logo  https://orcid.org/0000-0002-9877-2177
Abstract

How long has the extant flora been present in the Antarctic? Glaciological reconstructions propose that most areas in Antarctica were covered by thick ice sheets throughout the Last Glacial Maximum (LGM; ~22-18 kya) as well as previous glaciations, suggesting terrestrial life must have been extremely limited during these periods. In contrast, recent biogeographic and genetic studies support most extant groups of Antarctic terrestrial fauna having survived past glaciations in situ. However, studies on the origin and age of the Antarctic flora remain sparse. Applying population genetic, phylogeographic and divergence time analyses I assessed the global biogeography, origin and age of several abundant Antarctic moss species, including: four Polytrichaceae mosses, characterised by having bipolar distributions, the most common (~45% of species) distribution pattern amongst Antarctic mosses; the globally widespread moss Ceratodon purpureus; the bank-forming moss Chorisodontium aciphyllum, also known for its old sub-fossils in Antarctica and long-term viability from revival experiments; and, lastly, the genus Schistidium, the most species-rich moss genus in Antarctica, including many endemic species. Genetic analyses revealed evidence of long-term (multi-million year) survival of plants in Antarctica (several species of Schistidium, Ceratodon purpureus, and possibly Polytrichum juniperinum). However, evidence for a likely more recent (<100 ky) arrival of Chorisodontium aciphyllum was also found. Some species revealed multiple separate dispersal events to the Antarctic, suggesting the region may be less isolated for spore-dispersed organisms than previously thought. Evidence for increased genetic diversity in the northern maritime Antarctic compared to other regions point at it including potential refugial areas. Furthermore, genetic patterns revealed geographic features that enable and limit the connectivity of bryophytes globally as well as in Antarctica. This study suggests that, despite the harsh polar climate during glaciation periods, many bryophytes have had a much longer presence in Antarctica than previously thought.

Description
Date
Advisors
Convey, Peter
Jackson, Jennifer
Linse, Katrin
Griffiths, Howard
Keywords
Antarctic, Antarctica, Moss, Bryophyte, Population genetics, biogeography, genetics, evolution, Last Glacial Maximum, Biology, Polar, Arctic, cryptogam, spore, distribution, phylogenetic, phylogenetics, refugia, flora, climate
Qualification
Doctor of Philosophy (PhD)
Awarding Institution
University of Cambridge
Sponsorship
This PhD was funded by a Natural Environment Research Council (NERC) PhD studentship (ref NE/K50094X/1) to E.M.B. and NERC core funding to the British Antarctic Survey Biodiversity, Evolution and Adaptation Team