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The palaeobiogeography of the east Antarctic freshwater fauna


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Newman, Louise 2008 , 'The palaeobiogeography of the east Antarctic freshwater fauna', PhD thesis, University of Tasmania.

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The mechanisms and timing of the colonisation of Antarctica by lacustrine freshwater
fauna are unclear. Three scenarios are possible: anthropogenic introduction, dispersal
to the continent following late Pleistocene or Holocene deglaciation, and survival of
preglacial species in lacustrine refugia. Current distributions and dispersal modes can
be used to infer the colonisation mode of a species. They cannot, however, be used to
determine the minimum age of association between a species and a region,
palaeodistributions, or faunal response to environmental change. This knowledge is
important for understanding the adaptability and antiquity of the Antarctic fauna.
Analysis of faunal microfossils preserved in lacustrine sediment cores can
provide direct evidence of the timing and occurrence of these processes. Additionally,
informed selection of study lakes allows the minimum age of association to be
determined. This study applied this approach to three lakes that differ in glacial
history, distance to coast, age and present-day fauna, yet represent a geographically
coherent area.
Lake Reid, Larsemann Hills (76°23'E; 69°23'8) has a continuous 130 000
year sedimentary record. Microfossils of the cladoceran Daphniopsis studeri and the
rotifer Notholca sp. were recovered from every core depth, indicating their continued
presence throughout the lake's existence. In contrast, an unidentified copepod became
extinct during the Last Glacial Maximum (LGM). This record provides the first direct
evidence of a glacial lacustrine refugium for invertebrates in Antarctica and indicates
the presence of a relict freshwater fauna on the continent. Holocene colonisation,
therefore, need not be invoked.
Waterfall Lake, Vestfold Hills (68°32'S, 78°20'E; ca. 100 km from Lake
Reid) has contained a diverse faunal community throughout its 6000-year history.
Colonisation occurred immediately after development, suggesting a local faunal
source. All the species present in Lake Reid (excluding the copepod) were present in
Waterfall Lake, suggesting dispersal between the oases or the presence of a glacial
refugium in the Vestfold Hills.
Lake Terrasovoje (70°33'S, 68°01 'E) is located in the Amery Oasis, parts of
which have remained ice free for ca. 2 Myr. The lake's palaeofauna differed almost
entirely from those of the coastal lakes. The copepod Boeckella poppei was recorded
in nearly all core sections, indicating that its disjunct Antarctic distribution is not the
result of anthropogenic introduction, but rather the survival of an ancient relictual
population. Complex interactions within the lake were also identified, with local
extinction of three species, most likely due to environmental factors.
This study indicates that components of the Antarctic freshwater fauna
survived throughout the LGM, and provides the first direct evidence for an ancient
component to this fauna. In light of these results previous assertions of Holocene
dispersal must be questioned. Clear geographic distinctions in faunal distributions and
community response to environmental pressures have additionally been identified.

Item Type: Thesis - PhD
Authors/Creators:Newman, Louise
Copyright Holders: The Author
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Copyright 2008 the author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
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Available for library use only and copying in accordance with the Copyright Act 1968, as amended. Thesis (PhD)--University of Tasmania, 2008. Includes bibliographical references

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