第3回極域科学シンポジウム/第34回極域生物シンポジウム 11月27日（火） 統計数理研究所 ３階セミナー

A. Hodgson Dominic

Antoniades Dermot

Imura Satoshi

Kudoh Sakae

Nedbalová Linda

Sabbe Koen

Souffreau Caroline

Sterken Mieke

Tavernier Ines

Van de Vijver Bart

Van Nieuwenhuyze Wim

Vanormelingen Pieter

Verleyen Elie

Vyverman Wim

National Institute of Polar Research Repository

   Diatom distributions in space and time – a case study from the polar regions Elie Verleyen1, Bart Van de Vijver2, Koen Sabbe1, Dominic A. Hodgson3, Linda Nedbalová4, Dermot Antoniades5, Wim Van Nieuwenhuyze1, Ines Tavernier1, Mieke Sterken1, Caroline Souffreau1, Satoshi Imura6, Sakae Kudoh6, Pieter Vanormelingen1, Wim Vyverman1 1Ghent University, Protistology and Aquatic Ecology, Krijgslaan 281 S8, 9000 Gent, Belgium  2National Botanic Garden of Belgium, Domein van Bouchout, 1860 Meise, Belgium  3British Antarctic Survey, Natural Environment Research Council, High Cross Madingley Road, CB3 0ET, Cambridge, UK  4Charles University in Prague, Department of Ecology, Viničná 7, 128 44 Prague 2, Czech Republic  5Grupo de ecología y fisiología de fitoplancton, Sección Limnología, Universidad de la República, Iguá 4225, CP11400, Montevideo, Uruguay 6National Institute of Polar Research, 10-3, Midori-machi, Tachikawa-shi, Tokyo 190-8518, Japan  The composition, diversity and distribution of present-day biota are shaped by the geological, tectonic and climatic past, which resulted in the distinct biogeographical realms we observe in the terrestrial biosphere. Here I summarize our recent studies on the biogeography of polar freshwater diatoms. Antarctic lake-dwelling diatom communities are impoverished and imbalanced in comparison with Arctic communities, and characterized by high levels of endemism. Moreover, molecular data on ubiquitous morphospieces that are widespread in the Antarctic region are starting to reveal substantial hidden diversity, with distinct Antarctic and sub-Antarctic lineages. This suggests that estimates based on the morphospecies concept are conservative and may strongly underestimate the observed levels of endemism. The Antarctic communities are further characterized by the absence of key functional groups such as planktonic taxa, a general paucity of globally successful genera, and an overrepresentation of terrestrial lineages. Comparison of contemporary Antarctic floras with fossil Miocene assemblages points to high rates of local extinction during glacial maxima, in combination with radiations and the selective survival of aerophilic taxa in glacial refugia. We also observed strong bioregionalisation patterns within the Antarctic Realm, which are highly concordant with the three main biogeographical regions traditionally recognized in plants and animals, namely Sub-Antarctica, Maritime Antarctica and Continental Antarctica. Paleolimnological evidence suggests that diatom communities are relatively stable and remain within their respective biogeographical region throughout the Holocene. Within Continental Antarctica, the observed biogeographic provincialism is likely related to differences in the glacial history of the ice-free regions. Sediment records spanning the Late Quaternary period indicate that lake districts which escaped complete glacial overriding during the Last Glacial Maximum (LGM) hold a relict diatom flora, composed of Antarctic endemics and ubiquitous taxa that inhabit cold environments elsewhere. By contrast, in regions that were completely overridden by the East Antarctic Ice Sheet, the diatom communities are composed of aerophilic Antarctic endemics and ubiquitous taxa. These taxa were probably derived from a local diatom pool that was able to survive in local terrestrial nunataks. This is confirmed by a time-constrained molecular phylogeny of the aerophilic diatom Pinnularia borealis which suggests that the Antarctic lineage diverged 7.8 (2-15) Ma ago, and hence before the onset of Pleistocene glacial-interglacial cycles. In addition, there is evidence for large-scale extinctions during the LGM of species currently thriving in Sub-Antarctic habitats but which were present in Continental Antarctica during the warmer Eemian interglacial.     

Diatom distributions in space and time – a case study from the polar regions

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Diatom distributions in space and time – a case study from the polar regions

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