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The occurrence of mycothalli, symbioses between liverworts and fungi, is poorly documented in sub-Antarctica, and biogeographical patterns in Serendipita , the main fungal genus forming the symbiosis, remain understudied. Here, 83 specimens of 16 leafy liverwort species were sampled from sub-Antarctic South Georgia and were examined for mycothalli. Microscopy was used to enumerate fungal structures in liverwort tissues, and sequencing of fungal ribosomal DNA was used to determine the taxonomic and biogeographical affinities of the fungi. Stained hyphal coils, a defining feature of the symbiosis, were found to be frequent (>40% of stem length colonised) in Barbilophozia hatcheri , Cephaloziella varians and Lophoziopsis excisa. A single species of Serendipita , based on a 3% cut-off for ITS2 region sequence divergence, was a frequent colonist of these liverworts. A further 18 basidiomycete and ascomycete taxa colonised other liverwort species. The presence of the Serendipita species was positively associated with the occurrence of stained hyphal coils in stem epidermal cells. Phylogenetic analyses, incorporating worldwide accessions from leafy liverwort-associated Serendipita , showed that the same species, which also occurs in Chile, mainland Europe and on Svalbard, is apparently the sole symbiont of sub- and maritime Antarctic leafy liverworts, and indicated much higher species richness of the genus outside Antarctica. • Mycothalli were frequent in three leafy liverwort species on South Georgia. • A single Serendipita species frequently colonised these liverworts. • The Serendipita species is apparently the sole symbiont of Antarctic liverworts. • Serendipita species diversity in Antarctica is much lower than at lower latitudes. • Hyphal coils form frequently in liverworts colonised by Serendipita. [ABSTRACT FROM AUTHOR]

Forty-four herbarium specimens of the hepatic Barbilophozia hatcheri , collected from across the entire range of the species in Antarctica (54–68 °S), were examined for fungal colonisation. Mycothalli, consisting of hyaline hyphae in rhizoids or hyphal coils in rhizoid bases and stem medullary cells, were present in 42 specimens. The frequencies of mycothalli declined at higher latitudes and were associated positively with annual air temperatures. In contrast, the frequency of dark septate hyphae on stems increased at higher latitudes. Sequencing of ITS regions of fungal rRNA genes amplified from B. hatcheri from 54 °S, 61 °S and 68 °S indicated that Cladophialophora species colonised plants at higher latitudes, but that most fungi had >99 % homology with members of Sebacinales clade B, with best matches to mycobionts of B. lycopodioides , Lophoziopsis excisa and Protolophozia crispata . We propose the use of herbarium specimens of mycothalli as proxies for climate change in Antarctica. [ABSTRACT FROM AUTHOR]

Abstract: Although dark septate fungal endophytes (DSE) occur widely in association with plant roots in cold-stressed habitats, little is known of the taxonomic status of DSE in Antarctica. Here we investigate the phylogenetic affinities of DSE colonising the roots of Colobanthus quitensis and Deschampsia antarctica, the two maritime Antarctic vascular plant species. Two hundred and forty-three DSE were isolated from roots collected from 17 sites across a 1 470km transect through maritime and sub-Antarctica. The ITS1-5.8S-ITS2 nuclear ribosomal gene cluster of representative isolates was sequenced, and the sequences were recovered in 10 sequence groups and sub-groups. Nine of the sequence groupings could be placed in the Helotiales and the remaining one showed high homology to a large number of currently unassigned anamorphic ascomycete sequences. Of the Helotiales, Leptodontidium orchidicola, Rhizoscyphus ericae and species of Tapesia and Mollisia could be confidently identified. This study demonstrates that members of the Helotiales, including several widely-recognised DSE genera, commonly colonise the roots of C. quitensis and D. antarctica in the Antarctic. [Copyright &y& Elsevier]

The nutrient-poor soils of Antarctica are sensitive to change. Recent increases in the number of anthropogenic introductions mean that understanding the impact of non-native species on Antarctic soils is pertinent, and essential for developing future risk assessments and management strategies. Through comparative baseline assessments of vegetation, microbes, soil chemistry, substrate composition and micro-arthropod abundance, this study explored if there are detectable terrestrial ecosystem impacts resulting from the introduction of the chironomid midge Eretmoptera murphyi to Signy Island in maritime Antarctica. The key finding was that E. murphyi is the likely driver of an increase in inorganic nitrogen availability within the nutrient-poor soils in which it occurs. When compared with the levels of inorganic nitrogen present in soils influenced by native vertebrate wildlife aggregations, the increase in local nitrate availability associated with E. murphyi was similar to that caused by deposits from seals and giant petrel colonies. Overall, available nitrate has increased by three- to five-fold in soils colonised by the midge, relative to undisturbed soils. This may ultimately impact rates of decomposition as well as the native plant and micro-arthropod communities of Signy Island. • An invasive midge to Antarctica is likely to be increasing soil nitrate availability. • Colonised soils have a three- to five-fold increase in nitrate compared to uncolonised areas. • A single insect species is capable of disrupting polar soils with implications for soil development. [ABSTRACT FROM AUTHOR]