Soil fungal community composition does not alter along a latitudinal gradient through the maritime and sub-Antarctic
Introduction
The harsh environmental conditions that prevail along the Antarctic Peninsula result in isolated ice-free patches of land that typically have extremely sparse vegetation cover. This is advantageous in the context of investigations concerning relationships between patterns of microbial biogeography and latitude, because the effects of latitude-related environmental parameters, such as temperature, are not obscured by differences in plant biomass and diversity. Observations indicate that soil fungal communities may alter in composition along the Antarctic Peninsula and through into the continental Antarctic. Although fruit bodies of basidiomycetes such as Galerina spp. are present in the maritime and sub-Antarctic (Pegler et al. 1980), they appear to be very infrequent beyond 66°S, and have only been reported from a few maritime Antarctic sites, such as the Danco Coast (Gamundí & Spinedi 1988). In contrast, yeasts and zoosporic fungi appear to be frequent in soils at higher latitudes (Bridge & Newsham 2009). A previous report supports this view, with a change in fungal denaturing gradient gel electrophoresis (DGGE) profiles being recorded between Signy Island (60°S) in the South Orkney Islands and Coal Nunatak (72°S) on southern Alexander Island (Yergeau et al. 2007). Another study, however, found no change in soil fungal community composition, as determined by cloning and sequencing of eukaryotic SSU rRNA genes, between Signy Island and the La Gorce Mountains (86°S) in the continental Antarctic (Lawley et al. 2004). However, as both of these studies were based on soils sampled from between four and six locations in the Antarctic, it is not possible to draw any conclusions concerning the strength of any relationship between latitude and fungal community composition.
To determine whether or not soil fungal community composition alters at higher latitudes in the maritime and sub-Antarctic, we collected soil samples from multiple sites, of which 58 are considered in this report, along a 2370 km latitudinal gradient covering South Georgia, the South Orkney and South Shetland Islands, and the Antarctic Peninsula and its offshore islands. We generated fingerprints of fungal community composition and determined a range of environmental parameters for each sample. We then tested the hypothesis that latitude and its associated environmental parameters determine the composition of soil fungal communities.
Section snippets
Soil sampling and physicochemical characterisation
During the 2008–2009 austral summer, with logistic support from the UK Royal Navy and the British Antarctic Survey, soil samples from vegetation-free sites were collected along a latitudinal gradient ranging from 54°S to 72°S (Fig 1). The uppermost 5 cm of soil was collected in 50 ml tubes, immersed in a mixture of dry ice and ethanol (c. −80 °C) in the field, and then transferred to −80 °C freezers within a few hours of collection.
Soil pH and electrical conductivity (EC; μS) were measured in a
Results and discussion
Redundancy analyses indicated that fungal community composition was not associated with latitude along a transect from South Georgia through to Mars Oasis (Fig 2; RDA, F = 0.471, P = 0.908, T-RFs detected = 58, mean T-RFs per sample = 17.2). This observation is in agreement with the results of Lawley et al. (2004), but is in conflict with those of Yergeau et al. (2007), who found that fungal community composition was related to latitude along a transect from the South Orkney Islands through to
Conclusions
We conclude that latitude sensu stricto does not influence soil fungal community composition along a 2 370 km transect through the maritime and sub-Antarctic, but that it is key variables associated with soil nutrient availability which affect the composition of the communities. The current study, which is based on approximately ten times the number of samples included in previous studies (Lawley et al. 2004; Yergeau et al. 2007), indicates that fungal community composition is not related to
Acknowledgements
We gratefully acknowledge staff of the British Antarctic Survey's logistics group and the officers and ships companies of HMS Endurance and the RRS James Clark Ross, who arranged and provided transport to and from the sampling sites. We also thank staff (J Thompson, Dr AJ Karley and Dr RD Hancock) of the James Hutton Institute (formerly the Scottish Crop Research Institute) for assistance with the chemical analyses and Phil Coates, Mike Dunn, Paul Torode, Matt Jobson, Adam Clark, James Wake and
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Present address: Australian Centre for Ecogenomics, and Advanced Water Management Centre, The University of Queensland, Brisbane QLD 4072, Australia.