Abstract
Climatically extreme regions such as the polar deserts of the McMurdo Dry Valleys (78° S) in Continental Antarctica are key areas for a better understanding of changes in ecosystems. Therefore, it is particularly important to analyze and communicate current patterns of biodiversity in these sensitive areas, where precipitation mostly occurs in form of snow and liquid water is rare. Humidity provided by dew, clouds, and fog are the main water sources, especially for rock-dwelling crustose lichens as one of the most common vegetation-forming organisms. We investigated the diversity and interaction specificity of myco-/photobiont associations of 232 crustose lichen specimens, collected along an elevational gradient (171–959 m a.s.l.) within the McMurdo Dry Valleys. The mycobiont species and photobiont OTUs were identified by using three markers each (nrITS, mtSSU, RPB1, and nrITS, psbJ-L, COX2). Elevation, positively associated with water availability, turned out to be the key factor explaining most of the distribution patterns of the mycobionts. Pairwise comparisons showed Lecidea cancriformis and Rhizoplaca macleanii to be significantly more common at higher elevations and Carbonea vorticosa and Lecidea polypycnidophora at lower elevations. Lichen photobionts were dominated by the globally distributed Trebouxia OTU, Tr_A02 which occurred at all habitats. Network specialization resulting from myco-/photobiont bipartite network structure varied with elevation and associated abiotic factors. Along an elevational gradient, the spatial distribution, diversity, and genetic variability of the lichen symbionts appear to be mainly influenced by improved water relations at higher altitudes.
Highlights
The McMurdo Dry Valleys (MDV) in Southern Victoria Land, Continental Antarctica, are characterized by an environment that is exceptional even for Antarctica: it is extremely arid and cold, which makes it hostile for most organisms
This study focuses on saxicolous crustose lichens in continental Antarctica which are associated with green micro alga as photobionts
A total of 25 mycobiont species were identified with a composition that was mostly similar to the previous study but including a few additional specimens (Lecanora fuscobrunnea, unknown Lecidea and Buellia species)
Summary
The McMurdo Dry Valleys (MDV) in Southern Victoria Land, Continental Antarctica, are characterized by an environment that is exceptional even for Antarctica: it is extremely arid and cold, which makes it hostile for most organisms. Life is rare within the valleys of this polar desert, and only few life forms can cope with these extreme conditions (e.g., Adams et al 2006; Pointing et al 2009). The main limiting factor for life within the MDV is water availability with fog, clouds, dew, and ephemeral melting water of snow patches having important effects on the climatic conditions (Pannewitz et al 2005; Adams et al 2006; Green et al 2007; Stichbury et al 2011). Among the most diverse macro-organisms present in the MDV are lichens.
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