Myco- and photobiont associations in crustose lichens in the McMurdo Dry Valleys (Antarctica) reveal high differentiation along an elevational gradient

Abstract

The climate conditions of the McMurdo Dry Valleys (78° S) are characterized by low temperatures and low precipitation. The annual temperatures at the valley bottoms have a mean range from -30 °C to -15 °C and decrease with elevation. Precipitation occurs mostly in form of snow (3-50 mm a -1 water equivalent) and, liquid water is rare across much of the landscape for most of the year and represents the primary limitation to biological activity. Snow delivered off the polar plateau by drainage winds, dew and humidity provided by clouds and fog are important water sources for rock inhibiting crustose lichens. In addition, the combination of the extremely low humidity and drying caused by foehn winds, confined to lower areas of the valleys, with colder and moister air at higher altitudes creates a strongly improving water availability gradient with elevation.We investigated the diversity and interaction specificity of myco-/photobiont associations of a total of 232 crustose lichen specimens, collected along an elevational gradient (171-959 m a.s.l.) within the McMurdo Dry Valleys with regard to the spatial distribution caused by climatological and geographical factors. For the identification of the mycobiont and photobiont species three markers each were amplified (nrITS, mtSSU, RPB1 and nrITS, COX2, respectivley). Elevation, associated with a water availability gradient, 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, 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 mycobiont-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.

Macroecological diversification and convergence in a clade of keystone symbionts

“…Accessions not in our database were downloaded, parsed, and metadata (country, coordinates) recorded. As our final data query was in June 2018, data from more recent studies (Mark et al 2020;Muggia et al 2020;Ruprecht et al 2020;Wagner et al 2020) were not included. We then removed the 18S and 28S using ITSx 1.0.9 (Bengtsson-Palme et al 2013) and a custom hidden Markov model (HMM) that included a greater representation of Trebouxia sequences than the default HMM included with ITSx.…”

“…The globally distributed genus Trebouxia occupies diverse terrestrial biomes, but is most common in temperate, boreal, polar and alpine habitats (Honegger 1998(Honegger , 2009Sanders 2001;Pérez-Ortega et al 2012;Ruprecht, Brunauer and Printzen 2012;Wagner et al 2020). Climatic variables play important roles in structuring lichen associations (Peksa and Škaloud 2011;Fernández-Mendoza and Printzen 2013;Leavitt et al 2015;Singh et al 2017;Dal Grande et al 2018;Vančurov á et al 2018); however, our understanding of the ecological tolerances of lichen-forming algae (LFA) has long lagged behind those of LFF (Cordeiro et al 2005).…”

Lichen algae: the photosynthetic partners in lichen symbioses

“…(Continued) Trebouxia A 02Austrolechia sp., Buellia frigida, Carbonea vorticosa, Huea sp., Lecidea cancriformis, L. polypycnidophora, Lecidella greenii, Rhizoplaca macleaniiWagner et al (2020). Antarctic Dry Valleys.…”

Endolithic microbial composition in Helliwell Hills, a newly investigated Mars‐like area in Antarctica

“…Lichen‐dominated cryptoendolithic communities are dominated by eukaryotic Trebouxia while Cyanobacteria were only sparsely present, suggesting that prokaryotic and eukaryotic producers compete for access to the limited space within the rock suitable for photosynthesis (Pointing et al ., 2009; Archer et al ., 2017). Trebouxia , as well as the fungal classes Lecanoromycetes are well‐recognized for their tendency to form lichen symbiosis (Ahmadjian, 1988; Miadlikowska et al ., 2006), which are particularly well adapted to the cold‐extreme environments, including McMurdo Dry Valleys, being resistant than the photobiont or mycobiont components alone (Barták et al ., 2007; Perez‐Ortega et al ., 2012; Wagner et al ., 2020).…”