Abstract
The genetic diversity of green algal photobionts (chlorobionts) in soil crust forming lichens was studied as part of the SCIN-project (Soil Crust InterNational). A total of 64 lichen samples were collected from four different sites along latitudinal and altitudinal gradients in Europe (Tabernas/Spain; Hochtor-Großglockner/Austria; Gynge Alvar/Sweden; Ruine Homburg/Germany). The dominant lichen species at all four sites was Psora decipiens, often occurring with Buellia elegans, Fulgensia bracteata, F. fulgens and Peltigera rufescens. Genetic identification of chlorobionts was carried out using the nuclear marker (nrITS) and a chloroplast marker (psbL-J). We found P. decipiens to be associated with several different species of Trebouxia and Asterochloris, although previously described to only have Asterochloris sp. The phylogenetic analyses revealed a high chlorobiont diversity with 12 well supported clades, including Trebouxia asymmetrica, T. jamesii, T. impressa and other, as yet taxonomically unidentified clades (Trebouxia sp. URa1-4, T. sp. URa6, T. sp. URa7-13). Additionally, five clades of Asterochloris were identified (A. magna, A. sp. URa14 -17). Most of the chlorobiont species appeared to be cosmopolitan, but five clades were unevenly distributed between the sampling sites with only Trebouxia being found in the warm and dry Spanish habitats and combinations of Trebouxia and Asterochloris in the cooler and more humid habitats. The wide range of chlorobiont species might contribute to the observed domination of P. decipiens at all four research sites of the SCIN project which range from a desert in Spain to an alpine site in the Alps of Austria.Electronic supplementary materialThe online version of this article (doi:10.1007/s10531-014-0662-1) contains supplementary material, which is available to authorized users.
Highlights
Large parts of the world are covered by soils with a surface vegetative community of lichens, cyanobacteria, micro fungi, algae and bryophytes, so-called biological soil crusts (BCSs, Fig. 1; Belnap et al 2001)
We found P. decipiens to be associated with several different species of Trebouxia and Asterochloris, previously described to only have Asterochloris sp
The final data matrix of the molecular phylogeny of Trebouxia internal transcribed spacer region (ITS) comprised 101 OTUs with a length of 431 characters, 226 positions of the alignment were parsimony-informative with the following homoplasy levels consistency index (CI) = 0.647, retention index (RI) = 0.953, rescaled consistency (RC) = 0.617
Summary
Large parts of the world are covered by soils with a surface vegetative community of lichens, cyanobacteria, micro fungi, algae and bryophytes, so-called biological soil crusts (BCSs, Fig. 1; Belnap et al 2001). While cyanobacteria dominate soil crusts in hot desert regions, lichens tend to be more abundant in regions with higher precipitation (Belnap et al 2001). Due to their poikilohydric lifestyle, lichens are very well adapted to extreme habitats with rapid temperature and moisture fluctuations, such as high alpine areas and arid areas with high insolation in southern Europe and other parts of the world (Lange et al 1997; Lange 2000). The rhizines and rhizomorphs of lichens can stabilize soils more efficiently than cyanobacterial dominated BSC and contribute to a higher amount of soil carbon and nitrogen, soil moisture and plantavailable nutrients (Belnap et al 2006; Maestre et al 2011)
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