As part of a comprehensive study on lecideoid lichens in Antarctica, we investigated the photobiont diversity and abundance in 119 specimens of lecideoid lichens from 11 localities in the continental and maritime Antarctic. A phylogeny of these photobiont ITS sequences, including samples from arctic, alpine and temperate lowland regions, reveals the presence of five major Trebouxia clades in Antarctic lecideoid lichens. Two clades are formed by members of the T. jamesii and T. impressa aggregates but for all other clades no close match to any known Trebouxia species could be found in sequence databases. One genetically uniform and well-supported Trebouxia clade was found only in the climatically unique cold desert regions of the Antarctic (preliminarily called Trebouxia sp.URa1), where it is preferentially associated with the highly adapted Antarctic endemic lichen Lecidea cancriformis. Levels of genetic photobiont diversity differ slightly, but insignificantly among ecological regions of the Antarctic and do not decrease towards regions with more unfavourable ecological conditions. The genetic diversity of photobionts varies among mycobiont species. Most pairwise comparisons reveal that these differences are insignificant, probably due to the small sample size for most species. The Antarctic lichens studied here are predominantly not specific for a single photobiont species or lineage, except for Lecidella greenii and L. siplei. These two species are preferably associated with Trebouxia sp. URa2, although in the sampling areas of both species, a pool of several other photobionts is available. Lecidea cancriformis associates with the highest diversity of photobionts followed by L. andersonii.
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.
Abstract:The diversity of lichens, especially crustose species, in continental Antarctica is still poorly known. To overcome difficulties with the morphology based species delimitations in these groups, we employed molecular data (nuclear ITS and mitochondrial SSU rDNA sequences) to test species boundaries within the genus Lecidea. Sampling was done along a north-south transect at five different areas in the Ross Sea region (Cape Hallett, Botany Bay to Mount Suess, Taylor Valley, Darwin Area and Mount Kyffin). A total of 153 specimens were collected from 13 localities. Phylogenetic analyses also include specimens from other regions in Antarctica and non-Antarctic areas. Maximum parsimony, maximum likelihood and Bayesian analyses agreed in placing the samples from continental Antarctica into four major groups. Based on this phylogenetic estimate, we restudied the micromorphology and secondary chemistry of these four clades to evaluate the use of these characters as phylogenetic discriminators. These clades are identified as the following species Lecidea cancriformis, L. andersonii as well as the new species L. polypycnidophora Ruprecht & Türk sp. nov. and another previously unnamed clade of uncertain status, referred to as Lecidea sp. (L. UCR1).
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