High photobiont diversity in the common European soil crust lichen Psora decipiens

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 <i>Psora decipiens</i>, often occurring with <i>Buellia elegans, Fulgensia bracteata, F. fulgens</i> and <i>Peltigera rufescens.</i> Genetic identification of chlorobionts was carried out using the nuclear marker (nrITS) and a chloroplast marker (<i>psb</i>L-J). We found <i>P. decipiens</i> to be associated with several different species of <i>Trebouxia</i> and <i>Asterochloris</i>, although previously described to only have <i>Asterochloris</i> sp. The phylogenetic analyses revealed a high chlorobiont diversity with 12 well supported clades, including <i>Trebouxia asymmetrica</i>, <i>T. jamesii</i>, <i>T. impressa</i> and other, as yet taxonomically unidentified clades (<i>Trebouxia</i> sp. URa1-4, <i>T</i>. sp. URa6, <i>T</i>. sp. URa7-13). Additionally, five clades of <i>Asterochloris</i> were identified (<i>A. magna, A.</i> sp. URa14 -17). Most of the chlorobiont species appeared to be cosmopolitan, but five clades were unevenly distributed between the sampling sites with only <i>Trebouxia</i> being found in the warm and dry Spanish habitats and combinations of <i>Trebouxia</i> and <i>Asterochloris</i> in the cooler and more humid habitats. The wide range of chlorobiont species might contribute to the observed domination of <i>P. decipiens</i> 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.