Phylogeography of Psoroma hypnorum complex

Abstract

Psoroma is a squamulose tripartite lichen with algae as main photobionts and Nostoc in cephalodia. It is classified in Pannariaceae (Peltigerales, Lecanoromycetes) and occurs on bryophytes, soil, and tree barks. It is known as a predominantly Southern Hemisphere genus. From the phylogenetic studies on Psoroma and related species, it was revealed that Psoroma is closely related with Psorophorus, Xanthopsoroma, Pannaria, Protopannaria, Fuscopannaria, Santessoniella, and Moelleropsis, which are members of Pannariaceae s.str. (Ekman and Jørgensen, 2002; Wedin and Wiklund, 2004; Passo et al., 2008; Wedin et al., 2009; Elvebakk et al., 2010). Psoroma hypnorum, the type species of the genus Psoroma, is a cosmopolitan species recorded in Europe, Asia, North and South America, Australia, New Zealand, and the Antarctic. It occurs on moist bryophytes, on damp gravelly soil and rock ledges (Øvstedal & Lewis Smith, 2001). The species includes morphologically and genetically diverse samples and some of them appeared in phylogenetically diverse lineages (Passo et al., 2008). To understand relationships among Psoroma hypnorum complex from Northern and Southern Hemispheres and relationships among different localities in Southern Hemisphere, we collected samples of Psoroma hypnorum and related species from Norway, King George Island, Chile, and Falkland Islands. Phylogenetic relationships were reconstructed based on the sequence information of ITS1-5.8SD-ITS2-LSU rDNA and mitochondrial SSU rDNA. We could detect four major phylogenetic groups, three of which were composed of Southern Hemishere samples and one was composed of Norway samples. The main group of King George Island samples formed a basal lineage of P. hypnorum complex. It was clearly distinguished from other samples from Northern and Southern Hemispheres. The relationship was supported by both of nuclear and mitochondrial rDNA. Considering phylogenetic relationships and morphological characteristics, it is proposed that