| The lichen association is a mutualistic interaction between a mycobiont (fungal partner) and a photobiont (green algal or cyanobacterial partner); the most successful example of symbiosis is known as the "pioneer organisms". The photobiont is retained within the thallus of the lichen fungus, providing carbon to the mycobiont. The mycobiont is thought to control the growth and reproduction of the alga. Despite extensive studies, many basic aspects of biology about Cyanolichens remain poorly known, especially cyanobiont diversity and specificity.Here we used morphological and chemical methods to study lichen specimens that were collected from Yunnan province in China. Three specimens were considered as Nephromataceae according to the traditional viewpoint, but chemistry detected showed that they contained lecanoric acid. So we performed molecular identification and phylogenetic analysis on these samples. Based on the GAPDH sequence analysis, all the three samples belong to the genus Parmotrema, and samples 1 and 3 were the same species; based on the ITS sequence analysis, sample 2 was Parmotrema tinctorum, and samples 1 and 3 were the same species in the genus Parmotrema, which were most closely relationships to Parmotrema tinctorum.According to the MP and ML trees based on rbcL and ITS sequences of symbiotic Nostoc, the phylogenetic position and relationships of symbiotic Nostoc were investigated. Based on the rbcL and ITS sequence analysis, three specimens belong to the symbiont Nostoc, and they were the same species. Therefore, we considered that the photobiont in Parmotrema was cyanobacteria (Nostoc), which improved the traditional view that all the photobiont in Parmeliaceae were green algae. At the same time, the results of this paper also indicated that host specialization is low for the mycobiont. The history of phylogeny would have been acknowledged more truthfully when sampling number increased and more molecular data were combined.
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