Taxonomic Study On The Lichen Order Rhizocarpales From China

The lichen order Rhizocarpales is classified into Lecanoromycetes,Ascomycota,Fungi.This group includes 2 families,6 genera,and about 250 species.This group is widely distributed all over the world and is an important group among lichenized fungi.In this thesis,500 specimens of Rhizocarpales were studied,they were preserved in the Lichen Section of Botanical Herbarium(SDNU),Lichen Herbarium of Kunming Institute of Botany(KUN)and the Sectio Lichenum of Herbarium Mycologici Academiae Sinicae(HMASL).These specimens were collected from 17 provinces,autonomous regions and municipalities in China.Macromorphological characters,micromorphological characters,secondary metabolites and substrates of these specimens were studied by the method of classical taxonomy methods.The phylogenetic tree was constructed by the method of multi-locus,and the phylogenetic relationships among families,genera and intraspecies of Rhizocarpon were discussed.Through the combination of classical taxonomy and molecular phylogenetics,the relationship between phenotypic characteristics and phylogeny of lichens has been further understood.The main research results are as follows:1.A comprehensive and systematic study was made on the composition and distribution of Rhizocarpales species in China for the first time.51 taxa were described in detail in the aspects of morphology,anatomy,chemistry and geographical distribution.The key to Rhizocarpales species was also provided.In addition,the morphological and anatomical characteristics of each taxon were photographed and saved as digital herbarium.Each taxon and its similar species were compared and discussed.In this study we found eight new species to science―Rhizocarpon bispora,R.brunnea,R.globulans,R.ingens,R.laojunense,R.megasporum,R.rubella,R.yajiagengense;three new species to China―R.norvegicum,R.roridulum,R.sphaerosporum.2.The molecular phylogenies of Rhizocarpales in China were studied based on multi-locus data(ITS,mt SSU,nu LSU)by using ML and Bayesian analyses method.Phylogenetic analysis revealed that:1)Family-level divisionIt is reasonable to divide Rhizocarpales into Rhizocarpaceae and Sporastatiaceae according to the type of asci and the spores per asci.Their phenotypic characteristics were basically consistent with genotypic characteristics.2)Genus-level division(1)It is reasonable to divide Sporastatiaceae into Sporastatia and Toensbergia according to the thallus.Their phenotypic characteristics were basically consistent with genotypic characteristics.(2)In Rhizocarpaceae,the genera Epilichen and Catolechia species clustered together to form one branch which nested in Rhizocarpon,while species of Poeltinula and Rhizocarpon clustered into one clade.This is consistent with their phenotypic characteristics.The morphology,anatomy,and chemical characteristics of species in Epilichen,Catolechia and Poeltinula are not significantly different from those of Rhizocarpon,except that Epilichen and Catolechia produce ascospores with no halo,Poeltinula produces lirelliform apothecia and ascospores turning red in nitrate reaction.These results indicate that the taxonomy needs to be reassessed.However,there are few sequences available for analysis,especially for Epilichen and Poeltinula,more sequences are needed to be discovered.3)Sublevels division of Rhizocarpon(1)The species of Rhizocarpon subg.Rhizocarpon and R.subg.Phaeothallus did not form monophyletic groups.This suggests that it is unreasonable to divide the genus Rhizocarpon into two subgenera only based on the color of thallus.(2)The species included in different groups were obvious crossover in the phylogenetic tree,indicating that it is not appropriate to divide Rhizocarpon into groups only based on spore characteristics(color,size,number of separation)and iodine reaction.The chemical characteristics and color reaction of epihymenium and medulla were also important.