Taxonomic Study On The Lichen Genus Rhizocarpon From China

The lichen genus Rhizocarpon is classified into Rhizocarpaceae,Lecanorales,Lecanoromycetes,Ascomycota,Fungi.Holotype: Rhizocarpon geographicum.Rhizocarpon includes 231 species wordwide,of which 48 species have found in China.Rhizocarpon is a world-wide genus.The genus can best be characterized by the crustose,yellow-green,brown,grey or white thallus;black prothallus;black,lecideine apothecial;branched and anastomosed paraphyses;Rhizocarpon-type asci;ellipsoid halonate hyaline to brown or olive-green ascospores that can be transversely septate or submuriform to muriform;the genus is most diverse and abundant on siliceous or calcareous rocks in montane habitats and at temperate to higher latitudes.Foreign scholars have relatively systematic research on Rhizocarpon.While domestic scholars have few studies on the genus.At present,the genus has only been preliminarily studied in western of China,so further research is needed.Based on previous studies,this research has conducted a more in-depth and comprehensive study on the genus of lichens in China.The research on this genus is mainly based on morphological and chemical characteristics.Molecular phylogenetic research is still relatively weak.However,the relationship among the species of the genus Rhizocarpon is more complicated,especially the species with yellow-green thallus,which is difficult to be scientifically identified only by relying on traditional classification methods.Therefore,this research also further carried out the phylogeny of this genus the study.This research is based on the study of morphology,anatomy,chemical composition,geographical distribution and molecular systematics,combined with its phenotype and genotype characteristics,in-depth research has been conducted on nearly 400 lichen specimens collected in the Herbarium of the Shandong Normal University(SDNU)and Herbarium of Mycology,Academia Sinica(HMAS-L),The specimens were collected from 1984 to 2019,covered 17 provinces and autonomous regions.In this study,45 taxa of the Rhizocarpon lichens were identified,including 41 species and 4 subspecies.Among them,3 new species were discovered and described:Rhizocarpon orientalis,R.sichuenensis,R.vinosa;10 new records: including 9 new records in China: R.amphibium,R.cinereonigrum,R.cinereovirens,R.distinctum,R.postumum,R.sublavatum,R.submodestum,R.subpostumum,R.tavaresii;1 new record in China mainland: R.expallescens;the remaining 32 species or subspecies have been reported in China.Key to this species are presented in this thesis.And according to the model of the digital herbarium,the morphological and anatomical characteristics,chemical composition,and geographical distribution of each lichen are described in detail and added photos in appendix.In this study,18 obtained ITS sequences of 12 taxa from our studies,and 16 ITS sequences from Gen Bank were used to construct ML tree and Mr Bayes tree.They were found by preliminary phylogenetic analysis: the color and cells of the ascospores,I reaction of medulla,special chemicals are important for the identification and classification of Rhizocarpon,the phenotypic characteristics were basically consistent with the genotype characteristics;in the classification of subgenera,it was unreasonable for Thomson to divide the genus into two subgenera only according to the different thallus colors.In this study,through the combination analysis of phenotype and genotype,it was found that the characteristics of medullary layer I reaction was one of the important basis for the classification of the Rhizocarpon.In this study,the species composition and distribution of the genus Rhizocarpon from China were systematically reported for the first time.The ITS sequences of some species were also provided,which provided reliable molecular data for clarifying the subgenus and interspecific relationships of the genus.