Taxonomy And Phylogeny Of Auricularia (Auriculariales, Basidiomycota)

Auricularia is a cosmopolitan genus of wood-inhabiting fungi, and it includes some important edible species and has many medicinal functions. In the genus, "Heimuer"and "Maomuer" are important cultivated species in China, and their scientific names have always been focused. Previous studies on taxonomy and phylogeny of Auricularia are inadequate, and the global species diversity of the genus is still not well known. In China, a few studies on morphological taxonomy for a limited of Auricularia species were previously carried out, but the systematic taxonomy and phylogeny on Auricularia based on samples from the whole country have not been done. It is therefore, such studies are badly needed for not only improving the understanding of Auricularia diversity, but also providing an important theoretical basis for the mushroom industry.Morphological examinations and phylogenetic analyses for more than 500 specimens of Auricularia from 27 countries (including 17 type specimens) were carried out in present study. Traditional taxonomic methods were used in morphological studies, and the stable morphological characters were screened for taxonomy of Auricularia. In addition, ecological habits, host, geographical distribution and molecular phylogenetic relationships are important for taxonomy of the genus. Phylogenetic analyses are carried out using combinated sequences of ITS, nLSU and RPB2 by methods of Maximum parsimony analysis and Bayesian analysis.According to morphological and phylogenetic studies,15 Auricularia species are currently recorded in China, and 27 species in the world. In America, two species were recognized by phylogenetic analyses without sample examinations. Nine species are described as new to science: Auricularia angiospermarum, A. australasica, A. brasiliana, A. heimuer, A. minutissima, A. novozealandica, A. orientalis, A. submesenterica and A. tibetica. Three species, A. americana, A. fibrillifera and A. villosula are new to China. Morphological descriptions and microscopic structures for 25 species are given according to the presnt study, and the host and geographic distribution of each species are supplied. Meanwhile, differences of each species and its similar or phylogenetic related species are discussed.Scientific names of widely distributed and cultivated species "Heimuer" and "Maomuer" in China are corrected. Auricularia auricula-judae originally described from Europe had been inappropriately applied for "Heimuer" in China. "Heimuer" is distinctly different in the morphology from the European Auricularia auricula-judae, and the phylogenetic analyses also showed that "Heimuer" and Auricularia auricula-judae formed two distinct lineages. "Heimuer" is in fact a new species, and described as Auricularia heimuer. Auricularia polytricha was previously considered as a cosmopolitan species, and it had been applied for "Maomuer" in China. However, Auricularia polytricha originally described from North America. Later studies confirmed that it was a synonymy of Auricularia nigricans. According to the present morphological and phylogenetic studies, Auricularia nigricans has no distribution in China, and "Maomuer" is actually Auricularia cornea which is a cosmopolitan species.The ITS dataset, the combined ITS+nLSU dataset and the combined ITS+nLSU+RPB2 dataset are used in building phylogenetic trees, and the three datasets generate three similar topology with three clades (Clade 1, Clade 2 and Clade 3). All the sequenced specimens are clustered into 22 lineages according to the phylogenetic trees, and the 22 lineages represent 22 Auricularia species nested respectively in Clade 1, Clade 2 and Clade 3. Clade 1 includes 10 species:A, cornea, A. nigricans, A. novozealandica, A. fibrillifera, A. fuscosuccinea, A. delicata 1, A. delicata 2, A. delicata 3, A. scissa and A. subglabra. Clade 2 includes 7 species:A. americana, A. angiospermarum, A. auricula-judae, A. heimuer, A. minutissima, A. tibetica and A. villosula. Clade 3 includes 5 species:A. australasica, A. brasiliana, A. mesenterica, A. orientalis and A. submesenterica. In the phylogenetic trees, most species with similar morphology were clustered to the same clade, eg, species in Clade 2 and Clade 3. However, species in Clade 1 have different morphology. The ITS sequence can distinguish Auricularia species with different morphology, but it does not work for those species with similar morphology. RPB2 is a good DNA marker to distinguish species with similar morphology or phylogenetically related species.Based on morphological and phylogenetic studies,15 Auricularia species are currently recorded in China, and 27 species in the world. Nine species are described as new to science, and three species are new to China. Scientific names of widely distributed and cultivated species "Heimuer" and "Maomuer" in China are corrected as Auricularia heimuer and A. cornea respectively. The ITS sequence can not distinguish Auricularia species with similar morphology or phylogenetically related species, but RPB2 sequence can distinguish these species.