Taxonomic Revision And Molecular Phylogeny Of Hornworts In China

Hornworts are one of the three main components of bryophytes, representing a transition between the terrestrial plants and the aquatic ancestors. As a key lineage of the early diversification of land plants, hornworts have some special characters, however the classification system of hornworts still has been doubted. Up to now, there are only a few studies of taxonomic and molecular phylogenetic on hornworts in China have been reported. This study was carried out based on the examination of the493dry specimens, and337fresh specimens from herbaria and field trips throughout China and abroad. Two chloroplast genes rbcL and trnL-F, one ribosomal DNA ITS2and one mitochondrial nad5were amplified from the genomic DNA extraction. The phylogenies of hornworts were reconstructed by maximum parsimony (MP) analysis, maximum likelihood (ML) analysis and Bayesian interference (BI). By combining field investigations and morphology and molecular data, the taxonomic revision and phylogeny of hornworts in China was completed. Moreover, the geographical distribution was considered in this study. The main results are as follows:1In comparison with the world hornworts, the diversity of hornworts is low in China, containing one class, four orders, four families, eight genera and28species with one variety. However, it is abundant at the family and genus levels.2One new species, Notothylas yunnanensis has been described. Six new records were discovered for China:Anthoceros alpinus, A. bharadwajii, A. subtilis, Folioceros kashyapii, F. kashyapii, Phaeoceros kashyapii and P. evanidus.3Based on morphological evidences, Aspiromitus areolatus and Anthoceros esquirolii were proposed as new synonyms of Folioceros fuciformis and Phaeoceros carolinianus, respectively.4Based on the distribution of hornworts in China, the main diverse region is south China. The provinces which provide the highest homwort diversity are Taiwan (18species) and Yunnan (16species) followed by Sichuan (10species), Guizhou (7species), Fujian (6species), Hong Kong (6species), Hunan (6speceis) and Jilin (6speceis). There is low diversity of hornworts in other provinces.5Combining the molecular and morphological evidences, there were three sections existing in Anthoceros in China, and section Angustus is a new one:A Section Anthoceros:A. alpinus, A. bharadwajii, A. erectus and A. telaganus; B Section Fusiformes:A. punctatus, A. agrestis and A. subtilis; C Section Angustus:A. angustus.6Phymatoceros was grouped with subclass Notothylatidae which comprises of Notothylas and Phaeoceros, forming a clade inferred from MP analysis, ML analysis and BI analysis. Considering Phymatocerales of sole family is represented by Phymatoceros, we suggest that Phymatocerales should be moved to Notothylatide.In summary, there are one class, four orders, four families, eight genera, twenty eight species and one variety of hornworts in China. Their descriptions, illustrations and notes are provided in this paper as well.