Molecular Phylogeny Of Chinese Brachytheciaceae

Brachytheciaceae is one of the largest families of pleurocarpous mosses, belonging to Hypnobryales. Morphological characters of Brachytheciaceae, which can be easily affected by environment conditions, are obviously variable and show homoplasy to a large extent. So there are many arguments and difficulties in the generic and specific delimitations. About 2000 fresh specimens of Brachytheciaceae have been collected, and 59 species are classified according to the 100 type specimens borrowed from other herbariums, of which three species are newly reported from the Flora Bryophytorum Sinicorum (Rhynchostegium patulifolium, R. celebicum, Eurhynchium pulchellum), and 15 species are endemic to China. Chloroplasst DNA fragments trriL-F, psbT-H and nrDNA ITS2 were used and NJ MP ML BI criterions were applied separately to reconstruct the phylogenetic trees of Brachytheciaceae. The classification problems were discussed based on the phylogenetic trees, considering the morphological characters at the same time. The main conclusions are as following.1. Most species of Brachythecium were separated into two clades in the trees, so the genus Brachythecium can be divided into two genera: Sciurohypnum and Brachythecium, the former mainly includes Sciurohypnum plumosum , S. reflexum, S. populeum, S. monetise, S. amnicolum, S. viridefactum et al.; and the other Brachythecium species are included in the latter genus. Three new combinations are proposed: Sciurohypnum moriense (Besch.) Liu et Y. F. Wang S. amnicolum (C. Muell.) Liu et Y. F. Wang S. viridefactum (C. Muell.) Liu et Y. F. Wang2. The molecular characters clarified the establishment of Oxyrrhynchium as a genus. Three new combinations are proposed: Oxyrrhynchium filiforme (C. Muell.) Liu et Y. F. Wang; Oxyrrhynchium patulifolium (Cardot & Ther.) Liu et Y. F. Wang; Oxyrrhynchium celebicum (Lac.) Liu et Y. F. Wang. 7 Oxyrrhynchium species are reported from China so far: O. savatieri O.hians . O. filiforme O. laxirete O. patulifolium O. celebicum O. vegans.3. Rhynchostegium riparioides (Platyhypnidium riparioides) was always nested in the Rhynchostegium clade with great bootstrap value. The results don't support the establishment of Platyhypnidium as a genus. Platyhypnidium should be included in the genus Rhynchostegium.4. Bryhnia is polyphyletic and Bryhnia novae-angliae becomes the core of Bryhnia, along with B. trichomitria. This research proved that Bryhnia serricuspis shouldbe the synonymy of Kindbergia praelonga , based on the combined DNA sequences.5. Tomentypnum nitens was always nested in the outgroups, so the results support the view of Hedenas that Tomentypnum should be excluded from Brachytheciaceae.6. Okamuraea became one clade with Rhynchostegiella Cirriphyllu, which is congruent with the results of Ignatov, Huttunen, Tsubota et al.. Okamuraea should be a genus of Brachytheciaceae7. Rhynchostegiella laeviseta was nested in the Brachythecium clade, so the results obtained from the combined DNA sequences indicate that this species should in the genus Brachythecium. One new combinations Brachythecium laeviseta (Broth.) Liu et Y. F. Wang is proposed.8. The species of Rozea Isothecium Duthiella were always included in the outgroups, according to the structures of phylogenetic trees. So our results obtained from the combined DNA sequences also prove that these genera don't belong to Brachytheciaeceae.Based on the phylogenetic trees, 14 genera are included in Brachytheciaceae: Brachythecium, Bryhnia, Sciurohypnum, Kindbergia, Myuroclada, Camptothecium, Oxyrrhynchium, Cirriphyllum, Okamuraea, Rhynchostegiella, Rhynchostegium, Palamocladium, Eurhynchium, Homalothecium. Tomentypnum, which belonged to Brachyhteciaceae before, is excluded from Brachytheciaceae, in light of our results . 4 genera : Sciurohypnum Oxyrrhynchium. Okamuraea Kindbergia, are added to the Flora Bryophytorum Sinicorum Vol.7. Rhynchostegium , Palamocladium , Homalothecium are the base group of Brachytheciaceae. Huttunen & Ignatov divided Brachytheciaceae into 4 subfamilies, but our results don't support this viewpoint.The research on the morphological and genetic diversities of Myuroclada maximowiczii indicates that there are obvious diversities in different M. maximowiczii populations. Genetic distances between populations are related to the geographical distances to some degree. According to morphological observations, the shapes of leaves are very stable in different populations, which are stand of the species characters, but the size of median laminal cell and leaf tip are different, which can be easily changed according to environment and represent the subspecies characters. The relationship of morphological variation and genetic diversity is also discussed in this research, which may offer some suggestions to the delimitations between species, subspecies or variants.Chinese Brachytheciaeceae species (including 15 species endemic to China) are analyzed based on the trnL-F psbT-H and ITS2 sequences, in this study. 7 new combinations are proposed and 4 genera are added and one genus is excluded. Some problems about the Brachytheciaceae system are pointed out and some details are also offered to the phylogenetic studies of Brachytheciaceae and other allied families.