Taxonomic Revision And Phylogeny On The Genus Macromitrium In Asia

The genus Macromitrium is the third largest genus of mosses, belonging toOrthotrichaceae, Orthotrichales, and Bryopsida. It is distinguished mainly by the creeping,prostrate stems giving rise to branches terminated by sporophytes; the leaves are twistedand contorted around the branches, mostly with bulging, conic, uni-papillose orpluri-papillose median and upper cells, or tuberculate lower and basal cells; calyptrae arelarge, mitrate or cucullate, plicate, naked or hairy; ovate to cylindric capsules mostly haveperistomes, which are often reduced and fused, forming a low, single exostomialmembrane. It is a typical pantropical group, mostly growing on trees and scarcely onrocks．Asia is rich in Macromitrium species, about100species still have been accepted atpresent. There are many taxonomic problems in relation to Asian Macromitrium. In thepresent paper, we extensively checked the original literature about the genus, and morethan2,000specimens including75types from17herbaria around the world. We finished ataxonomic revision ofAsian Macromitrium based on herbarium specimens, and conducteda preliminary phylogenic study ofAsian Macromitrium according to the molecular data of16typical species. The main results are as follows:1. According to the taxonomic revision,12were found to be new symonyms. Amongthese synonymized names, Macromitrium dickasonii Bartr., M. laosianum Paris&Broth.and M. polygonostomum Dixon&P. de la Varde. are synonymized with M. japonicumDozy&Molk., M. muellerianum Mitt. and M. pseudoramentosum Herz. with M.sulcatum (Hook.) Brid., M. evrardii Thér. with M. fortunatii Card.&Thér., M. hamatumDix. with M. tosae Besch., M. himalayanum Dix.with Macrocoma orthotrichoides (Raddi)Wijk&Margad., M. minutum Mitt. with M. orthostichum Nees ex Schw gr., M.muellerianum Mitt. and M. pseudoramentosum Herz. with M. sulcatum (Hook.) Brid., M.seemannii Mitt. with M. microstomum (Hook.&Grev.) Schw gr., M. subleptocarpum Dix.&P. de la Varde. with M. leptocarpum Broth..2. Akey to the80confirmed species of the genus Macromitrium in Asia was listedbased on the following characters: the colour, size, dry status of plants, the length, shape,apex, costa of branch leaves, the layer of upper leaf cells, shape, length-width ratio andsurface characteristics of different parts of leaf cells, differentiation or not of basal leafcells, cell boundary, cell wall thick or thin, curvature magnitude of cell cavity, and capsule shape, the length, surface and twist direction of setae, and caplytra characteristics.3. For each of the80Asian species of Macromitrium, a complete list of theirsynonmys previously used in the study area, their original literature and type protologue,keys, description, illustration, ecology, distribution, morphological variation, distinguishedcharacteristics from related taxa, together with examined specimens were provided.4.16species ofAsian Macromitrium (62specimens) and5species of Groutiella,Macrocoma, Schlothemia, Drummonida (8specimens, as outgroups) were studied toconstruct a phylogenetic tree by using Bayesian Inference, Maximum Likelihood andMaximum Parsimony based on their chloroplast and nuclear genes sequence data.1) Wefound that Macomitrium is a monophyletic group as a sister group to Groutiella andMacrocoma.2) Chloroplast genes trnL-F, trnG and nuclear gene ITS2were useful toidentify the species ofAsian Macromitrium.3) Chen, Pan-chieh once divided ChineseMacrmitrium into Sect. Leiostoma Mitt. and Sect. Goniostoma Mitt., which was reasonableaccording to the phylogenetic trees.4) M. fortunatii is similar to M. tosae morphologically,but the former has a particular phylogenetic position on phylogenetic trees, obviouslydifferent from the latter. Therefore, M. fortunatii and M. tosae are two distinct species.5)Two widespread species, M. microstomum and M. sulcatum, were morphological stableamong the populations collected from different geographical locations, also genetic stablefrom their molecular data.6) Molecular phylogenetic trees reflects a close geneticrelationship and a clear boundary among three morphologically confusing species, M.turgidum, M. lorifolium, and M. sulcatum, also among M. angustifolium, M. cuspidatum, M.incurvifolium and M. fuscescens.Additionally, six species names including M. complicatulum Müll. Hal., M.lauterbachii Broth. ex M. Fleisch., M. nietneri Müll. Hal., M. papillisetum Dix., M.recurvifolium (Hook.&Grev.) Brid. and M. striatum Mitt. ex Bosch&Sande Lac. weretreated as doubtful names because their specimens and original literature were unavailableto us.