Taxonomic Revision On The Genus Macromitrium (Musci) In South-central South America

Macromitrium is the largest genus in the family Orthotrichaceae,also the third largest genus within moss taxa.The classification of the genus Macromitrium is a difficult problem in mosses.The classification revision of the genus Macromitrium has been completed in China and other parts of Asia,New Zealand,Australia,Huon region of Papua New Guinea,Malesia region(including tropical Southeast Asia and New Guinea of Oceania),Mexico,Central America,southern Africa,Japan,Eastern India and adjacent areas.In this paper,the classification and revision of the genus Macromitrium in south-central South America are conducted,which not only improves the classification of the genus Macromitrium in South America,but also provides an important document for the classification of the genus Macromitrium in the world.The south-central South America(including Peru,Brazil,Bolivia,Chile,Argentina,Uruguay and Paraguay)is one of the regions with highest diversity of the genus Macromitrium in the world.Until now 38,26,32,13,4 and one species of the genus have been reported from Brazil,Peru,Bolivia,Chile,Argentina,and Paraguay,respectively.No species of the genus has reported from Uruguay.Macromitrium is mainly distinguished by 1)the creeping,prostrate stems giving rise to branches terminated by sporophytes;2)twisted and contorted the leaves around the branches;3)upper and middle laminal cells somewhat flattened,often bulging,conic,mostly with uni-papilliae or pluri-papilliae;4)basal and lower laminal cells often porose and tuberculate;5)most of the setae are twisted to left,smooth;6)calyptrae are large,mitrate or cucullate,plicate,naked or hairy;7)capsules ovate to cylindric,smooth or furrowed,with double or single peristomes,which are often reduced and fused,forming a low,single exostomial membrane.It is a typical pantropical group,mostly growing on trees and scarcely on rocks.In the present paper,we extensively checked the original literature about Macromitrium,and about 1,000 specimens including 48 types from 10 herbaria around the world.We finished a taxonomic revision of the genus Macromitrium in south-central South America based on these herbarium specimens,as well as conducted a quantitative study of the genus Macromitrium on its morphological variation pattern by using Cluster Analysis and calculating coefficient of variation.A total of thirty-eight detailed line drawings were provided for 30 species of the genus Macromitrium in this area,and 104 color micrographs were provided for 45 species after typesetting.Based on our taxonomical revision,we found that M.subscabrum Mitt.is a new synonym of M.constrictum Hampe & Lorentz;We suggest to retain the species name M.aureum Mull.Hal,which had been wrongly treated as a synonym of M.longifolium(Hook.)Brid;We also suggest to keep the species name M.laevisetum Mitt.,which had been synonymized with M.cirrosum var.stenophyllum(Mitt.)Grout.A key to identifying the 48 species of Macromitrium in the study region was built.The morphologically similar sepcies were discussed on their classification relationship.The length of branches leaves,the width of upper,middle,lower and base parts of leaves,the length and width of each part of cells and the angle of leaf tip of 107 specimens were measured by Digimizer.The branch leaves are entire or serrated,fold or not,cells smooth or tubercualte,porose or not and other morphological characters of 114 specimens were evaluated.Morphological data satisfying all species were selected for clustering,and the results were clustered into three groups.The correlation of 19 quantitative traits,such as the tip of branch leaves,the length of branch leaves,the upper width of branch leaves,the upper width of branch leaves / the length of branch leaves,was analyzed.It was found that 19 quantitative traits had significant differences among species,which indicated that 19 quantitative traits were effective traits and were beneficial to the classification of the genus Macromitrium.