The Thuidiaceae, one of the large moss families, are widely distributed on every continent except Antarctica from tropical rain forests to temperate coniferous forests. Some of the genera in the Thuidiaceae are East Asiatic endemics, such as Hylocomiopsis endemic to Japan and Thuidiopsis to Japan and Korea. Worldwide, most of the Thuidiaceae occur in Asia, Central and South America, and Oceania. The species of this family grow in various places and frequently occur under grasses or on rock surfaces, rotten logs, tree trunks, and forest ground in large mats with other mosses. They can be found from sea level to above 4000 m. Many species of the family play an important role in protecting against water and soil erosion in alpine coniferous forests.
The distinct features of the Thuidiaceae include the Hypnum-type peristome, the pinnately branched stems often bearing paraphyllia, and papillose leaf cells. Brotherus’ (1925) classification and systematic arrangement of the family between the Leskeaceae and Amblystegiaceae are generally accepted among bryologists. However, some bryologists have different opinions on the classification. Crum and Anderson (1981) removed the primitive genera Haplohymenium, Anomodon, and Herpetineuron from Thuidiaceae to Leskeaceae and transferred Pseudoleskeella and Pseudoleskea of the Leskeaceae and Myurella of the Theliaceae to Thuidiaceae. Generally, the evolutionary relationships among genera of the Thuidiaceae are well established; nonetheless, there are some genetic differences in this family that reflect its systematic relationship with related families.
Brotherus (1925) divided the Thuidiaceae into four subfamilies: Heterocladioideae, Anomodontoideae, Thuidioideae, and Helodioideae. This classification reflects not only infra-family relationships, but also systematic relationships with related families such as the Leskeaceae. We move Haplocladium from the Anomodontoideae to Thuidioideae considering their appearance, branching forms, branch apices, leaf cells, and paraphyllia types. The remaining genera of the Anomodontoideae, with Anomodon, Haplohymenium, Herpetineuron, and Miyabea, are moved from the Thuidiaceae to the Anomodontaceae. Abietinella is transferred to Helodioideae. Both Crum and Anderson (1981) and Noguchi (1991) treated Abietinella and Rauiella in Thuidium; however, we maintain them separate from Thuidium based on the differences in habit and leaf morphology. We agree with Buck and Crum (1990) in elevating the subgenus Microthuidium Limpr. of Thuidium to generic rank as Cyrto-hypnum. In this study, 14 genera in the Thuidiaceae are treated. Touw (2001a) redefined the Thuidiaceae and presented a realignment of taxa traditionally accommodated in Thuidium; however, his opinions appeared too late to be taken into consideration for our treatment.
The systematic arrangement of Chinese Thuidiaceae:
Subfamily I. Heterocladioideae: Heterocladium Schimp. in B. S. G., Leptocladium Broth., and Leptopterigynandrum C. Müll.
Subfamily II. Thuidioideae: Boulaya Card., Claopodium (Lesq. & James) Ren. & Card., Cyrto-hypnum (Hampe) Hampe, Haplocladium (C. Müll.) C. Müll., Pelekium Mitt., RauiellaThuidium B. S. G. Reim., and
Subfamily III. Helodioideae: Abietinella C. Müll., Actinothuidium (Besch.) Broth., Bryonoguchia Iwats. & Inoue, and Helodium (Sull.) Warnst.
Key to the subfamilies
1. Plants delicate; leaf costae double, short or absent........................................ Subfamily 1. Heterocladioideae
1. Plants rather robust; leaf costa single, usually ending above the middle of leaf, rarely excurrent.................. 2
2. Plants usually simple or pinnately branched, rather robust; mostly growing in swampy or moist habitats.
....................................................................................................................................... Subfamily 3. Helodioideae
2. Plants 1–3 pinnately branched, rather small to medium-sized; often growing in moist, sometimes dry habitats
.................................................................................................................................. Subfamily 2. Thuidioideae
The history of studying Chinese Thuidiaceae started at the beginning of this century with most of the publications involving materials from one mountain or a localized region. Cardot and Thériot (1904) examined the specimens collected by Elm Bodinier and L. Martin in northern Guizhou, and published Thuidium japonicum Dozy & Molk. and T. pycnothallum C. Müll. Later, Par. (1909) published a new species, Anomodon rotundatus Par. & Broth., and reported Thuidium aciculum Broth. based on Courtois and Henry’s collection from Qiudong, Jiangsu province. Brotherus (1929) reported 10 genera and 28 species of Chinese Thuidiaceae from southwestern China. Among them Leptocladium Broth. was described as a new genus; six new species of Leptopterigynandrum C. Müll., Claopodium (Lesq. & Jam.) Ren. & Card., and Haplocladium (C. Müll.) C. Müll. were described. This was the first comprehensive treatment concerning Chinese Thuidiaceae. Reimers (1931) published the book entitled “Beiträge zur Mossflora China, I” after examining the collections of R.-C. Ching, S.-S. Sin, K.-K. Wang, and P. Klautke et al. from Mt. Magan, Zhejiang province, and Mt. Yao, Guangxi province. Six species of Thuidium were reported. Bartram (1935) reported Claopodium assurgens (Sull. & Lesq.) Card. and Haplocladium capillatum (Mitt.) Reim. based on S.-Y. Cheo’s collections from Guangxi and H. H. Chung’s collections from Fujian (Fukien) provinces. Although C.-W. Wang (1935) published a list of 1064 Chinese mosses from 18 provinces, he included only a few genera and species of the Thuidiaceae. Hylocomiopsis ovicarpa (Besch.) Card. was reported from Jilin province by Koponen et al. (1983). We are unable to confirm the specimen at this time. Touw (2001b) appeared too late to be considered for our study.