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Research Article
Didymodon manhanensis (Pottiaceae, Bryophyta), a new species from Inner Mongolia steppe, China and its phylogenetic position, based on molecular data
expand article infoChao Feng, Guo-Li Zhang§, Ting-Ting Wu§, Jin Kou§
‡ Inner Mongolia Agricultural University, Hohhot, China
§ Northeast Normal University, Changchun, China
Open Access

Abstract

Inner Mongolia steppe is one of the suitable habitats for Didymodon species and a new species, Didymodon manhanensis C. Feng & J. Kou from Manhan Mountain in semi-arid region in Inner Mongolia, China is described and illustrated. It is characterised by leaves incurved and slightly twisted when dry, spreading when moist, narrowly lanceolate from an ovate base; subulate and fragile leaf apices; distally bistratose leaf margins that are recurved in proximal 2/3–3/4; excurrent costa with guide cells in 2–3 layers and without ventral stereids; smooth laminal cells and red KOH laminal colour reaction. Our morphological analyses and molecular results, based on DNA sequences of ITS, rps4 and trnM-trnV, confirm that D. manhanensis belongs to a group that includes D. obtusus J. Kou, X.-M. Shao & C. Feng and D. daqingii J. Kou, R.H. Zander & C. Feng. This new species is compared with similar species and its phylogenetic position and ecology are discussed.

Keywords

Asia, Manhan Mountain, phylogenetic analysis, taxonomy

Introduction

Inner Mongolia, situated in Inner Eurasia, is located in the northern part of China and presents a strip distribution from the northeast to the west. The district habitats are temperate continental monsoon climate. The annual mean temperature is 8 °C, which increases from east to west and the annual precipitation is 35–530 mm, which decreases from southeast to northwest (Miao 2017). The area of grassland accounts for 60% of the whole Inner Mongolia and more than one-quarter of the total area of grassland in China. The grassland in Inner Mongolia is divided into three types: meadow steppe formed by, for example, Stipa baicalensis Roshev, Leymus chinensis (Trin.) Tzvelev; typical steppe formed by, for example, Stipa grandis P. Smirn., Stipa krylovii Roshev, Leymus chinensis (Trin.) Tzvelev and desert steppe formed by, for example, Stipa klemenzii Roshev, Stipa glareosa P.A. Smirn., Stipa breviflora Griseb (Hua et al. 2021). The main vegetation types of the steppes present distinct zonal features (Wu et al. 2005). The Inner Mongolia steppe is a suitable habitat for the Didymoodn Hedw. species and several new species were recently discovered (e.g. Kou et al. 2016a; Kou et al. 2019; Feng et al. 2022).

The taxonomy of genus Didymodon is complicated, involving the differentiation from related genera, such as Barbula Hedw. and the circumscriptions of its infrageneric sections (Zander 1993; Zander 2007; Zhang et al. in press). A recent important event associated with Didymodon s. lat. was the split of the genus into seven smaller genera: Aithobryum R.H. Zander, Didymodon s. str., Exobryum R.H. Zander, Fuscobryum R.H. Zander, Geheebia Schimp., Trichostomopsis Card. and Vinealobryum R.H. Zander, based on macro-evolutionary analysis and the dissilient genus concept applied (Zander 2013; Zander 2019). Although initially this revolutionary concept was considered unnecessary or unsupported (Blockeel and Kučera 2019), it has later been supported by molecular phylogenetic data, but with some alterations (Jiménez et al. 2022; Zhang et al. in press) and has gained acceptance by some other authors (e.g. Kou and Feng 2018; Osman et al. 2021; Feng et al. 2022). During our continuous investigations of xerophilic mosses, especially Pottiaceae Hampe, in China (e.g. Feng et al. 2016a, b; Kou et al. 2016b, 2018, 2019; Kou and Feng 2018), many specimens have been collected from different provinces. Amongst them, two samples collected from Manhan Mountain in Inner Mongolia of Didymodon s. lat. from stony habitats are different from species previously reported in the area (Li et al. 2001). They mostly resemble Didymodon obtusus J. Kou, X.-M. Shao & C. Feng. To clarify their taxonomic identity, we conducted phylogenetic analysis and confirm that these samples belong to the genus Didymodon s. str. (Zander 2013), but do not match with any species known in the genus. Here, we describe this unknown moss as a new species.

Materials and methods

Morphological observations

Over 3000 specimens of the genus Didymodon s. lat. were examined during our revision of Pottiaceae in China. More than 50 field investigations were conducted in past years and the specimens included in this study were housed in the Herbaria at IFP, KUN and NMAC. Microscopic examinations and measurements were taken with a ZEISS Primo Star light microscope and photomicrographs were obtained with a Canon EOS 70D camera, mounted on this microscope. Specimens were examined in 2% potassium hydroxide (KOH). Three plants were dissected from each collection and, for each shoot, every possible structure from the gametophyte had to be examined and a record kept of what was found for each individual species. Specific morphological and anatomical features of taxonomic importance were assessed mainly following Zander (1993). Leaves were always taken from the upper and middle parts of the stem and cross-sections were made in the middle part of the stem. Measurements of leaf width were taken at the base, mid-leaf and upper part. Cross-sections were made at mid-leaf.

Phylogenetic analyses

To test the phylogenetic position of the new species, two specimens collected from Manhan Mountain were sampled. Due to its great similarity with D. obtusus and Didymodon daqingii J. Kou, R.H. Zander & C. Feng, the isotypes of the two species were added to the dataset. We employed one nuclear (ITS) and two chloroplast markers (rps4 and trnM-trnV), which had been used successfully in previous phylogenetic studies in Didymodon s. lat. and enabled the re-use of earlier results and easier interpretation of new data (Werner et al. 2004, 2005, 2009; Kučera and Ignatov 2015; Kučera et al. 2018; Ronikier et al. 2018; Jiménez et al. 2022; Zhang et al. in press). Phylogenetic trees are created and shown separately. The complete list with sample names and GenBank accession numbers is presented in Tables 1 and 2. DNA extraction, PCR amplification and sequencing procedure followed the protocols described by Wang et al. (2010).

Table 1.

New sequences used in this study, including taxa vouchers information and GenBank accession numbers.

Species Voucher information ITS rps4 trnM-trnV
Didymodon manhanensis 4 China, Inner Mongolia, Chao Feng 2016060162 OL514237 OL450506 OL450515
Didymodon manhanensis a3 China, Inner Mongolia, Chao Feng 2016060176 OL514238 OL450507 OL450516
Didymodon obtusus China, Tibet, Xiao-Ming Shao & Jin Kou 20140815037 OL514239 OL450508 OL450517
Didymodon daqingii China, Inner Mongolia, Chao Feng 20170605032 OL514240 OL450509 OL450518
Table 2

. Sequences from GenBank used in this study, including taxa and GenBank accession numbers.

Species ITS rps4 trnM-trnV
Acaulon triquetrum MW398556
Aloina rigida MW398549
Aloinella andina MW398550
Andinella churchilliana MW398720
Andinella coquimbensis MW398711
Andinella elata MW398708
Andinella granulosa MW398714
Andinella limensis MW398710
Andinella oedocostata MW398733
Andinella pruinosa MW398726
Barbula unguiculata MW398553 HM147777 JQ890366
Bryoerythrophyllum recurvirostrum MW398547 JQ890468 JQ890407
Bryoerythrophyllum rubrum MW398548
Chenia leptophylla MW398561
Cinclidotus riparius MW398554
Crossidium squamiferum MW398558
Didymodon acutus AY437111 KP307551 KP307667
Didymodon alpinus MW398606
Didymodon andreaeoides MW398768
Didymodon anserinocapitatus MW398649 KP307545 KP307640
Didymodon asperifolius MW398594 JQ890472 KP307600
Didymodon australasiae (Trichostomum australasiae) MW398737 KP307571 KP307651
Didymodon brachyphyllus (Vinealobryum brachyphyllum) MW398817
Didymodon buckii MW398578
Didymodon caboverdeanus MW398607
Didymodon californicus (Vinealobryum californicum) MW398819
Didymodon canoae MW398584
Didymodon cardotii MW398729
Didymodon challaensis (Trichostomopsis challaensis) MW398748
Didymodon constrictus MW398613
Didymodon cordatus MW398664 KP307564 KP307668
Didymodon ditrichoides MW398642
Didymodon eckeliae (Vinealobryum eckeliae) MW398826
Didymodon edentulus MW398685
Didymodon epapillatus MW398665
Didymodon erosodenticulatus MW398792 MF536597 MF536635
Didymodon erosus EU835148 MF536609 MF536646
Didymodon fallax (Geheebia fallax) MW398779 KP307552 KP307663
Didymodon ferrugineus (Geheebia ferruginea) MW398796 MF536588 MF536625
Didymodon fragilicuspis KP307482
Didymodon fuscus MW398689 KP307537 KP307601
Didymodon aff. fuscus KP307546 KP307615
Didymodon gaochienii KP307538 KP307658
Didymodon gelidus MW398693
Didymodon giganteus MW398786 KP307548 KP307669
Didymodon glaucus MW398612
Didymodon guangdongensis (Vinealobryum guangdongense) MW398657
Didymodon hedysariformis MW398582 KP307569 KP307629
Didymodon hengduanensis MW398629
Didymodon hegewaldiorum MW398739
Didymodon herzogii MW398746
Didymodon humboldtii MW398667
Didymodon icmadophilus MW398632 KP307598 KP307604
Didymodon imbricatus MW398646
Didymodon incrassatolimbatus MW398572
Didymodon incurvus MW398680
Didymodon insulanus (Vinealobryum insulanum) MW398811
Didymodon japonicus MW398757
Didymodon jimenezii MW398622
Didymodon johansenii MW398589 KP307542 KP307662
Didymodon kunlunensis MW398610
Didymodon laevigatus MW398618
Didymodon lainzii MW398575
Didymodon leskeoides (Geheebia leskeoides) MW398777 MF536604 MF536642
Didymodon luehmannii MW398718
Didymodon luridus AY437098 MF536587 MF536624
Didymodon maschalogena MW398615
Didymodon maximus (Geheebia maxima) MW398784 MF536591 MF536628
Didymodon mesopapillosus MW398758
Didymodon molendoides MW398687
Didymodon mongolicus KU058175
Didymodon murrayae KP307513 KP307563 KP307650
Didymodon nevadensis MW398730
Didymodon nicholsonii (Vinealobryum nicholsonii) MW398808
Didymodon nigrescens LC545516 KP307543 KP307611
Didymodon norrisii MW398830 KP307585 KP307617
Didymodon novae-zelandiae MW398769
Didymodon obtusus MW398666
Didymodon occidentalis KP307533 KP307599
Didymodon ochyrarum MW398763
Didymodon paramicola (Trichostomopsis paramicola) MW398740
Didymodon patagonicus MW398675
Didymodon perobtusus KP307523 KP307539 KP307609
Didymodon revolutus (Husnotiella revoluta) MW398569 JQ890471 KP307646
Didymodon revolutus var. africanus MW398568
Didymodon rigidulus MW398602 KP307589 KP307647
Didymodon rigidulus var. subulatus MW398672
Didymodon rivicola MW398599 KP30756 KP307607
Didymodon santessoni MW398705
Didymodon sicculus MW398801 MF536606 MF536643
Didymodon sinuosus MW398567 JQ890476 JQ890410
Didymodon spadiceus (Geheebia spadicea) MW398795 MF536593 MF536631
Didymodon subandreaeoides AY437108 KP307570 KP307630
Didymodon tectorum MW398659
Didymodon tibeticus MW398638
Didymodon tomaculosus AY437114
Didymodon tophaceus MW398807 MF536607 MF536644
Didymodon tophaceus var. anatinus MF536589 MF536626
Didymodon torquatus MW398719
Didymodon umbrosus (Trichostomopsis umbrosa) MW398742
Didymodon validus MW398650
Didymodon vinealis (Vinealobryum vineale) MW398815 JQ890475 KP307606
Didymodon vinealis var. rubiginosus MW398822
Didymodon vulcanicus MW398636
Didymodon waymouthii MW398770
Didymodon wisselii MW398655
Didymodon xanthocarpus MW398696 KP307534 KP307638
Didymodon zanderi MW398585 KP307535 KP307621
Dolotortula mniifolia MW398555
Erythrophyllopsis andina MW398546
Gertrudiella uncinicoma MW398698
Gertrudiella uncinicoma var. serratopungens MW398701
Guerramontesia microdonta MW398543
Hennediella heimii GQ339750
Hennediella polyseta GQ339759
Leptodontium excelsum MW398545
Microbryum curvicolle JX679986 JX679936
Microbryum davallianum MW398557
Pseudocrossidium hornschuchianum MW398551 JQ890481 JQ890420
Pseudocrossidium revolutum MW398552
Pterygoneurum ovatum MW398560
Sagenotortula quitoensis GQ339761
Stegonia latifolia MW398559
Syntrichia ruralis MW398564 FJ546412 FJ546412
Tortula muralis MW398562 JN581679 JQ890421
Tortula subulata MW398563
Triquetrella arapilensis MW398544
Tridontium tasmanicum MW398750

The sequences were aligned by using MAFFT 7.222 (Kazutaka and Daron 2013) and then edited in BioEdit 7.0.1 (Hall 1999). The concatenation of individual rps4 and trnM-trnV fragments was performed by our custom Perl script. Phylogenetic analyses were performed by using the Bayesian Inference (BI) and Maximum Likelihood (ML) methods. MrBayes 3.2.6 (Ronquist et al. 2012) was used for BI analyses under the GTR substitute model. The following was used: two Markov Chain Monte Carlo (MCMC) searches were run for 10 million generations each, with a sampling frequency of 1000. The first 25% of the trees were discarded as burn-in. The convergence between runs in all cases dropped below 0.01. ML analyses were executed in IQ-TREE 1.6.3 (Nguyen et al. 2014) under the TPM3u+F+R3 (for cpDNA) and TIM3e+I+G4 (for ITS) substitute models, respectively, selected by the ModelFinder programme (Kalyaanamoorthy et al. 2017), based on the Bayesian Information Criterion (BIC) and 1000 fast bootstrapping replicates were used. The final obtained trees were visualised and edited in FigTree v.1.4.0 (Rambaut 2014).

Results

The chloroplast (cp) and ITS alignments comprised 1313 and 1364 nucleotide sites, respectively. The BI and ML phylogenetic trees have a consistent topology, although there are different levels of support depending on the method. Hence, only the topologies with branch lengths from the BI trees are presented, with added support from the ML method on the respective trees (Figs 34). Although the inference from analysed chloroplast regions (Fig. 3) and the ITS (Fig. 4) agrees in most aspects, the position of the new species is different between the two above phylogenetic trees and, thus, both of them are reserved. The topology of the ITS dataset shows that D. manhanensis is nested within the monophyletic group comprising Didymodon epapillatus J. Kou, X.-M. Shao & C. Feng, Didymodon mongolicus D.-P. Zhao & T.-R. Zhang, Didymodon validus Limpr., Didymodon wisselii (Dixon) D.H. Norris & T.J. Kop. and Vinealobryum guangdongensis C. Feng & J. Kou and is sister to D. obtusus, but with weakly-supported values. In the combined plastid dataset, D. manhanensis is nested within the group including Didymodon cordatus Jur. and is sister to D. daqingii and Didymodon anserinocapitatus (X.J. Li) R.H. Zander, with well-supported values.

Discussion

As indicated by Zander (1993), Didymodon s. lat. is heterogeneous and could be profitably split. In our phylogenetic analyses, this genus is polyphyletic and its species can be classified within several well-supported monophyletic clades, which correspond to other phylogenetic studies of the genus (Feng et al. 2022; Jiménez et al. 2022; Zhang et al. in press). Our results reveal a close relationship between D. manhanensis and two recently-described species in China: D. daqingii and D. obtusus. Although the latter two species were considered identical by Sollman et al. (2020), they are not closely related in our phylogenetic analyses, based on both ITS and chloroplast data.

Didymodon manhanensis is distinguished from all congeners by the following combination of diagnostic features: leaves incurved and slightly twisted when dry, spreading when moist, narrowly lanceolate from an ovate base; subulate and fragile leaf apices; distally bistratose leaf margins that are recurved in proximal 2/3–3/4; costal guide cells in 2–3 layers and without ventral stereids, smooth laminal cells and red KOH laminal colour reaction. This combination of characters suggests the placement of D. manhanensis in the sect. Didymodon (Zander 1978, 1993, 1998). Following the recent revolutionary work on the genus Didymodon s. lat. by Zander (2013, 2019), morphologically, it belongs in the amended genus Didymodon s. str. Its systematic position in Didymodon s. str. was also confirmed by our phylogenetic analyses, based on both ITS and chloroplast data.

Chloroplast data support that D. manhanensis is closely related to D. cordatus and sister to both D. daqingii and D. anserinocapitatus. However, D. manhanensis differs morphologically from D. cordatus by the costa with guide cells in 2–3 layers and without ventral stereids and smooth laminal cells. It differs from D. daqingii by the leaves that are narrowly lanceolate from an ovate base, smooth laminal cells and red KOH laminal colour reaction; it differs from D. anserinocapitatus by the distally bistratose leaf margins and lack of swollen and deciduous leaf apex (Zander 2007). In the ITS analyses, there is successive branching of clades, including D. obtusus J. Kou, X.-M. Shao & C. Feng, D. manhanensis, D. epapillatus J. Kou, X.-M. Shao & C. Feng, D. mongolicus D.-P. Zhao & T.-R. Zhang, D. validus Limpr., Vinealobryum guangdongensis C. Feng & J. Kou and D. wisselii (Dixon) D.H. Norris & T.J. Kop. Amongst these species, D. manhanensis is most similar to D. obtusus, a species that was recently described from Tibet in China (Kou et al. 2018), but the former can be distinguished from the latter by its narrowly lanceolate leaves from an ovate base and spreading when moist, subulate and somewhat fragile leaf apex and unistratose distal lamina.

There are three species distributed in China that have excurrent costa and smooth laminal cells may be confused with the new species. Didymodon ditrichoides (Broth.) X.-J. Li & S. He, a species known from North American, Asia (China) and the Atlantic Islands (Iceland) (Li et al. 2001; Zander 2007), differs from the new species by the unistratose leaf margins, costa with 1–2 layers of guide cells and with 0–1 layer of ventral stereids and yellowish KOH laminal colour reaction (Zander 2007). Didymodon validus Limpr. can be separated from D. manhanensis by the twisted and incurved leaves when dry, unistratose leaf margins, costa with 1 layer of guide cells and with 1–3 layers of ventral stereids and yellowish-green KOH laminal colour reaction (Shuayib et al. 2017).

The lanceolate to long-lanceolate leaves with a widely ovate base, distally bistratose leaf margins, excurrent costa and epapillose laminal cells are likewise found in Didymodon ochyrarum J.A.Jiménez & M.J.Cano, a species described from tropical South America (Jiménez and Cano 2019), which may be confused with the new species. However, D. ochyrarum can be separated from D. manhanensis by its plane leaf margins, marginal basal cells running up the margin forming a distinctly differentiated area of transversely thick-walled cells and yellowish KOH laminal colour reaction.

Taxonomic treatment

Didymodon manhanensis C. Feng & J. Kou, sp. nov.

Figs 1, 2 Chinese name: 蛮汉山对齿藓

Type

China. Inner Mongolia: Ulanqab City, Manhan Mountain, 40°39'19.2931"N, 112°19'36.3792"E, on soil under the grass, elevation 1417 m, 20 June 2016, Chao Feng 2016060162 (holotype: NMAC!; isotype: MO!).

Diagnosis

It is distinguished from all congeners by the following combination of diagnostic features: leaves incurved and slightly twisted when dry, spreading when moist, narrowly lanceolate from an ovate base; subulate and fragile leaf apices; distally bistratose leaf margins that are recurved in proximal 2/3–3/4; costal guide cells in 2–3 layers and without ventral stereids, smooth laminal cells and red KOH laminal colour reaction.

Description

Plants medium, growing in turfs, green-blackish distally, brown-blackish proximally. Stems very seldom branched, 0.8–1.6 cm in length, not papillose, transverse section rounded to rounded-pentagonal, central strand developed, sclerodermis present, hyalodermis absent; axillary hairs filiform, of 4–8 hyaline cells, the basal cell brown. Leaves crowded on stem, incurved and slightly twisted when dry, spreading when moist, narrowly lanceolate from an ovate base, constricted just above the base, 1.3–2.3 × 0.43–0.55 mm, distal lamina narrowly channelled ventrally; margins plane distally, recurved in proximal 2/3–3/4 of leaf, entire, distal margins bistratose; apex subulate, somewhat fragile; leaf base ovate, not sheathing, not decurrent; costa stout, tapering distally, 57.5–75 µm wide at base, excurrent as a long, thick subula, not spurred, ventral cells of costa in upper middle part of leaf quadrate or subquadrate, smooth, 4 rows of cells across costa ventrally at mid-leaf, dorsal cells of costa in upper middle part of leaf quadrate or subquadrate, smooth, transverse section semicircular to nearly rounded, epidermis present adaxially and abaxially, not or weakly bulging, ventral stereids absent, guide cells 10–16 in 2–3 layers, 2–4 layers of dorsal stereids, reniform or crescent-shaped, without hydroids; upper laminal cells quadrate to rhombic, usually with angular lumens, 7.5–10 × 5–10 µm, smooth, slightly thick-walled, weakly convex on both surfaces, distal lamina unistratose, basal cells weakly differentiated juxtacostally, rectangular, 12.5–37.5 × 5–7.5 µm, thin-walled, smooth; basal marginal cells subquadrate or quadrate, 5–8.75 × 6.25–7.5 µm, with weakly-thickened walls, smooth. Gemmae absent. Dioicous. Sporophytes unknown. KOH laminal colour reaction red.

Additional specimens examined

China Inner Mongolia: Ulanqab City, Manhan Mountain, on soil under the grass, 20 June 2016, Chao Feng 2016060176 (NMAC).

Etymology

The specific epithet refers to Manhan Mountain, the type locality.

Habitat and distribution

Manhan Mountain is situated in Liangcheng County in the southern section of the Yinshan Mountains in the middle of Inner Mongolia, with an average altitude of approximately 1500 m (Huang et al. 2014). Its soil types are mainly leaching grey, cinnamonic soil (Lyu et al. 2012). The vegetation on Manhan Mountain is typical forest shrub vegetation, including natural forest that consists of Betula platyphylla Sukaczev and Populus davidiana Dode, plantation that consists of Larix principis-rupprechtii Mayr and Pinus sylvestris var. mongolica Litv., natural shrubs that consists of Ostryopsis davidiana Decne., Spiraea salicifolia L. and Rosa davurica Pall. and the herbaceous plants including Stipa bungeana Trin., Cleistogenes squarrosa (Trin.) Keng, Lespedeza bicolor Turcz., Carex spp. and Leymus chinensis (Trin.) Tzvelev (Zhang et al. 2017; Li et al. 2021). Didymodon manhanensis is currently known only from the type locality at the foot of the Manhan Mountain, north-western Liangcheng County, Inner Mongolia, China, growing on soil under the grass.

Figure 1. 

Didymodon manhanensis A dry plants B moist plants C cross-section of stem D leaves E leaf apex F upper part of costa (dorsal) G upper part of costa (ventral) H axillary hairs. Photographed on 21 November 2021 by Chao Feng from the holotype (NMAC!).

Figure 2. 

Didymodon manhanensis A median leaf cells B basal juxtacostal cells C basal marginal cells; D–H cross-sections of leaves, sequentially from apex to base. Photographed on 21 November 2021 by Chao Feng from the holotype (NMAC!).

Figure 3. 

Phylogenetic relationships (50% majority consensus tree) from the Bayesian Inference of the concatenated rps4 and trnM-trnV datasets. Numbers above branches indicate posterior probability from the BI analysis, followed by bootstrap values for the ML analysis.

Figure 4. 

Phylogenetic relationships (50% majority consensus tree) from the Bayesian Inference on the ITS dataset. Numbers above branches indicate posterior probability from the BI analysis, followed by bootstrap values for the ML analysis.

Key to species morphologically similar to D. manhanensis

1 Leaf apices apically swollen as a propagulum D. anserinocapitatus
Leaf apices not swollen, usually evenly narrowing 2
2 Cells on the upper ventral surface of the costa elongate D. wisselii
Cells on the upper ventral surface of the costa quadrate 3
3 Laminal cells smooth 4
Laminal cells papillose 10
4 Costa with 2–3 layers of guide cells and without ventral stereids 5
Costa with 1 layer of guide cells and with ventral stereids 6
5 Leaves patent to spreading when moist, leaf lamina bistratose D. obtusus
Leaves spreading when moist, leaf lamina unistratose D. manhanensis
6 Costa percurrent or ending before the apex 7
Costa long-excurrent 8
7 Leaf margins bistratose near apex D. epapillatus
Leaf margins unistratose D. mongolicus
8 Plants flagellate, leaves linear-lanceolate D. ditrichoides
Plants thickly leaved, leaves short-lanceolate to long-lanceolate 9
9 Leaves appressed when dry D. acutus
Leaves twisted or incurved when dry D. validus
10 Leaf margins plane D. tibeticus
Leaf margins recurved 11
11 Costa without ventral stereids 12
Costa with ventral stereids 13
12 Costa excurrent D. daqingii
Costa ending below apex D. imbricatus
13 Marginal basal cells forming a distinctly differentiated area of smooth and transversely thick-walled cells D. hengduanensis
Marginal basal cells not forming a distinctly differentiated area 14
14 Distal laminal cell superficial walls thicker than the internal walls D. mesopapillosus
Distal laminal cell superficial walls of same thickness as the internal walls 15
15 Laminal cells with low papillae over the transverse walls, which reach the two adjacent cells 16
Laminal cells with papillae situated over the lumina 17
16 Leaves spreading when moist D. guangdongensis
Leaves erect to patent when moist D. vulcanicus
17 Leaf margins recurved in proximal 1/4–3/4 D. icmadophilus
Leaf margins strongly recurved or revolute to near apex 18
18 Leaf base squared in shape, costa slender D. tectorum
Leaf base usually ovate in shape, costa stout D. cordatus

Acknowledgements

Sincerest thanks are given to Dr Richard H. Zander, Missouri Botanical Garden, for his consistent help during the authors’ study of the Pottiaceae in China and for his valuable comments on the manuscript. We really appreciate Dr Jan Kučera, University of south Bohemia, for providing many valuable suggestions on the molecular experiment and help to obtain the sequences of D. daqingii and D. obtusus. We are very grateful to Dr Matt von Konrat of the Field Museum, Dr Grzegorz J. Wolski of University of Lodz and one anonymous reviewer for their constructive criticisms. This work was supported by the Natural Science Foundation of China (grant no. 42001045, 32060051, 31660051), Shenzhen Key Laboratory of Southern Subtropical Plant Diversity (grant no. 99203030) and the Innovative team of China’s Ministry of Education-Research on the sustainable use of grassland resources (IRT_17R59).

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