Research Article
Research Article
Didymodon changbaiensis (Pottiaceae, Musci), a new species from Changbai Mountain, China and its phylogenetic position based on molecular data
expand article infoTing-Ting Wu, Chao Feng§, Tao Bian, Guo-Li Zhang|, Jin Kou, Hong-Xing Xiao
‡ Northeast Normal University, Changchun, China
§ Inner Mongolia Agricultural University, Hohhot, China
| Tangshan Normal University, Tangshan, China
Open Access


Changbai Mountain, located in northeast China, is one of the areas with the most complete natural ecosystem preservation in China. A new species, Didymodon changbaiensis C.Feng, J.Kou, H.-X. Xiao & T.-T.Wu from north slope of Changbai Mountain in Jilin Province of China is described and illustrated. It is characterised by ovate or ovate-lanceolate leaves that are appressed when dry, acute leaf apex, lamina red or reddish-orange with KOH, unistratose lamina throughout, plane and unistratose leaf margins, percurrent costa with one layer of guide cells and without ventral stereids, upper and middle laminal cells with elliptical papillae over the transverse walls between two immediately adjacent cells and basal laminal cells not differentiated from the median cells. Our morphological analyses and molecular results, based on DNA sequences of ITS, rps4 and trnM-trnV, confirm that D. changbaiensis is revealed to be sister to 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.


Asia, northeast China, phylogenetic analysis, taxonomy


Changbai Mountain National Reserve is located at the junction of three counties: Antu County, Fusong County and Changbai County in the southeast of Jilin Province, with a total area of 196,000 ha2. It is one of the earliest national nature reserves established in China. The vertical height difference of the Nature Reserve is nearly 2000 m and the altitude is between 720 and 2691 m (Jia et al. 2020). From bottom to top, the landform can be clearly divided into three annular zones: lava platform, lava plateau and volcanic cone. The protected area belongs to the temperate humid monsoon climate, which is generally characterised by long and cold winters, short and cool summers, strong and dry winds in spring and foggy and cool autumns. The plants in the area belong to the flora of Changbai Mountain and the vegetation changes vertically with the altitude gradient. The vegetation in this area has obvious vertical zonal distribution due to the influence of climate and it is generally divided into four vertical vegetation zones. From the foot of the mountain to the top of the mountain are generally: broad-leaved Korean pine forest belt (below 1100 m), spruce fir forest belt (1100–1800 m), Yuehua forest belt (1800–2100 m) and alpine tundra belt (greater than 2100 m) (Ping et al. 2016). Due to the diverse characteristics of topography, climate and ecosystem, the area is rich in biodiversity resources. There are nine species of amphibians, 12 species of reptiles, 24 species of fish, 56 species of mammals, 230 species of birds and 1255 species of insects in the Reserve, respectively (Tang et al. 2011). In addition, there are 430 species of fungi, 200 species of lichens, 311 species of bryophyte, 78 species of ferns, 11 species of gymnosperms and at least 1325 species of neutrophils (Zhang et al. 2016).

Although the bryophyte flora of Changbai Mountain has been well studied, most of these studies were nearly twenty years ago (e.g. Koponen et al. 1983; Cao and Guo 2000; Cao et al. 2002; Guo et al. 2002). In the background of the recent revolution of genus Didymodon (Zander 2013; Zander 2019) which was split 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), a re-evaluation of Didymodon in China is being conducted by the authors (e.g. Feng et al. 2022a; Feng et al. 2022b). During a recent excursion in Changbai Mountain, many specimens have been collected. Amongst them, two samples of Didymodon s. lat. from stony habitats are different from species previously reported in the area (Li et al. 2001). They mostly resemble Didymodon tibeticus 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, one specimen (234) collected from Changbai Mountain was sampled. Another species (188) that was discovered nearby the new species was also sampled. 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 (Zhang et al. 2022). 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
234 (new species) China, Changbai Mountain, Jin Kou 20200902234 OP641837 OP641840 OP656316
188 (unknown species) China, Changbai Mountain, Jin Kou 20200902188 OP641838 OP641839 OP656315
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. The phylogenetic position of the new species was analysed within a comprehensive phylogenetic analysis of Didymodon s. lato. species by our previous study (Zhang et al. 2022). Phylogenetic analyses were performed by using the Bayesian Inference (BI) and Maximum Likelihood (ML) methods. Parameter configuration and convergence estimation followed Zhang et al. (2022).


The combined length of ITS and cpDNA (rps4 and trnM-trnV) is 4622 bp. The position of the new species is different between the BI and ML phylogenetic trees and, thus, both of them are reserved. The topology, based on ML analyses, shows that the new species is sister to Didymodon daqingii J. Kou, R.H. Zander & C. Feng and they nested within the monophyletic group comprising Didymodon hengduanensis J.A. Jiménez, D.G. Long, Shevock & J. Guerra, D. icmadophilus (Schimp. ex Müll. Hal.) K. Saito, D. mesopapillosus J. Kou, X.-M. Shao & C. Feng, D. tibeticus and D. vulcanicus J.A.Jiménez, Hedd. & Frank Müll (Fig. 1). The BI tree was more similar to that of the ML tree, but with weakly-supported values (Fig. 2).

Figure 1. 

Maximum Likelihood tree inferred from concatenated ITS, rps4 and trnM-trnV datasets. Numbers indicate Maximum Likelihood bootstrap values. The numbers 234 and 188 show the sample of D. changbaiensis and an unknown species, respectively.

Figure 2. 

Phylogenetic relationships (50% majority consensus tree) from the Bayesian Inference of the concatenated ITS, rps4 and trnM-trnV datasets. Numbers indicate posterior probability from the BI analysis. The numbers 234 and 188 show the sample of D. changbaiensis and an unknown species, respectively.


Our molecular analyses reveal that the new species belongs to Didymodon s.str. Morphologically, the combination of characters: concave leaves, plane leaf margins, percurrent to excurrent costa, seldom papillose laminal cells, costa with quadrate or occasionally short-rectangular superficial adaxial cells and absence of costal adaxial stereid band also suggests the placement of the new species in the emended genus Didymodon s.str. Zander (1978, 1993, 2013). The new species is distinguished from all congeners by the following combination of diagnostic features: ovate or ovate-lanceolate leaves that are appressed when dry, acute leaf apex, lamina red or reddish-orange with KOH, unistratose lamina throughout, plane and unistratose leaf margins, percurrent costa with one layer of guide cells and without ventral stereids, upper and middle laminal cells with elliptical papillae over the transverse walls between two immediately adjacent cells and basal laminal cells not differentiated from the median cells.

The phylogenetic analyses support that the new species is closely related to D. daqingii, a species that was recently described from Inner Mongolia, China (Kou et al. 2019). They have similarity in quadrate or subquadrate ventral cells of costa in the upper middle part of the leaf, bulging costal ventral surface cells, transverse section of costa round at mid-leaf and costa without ventral stereids. However, D. daqingii differs from the new species by the long-lanceolate leaves, very fragile and bistratose leaf apices, distally bistratose and recurved leaf margins, costa with guide cells in 2–3 layers, laminal cells with 1–3 simple papillae per cell and yellow-green KOH laminal colour reaction.

There are five species that are related to the new species, based on our phylogenetic analysis. Amongst them, the new species is most similar to D. tibeticus, based on morphological characters. They share such distinctive characteristics as the shape of the leaves, lamina red or reddish-orange with KOH, unistratose lamina throughout, plane and unistratose leaf margins and percurrent costa. Nevertheless, D. tibeticus can be separated from the new species by the costa with a ventral costal pad of cells and 0–1 layer of ventral stereids, transverse section of costa flattened at mid-leaf and laminal cells with 1–2 simple or bifurcate papillae per cell. Other species, Didymodon hengduanensis J.A. Jiménez, D.G. Long, Shevock & J. Guerra, D. icmadophilus (Schimp. ex Müll. Hal.) K. Saito, D. mesopapillosus J. Kou, X.-M. Shao & C. Feng and D. vulcanicus J.A.Jiménez, Hedd. & Frank Müll. are distinguished from the new species by their recurved leaf margins and costa with ventral stereids.

Taxonomic treatment

Didymodon changbaiensis J.Kou, C.Feng, H.-X.Xiao & T.-T.Wu, sp. nov.

Figs 3, 4 Chinese name: 长白山对齿藓


China. Jilin Province: Changbai Mountain, 42°3'35.316"N, 128°3'51.516"E, on soil over rocks, elevation 1864 m, 2 September 2020, Jin Kou 20200902234 (holotype: NENU!; isotype: NMAC 20200902234!).


It differs from the otherwise similar D. tibeticus in its costa without a ventral costal pad of cells and ventral stereids, transverse section of costa round at mid-leaf and laminal cells with elliptical papillae over the transverse walls between two immediately adjacent cells.


Plants to 1 cm high, growing in dense turfs, brown-reddish below, green above. Stems erect, frequently branched, in transverse section rounded, central strand weakly differentiated, hyalodermis and sclerodermis absent; axillary hairs filiform, usually 3–4 cells long, with one brown basal cell and hyaline upper ones. Rhizoidal tubers absent. Leaves appressed when dry, erect when moist, ovate or ovate-triangular with a broad base, 0.85–1.3 × 0.43–0.65 mm, channelled ventrally in the upper part; lamina completely unistratose, reddish-orange in KOH; apex acuminate to acute, not cucullate; margins entire, plane, completely unistratose; costa 51.7–86.2 µm wide at base, percurrent to short-excurrent; ventral cells of costa in upper middle part of leaf quadrate or subquadrate, sparsely papillose; dorsal cells of costa in upper middle part of leaf quadrate or subquadrate, sparsely papillose; transverse section of costa round at mid-leaf; with 3–4 guide cells in one layer, absence of ventral stereids, 1–2 layers of dorsal stereids, without hydroids, ventral surface cells bulging, not forming a pad of a single layer of cells, papillose, dorsal surface cells papillose; upper and middle laminal cells subquadrate, hexagonal or shortly rectangular, 5.5–11.1 × 8.9–12.2 µm, dorsally with one low elliptical papilla over the transverse walls which reaches the two immediate cells; basal cells weakly differentiated, smooth, basal juxtacostal cells hexagonal or short-rectangular, 11.1–20 × 5.56–10 µm, evenly thick-walled; basal marginal cells oblate, 5.56–10 × 6.67–10 µm, with regular thickened transverse walls and thin longitudinal walls. Gemmae absent. Dioicous. Sporophyte unknown.

Figure 3. 

Didymodon changbaiensis A dry plants B moist plants C cross-section of stem D axillary hairs E leaves F leaf apex G upper part of costa (dorsal) H upper part of costa (ventral) I upper leaf margin, arrows shows the laminal cells with elliptical papillae over the transverse walls between two immediately adjacent cells. Photographed on 25 May 2022 by Chao Feng from the isotype.

Figure 4. 

Didymodon changbaiensis A, B median leaf cells, arrows show the laminal cells with elliptical papillae over the transverse walls between two immediately adjacent cells C basal juxtacostal cells D basal marginal cells E–J cross-sections of leaves, sequentially from apex to base. Photographed on 25 May 2022 by Chao Feng from the isotype.


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

Habitat and distribution

The new species is currently known only from the type locality at the north slope of Changbai Mountain, Jinlin Province, China, growing on thin soil over rocks.


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 are very grateful to Dr Grzegorz J. Wolski of University of Lodz for his 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), Natural Science Foundation of Inner Mongolia (grant no. 2022MS03066) and the Innovative team of China’s Ministry of Education-Research on the sustainable use of grassland resources (IRT_17R59).


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