Nordic Journal of Botany 000: 001–004, 2016 doi: 10.1111/njb.01285, ISSN 1756-1051 © 2016 Th e Authors. Nordic Journal of Botany © 2016 Nordic Society Oikos Subject Editor: Rayna Natcheva. Editor-in-Chief: Torbj ö rn Tyler. Accepted 28 June 2016

Didymodon mesopapillosus sp. nov. () from Tibet, China

Jin Kou , Chao Feng, Yan-Bin Jiang and Xiao-Ming Shao

J. Kou and X.-M. Shao ([email protected]), Beijing Key Laboratory of Biodiversity and Organic Farming, College of Resources and Environmental Sciences, China Agricultural Univ., Beijing, P. R. China. – C. Feng, College of Ecology and Environmental Sciences, Inner Mongolia Agricultural Univ., Hohhot, P. R. China. – Y.-B. Jiang, College of Resources and Environment, Huazhong Agricultural Univ., Wuhan, P. R. China.

Didymodon mesopapillosus J. Kou, X.-M. Shao & C. Feng is described and illustrated as a new species from Tibet, China. It is characterized mainly by its ovate to ovate-lanceolate leaves appressed to weakly erect when dry, margins recurved from leaf base to apex, laminal cell superfi cial walls markedly thicker than the internal walls, laminal papillae present only on both sides of costa, short-excurrent costa, undiff erentiated basal cells and diff erentiated perichaetial leaves. Th is species is compared with similar species and its ecology is discussed.

Pottiaceae are one of the most complex and diverse Etymology taxa. Within this family, Didymodon Hedw. is an essentially Th e specifi c epithet refers to one of the striking characters cosmopolitan genus with approximately 126 species, found of the new species: laminal papillae present only on both on a variety of substrates but mostly rock or soil (Zander sides of costa. 1993, 2007, Frey and Stech 2009, Jimé nez et al. 2014). Th e most important features distinguishing species in Didymdon Description are color reaction in KOH, stratifi cation of the lamina and medium-sized, 0.8 – 1.3 cm high, growing in dense margins in the upper part of the leaf, and the shape of cells turfs, yellowish-green above, yellow in lower parts. Stems on the ventral surface of the costa (Jim é nez 2006). Besides, branched; hyalodermis absent; sclerodermis present; cen- papillae also can play an important role in classifying many tral strand developed. Axillary hairs fi liform, 3 – 5 cells long, Didymodon species (Jim é nez 2006, Kou et al. 2014). with 1 brown basal cell and hyaline upper cells. Rhizoidal During the past nearly 10-years of fi eld work, the team tubers absent. Leaves appressed to weakly erect when dry, of Dr Shao collected a large quantity of specimens in diff er- patent to spreading when moist, ovate to ovate-lanceolate, ent regions of Tibet. In the course of identifying these, we weakly channeled ventrally in the upper part, 1.2– 1.6 ϫ noted several interesting fertile samples of Didymodon from 0.40 – 0.68 mm; lamina unistratose, brown to red with two diff erent localities. Th ese specimens were apparently KOH; apex acute, not deciduous, non-cucullate; margins similar to Didymodon tectorum (C. M ü ll.) Saito. However, recurved from leaf base to apex, entire, not decurrent at subsequent detailed observations revealed further diff erences base, unistratose; costa short-excurrent, 100.0– 122.5 μ m between these unique specimens and D. tectorum which wide at base, not spurred; ventral cells of the costa subquad- prompted us to describe them as a new species. rate to shortly rectangular, papillose; dorsal surface cells of the costa in the upper half subquadrate to quadrate, sparsely Didymodon mesopapillosus J. Kou, X.-M. Shao papillose; costa cross-section below mid-leaf elliptic to & C. Feng sp. nov. (Fig. 1 – 2) semicircular, with 4– 6 guide cells in 1 layer, 2– 3 layers of ventral stereids, and 3– 5 layers of dorsal stereids, lunulate Similar to D. tectorum, but diff ering in the bulging ventral in shape, with hydroids; dorsal surface cells diff erentiated, surface cells of the costa, laminal cell superfi cial walls markedly papillose, and ventral surface cells diff erentiated, bulging, thicker than the internal walls, laminal cells papillose only in papillose; upper and middle laminal cells subquadrate to the middle of leaves, and basal cells undiff erentiated. quadrate, 5.0 – 7.5 ϫ 6.25 – 10.00 μ m, thick-walled, not bulging, smooth near margins but in 2– 8 rows on both Type : People ’ s Republic of China. Tibet, Shigatse Prefec- sides of the costa with 1 – 2 simple or bifurcate, coarse ture, Ngamring County, Bangla Mountain, 29° 23 ′ 10 ′ N, papillae; basal juxtacostal cells usually quadrate to short- 86 ° 57 ′ 34 ′ E, on rocks, 4529 m a.s.l., 15 Aug 2014, Xiao- rectangular, 11.25 – 25.00 ϫ 7.50 – 10.00 μ m, slightly thick- Ming Shao and Jin Kou 20140815038 (holotype: BAU). walled, smooth; basal marginal cells isodiametric or quadrate,

Early View (EV): 1-EV Figure 1. Didymodon mesopapillosus sp. nov. (a) dry (scale in mm), (b) moist plant (scale in mm), (c) cross-section of stem, (d) leaves, (e) leaf apex (dorsal side), (f) leaf apex (ventral side), (g) upper part of costa (ventral side), (h) mid-leaf cells, (i) middle part of costa (dorsal side), (j) basal juxtacostal cells, (k) basal marginal cells. Scale bar: (c), (e), (f) ϭ 100 μ m, (d) ϭ 0.4 mm, (g) – (k) ϭ 40 μ m. Arrows marked: thickened cell walls. Photos prepared from the holotype.

6.25– 12.50 ϫ 7.50 – 10.00 μ m, slightly thick-walled, smooth. Distribution and habitat Gemmae absent. Sexual condition dioicous. Perichaetial Occurring on rocks and soil in open habitats. Some speci- leaves diff erentiated, broadly ovate-rectangular, abruptly mens were collected along national highway 219, mainly in narrowed to a subulate apex, longer than vegetative leaves, the Bangla Mountains which belong to the semi-arid region. 1.33 – 1.48 mm long. Seta 0.45 – 0.62 cm long, twisted to One specimen was collected in Chabu Village in Ngari the left, yellowish orange. Capsule erect, cylindrical, 1.08– Dagzê , which is part of the arid region. Th e most important 1.25 ϫ 0.55 – 0.63 mm, brown; annulus persistent, composed ecosystems are alpine meadow communities. of 2– 3 rows of vesiculose cells, thick-walled; peristome of 32 Tibet is the principal part of the Qinghai-Xizang Plateau fi liform teeth, densely papillose, spirally twisted, 0.65– 0.70 which has long been known as the roof of the world. Th e mm long; operculum long rostrate. Calyptra not seen. Spores province possesses the characteristics of high elevation, 12.5 – 15.0 μ m in diameter, weakly papillose, yellowish undulating relief, diverse climatic conditions, many towering brown. mountains and rivers dispersed in this district. Owing to

2-EV Figure 2. Didymodon mesopapillosus sp. nov. (a) axillary hairs, (b) capsule (scale in mm), (c) perichaetial leaves, (d)– (l) cross-section of upper part of leaf. Scale bar on (a), (d) – (j) ϭ 100 μ m, (c) ϭ 1 mm, (k) – (l) ϭ 40 μ m. the orogeny and the occurrence of glacial and interglacial Ngari Prefecture is located in the western Qinghai-Xizang periods, the Qinghai– Tibetan plateau has been uplifted on Plateau and has an average elevation of more than 4500 m a large scale and its climate has repeatedly been drying and a.s.l., with the topographic and geomorphic conditions of growing chilly. Th e devolpement continued by interactions erosion mountains, hills and the piedmont alluvial fans, among diluvia, slope deposits, glacial debris, lacustrine forming various parent materials including alpine frozen deposits and glacial outwash under the action of the climate, soil, alpine steppe soil, alpine desert soil, subalpine steppe biology, physics, chemistry and human activities. Several soil, meadow soil, and so on. Ngari Prefecture belongs to types of soils have been formed in diff erent topographic the plateau temperate monsoon-arid climate, plateau sub- positions, giving rise to distinctive plateau characteristics. frigid monsoon-arid climate and plateau frigid monsoon- From the River Valley in southeast Tibet to the high plateau arid climate regions. Th e climate in the region is dry and in northwest Tibet, the temperature decreases and the has scarce precipitation and annual evaporation of more climate changes from humid and semi-humid to arid and than 2000 mm. Owing to the harsh environment, the two semi-arid. localities are covered mainly in herbs, lichens and bryophytes Th e two sites where the new species were found are (Chen and Liu 1997, Li et al. 2004, Zhong et al. 2005). located in Shigatse Prefecture and Ngari Prefecture. Shigatse Prefecture has an average elevation of more than 4000 m and Similar species belongs to the warm-moist semi-arid climate; the sunshine Didymodon mesopapillosus is characterized by its ovate to hours amounts 3216.1 h, and annual precipitation to 422.3 ovate-lanceolate leaves that are appressed to weakly erect mm. Th e zonal soils of the Shigatse Prefecture are mountain when dry, margins recurved from leaf base to apex, with lami- shrubby steppe soil, alpine shrub meadow soil and alpine nal cell superfi cial walls markedly thicker than the internal meadow soil. Th e most common plants in this region belong walls as seen in cross section, laminal papillae present only in to the Compositae, Gramineae, Fabaceae and Rosaceae. 2– 8 rows on both sides of the costa, short-excurrent costa,

3-EV undiff erentiated basal cells and diff erentiated perichaetial 86 ° 52 ′ 29 ′ E, on soil, 4532 m a.s.l., 15 Aug 2014, Xiao-Ming leaves. According to Zander (1993), spreading leaves when Shao and Jin Kou 20140815052(BAU); Shigatse Prefecture, dry, channeled along the adaxial surface of the costa, with Ngamring County, Bangla Mountain, 29 ° 19 ′ 58 ′ N, margins recurved below to near the apex, apiculate by a con- 86° 53 ′ 28 ′ E, on soil, 4622 m a.s.l., 15 Aug 2014, Xiao-Ming ical cell, short-excurrent costa, quadrate adaxial superfi cial Shao and Jin Kou 20140815063(BAU); Ngari Prefecture, cells of the costa, and red to red – orange KOH color reac- Chabu Village 29° 3 ′ 52.5 ′ N, 87° 33 ′ 31.5 ′E on soil, 4217 tion of lamina suggest the placement of D. mesopapillosus in m a.s.l., 16 Aug 2014, Xiao-Ming Shao and Jin Kou the D. sect. Vineales (Steere) R.H. Zander. In this section, 20140816062 (BAU). the close relatives of the new species are D. tectorum , D. brachyphyllus (Sull.) Zander and Didymodon cordatus Jur. Didymodon mesopapillosus is most similar to D. tectorum , Acknowledgments – We give our special thanks to Yu Jia and Ning- Ning Yu, Inst. of Botany, Th e Chinese Academy of Sciences, for a species known from Asia, North America and Africa providing important literature. Th is work was supported by (Hedderson et al. 2014), in its ovate to ovate-lanceolate Natural Science Foundation of China (grant no. 31570474) and leaves, margins recurved or revolute to near the apex, costa Major Project of Prataculture from the Tibet Autonomous Region short-excurrent, quadrate adaxial costal cells and costa (2015ZDKJZC01), and National Natural Science Foundation of with both ventral and dorsal stereids. However, D . meso- China (31300356). papillosus diff ers from D. tectorum by its bulging ventral surface cell layer in the costa, laminal cell superfi cial walls markedly thicker than the internal walls, laminal papillae References restricted to the middle of leaves, and undiff erentiated basal cells. In addition, the laminal walls are weakly Chen, H.-S. and Liu. Z.-M. 1997. Th e characteristics of the convex on both surfaces in D. tectorum, while plane in vegetation composition of jiangdang and its adjacent area atrigaze county in Tibet. – J. Desert Res. 17: 63 – 69, in D. mesopapillosus . Chinese. Ovate to ovate-lanceolate leaves, with margins recurved Frey, W. and Stech, M. 2009. Marchantiophyta, Bryophyta, or revolute to near the leaf apex, quadrate adaxial costal Anthocerotophyta. – In: Frey, W. (ed.), Syllabus of plant cells and costa with both ventral and dorsal stereids are families. Gebr. Borntraeger Verlagsbuchhandlung, part also characters of Didymodon brachyphyllus (Sull.) Zander. 3: 179. Nevertheless, D. mesopapillosus diff ers from that species in its Hedderson, T. A. J. et al. 2014. New and additional moss records acute leaf apex, short-excurrent costa and undiff erentiated for Rwanda. – J. Bryol. 36: 72 – 75. Jim é nez, J. A. 2006. Taxonomic revision of the genus Didymodon proximal laminal cells. Hedw. (Pottiaceae, Bryophyta) in Europe, north Africa Didymodon cordatus Jur., like D. mesopapillosus, has ovate- and southwest and central Asia. – J. Hattori Bot. Lab. 100: lanceolate leaves with margins recurved or revolute to near the 211 – 292. leaf apex and a short-excurrent costa. However, the new species Jim é nez, J. A. et al. 2014. Didymodon californicus (Pottiaceae), can be readily separated from D. cordatus by its bulging ven- a new species from California, USA. – Phytotaxa 158: tral costa surface cells, laminal cell superfi cial walls markedly 105 – 110. thicker than the internal walls, laminal papillae present only in Li, S. et al. 2004. Dynamic changes and developmental trends of the land desertifi cation in Tibetan Plateau over the past 10 the middle of leaves and undiff erentiated basal cells. years. – Adv. Earth Sci. 179: 63 – 70, in Chinese. Didymodon constrictus (Mitt.) K. Saito is easily confused Kou, J. et al. 2014. Morphology and of leaf papillae with D. mesopapillosus due to their similar leaf shape and and mammillae in Pottiaceae of China – J. Syst. Evol. 52: bulging ventral surface cells of the costa. However, the former 521 – 532. can be separated from the latter by its margin recurved in Zander, R. H. 1993. Genera of the Pottiaceae: of harsh proximal 2/3, much enlarged, oblong laminal basal cells and environments. – Bull. Buff alo Soc. Nat. Sci. 32: 1 – 378. undiff erentiated perichaetial leaves. Zander, R. H. 2007. Didymodon Hedw. – In: Flora of North America Editorial Committee (eds), Flora of North America. Vol. 27. Oxford Univ. Press, pp. 539 – 561. Additional specimens examined (paratypes) Zhong, G.-H. et al. 2005. Soil fertility of croplands in major People ’ s Republic of China. Tibet, Shigatse Prefecture, agricultural areas in Tibet. – Acad. Pedol. Sin. 42: 1030– 1034, Ngamring County, Bangla Mountain, 29 ° 23 ′ 11 ′ N, in Chinese.

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