Nordic Journal of Botany 32: 437–440, 2014
doi: 10.1111/j.1756-1051.2013.00431.x,
© 2014 The Authors. Nordic Journal of Botany © 2014 Nordic Society Oikos
Subject Editor: Rayna Natcheva. Accepted 26 November 2013
Taxonomic notes on Macromitrium densum (Bryopsida)
with a new synonym, M. brevissimum
Jing Yu, Kien-Thai Yong and Shui-Liang Guo
J. Yu and S.-L. Guo ([email protected]), College of Life and Environmental Sciences, Shanghai Normal Univ., CN-200234 Shanghai, China.
K.-T. Yong, Inst. of Biological Sciences, Faculty of Science, Univ. of Malaya, 50603 Kuala Lumpur, Malaysia.
Macromitrium densum Mitt. (from Nepal) is well differentiated from other Asian congeners by its lingulate and strongly
rugose leaves having cucullate, obtuse to retuse apices with a mucro, distinctly bulging upper and median leaf cells, and
tuberculate lower and basal cells. Comparisons of the type and other specimens of M. brevissimum Dixon from Thailand
with those of M. densum show that they belong to a single species, and hence, that the names are synonyms. By including M. brevissimum, the geographic range of M. densum is considerably expanded to cover Nepal, Thailand to north
Peninsular Malaysia and Vietnam. The phenetic relationship between M. densum and other species of Macromitrium is also
discussed.
Macromitrium Brid. (Orthotrichaceae, Bryopsida) is the
third most speciose moss genus (Crosby et al. 1999).
Although ninety species are currently accepted from Asia
(Noguchi 1967, Gangulee 1976, Noguchi and Iwatsuki
1989, Tan and Iwatsuki 1991, 1993, Eddy 1996, Redfearn
et al. 1996, Crosby et al. 1999, Xiong 2000, O’Shea 2002,
Guo et al. 2006, 2007, Guo and He 2008a, 2008b), only a
few studies have been conducted in Asia (Gangulee 1976,
Noguchi and Iwatsuki 1989, Vitt 1995, Eddy 1996, Jia et al.
2011). As part of our revision of the genus Macromitrium in
Asia, we have studied M. densum Mitt. from Nepal and
M. brevissimum Dixon from Thailand. We then found that
the specimens should be considered to belong to a single
species and M. brevissimum is hence proposed as a new synonym of M. densum. The species is here described and its
morphological variation and phenetic relationships with
related species discussed.
Macromitrium densum Mitt. (1859) (Fig. 1)
Type: Nepal, Wallich s.n. (Lectotype designated here: NY!,
isolectotypes: BM000852422(H666b), BM000852423
(H666b), BM000852425(H666b)).
Taxonomic synonym: Macromitrium brevissimum Dixon
(1932) syn. nov.
Type: Thailand. “Udawn. Nakawn Panom, Muk Dāhān, ca
200 m. a.s.l., on rock in open deciduous forest, Feb 1924,
Kerr 74” (holotype: Hb Dixon, BM-000845010!, isotype:
Hb Kerr, BM-000825423!); “Lôi, Wang Sapung, ca 300 m
a.s.l., on rock in deciduous forest, Mar 1924, Kerr 79” (paratypes: BM-000825420!, BM-000825424!)
Description
Plants small to medium-sized, yellowish–brown or yellowish–green, in large scattered, tufts or cushion-forming. Stems
covered by numerous rhizoids, with densely short erect
branches; branches up to 4–6 mm tall. Branch leaves dense,
distinctly funiculate, spirally wound around the branch when
dry, erect-spreading to wide-spreading when moist; leaves
lanceolate linguate to short-lingulate, 1.0–1.5(–1.8) ⫻ 0.3–
0.4(–0.6) mm, length-width ratio 2–3:1, cucullate above,
rugose and often plicate, obtuse to retuse with a mucro;
margins entire, carinate at leaf base; upper and median leaf
cells similar, rounded-quadrate, 5–10 ⫻ 5–10 μm, strongly
bulging to mamillose; basal leaf cells short-rhombic to elliptic-rhombic, 10–32(–40) ⫻ 6–10 μm, unipapillose to tuberculate, shorter and moderately thick-walled along costa,
but elongate with distinctively thickened-walls toward the
leaf margin; the extreme basal marginal cells differentiated,
often pellucid, short-rectangular to irregularly rectangular,
13–26 ⫻ 6–9 μm, thin-walled. Pseudo-autoicous; dwarf
male plants bud-like; perigonial leaves 0.4–0.5 mm long.
Perichaetia terminal on branches. Perichaetial leaves erect to
ercto-patent, similar to branch leaves. Setae 6–9 mm long,
twisted to the left when dry. Capsules erect, ovoid, oblongovoid, to short-cylindrical, 1.4–1.8 mm long, 0.6–1.0 mm
in diameter at the widest part, contracted below the mouth.
Peristome single; exostome teeth fused into a continuous
membrane, erect to recurved at top in both dry and wet
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Figure 1. Macromitrium densum. (1)–(9) branch leaves, (10) calyptra, (11)–(14) capsule when dry, (15) transverse section of the median
part of branch leaf, (16) transverse section of the basal part of branch leaf, (17)–(18) basal leaf cells near leaf margin, (19)–(21) median leaf
cells, (22) median leaf cells near leaf margin, (23)–(24) upper leaf cells. (1)–(5), (17), (20), (22), (24) from lectotype of M. densum (NY);
(6)–(16), (18)–(19), (21), (23) from holotype of M. brevissimum). Scale bars: A ⫽ 0.66 mm (11)–(14), B ⫽ 0.44 mm (1)–(9), C ⫽ 44 μm
(15)–(24), D ⫽ 0.44 mm (10).
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conditions; teeth reticulate-papillose on both dorsal and
ventral sides. Calyptrae mitrate, plicate, naked or scabrous
above, almost covering the whole capsule; base of calyptra
fringed or lacerated. Spores anisomorphic, larger spores
34–40 μm in diameter, smaller spores 22–24 μm in diameter, minutely papillose.
distribution of M. densum from Nepal to India, Malaysia,
Thailand and Vietnam. The occurrence of this species in
Perlis, in the extreme northwest of Peninsular Malaysia,
appears to be its southernmost limit.
Habitat and ecology
India: Tamil Nadu, Tirunveiveli district, Narakkad,
Daniels 3537 (MO). Malaysia: Perlis, Wang Kelian,
Damanhuri 99-179 (UKMB). Nepal: Schwag 10.
(BM-000745392); Wallich H666b (as Macromitrium
densifolium Mitt., BM-000852422; BM-000852425); Wallich s.n. (BM-000745391); Willson 373 (BM-000852424).
Thailand: Kerr 461 (Hb. Dixon, BM-00825421); Aram
Pratet, Kerr 546 (Hb. Dixon, BM-00825422); Mae
Sariang, Larsen, Santisuk and Warncke 2266a (MO);
Payap, Bo Luang near Ban Om Khut, Larsen, Santisuk and
Warncke 2224 (H-3090208; MO; NY); Larsen, Santisuk
and Warncke 2756a (MO); Payap, Chiengmai, Doi Sutep,
Sørensen, Larsen, Hansen 5362 (NY). Phitsanulok, Tung
Salaeng Luang, Larsen, Smitinand and Warncke 858 (MO),
860 (H-3090207; MO; NY). Pequ, Jon Rqeghat, Kurz
(Pegu) 2924 (BM-000745393); Lôi, Kerr 563 (Hb Dixon,
BM-00825426); Rachasima, Buriram, Nang Rawng, Kerr
73 (Hb Dixon, BM-00845011); Tom Pawa, Vdakr, Kerr
463 (Hb Dixon, BM-00825427); Udawn, Loi, Dan Sai,
Kerr 100 (Hb Dixon, BM-000845012). Vietnam: Yokdon
National Park, Daklak, Huong H050 (SING).
On tree trunks and branches, or on granitic rocks or sandstones, usually in rather open areas. The species is only known
from sites of low elevation, from sea level to 600 m a.s.l.
Distribution
India (Gangulee 1976), Myanmar (Tan and Iwatsuki 1993),
Peninsular Malaysia, Thailand (northern, northeastern,
southeastern), and Vietnam.
Similar species
When Dixon (1932) described M. brevissimum from
Thailand, he noted that the species differs from other congeneric species by its cucullate leaf apex with an excurrent
costa. Just like many other Macromitrium species, M. densum
is highly variable in plant and leaf size. The species, however,
can be easily recognized by: 1) dense and distinctly funiculate branch leaves that usually spiral around the branch when
dry, 2) lanceolate-lingulate to lingulate branch leaves with
a rounded, mucronate and cucullate apex, 3) strongly bulging to mamillose upper and median leaf cells, and unipapillose or tuberculate lower and basal cells, and 4) mitrate and
naked calyptrae that almost cover the whole capsule.
Macromitrium densum shows high morphological variation. Although the branch leaves are mostly cucullate
because of narrowly incurved apical margins (occasionally
flat above), the upper and median leaf cells are often strongly
bulging or conic-bulging, sometimes with weakly mammillate cells. The capsules are often ovoid, oblong-ovoid, sometimes shortly cylindrical.
When Mitten (1859) described M. densum from
Nepal, he remarked that M. densum was similar to
M. wagnerianum Müll. Hal. (⫽ Groutiella wagneriana
(Müll. Hal.) H. A. Crum & Steere), but the latter has a
differentiated basal marginal leaf border with several rows
of narrow, elongate cells often extending from the base
to 1/4–2/3 of the leaf length. Among the members of
genus Macromitrium, M. densum is somewhat similar to
M. carionis Müll. Hal. from Central America, but the
latter differs in having enlarged basal teeth at the leaf
insertion, and lacks a cucullate leaf apices (Allen 2002).
Macromitrium densum was thought to be endemic to eastern Nepal (Gangulee 1976) until Dixon (1932b) described
the species (as M. brevissimum) from Thailand. In fact, the
species is common in Indochina (Noguchi 1972), but there it
has often been mistaken for M. concinnum Mitt. ex Bosch &
Lac. because they are similar in plant size, branch leaf shape
and the bulging and smooth upper leaf cell features. By its
rather rugose branch leaves with cucullate apices, and shorter
and smooth setae, M. densum could be easily separated from
M. concinnum. The present synonymization extends the
Additional specimens examined
Acknowledgments – The corresponding author thanks Dr S. He and
B. Allen at the Herbarium of Missouri Botanical Garden, for their
hospitality and help during his visit. Thanks to the curators of BM,
H, MO, NY, SING and UKMB for the loans of specimens. This
work was financially supported by a research grant provided by the
Univ. of Malaya, the National Nature Science Foundation of China
(no. 31370233, 30970184, 30570121), the Science and Technology Commission of Shanghai Municipality (no. 11391901200,
12490502700).
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