Gymnomitrion rubidum subsp. subvittatum Vilnet, Bakalin et D.G. Long, 2022

Bakalin, Vadim, Vilnet, Anna, Long, David, Klimova, Ksenia, Maltseva, Yulia, Nguyen, Van Sinh & Ma, Wen Zhang, 2022, On two species of Gymnomitrion (Gymnomitriaceae, Marchantiophyta) in the Eastern Sino-Himalaya, Phytotaxa 533 (2), pp. 117-136 : 131-132

Gymnomitrion rubidum subsp. subvittatum Vilnet, Bakalin et D.G. Long subsp. nov. (haplotype 2)

Description: The subspecies differs from subsp. rubidum in always narrowly revolute antical leaf margin and well differentiated ‘vitta’ in the leaf base ( Fig. 4 , 5 , 6 ) as well as in several single base pair substitutions in ITS1-2 and trn L-F.

Holotype:— CHINA. Yunnan Province: Fugong County, Lishadi Xiang, Yaduo Cun , E slope of Gaoligong Shan (Nu Jiang catchment), N bank of North Fork Yamu River, side valley 11 km above Shibali Forestry Station on way to ‘Yaping Pass’, rocky valley with bouldery Betula -bamboo forest, on tree branches, 3200 m a.s.l., 27°12’30.7”N 98°43’23.7”E, 08 August 2005, Long 34462 ( E). ITS1-2: MW822010 , trn L-F: MW841071 ( KF943103 ) .

Paratypes:— NEPAL. Kangchenjunga: Simbua Khola below Tseram, AbiesRhododendron forest, on wet rocks, 3550 m a.s.l., 27°31’N 87°56’E, 21 September 1989, Long 17112 ( JE) (the identification based on morphology). NEPAL. Sankhuwasabha District: ridge between Kauma and Shipton La, rocky ridge with Rhododendron , on branch of Sorbus , 3670 m a.s.l., 27°39’N 87°13’E, 26 September 1991, Long 20655 ( JE). Note: the purple pigmentation is distinctly present near apices (other parts are ferruginous), narrowly revolute lateral leaf margins, fewer ventral innovations and slightly larger size (up to 2.0 mm wide) than in subspecies type (the identification based on morphology). NEPAL. Vorhimalaja: Tanga, Rhododendron forest, 4000 m a.s.l., 1962, J. Poelt H170 ( JE). Note: plants similar to type, but with purple tint in shoot tips and narrowly recurved leaf margin in lower half of leaves (the identification based on morphology).

Ecology and distribution: In the taxonomically broad sense, Gymnomitrion rubidum is a distinctly Sino-Himalayan taxon while the distribution of the two subspecies revealed in the present paper is difficult to estimate. Based on sequenced specimens, at least in Yunnan Province of China both subspecies are present. However, the record of subsp. rubidum from the slope of Mt. Phan Xi Pang is the southernmost record of the species. The distribution of subsp. rubidum in North Vietnam may conditionally confirm its broader distribution, while the subsp. subvittatum may be more narrowly distributed and hidden within the more broadly distributed subsp. rubidum . The latter may correlate with the ecological plasticity of subsp. rubidum that allowed the distribution to be wider than that of subsp. subvittatum . Both subspecies are predominantly epilithic,occurring on dripping cliffs above the timberline, at elevations commonly exceeding 3500–4000 m a.s.l. However, both subspecies may be found on woody substrates also: the specimen of subsp. rubidum from Vietnam, being the southernmost across the species range, was collected on decaying wood in very scattered Abies delavayi Franchet (1899: 255–256) forest. This forest species is locally quite abundant in Yunnan and was described from “ad cacumina montis, Tsang-chan supra Tali, alt. 3500–4000 m ” ( Franchet 1899: 255) (= Mt. Cangshan above Dali). Thus, this is an area where Gymnomitrion rubidum occurs. The distribution of Abies delavayi in North Vietnam shows a distinctly relictual character and the sparse population of this species is unfortunately noticeably decreasing in size (almost no seedling establishment and no suite of taxa) that would be specific to A. delavayi scattered population (probably except of Gymnomitrion rubidum ). The latter is a direct consequence of the contrasting current environment of Abies delavayi stands in Vietnam. The area of Abies Miller (1754: 1) distribution in Vietnam is surrounded by true southern subtropical mountain forest with a distinct dominance of evergreen shrubs and trees including those from Lauraceae , while in the Yunnan Province of China, the environments are represented by shrubby Rhododendron communities or even dwarf shrubs and grass communities close to the timberline. Subspecies subvittatum was also collected at least once on tree branches in a rocky valley with bouldery Betula -bamboo forest (Long 34462) at an elevation above 3000 m a.s.l.

Unlike so many Gymnomitrion taxa (like G. concinnatum , G. corallioides Nees (1833: 118–119) in North-East Asia or G. sinense , G. crenatilobum in Sino-Himalaya), distributed strictly above the timberline in tundra-like or heathland communities, Gymnomitrion rubidum (especially its subsp. rubidum ) is mostly distributed within the forest belt. Moreover, it descends to the evergreen dominated forest in Dali County of Yunnan Province and even lower into the subtropical vegetation belt in North Vietnam. This feature puts the distribution of G. rubidum apart from many other known Gymnomitrion taxa although it links the species to some taxa of Gymnomitrion formerly belonging to Apomarsupella (shown as nested within Gymnomitrion by Shaw et al. 2015), like Gymnomitrion parvitextum and G. verrucosum commonly occurring in oroboreal and even oro-hemiboreal forests. The type of G. rubidum (Kumaon, Champawat) collected at an elevation of 10,000 feet (= slightly over 3000 m alt.) most probably (thanks to photographs placed on Google Earth) covered by mixed forests composed of broadleaved and coniferous trees.

One more observation should be made on the possible parallelism in evolution of two related genera: Gymnomitrion and Marsupella . Gymnomitrion rubidum is superficially very similar to the recently described Marsupella vietnamica Bakalin & Fedosov (2019: 66) due to its peculiarly ventrally turned shortly lobed leaves with unequal lobes (Bakalin et al. 2019). The latter, however, may be easily distinguished due to larger cell size, presence of short, but distinct perianth and it’s distribution in lower elevations and more southern localities. However, this species pair underlines the value of morphology with its ventrally turned leaves appearing to be incubously inserted and even somewhat resembling a small brown Bazzania Gray (1821: 704) .

The coordinates were precisely measured in two localities where the subsp. rubidum was collected by authors ( Table 1 ), and, therefore, the climate might be more or less clearly reconstructed by the WorldClim facility (the data are provided in Table 1 ). Both localities are in monsoon climate dominant areas, with about half of the years precipitation falling in the wettest quarter. The absolute volumes of precipitation are noticeable different (868 mm per year in Yunnan Province of China versus 1,929 mm per year in Vietnam locality). The warmest quarter mean temperature is almost the same in the Vietnam and Yunnan localities (near 20°C), whereas the coldest quarter is almost -5°C in the Yunnan locality versus 1.4°C in the Vietnam locality. In general, mean temperatures suitable for subsp. rubidum (based on available and surely incomplete data) are above 7°C and summer temperatures are near 20°C. This feature may identify the general distribution of the taxon in that it could never be recorded in cold climates or high altitudes like Gymnomitrion sichuanicum discussed above, or even hemiboreal and boreal zones in Asia.

Figures

FIGURE 4. Gymnomitrion rubidum subsp. subvittatum Vilnet, Bakalin & D.G. Long: A—plant habit, fragment, lateral view; B—plant habit, fragment, ventral view; C, D—leaves; E—part of leaf base with ‘vitta’ cells. Scales: a—1 mm, for A, B; b—1 mm for C, D; c—100 µm for E. All from Long 34462 (E).

FIGURE 5. Gymnomitrion rubidum subsp. subvittatum Vilnet, Bakalin & D.G. Long: A—mat, dorsal view; B—part of leaf base with ‘vitta’ cells (reddish rusty colored group of cells); C, E—midleaf cells; D—leaf lobe cells. Scales: for A—5 mm; for B–E—50 µm. A, C, D from Long 20655 (E), B, E from Long 34462 (E).

FIGURE 6. Gymnomitrion rubidum subsp. subvittatum Vilnet, Bakalin et D.G. Long: A—plant habit in dorsal and ventral views; B, C—lower part of leaf with ‘vitta’ cells. Scales: for A—1 mm; for B, C—300 µm. A from Long 20655 (E), B, C from Long 34462 (E).