Saturday 29 December 2018

Mawenzhangia thamnobryoides: A new species of Moss from Shangri-la.

Mosses (Bryophytes) are simple plants which lack vascular systems to pump water and nutrients from a root system, instead relying on what they can absorb through their leaves, and generally only reaching a few cm in height. This means that they are at their most diverse in moist habitats, though some species are surprisingly drought-tolerant. Despite their simple nature, Mosses are an important part of ecosystems the world over, creating a water-holding layer which covers soil, rocks, trees and some animals, inside which entire miniature communities of organisms thrive. Mosses also differ from vascular plants in that they are haploid (have one set of chromosomes) rather than diploid (have paired chromosomes); though they have a diploid spore stage used to propagate the species in the same way that the (haploid) pollen of vascular plants is.

In a paper published in the journal Phytotaxa on 6 April 2018, Johannes Enroth of the Department of Biological Sciences and Botany Unit at the Finnish Museum of Natural History, James Shevock of the Department of Botany at the California Academy of Sciences, and Michael Ignatov of the Main Botanical Garden of the Russian Academy of Sciences, describe a new species of Moss from the Niru River watershed in the Hengduan Mountains of Shangri-la County in Yunnan Province, China.

The Hengduan Mountains form the southeastern tip of the Himalayas, stretching from eastern Sichuan Province through northern Yunnan and southeaster Tibet into southern Myanmar. The range comprises a series of parallel north-south mountain ridges with south-flowing rivers between. The area is considered to be one of the world's biodiversity hotspots, with sharp divisions in flora and fauna both between the valleys of the range and at different altitudes on the mountains, leading to a very high number of endemic species.

The new species is placed in a new genus, Mawenzhangia, named in honour of Wen Zhang Ma, the Curator of Bryophytes at the Kunming Institute of Botany, and given the specific name thamnobryoides, in reference to the thickened dendroid erect shoots and branches of younger plants. The species was found growing on metamorphic boulders along the banks of the Niru River in a Pine/Oak forest. The individual plants grow up to 5 cm in height, and are yellowish green or brownish-grey and slightly glossy, with branching fronds.

 Mawenzhangia thamnobryoides. (1)−(2) Habit. (3) Portion of flagelliform branch. (4) Portion of leafy flagella. (5) Portion of leaf stipe. (6)−(8) Main branch leaves. (9)−(10) Secondary branch leaves. (11)−(12) Stipe leaves. (13) Perichaetium. (14) Inner perichaetial leaf. (15) Innermost perichaetial leaf with archegonia. (16) Perigonium. (17) Inner perigonial bract. (18) Innermost perigonial bract with antheridia. Scale bars: (a) 0.5 cm (3); (b) 1 mm (14)−(15), (17)−(18); (c) 1 mm (11)−(12); (d) 1 cm (1)−(2) and 1 mm (13), (16); (e) 1 mm (6)−(10); (f) 1 mm (5); (g) 100 μm (4). Enroth et al. (2018).

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