Diplophyllum purpurascens Bakalin et Vilnet, 2020

Diplophyllum purpurascens Bakalin et Vilnet sp. nov.

Description: Plants erect, in loose patches, merely rigid, rusty colored to green brown, commonly with purplish or pinkish apices bearing ill-defined purple masses of gemmae, 0.7–1.5 mm wide and 0.8–2.0 cm long. Stem sparsely laterally (lateral intercalary) branched, brownish to greenish, ventrally brownish to brown and purple-brown, well developed, 150–180 μm in diameter, nearly orbicular in cross section, external wall strongly thickened (to 3 μm thick), outer surface papillose, the outer layer of cells with unequally thickened walls, with moderate in size, concave trigones, 10–12 μm in diameter, inward cell walls become thin, with small to vestigial, concave trigones, 7–12 μm in diameter in dorsal half of the cross section and 5–9 μm wide in ventral half of the section, were densely infected by fungal hyphae. Rhizoids sparse to more or less numerous, their density varying from shoot to shoot, commonly spreading from the stem at right angles near apex and then forming distinct mat on the ventral side of the shoot towards the posterior end of the plant, colorless to light grayish, rarely purplish in basal part, if the stem ventral side is purple-brown in color. Leaves contiguous, rarely somewhat distant, turned dorsally, distinctly sheathing the stem near base, obliquely spreading and keeled above; dorsal lobe narrowly obliquely ovate, its axis ca. 25–30° with the stem axis, 0.4–0.8 × 0.18–0.25 mm, always with narrowly acute apex and roughly and irregularly dentate along outer (dorsal) lobe margin; leaf keel commonly arched, with 20–30° with axis in its lower third to 60–70° with stem axis in its upper third (average is near 45°), not winged, absent in the leaf base (where leaf is sheathing the stem), ca. 1/3 of dorsal lobe length; ventral lobe curved, its axis in 15–20° with stem axis near the leaf base to 90–110° with stem axis in its upper third, lanceolate, 0.6–0.95 × 0.25–0.36 mm, apex always acute, toothed in apical part and outer (the ventral most) side, the inner side not or infrequently toothed, the upper part of ventral margin only weakly toothed, largest and prominent teeth near base. Cells in middle part of outer margin of ventral lobe with thickened walls commonly elongate in direction perpendicular to margin, 5–7 μm along margin, strongly thickened, trigones small, in diameter less than 1/4 of the cell lumen, concave; cells in the middle part of leaf ventral lobe oblong, 4–6-angled, 10–23 × 7–13 μm, thin-walled, with small to moderate in size, concave trigones, with trigone diameter varying from 1/5 to 1/3 of cell lumen; surface papillose in the middle part of leaf ventral lobe, papillae difficult to observe, oblong, 6–10(–14) × 2–4 μm. Gemmae 10–12 μm in diameter, 4–6-angled distinctly thickened, unicellular, greenish to pinkish and purplish. Otherwise unknown ( Fig. 2 View FIGURE 2 , 3 View FIGURE 3 ).

Holotype:— China. Yunnan Province: Dali Prefecture, Jianchuan County, Yang-Cen Xiang , ridgeline of one of the spurs of the Lao-Jun-Shan Range (26°35’41.8”N 99°45’51.6”E), 3380 m a.s.l., broadleaved (evergreen and deciduous) forest along ridge, with some rocky outcrops. Leg. V.A. Bakalin & W.Z. Ma 11 October 2018, С-73-29-18 ( VBGI, GoogleMaps isotypes – KPABG, GoogleMaps KUN). GoogleMaps

Discussion

Scapaniaceae is not a genus-rich family and includes six genera: Diplophyllum (23 species, including data from the present account), Douinia (3 species), Pseudotritomaria (monotypic), Saccobasis (2 species), the species-rich Scapania (ca. 100 species), and Schistochilopsis (9 species) ( Söderström et al. 2016, Bakalin & Klimova 2016, Bakalin & Vilnet 2018). Pseudotritomaria and Saccobasis are restricted to the northern latitudes in the Holarctic, Douinia is generally found in the amphi-Atlantic and amphi-Pacific regions, and Scapania is mainly in the Holarctic, with relatively few representatives in the tropics and extratropical Southern Hemisphere. Schistochilopsis is generally hemiarctic, with a few representatives reaching tropical latitudes in high elevations of mountains in East Asia and even northern Andes in South America. In contrast, Diplophyllum is quite diverse in the Southern Hemisphere, not only in terms of species diversity but also in the subgeneric sense; for example, subg. Austrodiplophyllum (plants with subequally bilobed leaves) is restricted to the Australasia. The morphological peculiarity, ecology and distribution pattern of the genus inspired the concept of Diplophyllaceae as an independent bigeneric (including Douinia ) family by Potemkin (1999), which is, however, not confirmable by genetics. Potemkin (1999) provides data (partly out of date now) showing that 16 of 24 species of Diplophyllum are restricted to the Southern Hemisphere (where many of them are relatively narrowly distributed endemics) and only 8 species are restricted to the Holarctic. Contrary to many other liverwort genera ( Solenostoma Mitten (1864 [1865]: 51), Scapania , Anastrophyllum Spruce (1876: 235) , Frullania Raddi (1818: 9) , etc.) the Sino-Himalaya is not remarkable in the presence of the narrowly distributed Diplophyllum taxa. Diplophyllum trollii (genetically closely related to the amphi-Pacific temperate D. serrulatum ) was previously known as the only taxon restricted to the Sino-Himalaya and the eastern macroslope of the Hengduan range. Diplophyllum purpurascens is another example of the same group of Sino-Himalayan Diplophyllum .

The most distinct and observable feature (even at first glance) of Diplophyllum purpurascens are the pinkish to purplish gemmae; this feature rarely occurs and is usually not described for the genus. In the vast majority of taxa, the gemmae are colorless to greenish, rarely tending to be yellowish, slightly brownish and golden, although the rest of the plant may be distinctly green-brown to yellow-brown. An exception is Diplophyllum sibiricum which does have brown to purplish brown gemmae (Bakalin & Vilnet 2018). Another exception is in the New Zealand D. gemmiparum , which has brownish-orange gemmae. The latter, however, is a New Zealand endemic taxon strikingly different in morphology, especially in its subequally lobed leaves (a feature characteristic of the entirely southern hemisphere subg. Austrodiplophyllum, the taxonomic status of which was never tested genetically). Within the Scapaniaceae , red gemmae are also known in Scapania , Pseudotritomaria and Saccobasis , and the last two genera occupy early diverging positions in the known phylogeny of the family ( Vilnet et al., 2010). Purple and red gemmae also occur in several sections of Scapania , although they are more common (if not dominant) in the subgenera Plicaticalyx Müller (1903: 36) and Protoscapania Amakawa & Hattori (1954: 109); both occupy early diverging positions ( Bakalin et al., 2019; Heinrichs et al., 2012). These colored gemmae in Scapaniaceae may be regarded as plesiomorphic feature in contrast to the general trend of greenish gemmae in all other known genera of Scapaniaceae .

Due to the colored gemmae, Diplophyllum purpurascens can be easily distinguished among the bulk of the Holartic taxa. If gemmae are not available, this species may be misidentified for some other taxa, including 1) D. serrulatum (differs in its sparsely dentate, not serrulate leaf margin, versus serrulate leaf margins in D. serrulatum ), 2) D. trollii (differs in its less well-developed leaf cuticle verrucae and rusty coloration versus verrucose leaf surfaces and greenish coloration in D. trollii ) and 3) D. apiculatum (different from D. purpurascens in its distinct ‘vitta’ area in the ventral leaf lobe; moreover, the occurrence of D. apiculatum is unlikely in the East Asian flora).

The distribution of Diplophyllum purpurascens is greatly restricted as it is only known from one specimen. The species was collected from partly shaded moist cliff crevices in broadleaved forest (both deciduous and evergreen trees dominating), along ridge with some rocky outcrops at the spur of the Lao Jun Shan Range at an elevation of 3380 m a.s.l. The most common liverwort represented in the area is Anastrepta orcadensis , a sparsely distributed (although locally abundant) taxon from mountainous Asia in orotemperate to orohemiboreal regions. Previously we showed that D. trollii , which was known from Abies Miller (1754: 1) - Rhododendron Linnaeus (1753: 392) forests in Bhutan, Nepal, and Sikkim in India and Yunnan in China ( Long, 2005), can also occur in subtropical forests at 1200–1300 m a.s.l. in the Guizhou Province of China (Bakalin & Vilnet, 2018). Diplophyllum purpurascens may belong to that group of taxa, such as D. trollii and many others in Scapaniaceae ( Amakawa, 1964, 1966; Grolle, 1966; Müller, 1905) and in other families of Marchantiophyta ( Bakalin et al., 2018a, 2018b, 2019; Herzog, 1939; Long, 2005; Mitten, 1860; Váňa & Long, 2008, 2009, etc.) which are described from or restricted to the Sino-Himalaya