Liochlaena sichuanica Bakalin et Vilnet, 2018

Bakalin, Vadim, Vilnet, Anna & Ma, Wen Zhang, 2018, Liochlaena sichuanica-a new species from the Tibetan Spur and diversification in Liochlaena (Jungermanniaceae, Marchantiophyta), Phytotaxa 371 (5), pp. 283-292 : 287-290

Liochlaena sichuanica Bakalin et Vilnet sp. nov.

Description. Plants prostrate, closely attached by rhizoids to the substratum, with loosely ascending apices, 2.5−4.5 mm wide and 10−30 mm long (older portions decaying), yellowish greenish to brownish green, become paler on drying, with more deeply colored apical part of leaves near shoot apices. Rhizoids numerous, erect-spreading, forming a mat under the stem, originating evenly from the ventral side of stem, soft, grayish. Stem greenish to brownish; branching seen as subfloral innovations only, of the lateral-intercalary, Plagiochila - type; cross-section of well-developed stems ca 400 μm in diameter, nearly orbicular; cross section of marginal cells with papillae on the external wall, the external wall thicker than the other walls, with moderate sized trigones, the trigones becoming vestigial at the centre of the stem, the cell size nearly the same across the section, slightly larger on the dorsal side of the stem, 25−38 μm in diameter, infested by fungal hyphae irregularly across the cross section. Leaves with plagiochiloid insertion type (insertion line more or less oblique on lateral side of stem, then curved and becoming sub-horizontal dorsally) thus making the dorsal side of the leaf convex, the ventral half canaliculate and upper portion of the leaf concave, leaves contiguous, commonly overlapping 1/3−1/2 of the leaf below, obliquely spreading, obliquely to sub-horizontally oriented, in smaller shoots somewhat laterally appressed to the stem, when flattened nearly ovate to obliquely ovate, 1.5−2.4 × 1.3−1.8 mm, margin entire. Underleaves absent. Midleaf cells thin-walled, sub-isodiametric to oblong, 37−65 × (25−)32−50 μm, trigones large to moderate in size, convex, with a more or less distinct middle lamina; cells along margin 25−50 μm, with thickened external wall, cells near base to 70 × 50 μm, leaf surfaces distinctly papillose at midleaf and at the leaf base, but only slightly papillose or verrucose along the leaf margin. Gemmae sparsely produced, in attenuate, isophyllous tips of shoots, in greenish to yellowish masses, when soaked in water becoming greenish colored, nearly ellipsoidal, 1−2-celled, with mammillae on one or both ends, 15−30 × 12−18 μm. Dioicous. Only unfertilized archegonia seen. Gynoecia terminal on leading axis, with 1(−2) subfloral innovations, freely become gynoecious again, bracts similar to large leaves, bracteole absent. ( Figure 2 )

HOLOTYPE:— China, Sichuan Province, Kangding County, Zheduotang Village, north side of Zheduoshan (29°58'37.4"N, 101°53'05.2"E), 3579 m alt., 13 October 2017, V. A. Bakalin & K. G. Klimova C-39-5-17 ( VBGI, isotypes in KPABG and KUN).

PARATYPES:— China, Sichuan Province, Kangding County, Zheduotang Village, north side of Zheduoshan (29°58'34.9"N, 101°53'06.7"E), 3638 m alt., 13 October 2017, V. A. Bakalin & K. G. Klimova C-39-4-17 ( VBGI, KPABG) ; the same, (29°58’34.9”N, 101°53’06.7”E), 3638 m alt., 13 October 2017, V. A. Bakalin & K. G. Klimova C-40-10-17 ( VBGI, KPABG) ; the same, (29°58’53.1”N, 101°53’11.0”E), 3469 m alt., 13 October 2017, V. A. Bakalin & K. G. Klimova C-38-1-17 ( VBGI, KPABG) .

The ecology of the species is poorly understood due to limited material. All specimens were collected in a narrow altitudinal range covering elevations from 3469 to 3638 m a.s.l. in the narrow valley of a small stream vegetated by fir, birch and rhododendron tree forest with moss cover. Among mosses the dominant species is Hylocomium splendens ( Hedwig 1801: 262–263) Schimper (1852: 153) , a species widely distributed in the Northern Hemisphere. All collections were made from moist boulders (sometimes covered with a thin layer of humus) on steep N-facing slopes. Liochlaena sichuanica formed pure mats but once was observed together with Plagiochila porelloides (Torrey ex Nees 1833: 170) Lindenberg (1840: 61) and Blepharostoma aff. trichophyllum ( Linnaeus 1753: 1135) Dumortier (1835: 18) .

The three existing taxa of Liochlaena are somewhat different in geography and morphology. Liochlaena lanceolata and L. subulata have largely overlapping distributions, but the core areas of both taxa are quite distant from one another. The center of frequency of L. lanceolata is in amphi-Atlantic areas of boreal to temperate Europe and North America. Eastward of this land L. lanceolata is widespread in western parts of European Russia, becoming sparse in eastern European Russia, the Urals and Caucasus, and even penetrating into South Siberia ( Konstantinova et al., 2009). Westward the species goes through North America to the West Coast (from Alaska to California), but does not penetrate East or North-East Asia. On the other hand, L. subulata has a distinct frequency center in boreal to hemiboreal Asia, sparsely penetrating northward to subarctic and southward to oro-temperate and oro-subtropical belts and even the tropics in India (?), Sri Lanka and Thailand. Westward it occurs sparsely in Europe to Italy and France and eastward terminates in the Hawaiian Islands and middle states of the U.S.A. (Minnesota, Missouri) ( Váňa 1973).

The distribution of newly described Liochlaena sichuanica is probably underestimated. It is recorded from Kangding County of Sichuan Province that is situated in the source of a large mountain range that begins at the Tibetan Plateau and goes southeastward as far as northern Indochina. The climate in Kangding is considerably milder both in temperature and moisture conditions than the Tibetan Plateau. The data provided for Kangding (Climate-data.org: https://en.climate-data.org/location/1062473/) estimates yearly precipitation is approximately 824 mm, with a distinct maximum from June to September and relatively slight variation in temperature, from -1.3° C in January to 15.5° C in July, with an annual mean temperature of 7.5° C. The aforementioned data are for Kangding town, located at an elevation near 2600−2700 m a.s.l., whereas our collections were gathered at an elevation near 3500 m a.s.l., where considerable changes occurs in vegetation (oro-boreal coniferous forests are well developed), air moisture (becoming higher and distinctly influencing the vegetation) and temperatures (become lower). Although preliminary, we estimate the annual temperature of the collecting site to be near 4−5° C and annual precipitation near 1500−2000 mm, with a snowy period from November to March (the permanent snow cover occurs in mountains nearby to collecting localities starting from ca. 5000 m a.s.l.). These characteristics are nearly comparable with those occurring in the oro-boreal belt of the middle part of the Korean Peninsula, at elevations near 1500−1800 m a.s.l. (e.g. at 38°N in Sarak-san National Park in the northern part of South Korea), where L. subulata is quite abundant. Therefore there are no unique environmental characteristics of the L. sichuanica locus classicus, other than florogenetic features.

In terms of geomorphology, the aforementioned range going from the Tibetan Plateau is a continuation of the Tibetan Plateau itself, whereas in terms of phytogeography it occupies quite a different position, resembling that of the Himalaya bounding the Tibetan Plateau on its southern extremes. Indeed, the Tibetan Plateau is characterized by a dry and relatively cold and continental climate, whereas the southern macro-slope of the Himalaya has a mild and humid climate that provides conditions for the development of a broad water-dependent flora in mid- to high elevations. This circumstance permits the Himalayan taxa to spread widely southeastward by the mountainous continuation of the Tibetan Plateau and to reach northern Indochina. The latter phenomenon was first evaluated on liverwort material by Kitagawa (1988) and then discussed by Bakalin et al. (2018) who proposed the term meta-Himalayan for taxa of such distribution.The most striking examples of the latter element includes Bazzania himalayana ( Mitten 1860:105) Schiffner (1899: 132) , Cephalozia conchata ( Grolle & Váňa 1992: 3) Váňa (Shaw et al. 2015: 38), Delavayella serrata Stephani (1894: 211) , Lophocolea sikkimensis ( Stephani 1922: 349) Herzog & Grolle (1958: 164) , Scapania ciliatospinosa Horikawa (1934: 222) and many others that spread southeastward as far as northern Indochina. Moreover, this ‘route’ may not be the only way for migration, but also the way for speciation. One example of the latter may be Liochlaena sichuanica , described here. We may speculate that it is a derivative of a much more widely distributed L. subulata (the situation seems to be the same with L. lanceolata that is a possible diploid derivate of L. subulata , but distributed more widely than L. sichuanica ). The latter certainly does not mean that L. sichuanica is distributed more widely than it is now known, although such probability exists. Three years before Bakalin et al. (2015) published a floristic account on a collection from Guizhou Province of China with a record of L. subulata , all known gatherings were from an area of wide distribution of basic rocks. In the course of the present study we again investigated the specimens upon which the previous study was based and we found that at least morphologically they belong to ‘true’ L. subulata , not to L. sichuanica . This circumstance inclined us to treat the new species as a possible local endemic (although locally abundant due to obtained data). We did not see other specimens or reports of both L. subulata and L. lanceolata from such high elevations (3500−3700 m a.s.l.), with the possible exception of records from Western Himalaya ( India: Váňa, 1973) where elevation is difficult to estimate since the label does not provide the exact location.

The present distribution of Liochlaena sichuanica may be a result of recent speciation (this explanation has a low probability of being correct due to the strong divergence in the DNA data) or a result of ancient area reduction. The latter hypothesis, based on the refugial value of the Tibetan spur during drastic climate and biota changes starting from the Tertiary, finds confirmation in Takhtajan (1986) who listed 27 endemic genera, but estimated that there were probably more vascular plants for that region, with most of them being restricted to mountainous areas in the southeastern Tibetan spur.

Morphologically, Liochlaena sichuanica has evident similarity with both L. subulata and L. lanceolata . Due to the large leaf cells, L. sichuanica resembles L. lanceolata . The size largely overlaps in L. sichuanica and L. lanceolata but being slightly larger in L. sichuanica and neither seems to produce gemmae very often. The two taxa however differ in sex organ distribution and leaf surface features. Liochlaena lanceolata is a paroicous species, although sometimes highly protandrous as Váňa (1973) noted, whereas L. sichuanica is most probably dioicous. Indeed we did not observe androecia at all, but we found several successions of unfertilized (and perianth-less) gynoecia, each with a subfloral innovation that produced gynoecia, that again were never fertilized. Another difference is in the leaf surfaces that in L. lanceolata are commonly smooth or obscurely verrucose in the midleaf and slightly papillose at the base, while in L. sichuanica they are densely papillose throughout the leaf. Similarly, the stem is smooth in L. lanceolata , but papillae are common on the stem of L. sichuanica . Minor differences may be found in the gemmae that are slightly smaller than those in L. lanceolata (15−30 × 12−18 versus 25−30 × 18−20 μm) and about 50% of them are unicellular, versus predominantly bicellular in L. lanceolata .

Liochlaena sichuanica differs from L. subulata in cell size and surface ornamentation. Cells at mid-leaf in L. subulata are 25−40 × 25−35 μm; that is at the lower limit for L. sichuanica which commonly has cells larger than 35 × 35 μm. The leaf surfaces of L. subulata are virtually smooth to scarcely papillose, never regularly papillose as in L. sichuanica . While L. sichuanica preserves green and yellowish green in the herbarium, the plants of L. subulata commonly become sepia to pale brown soon after drying.

One more thing needs to be discussed in the context of distribution of Liochlaena taxa. Váňa (1973) reported two specimens from South Asia ( India and Sri Lanka), both, as he wrote, were previously identified as ‘ Jungermannia lanceolata ’ auct. Unfortunately we were not able to examine these cited collections, but we found another specimen in TNS, previously named as Jungermannia sp. , collected in Indian Nainital (ca. 1500–2000 m a.s.l.) (“Kumaon Hill; on moist surface of rocks; coll. S. D. Tewari, 20 May 1982 ”; TNS-064503). The plants in the specimen belong to Liochlaena , however we are not able to identify the species with confidence. The leaf cells are large and comparable in size with those in L. lanceolata or L. sichuanica . The specimen differs from L. sichuanica in having completely smooth leaf surfaces that should refer the plants to L. lanceolata . The specimen is too old to test genetically and either it belongs to L. lanceolata or, if it belongs to another undescribed species of the genus, additional study is needed.

Figures

FIGURE 2. Liochlaena sichuanica Bakalin & Vilnet: 1—plant habit, dorsal view; 2—gemmae; 3—stem cross section, fragment; 4—cells in midleaf; 5—cells along leaf margin; 6—cells in midleaf, showing papillae; 7–10—leaves. Scales: a—1 mm, for 1; b—100 μm, for 2; c—100 μm, for 6; d—100 μm, for 3-5; e—1 mm, for 7-10. All from holotype, C-39-4-17 (VBGI).