Pycnolejeunea zhuiana Promma & Chantanaorr., 2025

Promma, Chatchaba & Chantanaorrapint, Sahut, 2025, The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand, with the description of Pycnolejeunea zhuiana, PhytoKeys 259, pp. 145-160 : 145-160

publication ID	https://doi.org/10.3897/phytokeys.259.156710
DOI	https://doi.org/10.5281/zenodo.15786111
persistent identifier	https://treatment.plazi.org/id/89C57BD5-CCB9-501A-856F-0CE66FBC350A
treatment provided by	PhytoKeys by Pensoft
scientific name	Pycnolejeunea zhuiana Promma & Chantanaorr.
status	sp. nov.

Treatment

3. Pycnolejeunea zhuiana Promma & Chantanaorr. sp. nov.

Figs 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7

Type material.

Thailand. Krabi: Hat Noppharat Thara - Mu Ko Phi Phi National Park, Khao Ngon Nak Mountain , 8°5.2767'N, 98°46.47'E, 480 m elev., 15 Feb 2025, C. Promma & K. Chanakarn 20250215-30 (holotype: PSU!; isotypes: BKF!, NICH!) GoogleMaps .

Diagnosis.

Pycnolejeunea zhuiana similar to P. papillosa , but differs in having 1–8 ocelli per leaf lobe, stems in transverse section composed of 9–11 epidermal cells surrounding 13–15 medullary cells and male bracteoles occurring along nearly the whole of the androecial branch length.

Description.

Plants whitish-green or light green when fresh, yellowish-brown or light brown in dry condition; shoots with leaves 0.71–1.32 mm wide; usually scarcely and irregularly branched; branches Lejeunea - type. Stems 117–132 µm diameter, in transverse section with 9–11 epidermal cells, surrounding 13–15 medullary cells, epidermal cells larger than medullary cells; cell walls pale brown or yellowish-brown, thick-walled, with triangular to bulging trigones, wall between trigones with thin to rather thick continuous thickenings; ventral merophyte 2 cells wide. Rhizoids at base of underleaves, few, tufted, usually hyaline, rhizoid disc not seen. Leaves imbricate, wide-spreading when moist. Leaf lobes ovate to oblong-ovate, occasionally falcate-ovate, 563–698 µm long, 429–512 µm wide, dorsal margin broadly arched, ventral margin slightly to strongly arched, margin entire or conspicuously crenulate with projecting cells, apex rounded, incurved. Lobe cells strongly mammillose on dorsal side, thin-walled, with small to large triangular trigones, intermediate thickenings absent or occasionally seen in the basal cells; marginal cells rectangular or quadrate, 12.5–20.5 × 12–18 µm, median cells hexagonal to rounded, 20.5–34.0 × 19.0–27.5 µm, basal cells hexagonal to rectangular, 22.0–42.6 × 20.0–30.5 µm; ocelli rectangular to long hexagonal, 35.0–61.7 × 23.6–36.0 µm, 1–8 per leaf lobe, basal, aggregated or isolated; oil bodies 2–5 per cell, long ellipsoidal to ovoid-cylindrical, 7.0–19.0 × 4.0–7.0 µm, Calypogeia - type, coarsely granular. Lobule small, ovate, 138–170 µm long, 125–156 µm wide, strongly inflated, 0.20–0.25 of lobe length, free margin slightly involute, formed by 5–6 elongated cells, apex semicircular, apical tooth short, obtuse; keel strongly arched, papillose; lobule cells strongly unipapillose. Underleaves contiguous to imbricate, sometimes slightly remote, suborbicular to subreniform, 234–316 µm long, 257–360 µm wide, wider than long, 3.0–3.5 of stem width, bifid to 1 / 3–1 / 2 of its length, lobes triangular with acute to obtuse apex, margin nearly entire, rarely bluntly toothed at side, sinus V-shaped, bases rounded to cuneate, insertion line arched. Asexual reproduction by unmodified caducous leaves, lobules remain attached to the stem. Sexuality autoicous. Androecia on short branches, terminal or intercalary on branches, inflated, spicate, 515–913 µm long, 408–561 µm wide; bracts in 3–5 pairs, densely imbricate, isolobous; bracteoles occurring nearly throughout androecium, composed of 2 (– 3) bilobed bracteoles restricted at the base of the branch and 1–2 reduced once above. Gynoecia on short branches, with 1 subfloral innovation; bracts in one pair, subequal in size, bract lobe obovate, 526–822 µm long, 317–488 µm wide, apex rounded, incurved, margin entire, ocelli 0–14 per lobe, isolated; bract lobules lingulate, narrowly oblong to ovate, 330–442 µm long, 132–258 µm wide, 0.6–0.8 of lobe length, ca. 2 / 3 of the bract-lobe area, apex acute to broadly obtuse, keel slightly arched, short; bracteole shortly connate with the bracts at the base on one side or rarely on both sides, ovate to obovate, 418–587 µm long, 276–409 µm wide, apex usually emarginate or slightly bifid, lobe acute, margin entire; perianths obovate, ca. 0.5 emergent beyond bracts or sometimes almost entirely covered by bracts, 664–921 µm long, 464–624 µm wide, inflated, 5 - keeled, keels crenulate or rough from projecting cells, apex usually truncate, beak short. Sporophytes not seen.

Etymology.

The specific epithet “ zhuiana ” honours Prof. Dr. Rui-Liang Zhu of East China Normal University, Shanghai ( China), who has dedicated his entire life to the study of bryophytes, particularly in the taxonomy and systematics of Lejeuneaceae and the advancement of liverwort research in Asia.

Distribution, habitat and ecology.

Endemic to peninsular Thailand. So far known only from its type locality at Khao Ngon Nak Mountain, Hat Noppharat Thara - Mu Ko Phi Phi National Park, Krabi Province; however, it may also occur in other areas in southern Thailand with a similar vegetation type. Pycnolejeunea zhuiana was found growing on tree trunks in tropical lowland forests dominated by Baeckea frutescens L. , Podocarpus neriifolius D. Don. and Syzygium antisepticum (Blume) Merr. & L. M. Perry ., at elevations of 380– 480 m. It is often found growing in association with Lejeunea flava (Sw.) Nees and P. contigua .

Taxonomic notes.

Pycnolejeunea zhuiana is readily distinguished by a combination of the following characters: ventral merophyte consistently 2 cells wide; oblong-ovate to oblong leaf lobes; strongly mammillose on dorsal side of leaf lobe cells; presence of 1–8 ocelli per leaf lobe which are either aggregated or isolated at the basal region of the lobe; the strongly papillate lobules with 5–6 elongate cells along the free margin; and male bracteoles occurring nearly throughout the androecial branch.

Pycnolejeunea zhuiana can be confused with P. papillosa from tropical America, which also have papillose lobues and unipapillose leaf cells. However, P. zhuiana is distinguished by its larger size and ovate to oblong-ovate leaf lobes, while P. papillosa has smaller shoots and orbicular-ovate leaf lobes. Additionally, P. zhuiana has 1–8 ocelli per leaf lobe, while P. papillosa has only 1–2 (– 3) ocelli per leaf lobe. Pycnolejeunea zhuiana also has male bracteoles almost throughout the androecial branch. In contrast, P. papillosa has only one male bracteole restricted to the base of the branch. The differences between the two species are shown in Table 1 View Table 1 .

With regards to the male bracteole, most species of Pycnolejeunea have only 1 or 1–2 bracteoles per androecial branch and restricted to the base of the androecium. Except for P. macroloba (Nees & Mont.) Schiffn. from the Neotropics, male bracteoles are present throughout the androecium or nearly so ( He 1999). However, P. macroloba differs from P. zhuiana in the larger plant (to 2.5 mm wide), the rectangular lobules (0.5–0.6 of lobe length) with 9–20 elongated cells along the lateral margin and nearly smooth lobule surface.

Additional specimens examined.

Thailand. Krabi: Hat Noppharat Thara - Mu Ko Phi Phi National Park, Khao Ngon Nak Mountain , 8°5.415'N, 98°46.1683'E, 380 m elev., 24 Mar 2018, A. Senayai 64 ( BKF, PSU) GoogleMaps ; 8°5.2767'N, 98°46.47'E, 480 m elev., 9 Apr 2022, S. Chantanaorrapint & A. Chantanaorrapint s. n. ( PSU) GoogleMaps ; 8°5.2767'N, 98°46.47'E, 480 m elev., 15 Feb 2025, C. Promma & K. Chanakarn 20250215-27, 20250215-28 A, 20250215-29, 20250215-31 ( PSU) GoogleMaps .