Peliosanthes crassicoronata K.S.Nguyen, Aver. & N.Tanaka, 2020

Nguyen, Khang Sinh, Averyanov, Leonid V., Tanaka, Noriyuki, Quang, Bui Hong, Hai, Do Van, Binh, Tran Duc & Qao, Qi, 2020, Peliosanthes crassicoronata (Asparagaceae), a new species from southern Vietnam, Phytotaxa 429 (1), pp. 39-47 : 41-43

Peliosanthes crassicoronata K.S.Nguyen, Aver. & N.Tanaka , sp. nov. ( Fig. 1 )

Type:— VIETNAM. Central Highlands, Gia Lai Province, K’Bang District, Son Lang Commune, Kon Chu Rang Nature Reserve, primary evergreen broad-leaved submontane forest mixed with conifers on non-limestone substratum at elevation of 850 m a.s.l., around point 14.49900°N 108.56561°E, 26 July 2017, Nguyen Sinh Khang, Bui Hong Quang, Do Van Hai, Duong Thi Hoan, Tran Duc Binh, Doan Hoang Son, NSK 964 (holotype HN 0000074116!, isotype LE 01058142!).

Paratypes:— VIETNAM. Central Highlands, Gia Lai Province, K’Bang District, Son Lang Commune, Kon Chu Rang Nature Reserve, primary evergreen broad-leaved submontane forest mixed with conifers on non-limestone substratum, at elevation of 927 m a.s.l., around point 14.52014°N 108.54867°E, 20 September 2017, Bui Hong Quang, Do Van Hai, Le Ngoc Han, Tran Duc Binh, KCR 361 ( HN 0000074117!, HN 0000074118!).

Description: ―Herb terrestrial, acaulescent, rhizomatous, evergreen, perennial. Rhizome almost horizontally creeping, subterete, (3–)4–6(–7) cm long, (6–) 7–9 mm in diameter, simple or rarely branched, bearing numerous roots. Roots cordlike, semi-ligneous, 10–18 cm long, 2–3 mm in diameter. Apical part of young stem bears leaf petioles and peduncle covered with 7–9 imbricate sheath leaves. Sheath leaves ovate, lanceolate, linear-lanceolate or ensiform, 1–4.5 cm long, 8–12 mm (when flattened), subacute or blunt, concave or convolute, membranous along margins, light green, soon become disintegrated into fibrous remains. Leaves basal, tufted, erect, to 97 cm long, petiolate; petioles rigid, straight, (47–)50–54(–56) cm long, (4–) 4.5–5.5 mm in diameter; blades narrowly elliptic, elliptic-oblanceolate or oblanceolate, (33–)35–38(–41) cm long, (7.5–)8–10(–10.5) cm wide, base attenuate, oblique, margins entire, apex acuminate, longitudinally somewhat plicate, slightly revolute laterally, adaxial side green, glossy, abaxial side paler, longitudinal veins (35–)42–48(–49), transverse veinlets distinct, numerous, closely spaced with intervals mostly (0.5–)0.7–1.5(–2.0) mm, slightly oblique to longitudinal veins. Flowering stem (including peduncle and inflorescence rachis) suberect or sigmoidally ascending, shorter than half of leaf petiole, (11.5–) 20–22.5 cm long. Peduncle terete, (3.5–) 5.5–7.5 cm long, 2–3 mm in diam., light brownish to white, pale green or dark purple, bracteate; sterile bract 1 (excluding those congested at base), ascending, narrowly deltoid, 12–15 mm long, 5–7 mm wide at base, margins membranous, undulate, apex acute, dull white or brownish, scarious. Inflorescence racemose, densely many-flowered, (8–) 14.5–16.5 cm long, about twice longer than peduncle. Pedicels slightly curved downward, terete, (1.5–) 2–3 mm long, 1.3–1.5 mm in diam., purple to dark violet. Floral bracts 2 at basal portion of pedicel, narrowly to broadly triangular-ovate, cymbiform, unicostate, scarious, margins entire, somewhat undulate, apex acuminate to caudate, white or dull purplish, midvein greenish; the lower bract larger, (6–)8–10(–12) mm long, (3–)4–5(–6) mm wide near base, descending; the bracteole (3–)4–5(–6) mm long, (2–)2.5–3.0(–3.5) mm wide, ascending. Flowers 40– 60 per rachis, acropetally blooming, solitary in axils of bracts, pedicellate, cernuous, buds subglobose, open flowers crateriform, (9–)10–11(–12) mm in diam., 5–6(–7) mm high; perianth fleshy, 6-cleft, abaxially greenish purple or dark violet, adaxially purple or dark violet; proximal tubular part broadly crateriform, (6–)6.5–7(–7.5) mm in diam., (1.5–) 2–2.5 mm high; perianth segments 6 in 2 whorls of 3, broadly ovate to nearly orbicular, abaxial side slightly concave, medially furrowed, adaxial side somewhat convex, 4.5–5.5(–6) mm long, 5.0– 5.5 mm wide, 0.8–0.9 mm thick, margins entire, apex nearly rounded. Corona broadly hemispheric, hexagonal at base, (5.5–)6–6.5(–7) mm in diam., 2.7–3.2 mm high, fleshy, purple or dark violet, conspicuously ribbed below anthers, ribbed portions transversely rounded, 2.0– 2.5 mm thick at base; orifice 2–2.5(–3) mm in diam., shallowly 6-lobed. Stamens 6; anthers ellipticovate, 0.9–1 mm long, 0.7–0.8 mm wide, sessile, dorsally attached to upper inner portion of staminal corona, bilocular, slightly introrse, brownish yellow. Pistil 1, tricarpellate, almost superior, conoid-pyramidal, proximally hexagonal, apex obtuse or subtruncate, 2.8–3.0 mm high, 2.0– 2.5 mm in diam. at base, pale green, minutely speckled with purple, three ridges decurrent from stigmas purple; ovary hexagonal, 3(–5 or 6)-lobed, 3-locular; ovules 3–5 per locule, borne at base of central axis of ovary, suberect, oblong; style conoid, indistinct; stigma tripartite, 0.6–0.7 mm wide, lobes narrowly elliptic, 0.3–0.5 mm long, 0.15–0.25 mm wide, almost horizontal or slightly decurved, finely papillose. Immature seeds pyriform or ovoid, 1.5–1.7 cm long, 0.9–1.1 cm in diameter, testa green, glossy.

Etymology: ―The specific epithet refers to the incrassate staminal corona.

Habitat and phenology: ―The new species grows at wet places near streams in a primary evergreen broad-leaved submontane forest mixed with conifers developed on a non-limestone parental rocks at elevations 800–1000 m. a.s.l. It flowers from July to August, and fruits from September to November.

Distribution and conservation status: ― Peliosanthes crassicoronata is currently known only from its type locality at Kon Chu Rang Nature Reserve in Gia Lai Province. Approximately 20 individuals occur sporadically in the protected areas of the same nature reserve where any agricultural activities and exploitation of non-timber forest products are prohibited. Since our knowledge on the distribution and the mode of occurrence of the species is currently very limited, the conservation status of P. crassicoronata is assessed here as Data Deficient (DD), following the guidelines in the IUCN Red List Categories and Criteria version 13 ( IUCN 2017). There seems to be the strong possibility that some more populations of this species will be found in the future especially on high mountains of Kon Ka Kinh Nature Reserve, Ngoc Linh Nature Reserve, Chu Mom Ray National Park National Park and Chu Yang Sin National Park in Gia Lai, Kon Tum and Dak Lak provinces in the central highlands of Vietnam, as these areas resemble the type locality in vegetation, flora, climate and some other environmental edaphic one.

Similar species: ― Peliosanthes crassicoronata appears closely related to P. macrostegia ( Averyanov et al. 2016 a, Tanaka 2018) in having drooping bowl-shaped purplish flowers with a hemispheric corona, but differs mainly by its larger leaves reaching nearly 1 m in length (vs. up to 0.7 m), blades with more longitudinal veins (35–49 vs. 13–28), corona internally thickly ribbed (vs. not markedly ribbed), and by the conoid (vs. distally acuminately narrowed) pistil with a hexagonal (vs. trilobed) ovary and a less distinct style. The new species also appears close to P. yunnanensis Wang & Tang (1978: 254 ; see Peng & Zhang [2016] for the correct authorship) distributed in southern China ( Chen & Tamura 2000) and northern Vietnam ( Nguyen et al. 2017), but is distinguished chiefly by the larger leaves (petiole 47–56 vs. 15–26 cm long in material from Vietnam; blade 33–41 × 7.5–10.5 vs. 25–35 × 3–5.5 cm in material from Vietnam) with more longitudinal veins (35–49 vs. up to 20), staminal corona internally with incrassate rounded (vs. subacute or angulate) ribs, shorter anthers (0.9–1 vs. 2 mm long), and the pistil with a hexagonal ovary (vs. distinctly 6-lobed) and a less indistinct style. It may also look somewhat similar to P. macrophylla Wall. ex Baker (1879: 505) from northeast India, Nepal and Bhutan ( Hara 1978, Noltie 1994, Roy et al. 2017) in having large leaves (to about 1 m vs. to 1.3 m or longer), but differs principally in its leaves with fewer longitudinal veins (35–49 vs. over 50), more distinct, much closer (usually less than 2 vs. more than 8 mm), near horizontal (vs. oblique) transverse veinlets, shorter peduncle (to 7.5 vs. to 37 cm), shorter anthers (0.9–1 vs. 1.5–2 mm long) and less distinct styles. Some diagnostic characters in P. crassicoronata and species dealt with in phylogenetic analysis ( Fig. 2 ) are compared in Table 1.

Phylogenetic relationships: ―The combined matrix had 2923 aligned characters (ITS 782 bp, trn L-F 945, rbc L 1196). Out of 139 variable characters, 39 were parsimony informative, including 7 indels. Maximum parsimony (MP) generated only a single phylogenetic tree 158 step long.. Both methods returned the same phylogenetic tree in terms of topology and branching ( Fig. 2 ). The phylogenetic tree obtained, like that presented by Wang et al. (2014), did not solve the relationships among Ophiopogon Ker Gawler (1807 : t. 1063), Liriope Loureiro (1790: 200) and Peliosanthes because of weak bootstrap value (under 50%). However, in our tree, Ophiopogon diverges earlier with respect to both Liriope and Peliosanthes , a result that is in agreement with the result obtained by Tamura et al. (2004), who also found this kind of relationship with a moderate support using mat K and rbc L. The seven species of Peliosanthes ( Fig. 2 ) branched out as a monophyletic clade from the sister clade of Liriope . Phenotypically Peliosanthes is deemed as monophyletic, as its species share monadelphous stamens, a state that is undoubtedly apomorphic. Thus both molecular data and phenotypic observations are congruous in supporting the monophyly of Peliosanthes . Within the clade of Peliosanthes , P. sinica Wang & Tang (1978: 253 ; see Peng & Zhang [2016] for the correct authorship) and P. teta Andrews (1810 : t. 605) together diverged from the sister clade constituted by the five other species of Peliosanthes . Both P. sinica and P. teta appear phenotypically fairly distinct from the other five species in having a typical repent stem or multiple flowers in the axils of bracts, respectively. In this regard, the phyletic segregation of P. sinica and P. teta from the other five species appears plausible, although presently we find no particular synapomorphy for the clade reuniting these two species. As for the clade of the other five species, the data suggest with the strong support of bootstrap values (100% for both MP and ML) that P. crassicoronata is a distinct species and sister to the clade containing P. macrophylla , P. ophiopogonoides Wang & Tang (1978: 253 ; see Peng & Zhang [2016] for the correct authorship) and P. yunnanensis . It is noteworthy that P. macrostegia separated earlier than the other four species did, as it appears to display plesiomorphic states of some phenotypical characters with respect to the other four species. For instance, each of the four species shows apomorphic character-states (autoapomorphies) with respect to P. macrostegia in the following traits: thickly ribbed staminal coronas in P. crassicoronata (vs. indistinctly ribbed coronas in P. macrostegia ); leaves with extremely numerous longitudinal veins in P. macrophylla (vs. 13–28 in P. macrostegia ); leaves with oblique transverse veinlets in P. ophiopogonoides (vs. near horizontal in P. macrostegia ); markedly 6-lobed ovary in P. yunnanensis (vs. 3-lobed ovary in P. macrostegia ). Although synapomorphies characterizing this clade are currently unknown, it appears likely that these four species, acquiring their own specialized traits, separated later. The branching pattern (or topology) of the lineages may change to some degree if more samples of other species would be added to the phylogenetic analysis. Accordingly, it is recommended to undertake further analyses of DNA sequences on more species to elucidate better the phylogenetic relationships within the genus.

Figures

FIGURE 1. Habit and organs of Peliosanthes crassicoronata (NSK 964). Photos by K.S. Nguyen; layout by L. Averyanov and T. Maisak.

FIGURE 2. Phylogenetic tree of Peliosanthes crassicoronata and its related species and genera based on maximum parsimony (MP) and maximum likelihood (ML) analyses. Numbers above branches are MP (left) and ML (right) bootstrap values.