Thladiantha longipedicellata Gao Xie, Ying Qin & Yan Liu, 2022

Xie, Gao, Qin, Ying, Huang, Yu-Song, Guo, Jing & Liu, Yan, 2022, Thladiantha longipedicellata (Cucurbitaceae), a new species from Guangxi, China, Phytotaxa 548 (1), pp. 113-118 : 114-117

Thladiantha longipedicellata Gao Xie, Ying Qin & Yan Liu , sp. nov. ( Fig. 1 )

Type:— CHINA. Guangxi Zhuang Autonomous Region : Baise City , Napo County , Bainan Town , Laohutiao Gorges , elev. 297 m, 22 September 2021, Ying Qin, Gao Xie & Xiao-fei Song ZYA02683 (holotype: IBK, isotype: IBK, PE) .

Diagnosis:—The new species is similar to T. cordifolia ( Blume 1826: 929) Cogniaux (1881: 424) and T. grandisepala Lu & Zhang (1981: 67) in the imbricate bracts in the male inflorescence, but can be distinguished from both species by having vestigial leaves (vs. vestigial leaves absent), male inflorescence shortly racemose or shortly paniculate (vs. racemose), male pedicels 2 to 3 times as long as bracts (vs. nearly as long as the bracts), female styles 3-fid almost to base (vs. to the apex and middle respectively), and apex of fruit rostrate (vs. obtuse).

Vines, climbing, herbaceous. Stems robust, angular-sulcate, at first densely pubescent, glabrescent. Petioles 4–9 cm long, pubescent. Leaf blades narrowly ovate-cordate, 7.5–15.0 × 6.0– 12.5 cm, papery, adaxially scabrous, with setae on an enlarged base, basal vein along margin of base of leaf, abaxially pubescent at first, glabrescent, veins densely pubescent, base cordate, margin dentate, apex shortly acuminate; sinus at base open, semicircular, 1.0– 2.2 cm deep, 1.5–3.5 cm wide; vestigial leaf blade narrowly ovate-cordate, margin revolute, pubescent; tendrils simple, pubescent at first, glabrescent. Male flowers: inflorescences 1–3, inserted at the nodes of old stems, shortly racemose or shortly paniculate; peduncle short, robust, 1.0–2.5(–3.5) cm long, pubescent; bracts imbricate, flabelliform, 10–25 × 6–15 mm, both surfaces pubescent, margin irregularly dentate; pedicels long and slender, (1.8–)3.0–7.0 cm long, 2 to 3 times as long as bracts, pubescent; calyx tube campanulate, 5–8 mm long, 5-partite; segments linear, 10–12 mm long, ca. 1 mm wide, indistinctly 3-veined, apex caudate-acuminate, sparsely pubescent; corolla segments ovate or elliptic, 17–20 × 8–10 mm, apex shortly acuminate or acute; rudimentary ovary semiglobose. Female flowers solitary; pedicels robust, 2.5–4.0 cm long, pubescent; calyx and corolla as in male flowers; ovary narrowly oblong, 6–9 × 3–5 mm, narrow at both ends, pubescent; style filiform, 3-fid almost to base; stigma enlarged, 2-lobed. Fruit: pedicel robust, 1.5–4.0 cm long, pubescent; fruit narrowly oblong, 2.0–3.2 × 1.5–2.5 cm, with 10 raised tumorous ridges, apex rostrate, pubescent at first, glabrescent, blackish green at maturity. Seeds broadly ovate, 4.0–5.0 × 3.0– 3.5 mm, reticulate.

Phenology: —Flowering from July to September, fruiting from September to November.

Notes: — Thladiantha longipedicellata is most similar to T. cordifolia but differs in having vestigial leaves (vs. vestigial leaves absent), male inflorescence shortly racemose or shortly paniculate (vs. racemose), male bracts margin dentate (vs. incised), male peduncle 1–2.5(–3.5) cm long (vs. 4–15 cm), male pedicel (1.8–) 3–7 cm long (vs. ca. 0.5 cm), female style 3-fid almost to base (vs. to apex), fruit with 10 raised tumorous longitudinal ridges (vs. 10 slightly raised longitudinal striae), and apex of fruit rostrate (vs. obtuse). In addition, T. longipedicellata is also similar to T. grandisepala , but the latter species strongly differs in not having vestigial leaves, the length of peduncle and pedicel, the shape of male inflorescence, female style, calyx segments and fruit. A detailed comparison to distinguish the three species is presented in Table 1 .

The male pedicel length in all known species of Thladiantha is mostly between 1–2 cm or shorter, except for 3 species ( T. pustulata (H.Lév.) C.Jeffrey ex Lu & Zhang (1981: 74) , 2–4 cm; T. dubia Bunge (1833: 29) , 1.5–3.5 cm; T. longisepala Lu & Zhang (1981: 86) , 1–4 cm). The longest male pedicel of these species is nearly 4 cm. However, the male pedicel length of T. longipedicellata is mostly between 3–7 cm, which is easily distinguished from other species of Thladiantha . In addition, we found that T. longipedicellata has few leaves during the flowering and fruiting phase, and grows next to the ground in the shade (figure 1A–C). Because of the short peduncle and long pedicel, it seems that male flowers are clustered and apart from bracts (figure 1C–E). We also found that most leaves grow at height, far away from flowers and fruits (figure 1D). Compared with other species of Thladiantha , the leaf growth pattern of T. longipedicellata is unique.

Etymology: —The species epithet is derived from its extremely long male pedicel.

Vernacular name:—RDZṭ瓟 (Chinese pinyin: cháng gěng chì páo).

Distribution and ecology: — Thladiantha longipedicellata is currently only known from the type locality in Napo county, southwestern Guangxi, China. It climbs on trees or grows on shaded rocky limestone, in ravines and under evergreen broad-leaved forests at elevation range of 250– 800 m.

Conservation status: —Although field surveys have been conducted at the Sino-Vietnamese border for more than 10 years, we have not discovered this species until 2021. Up to now, 2 subpopulations (4 mature individuals and 6 mature individuals respectively) were discovered in the Laohutiao Nature Reserve, and more subpopulations of T. longipedicellata could probably be found in similar habitat in surrounding areas in the future. However, the two subpopulations found at present are located at the edge of the Laohutiao Nature Reserve, near to the road and surrounded by cultivated land, so the quality of habitat is continuously declining due to man-made interference (e.g. cultivation, grazing and tree-cutting). Based on current data, its population size is very small, and the area of occupancy (AOO) is restricted. According to Guidelines for using the IUCN Red List Categories and Criteria ( IUCN 2022), the conservation status of T. longipedicellata should be assessed as Critically Endangered (CR) on the basis of the criterion D ( IUCN 2012).

Additional specimens examined (paratypes): — China. Guangxi: Baise City, Napo County, Bainan Town , Naba Village , elev. 790 m, 22 September 2021, Ying Qin, Gao Xie & Xiao-fei Song ZYA02682 ( IBK); Baise City , Napo County , Bainan Town , Laohutiao Gorges , elev. 297 m, 16 September 2021, Ying Qin & Yu-jiao Chen ZYA02425 ( IBK) .

Figures

FIGURE 1. Thladiantha longipedicellata Gao Xie, Ying Qin & Yan Liu (photographs from the type collection). A. Old stems with fruits; B. Old stems with female flowers; C & D. Stems with male flowers; E. Habit (E1, habit with leaves at height; E2, habit with flowers near the ground); F. Male inflorescence; G. Female flower; H. Pistil (side view); I. Pistil (front view); J. Calyx; K. Bract; L. Male flower: corolla segments, calyx, stamens; M.Adaxial and abaxial surface of leaves; N. Fruit; O. Vestigial leaf; P. Seeds; Q. Female flower: corolla segments, calyx, ovary, stigma.