Dysosma xishuiensis Y. B. Yang, M. T. An & C. H. Yang, 2025

Dysosma xishuiensis Y. B. Yang, M. T. An & C. H. Yang sp. nov.

Fig. 2 View Figure 2

Diagnosis.

Dysosma xishuiensis is morphologically most similar to D. versipellis in its stems (erect, unbranched, glabrous), leaves (alternate, blade suborbicular, to 25–30 cm in diam, palmately lobed), flowers (attached near base of blade, red), but differs by the following characters: leaf abaxial surface, pedicels, and sepals glabrous (vs. pubescent); inflorescences bearing more flowers (8–20 vs. 5–8); larger obovate-oblong petals (2.8–3.4 × 1.5–2.0 cm vs. 2.5 × 0.8 cm); and ovary obpyriform (vs. ellipsoid).

Type.

China • Guizhou, Xishui County, Sanchahe Town, Xishui National Nature Reserve , alt. 975 m, under broadleaf forest beside the stream of Danxia landform, 20 May 2022, Yan-Bing Yang, Cheng-Hua Yang & He Li ( holotype: GF!; isotype: GZAC!) . • Xishui County, Tucheng Town, Tongyi Village , Xishui National Nature Reserve , alt. 1168 m, in the middle of a mountain under broadleaf forest of Danxia landform, 22 May 2022, Cheng-Hua Yang, He Li & Mao Li C 1031 ( isotype: KUN!) .

Description.

Herbs, 80–120 cm tall. Rhizomes stout, densely fibrous. Aerial stems erect, pale green, unbranched, glabrous. Leaves alternate; petioles of lower leaves 10–20 cm, upper leaves ca. 3 cm; leaf blade suborbicular, up to 25 cm in diameter, thinly papery, glabrous on both surfaces, abaxially with prominent venation, palmately 5–8 - lobed, lobes deeply divided (ca. 2 / 3 of radius); lobes obovate to obovate-oblong, margins remotely serrate, apex shallowly 3 - lobed or bearing 2–3 mucronate teeth. Inflorescence an 8–20 - flowered fascicle. Pedicels pendulous, slender, glabrous. Flowers dark red, attached near leaf base. Sepals long-elliptic, 1.5–2.0 × 0.5–0.8 cm, glabrous, apex acute. Petals oblong-obovate, 2.8–3.4 × 1.5–2.0 cm, glabrous. Stamens ca. 2 cm; filaments shorter than anthers; anther connective slightly prolonged, glabrous, acute. Pistil ca. 1.5 cm; ovary obpyriform, glabrous; style ca. 0.3 cm; stigma shield-shaped. Berry ellipsoid. Seeds numerous.

Phenology.

Flowering from April to June, fruiting from June to September.

Distribution and habitat.

Dysosma xishuiensis is only known from two localities in Xishui County, Guizhou, China, where it grows under the broadleaf forest by the stream or in the middle of a mountain of Danxia landform.

Preliminary conservation status.

Currently, Dysosma xishuiensis is documented exclusively in two discrete populations within Xishui National Nature Reserve. These populations occur in mid-subtropical to warm temperate zones characterized by a humid monsoon climate. The species exhibits a restricted distribution range, with both populations each comprising fewer than 100 mature individuals. In accordance with the International Union for Conservation of Nature (IUCN) Red List criteria B 2 (a, b (iii )) (extent of occurrence < 500 km 2, fewer than five locations, continuing decline in habitat quality) and D (population size <250 mature individuals), we propose that D. xishuiensis be designated as Endangered ( EN) ( IUCN 2022).

Etymology.

The species epithet “ xishuiensis ” refers to the type locality of the new species.

Vernacular name.

The Chinese name is “ xí shuĬ bā jiăo lián ” (习水八角莲).