Oxalis xishuiensis Y.B. Yang, M.T. An & H. Li, 2024

Yang, Yan-Bing, Li, He, An, Ming-Tai, Huang, Lang, Hu, Guo-Xiong, Yang, Cheng-Hua & Dai, Zheng-Xian, 2024, Oxalis xishuiensis (Oxalidaceae), a new species from Danxia landforms in Guizhou, China, PhytoKeys 239, pp. 267-273 : 267

Oxalis xishuiensis Y.B. Yang, M.T. An & H. Li sp. nov.

Figs 1 , 2

Type.

China. Guizhou Province, Xishui County, Xishui National Nature Reserve , 28°8'25"N, 105°53'32"E, alt. 1200 m, 10 November 2022, xs2022103 (holotype: GF, isotypes: GZAC) .

Diagnosis.

The new species is most morphologically similar to Oxalis wulingensis , but differs from the latter by its leaf blade ca. as long as wide, obliquely obcordate lateral leaflets (vs. long obtriangular), shorter peduncle (ca. 3-4 cm long, shorter than leaves vs. 10-12 cm long, longer than leaves), longer capsule (1.2-1.5 cm long vs. 0.5-0.7 cm long) and alveolate seeds (vs. only with longitudinally ridge).

Description.

Perennial herbs, 8-15 cm tall; rhizome creeping underground, densely covered by dark brown, scale-like remains of leaf bases, ca. 1 cm thick including scales; scales pilose. Leaves radical, 3-foliolate, the two lateral leaflets arranged at about 180° angle; petioles 4.5-8 cm long, densely covered with white, pubescent over their entire length; lateral leaflets blades obliquely obcordate, 1.4-2.1 × 1.3-2 cm; middle leaflet blades obcordate, 2-3.1 × 1.9-3 cm; leaflets blades adaxially light green to green, abaxially pale green, purple when young; both surfaces white pubescent or adaxially glabrous, apex broadly emarginate, base cuneiform, lobe apices obtuse. Flowers solitary, nodding; peduncles ca. 3-4 cm long, shorter than leaves at flowering time, peduncle much longer than petioles due to pedicel extension at maturity of capsule; bracts at middle of flowering stalk, triangular, ca. 4 mm long, apex bifid with dense trichomes along mid-vein and margins; sepal oblong, ca. 7 × 3 mm, green, surface and margins with some hairs, persistent; petals pink with lilac veins and a yellow patch at base, oblong, ca. 2 × 1 cm, apex obtuse or irregularly denticulate; stamens 10, alternately long and short, the longer ones ca. 1.8 cm, the shorter ones ca. 1.4 cm, all basally connate, filaments purple-red, glabrous, anthers white; pistil ca. 2.1 cm long; ovary glabrous, locules 5, each with a single ovule, styles 5, slender, stigma linear. Capsule erect, cleistogamous capsule with persistent calyx, ovoid to oblong 1.2-1.5 × 0.4-0.5 cm, with five alar ridges; seeds ovoid, ca. 3 × 2 mm, with longitudinally ridge and alveolate on surfaces, dark brown when dry.

Distribution and habitat.

Oxalis xishuiensis is currently only known from Danxia landforms hills in the Xishui National Nature Reserve, Xishui County, Guizhou Province, south-western China. It grows on humid slopes in purple sand shale under the evergreen broad-leaved forest, at an altitude of 1200 m, along with Marchantia polymorpha L., Pteris cretica L., Metathelypteris laxa (Franch. & Sav.) Ching, Trigonotis omeiensis Matsuda, Saxifraga stolonifera Curtis, Carex baccans Nees and Lysimachia paridiformis Franch.

Phenology.

Chasmogamous flowers from February to March; Cleistogamous flowers from May to June. Fruiting from February to July.

Etymology.

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

Vernacular name.

习水酢浆草 ( xí shuǐ cù jiāng cǎo)

Conservation status.

Currently, only one population of the new species with approximately 60 individuals has been found. Danxia landforms are widely distributed in this area, so we speculate that there may be other populations of this new species. Due to insufficient field investigations, the natural range of this species in the wild is unclear. According to the IUCN Red List Categories and Criteria ( IUCN 2022), we recommend this species placement in the 'Data Deficient’ (DD).

Figures

Figure 1. Oxalis xishuiensis Y. B. Yang, M. T. An & H. Li A, B habitat C plants D rhizome E upper surface of leaves F lower surface of leaves G flowering plant H lateral view of the flower I frontal view of the flower J dissected flower K bract L capsule M seeds.

Figure 2. Oxalis xishuiensis Y. B. Yang, M. T. An & H. Li A habit B lower surface of leaves C upper surface of leaves D lateral view of the flower E frontal view of the flower F petals G stamens H chasmogamous capsule I cleistogamous capsule J seeds.