Hydrangea xinfeniae W.B.Ju & J.Ru, 2024

Ru, Jian, Ju, Wen-Bin, Deng, Heng-Ning, Xu, Bo, Zhou, Xiang, Liu, Chuan-Jiong & Huang, Wei, 2024, Hydrangea xinfeniae (Hydrangeaceae), a new species from Sichuan, China, PhytoKeys 238, pp. 65-73 : 65

Hydrangea xinfeniae W.B.Ju & J.Ru sp. nov.

Figs 1 , 2 , 3

Diagnosis.

Hydrangea xinfeniae can be distinguished from the morphologically similar species H. yaoshanensis by the presence of densely hirsute trichomes on branchlets, leaves, peduncles and pedicels; leaf blades that are broadly elliptic to rectangular-elliptic with a nearly rounded base and coarse teeth along the leaf margin, lateral veins 3-4 on each side of the midvein; a corymbose cyme with few, loosely arranged branches and lanceolate bract; calyx tube sparsely covered with hirsute trichomes, with only the edges of the lobes bearing such hairs; a glabrous adaxial surface of the petals, while the abaxial surface is adorned with scattered hirsute trichomes; outer whorl filaments are linear, inner ones are awl-shaped; styles are glabrous, and a nearly superior ovary.

Type.

China. Sichuan Province: Xuyong County, Shuiwei Town, Huagaoxi National Nature Reserve , growing on the moist soil under the broadleaved forest, 28°13′29.97″N, 105°36′40.39″E, alt. 1368 m, 22 Jul. 2023, W.B.Ju & R.Jiang J-1290 (holotype: CDBI!; isotype: KUN!) .

Description.

Shrub, 55-80 cm tall, slightly curved in the upper part, usually prostrate in the lower part. Branchlets densely covered with hirsute trichomes. Leaves papery, opposite; petioles 2-4.5 cm long, densely covered with hirsute trichomes; blades broadly elliptic to rectangular-elliptic, 6-8 cm long, 4-6 cm wide, covered with hirsute trichomes on both surfaces, denser on the abaxial surface, apex acute or shortly acuminate, base entire and nearly rounded, non-decurrent, margin with coarse teeth, midrib and lateral veins conspicuous, raised on the abaxial surface, 3-4 lateral veins on each side of the midvein, not reaching the leaf margin, extending obliquely. Inflorescence corymbose cymose, loosely few branches; bracts lanceolate, 3.5-4.5 cm long, 1.5-1.8 cm wide, covered with hirsute trichomes on both surfaces; peduncle 0.4-1.2 cm long, densely covered with hirsute trichomes. Flower buds ovate; pedicels ca. 2 cm long, covered with densely hirsute trichomes; calyx tube inverted conical, ca. 2 mm long, sparsely covered with hirsute trichomes, lobes 5-6, lanceolate, ca. 2 mm long, with sparse hirsute trichomes only on the margin; corolla blue, lobes 5-6, free, narrowly ovate-triangular, base flat, gradually narrowing towards the apex, ca. 6 mm long, ca. 2 mm wide, slightly inwardly curved at the apex to form a hook, glabrous adaxially, covered with scattered hirsute trichomes abaxially; stamens 10-12 in two whorls, the outer stamens alternate the petals, and the inner stamens opposite the petals; anthers ovoid, longitudinally split; outer whorl filaments are linear, the base sometimes slightly widens, 2.8-3 mm long, inner ones awl-shaped, slightly wider at the base, gradually narrowing upwards, 2.2-2.3 mm long; styles 3-6, ca. 3 mm long, glabrous, ovary nearly superior, with numerous ovules. Berry nearly spherical, 5.5-6 mm in diameter, sparsely covered with hirsute trichomes. Mature seeds not observed.

Phenology.

Flowering from May to June; Fruiting from July to October.

Distribution and habitat.

Hydrangea xinfeniae sp. nov. is found in its type locality, the Huagaoxi National Nature Reserve in Shuiwei Town, Xuyong County, Sichuan Province, China. It grows on moist soils under the broadleaved forest at an elevation of 1200-1300 meters.

Etymology.

The species epithet xinfeniae is in honor of Prof. Xinfen Gao, a distinguished female botanist who made significant contributions to the plant diversity survey of Huagaoxi National Nature Reserve.

Vernacular name.

Simplified Chinese: 信芬常山; Chinese pinyin: Xìnfēn cháng shān.

Additional specimens examined

(paratypes). China. Sichuan Province: Xuyong County, Shuiwei Town, Huagaoxi National Nature Reserve , 28°15′26.33″N, 105°28′58.89″E, alt. 1220 m, 5 Jun. 2015, W.B.Ju J-441 (CDBI); ibid., 28°13′51.04″N, 105°37′3.80″E, alt. 1272 m, 10 Sep. 2023, W.B.Ju & J.Ru J-1374 (CDBI) .

Preliminary conservation assessment.

Based on the currently available survey data, only three relatively small populations have been discovered in Huagaoxi National Nature Reserve. Our knowledge regarding the status and distribution range of populations outside this area is limited. According to IUCN red list categories and criteria ( IUCN 2022), the conservation status of the new species is temporarily assessed as Data Deficient (DD) due to insufficient available data. Further comprehensive surveys in similar environments and neighboring regions are necessary to provide a better assessment of the distribution and abundance of this species.

Figures

Figure 1. Hydrangea xinfeniae W. B. Ju & J. Ru, sp. nov. A plant B leaf adaxial C twig D a branch with inflorescence E flower F petal G stamen H berry. Illustration drawn based on living plants (flower and berry) combined with specimens from the holotype by Zhenlong Liang.

Figure 2. Hydrangea xinfeniae W. B. Ju & J. Ru, sp. nov. A plant B leaves (upper: adaxial, lower: abaxial) C a branch with inflorescence D, E flower F petal (upper: adaxial, lower: abaxial) G stamen H infructescence I young berry J indumentum on different organs, from upper to lower, including old branchlet, young branchlet, petiole, carpopodium, leaf adaxial, and leaf abaxial.

Figure 3. Hydrangea xinfeniae W. B. Ju & J. Ru, sp. nov. in the wild A habit B a branch with inflorescence C fruiting branch.