Mitreola quanruii L.Wu & R.C.Hu, 2023

Hu, Renchuan, Liao, Xiaowen, Luo, Binsheng, Liu, Cheng, Nong, You & Wu, Lei, 2023, Mitreola quanruii (Loganiaceae), a new species from a karst region in Guangxi, China, PhytoKeys 232, pp. 67-75 : 67

Mitreola quanruii L.Wu & R.C.Hu sp. nov.

Figs 1 , 2

Diagnosis.

Mitreola quanruii is most similar to M. liuyanii , but can be distinguished from the latter by its larger plant height up to 20-50 cm tall (vs. up to 9 cm), its linear leaves, 4-18 × 0.3-1 cm (vs. leaves oblanceolate, 0.4-5.6 × 0.2-1 cm) with acuminate apex (vs. apex acute to rounded) and 8-10 lateral veins on each side of the mid-rib (vs. 4-6 pairs), its narrowly triangular stipules (vs. stipules linear), its linear bracts, ca. 1.0 cm long and glabrous (vs. bracts narrowly lanceolate, 2-3 mm long, sparsely pilose on abaxial surface) and its glabrous calyx (vs. abaxial surface of calyx sparsely pilose).

Type.

China. Guangxi Zhuang Autonomous Region: Nandan County, Wuai Town , Tonggong Village , growing in limestone areas, under evergreen broad-leaved forests, rare, 24°54'29.65"N, 107°21'43.83"E, 235 m a.s.l., 31 Mar 2021 (fl.), R.C. Hu HRC210331003 (holotype: GXMI051178!, isotypes: CSFI!, IBK!, GXMI051179!) .

Description.

Perennial herb, up to 20-50 cm tall. Stems terete, creeping, branched at the base, bearing adventitious roots; internodes 1-5 cm long, shoots sparsely pilose. Leaves opposite, papery, linear, 4-18 × 0.3-1 cm, pilose on both surfaces, base decurrent and narrowly cuneate, apex acuminate, margin ciliate, lateral veins 8-10 on each side of the mid-rib. Petioles 3-8 mm long, sparsely pilose. Stipules narrowly triangular, ca. 1 mm long, interpetiolar. Cymes terminal, 2-3-branched, many-flowered; peduncles slender, 3-8 cm long, glabrous; bracts linear, ca. 1.0 cm long, glabrous; bracteoles narrowly triangular, 1-2 mm long, glabrous; pedicels ca. 1 mm long, glabrous. Calyx lobes 5, ovate, ca. 1.3 × 1 mm, glabrous, margin membranous. Corolla urceolate, white, ca. 2 mm in diam. tube 1.3-1.7 mm long; lobes 5, ovate, 1.0-1.3 × 1.3-1.8 mm, glabrous, except for a ring of long hairs at the throat. Stamens 5, inserted near the middle of the corolla tube, glabrous, filaments ca. 0.8 mm long, anthers broadly ovate, ca. 0.3 mm long. Ovary semi-inferior, bilocular, ca. 0.5 × 1.3 mm, ovules numerous per locule; style ca. 1.2 mm long, free at base, stigma capitate. Capsules glabrous, bilobed, connate for 2/3rds of their length, with two erect horns, 1.2-3 mm long, sepals persistent at the base.

Phenology.

Flowering from March to April; Fruiting from May to June.

Distribution and habitat.

Mitreola quanruii is found growing on a watery stone wall near a rivulet, under evergreen broad-leaved forests in the hill region of Nandan County, Guangxi, China.

Preliminary conservation status.

According to currently available data, Mitreola quanruii is only found in its type locality and there are only 63 adult plants and 21 seedlings in an area of ca. 450 m2 (30 × 15 m). Further detailed investigation of similar habitats is needed to give a better understanding of the species’ natural distribution and abundance. Mitreola quanruii is temporarily assessed as data deficient (DD) according to IUCN ( IUCN 2022). At the type locality of Mitreola quanruii , only a small area of native vegetation remains along the creek, surrounded mostly by plantation forests. The habitat of the Mitreola quanruii is extremely fragile. Therefore, this species deserves close attention and protection.

Additional specimens examined.

China. Guangxi Zhuang Autonomous Region: Nandan County, Wuai Town , Tonggong Village , under evergreen broad-leaved forests, rare, 24°54'29.65"N, 107°21'43.83"E, 235 m a.s.l., 27 May 2021 (fr.), R.C. Hu HRC210527003 (GXMI!); ibid., 28 March 2023 (fl.), Y. Nong NY230328 (GXMI!), ibid., 23 April 2021 (fl.), C. Liu 21CS20379 (KUN!) .

Etymology.

We dedicate this new species of Mitreola to Prof. Quanru Liu for his substantial contributions to botanical research and education in China.

Vernacular name.

The Chinese name is proposed as xiàn yè Dù Liáng Cǎo (线叶度量草), which means that the leaves are linear.

Taxonomic notes.

Mitreola quanruii is most similar to M. liuyanii because they share terete stems, creeping and branched at the base, leaves pilose on both surfaces and bilobed capsules with two erect horns. However, M. quanruii is well distinguished from M. liuyanii by its linear leaves, 4-18 × 0.3-1 cm (vs. leaves narrowly oblanceolate, 0.4-5.6 × 0.2-1 cm), with acuminate apex (vs. apex acute to rounded) and 8-10 lateral veins on each side of the mid-rib (vs. 4-6 pairs); its linear bracts (vs. bracts narrowly lanceolate). Additionally, it is morphologically similar to M. pingtaoi in the conspicuous, terete stems, the white corollas, the linear bracts and the capsules with two erect horns, but it differs from M. pingtaoi in having linear leaves, 4-18 × 0.3-1 cm (vs. leaves obovate, 2-8 × 1.2-3 cm), glabrous bracts and calices (vs. bracts and calices tomentose). Morphologically, M. quanruii is easily distinguishable from other species of Mitreola by its linear leaves. A key to the species of Mitreola in China is provided below.

Figures

Figure 1. Mitreola quanruii L. Wu & R. C. Hu. A flowering branch B stipule C top view of flower D longitudinally opened corolla showing the position of the stamens and the hair ring in the throat E ovary, calyx, style and stigma F lateral view of fruit.

Figure 2. Mitreola quanruii L. Wu & R. C. Hu. A habitat B habit C inflorescence D fruiting branch E leaves F lateral view of flower G lateral view of fruit.