Perilimnastes nana C.Y.Zou & Ying Liu, 2024

Liu, Ying, Dai, Jin-Hong, Zhuang, Qi-Yuan, Zou, Chun-Yu & Ma, Kai-Nan, 2024, Resurrection of Perilimnastes (Sonerileae, Melastomataceae) with description of a new species P. nana, PhytoKeys 238, pp. 11-31 : 11

Perilimnastes nana C.Y.Zou & Ying Liu sp. nov.

Figs 6 , 7

Type.

China. Guangdong Province: Taishan County, Chixi Town, near Zhuxing Village , 200-300 m elevation, amongst rocks along a stream in forests, 15 Jun 2022, Chun-yu Zou 3608 (holotype: IBK; isotypes: IBK, PE) .

Diagnosis.

Resembles P. stenophylla in leaf morphology, but differs in height (to 0.15 m vs. 0.8 m tall), number of flowers per inflorescence (1 vs. 2-3-flowered), length of the peduncle (10-22 mm vs. 4 mm) and the shape of calyx lobes (broadly obovate vs. narrowly triangular). Resembles P. setotheca in having 4-sided branchlets, large and persistent bracts below flower and stamen morphology, but differs in plant size (to 0.15 m vs. 1 m tall), leaf shape and size (oblong-lanceolate or obovate-lanceolate, 1.7-7 × 0.73-2.2 cm vs. oblong-lanceolate, elliptic or obovate, 10-20 × 3-8 cm) and number of flowers per inflorescence (1-flowered vs. 3 to more than 20-flowered).

Description.

Dwarf shrubs, much-branched, ascending, to 0.15 m tall, with druses in many parts. Stems and leaves sparsely puberulent with minute brown hairs (with few-celled stalk and a glandular head) when young, glabrous when mature. Stems obtusely 4-sided; branchlets 4-sided, with four ribs and two additional ridges extending from the base of the leaf petioles. Leaves opposite, equal to subequal in a pair, glabrous when mature; petiole 2-22 mm; leaf blade oblong-lanceolate or obovate-lanceolate, 1.7-7 × 0.73-2.2 cm, thick papery, 3-veined, green to dark green adaxially, pale green abaxially, base cuneate, apex acute, margin basally entire and remotely denticulate to repand above the base or the middle. Inflorescences terminal, peduncles 1-2.2 cm long; flower solitary, subtended by one or two pairs of leaf-like bracts, bracts 1-1.8 × 0.7-0.9 cm, persistent in fruit. Flowers 4-merous; pedicel 4-sided, ca. 4 mm long in flower and 4-10 mm in fruit; hypanthia funnel-shaped, glabrous, ca. 7 × 6 mm; calyx lobes 4, broadly obovate, glabrous, 4-5 × 5 mm; petals pinkish-purple, ca. 15 × 7 mm, obovate, oblique, apex acute or short acuminate, glabrous on both sides; stamens 8, isomorphic, filaments 8-10 mm long, white or pink, glabrous, anthers ovate-lanceolate, curved to ventral side, pinkish-purple with yellow base, ca. 9 mm long, connective dorsally forming a 0.7-1 mm long spur and ventrally forming two yellow ridges; ovary ca. 3 mm long, half as long as hypanthium (crown excluded), ovary crown wedge-like, 4-lobed; styles 20 mm long. Old (post-mature) capsules cup-shaped, 7-9 × 4-7 mm, 4-sided; hypanthium 8-ribbed; crown enlarged and enclosing an obpyramidal space; placental column unbeaked, 4-horned; placenta thready.

Phenology.

Flowers in May and June, old capsules in October.

Etymology.

The specific epithet is based on the habit of this species, viz. dwarf shrubs to 15 cm tall.

Distribution.

Perilimnastes nana is currently known from Taishan County, Guangdong Province, China (Fig. 8 ). It grows amongst rocks along streams in the forest, at 200-300 m elevation.

Notes.

During a survey of herbarium specimens of Phyllagathis in IBSC, a collection (Ze-xian Li et al. 516) from Taishan, Guangdong, China caught our attention. This plant ( P. nana ) closely resembles P. stenophylla from Hainan Island in the oblong-lanceolate leaf blades and was misidentified as the latter species. Closer inspection reveals that it has strictly 1-flowered inflorescences and broadly obovate calyx lobes, which distinguishes it from P. stenophylla . Field trips in 2022 and 2023 revealed other differences between the two species, such as plant size and peduncle length. Perilimnastes nana is phylogenetically closest to P. setotheca , a species found in Guangdong, Guangxi and Hainan China (Fig. 8 ). However, they differ markedly in plant size, leaf shape and size and number of flowers per inflorescence. As a result, P. nana is quite distinct from its closest relatives, prompting us to describe it as a new species.

Additional specimen examined.

China. Guangdong Province: Taishan County, Chixi Town, Zhuxing Village, 220 m elevation, 17 Oct 2023, Ying Liu 892 (SYS); Taishan County, Chixi Town, Liugushan, 8 May 1981, Ze-xian Li et al. 516 [IBSC (IBSC0223903)].

Figures

Figure 6. Holotype of Perilimnastes nana, Chun-yu Zou 3608 (IBK). The insets show details of leaf surface under stereoscope, branchlet and flower. Scale bars: 10 cm, 1 mm (upper right inset); 3 mm (lower insets).

Figure 7. Perilimnastes nana A habitat B habit C close-up of a branchlet D adaxial leaf surfaces E abaxial leaf surfaces F a flowering branch showing an inflorescence with a single flower and two large bracts G lateral view of a flower H longitudinal section of a flower showing stamen morphology I lateral view of an old capsule with one persistent bract removed J longitudinal section of an old capsule showing enlarged ovary crown and morphology of the placental column and placentas. Scale bars: 5 mm (G-I); 3 mm (J). All from Chun-yu Zou 3608 (IBK, PE).

Figure 8. Distribution of Perilimnastes nana (solid circle), P. setotheca (triangle) and P. stenophylla (square).