Stellaria abaensis H. F. Xu & Z. H. Ma 2018, sp. nov.
Creators: name: Xu, Han-Feng
name: Ma, Zhong-Hui
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Caryophyllales
Caryophyllaceae
Stellaria
Stellaria abaensis

description: Stellaria abaensis H.F. Xu & Z.H. Ma, sp. nov. (Fig. 1–3, Table 1)
Type:— CHINA. Sichuan: Xiaojin county, Rilong town, 2 km from the gate of national nature reserve Mountain Siguniang, 3450 m, 102°52’32” E, 31°02’51” N, 16 September 2017, Xu SC0038 (holotype GAUA!).
Paratypes:— CHINA, Sichuan: Maomuchu Village, at roadside, 3207 m, 102°28’58” E, 31°48’30” N, 7 September 2017, Xu SC0007 (GAUA!).
Diagnosis (Table 1):— Stellaria abaensis is similar to S. media from which differs by glabrous stem (vs. 1 line of hair), blade margins shortly ciliate (vs. glabrous), glabrous pedicel (vs. 1-line hairy) and sepals (vs. glandular-pubescent), and undulate tuberculate seeds (vs. semiglobose-tuberculate). Moreover, S. abaensis is similar to S. reticulivena it can be distinguished by the latter in having terete-glabrous stem (vs. quadrangular-pilose stem), long pedicel (vs. sessile pedicel), 6-valved to base capsule (vs. 6-valved to middle capsule), and undulate tuberculate seeds (vs. inconspicuously muriculate seeds).
Description (marco-morphology) (Figs. 1–2):—Herbs annual. Stems 10–30 cm tall, 1–2 mm in diameter, decumbent or ascending, glabrous; multibranched, all nodes swollen, internodes 1.5–7.5 cm. Stipules absent. Distal leaves petiolate (petiole 5–15 mm), middle and basal leaves long petiolate (petiole 10–20 mm), sunken, ciliate; leaf blade ovate to oblong-ovate (1.5–4.5 × 0.5–2.0 cm), base rounded, apex acuminate, both surface glabrous, abaxially midvein prominent, adaxially midvein impressed, margin shortly ciliate. Flowers arranged in terminal dichotomous cymes, numerous, upper false dichotomous; involucre herbaceous (13–25 × 3–9 mm), oblong-ovate to lanceolate, margin ciliate, bractlet membranous, 1.5–2.0 mm long, white, lanceolate, glabrous; peduncle glabrous (3–6 cm long), pedicel glabrous (1–2.5 cm long), slender; sepals 5, ovate-lanceolate, 2.5–3.0 mm long, outside glabrous, 3-veined, margin membranous, apex acuminate; petals 5, white, 2.0– 2.5 mm, slightly shorter than or subequaling sepals, 2-cleft nearly to base; lobes ovate-oblong, apex obtuse; stamens 10, shorter than petals; filaments linear; anthers mauve, yellow after dry; styles 3, linear; ovary ovoid-orbicular. Capsule oblong-ovoid, 4–5 mm long, longer than persistent sepals, 6-valved to base; seeds numerous (9–15), brown, suborbicular, slightly compressed, undulate tuberculate.
Description (pollen morphology) (Fig. 4):—Pollen grains are spheroidal-polyhedral, 25.44 ± 0.75 (23.98–26.95) μm in diameter, with 16 (12–20) pores, each pore 3.69 ± 0.59 (3.01–4.81) μm in diameter, distance between pores is 9.21 ± 1.95 (6.47–13.25) μm. Aperture membrane are prominent or sunken, annulus are present, ornamentation is microechinate-punctate-perforate, sculptural density is 58 ± 9 (44–72) / 100 μm 2.
Etymology:—The specific epithet is derived from the name of its type locality.
Phenology: —Flowering time August–September; fruiting time September.
Distribution and ecology:— Stellaria abaensis is distributed in Barkam County and Xiaojin County (Aba prefecture, Sichuan Province, China). Populations of this species were found along the roadside under the wet coniferous and broad-leaved mixed forest, 3200–3450 m (Fig. 3).
Taxonomical notes:—Based on the characters referring to number of seeds (9–15), 2-cleft petals, 3 styles, and 6-valved capsule, Stellaria abaensis can be classified under the sect. Stellaria (see, Ke 1985: 70). Long petioles, and number of stamens (10) suggest that the species belongs to ser. Petiolares Fenzl (1840: 969).
When checking the collected specimens and related literature, we found that Stellaria abaensis shared some similarities in morphological features with the following four species: S. neglecta Weihe & Bluff (1825: 560), S. media var. micrantha (Hayata 1911: 36) Liu & Ying (1976: 350), S. media, and S. reticulivena (Table 1). There are no significant differences in the stem length, blade shape, inflorescence, and bracts morphology. But the indumentum and shape of stem, petiole, pedicel, stamens, seeds, and pollen morphology can easily differ them (Figs. 4–5). More similar species are S. media var. micrantha, and S. reticulivena. S. media var. micrantha has sessile leaves, 5 stamens, and sunken pollens which clearly distinguishes it from S. abaensis that has long petiolate leaves, 10 stamens, and also prominent pollens. Compared with S. reticulivena, S. abaensis can be easily distinguished by its terete (vs. quadrangular) and glabrous stems, long petiolate leaves (vs. sessile), 6-valved to base capsule (vs. to middle), long linear tuberculate seeds, and prominent or sunken pollen grains.
description: Published as part of Xu, Han-Feng & Ma, Zhong-Hui, 2018, Stellaria abaensis (Caryophyllaceae), a new species from China, pp. 48-54 in Phytotaxa 383 (1) on pages 49-52, DOI: 10.11646/phytotaxa.383.1.2, http://zenodo.org/record/13724562