Phyllagathis impressinervia Y. L. Su, Yan Liu & Ying Liu, 2021

Su, Yu-Lan, Liu, Yan & Liu, Ying, 2021, A new species of Phyllagathis (Melastomataceae, Sonerileae) from Guangxi, China, Phytotaxa 500 (2), pp. 117-124 : 117-123

Phyllagathis impressinervia Y. L. Su, Yan Liu & Ying Liu , sp. nov. Figs. 3–6

Type: — CHINA. Guangxi: Tianlin County, Lang-ping Town, Cen-wang-lao-shan Nature Reserve , Tian-huang Temple , on slope in dense forests, 1,500–1,600 m, 7 July 2020, QYLS081 (holotype: IBK!; isotypes: A!, IBSC!, PE!) .

Diagnosis: — Resembles P. cavaleriei in leaf shape, inflorescence type, and morphology of stamens and capsule, but differs in all veins strongly sunken adaxially (vs. not strongly sunken), hypanthium pubescent with ca. 1 mm long, spreading glandular hairs (vs. without spreading hairs), creamy white (vs. purplish-blue) anthers, and conspicuous (vs. inconspicuous) ovary crown at anthesis.

Perennial acaulescent herbs 5–17 cm tall. Stems short, densely hirsute with 2–11 mm long, multiseriate hairs. Leaves 5–9; petiole 3–10 cm long, with short-stalked minute brown glands and dense, spreading multiseriate hairs; leaf blade ovate, broadly ovate to ovate-orbicular, 5.5–15 × 4.5–11.6 cm, papery to thick papery, green adaxially and pale green abaxially, or dark green adaxially and purplish red abaxially, sometimes with whitish areas between primary palmate veins, densely to sparsely pubescent with multiseriate hairs and minute glands adaxially, more so abaxially, 7–9(–11)-veined, all veins strongly sunken adaxially and prominent abaxially, base cordate, margin inconspicuously denticulate, ciliate, apex obtuse to acute, sometimes rounded. Inflorescences terminal, umbellate, 3–13-flowered; peduncle 4–15 cm long, sparsely pubescent with ca. 1 mm long, multiseriate hairs, short appressed uniseriate hairs, and minute glands. Flowers radial, 4-merous. Pedicels 4–9 mm long at anthesis, 6–14 mm long at fruiting stage, pubescent with appressed uniseriate hairs. Hypanthium funnel-shaped, 3–5 × 2–3 mm, 4-sided, pubescent with ca. 1 mm long, spreading, multiseriate glandular hairs and appressed uniseriate hairs. Calyx lobes triangular, 0.5–1 mm long. Petals pink, 4.5–5.5 × 3.5–5 mm, broadly ovate, very slightly oblique, apex acute. Stamens 8, unequal in length, isomorphic; filaments white, glabrous, 5.5–6.5(–8.5) and 3–4 mm long in alternipetalous and antepetalous stamens, respectively; anthers lanceolate, creamy white, 4.5–6 and 2.5–3.5 mm long respectively, not tuberculate ventrally, connective slightly decurrent, forming a short spur dorsally. Ovary locules 4, apex with a conspicuous crown ca. 1 mm long, crown margin dentate. Style 8–11.5 mm long. Mature capsule cup-shaped, ca. 3.5 × 3.5 mm, 4-sided; crown enlarged enclosing an inverted frustum-shaped space; placental column 4-horned; placenta thready.

Distribution and habitat:— Phyllagathis impressinervia is currently known from Tianling, Lingyun and Leye

County, northwestern Guangxi, China ( Fig. 7 ). It grows on slopes in dense forests at elevations of 1,500–1,800 m. Phenology :— Flowers and fruits in July. Etymology:— The specific epithet refers to the strongly sunken leaf veins of the new species. Additional specimen examined:— CHINA. Guangxi: Lingyun County, Yu-hong District , Lao-shan , 11 June

1959, Z. T. Li 603073 ( IBK, IBSC); Lingyun County, Yu-hong District , 8 June 1959 , Z. T. Li 603040 ( IBK); Lingyun

County, Lan-jin-lin, 16 August 1928, L. Q. Chen 92623 ( IBK); Tianlin County, Lang-ping Town, Cen-wang-lao-shan

Nature Reserve, on slope in dense forests, 1,773 –1,789 m, 1 July 2020, QYLS016 (IBK). Conservation status:— Phyllagathis impressinervia is currently known from Tianlin, Lingyun and Leye County, northwestern Guangxi, China. The three populations we visited on Cen-wang-lao-shan, Tianlin County comprise ca. 750 individuals on slopes under forests, but the population size in Lingyun and Leye remains unknown. Discovery of additional populations are expected when mountainous areas above 1,500 m are better explored in the latter counties. Habitat fragmentation can be listed as a potential factor that increases extinction risk, as P. impressinervia is only recorded from habitats with low human disturbance. Based on the above data, we consider P. impressinervia vulnerable (VU) according to the IUCN red list criteria A1ab and B1ab (IUCN Standards and Petitions Committee 2019).

Notes:— Phyllagathis contains over 70 species distributed from southern China, Indochina, western Malaysia to Sumatra and Borneo. The polyphyletic nature of this genus has been confirmed by molecular phylogenetic data ( Zhou et al. 2019a & b). However, no formal taxonomic adjustment at the generic level is proposed to date as relationships among some of the lineages have remained poorly resolved ( Zhou et al. 2019a & b). We therefore describe P. impressinervia as a member in Phyllagathis as defined by the most recent revisions ( Cellinese & Renner 1997, Cellinese 2002, Cellinese 2003). The new species can be readily recognized in Phyllagathis by its leaf veins strongly sunken adaxially, a character only recorded from P. bicolor C. W. Lin, C. F. Chen & T. Y. A. Yang (2017: 202) , a species endemic to Borneo. The two species differ markedly in habit (acaulescent vs. caulescent), leaf shape (ovate, broadly ovate or ovate-orbicular vs. narrowly elliptic to lanceolate, oblanceolate, or obovate-elliptic), length of peduncle (7–17 vs. 0.4–1.5 cm), shape of hypanthium (funnel-shaped vs. campanulate), and anther color (creamy white vs. purple-blue). Phyllagathis impressinervia most closely resembles P. cavaleriei in morphology and habitat preference. The two species cooccur in similar habitat on Cen-wang-lao-shan, northwestern Guangxi. Phyllagathis impressinervia was found at 1,500 –1,789 m, while P. cavaleriei at 1,600 –1,784 m, with their nearest colonies ca. 20 m apart. The flowering seasons were partly overlapped, but no morphologically intermediate individuals were observed. Phylogenetic relationship between the two species remains to be tested, as morphological resemblance may not always reflect true relationships in case of homoplasy.

Figures

FIGURE 3. Phyllagathis impressinervia, all from QYLS081 (A, IBK, IBSC, PE). A. Habit. B. Hairs on the petiole. C. Detail of adaxial surface of leaf, showing sunken veins. D. Adaxial (top) and abaxial (bottom) views of leaves, showing leaf coloration. E. Inflorescences. F. Fructescences. G. Flower, top view (left), side view (middle) and longitudinal section (right), showing unequal stamens, creamy white anthers, and conspicuous ovary crown (arrow). H. Anthers in detail. Scale bars: 5 mm (G), 3 mm (H).

FIGURE 4. Phyllagathis impressinervia, all from QYLS081 (A, IBK, IBSC, PE). A. Top view of young capsules. B. Side view of young capsules. C. Longitudinal section of a young capsule. D. Top view of an old capsule. E. Longitudinal section of an old capsule, showing the enlarged ovary crown, horned placental column, and thready placentas. Scale bars: 3 mm (C, D, E).

FIGURE 5. Line illustration of Phyllagathis impressinervia. A. Habit. B. Abaxial view of a leaf. C. Abaxial surface of the leaf blade. D. Adaxial surface of the leaf blade showing the strongly sunken leaf veins. E. Side view of a flower. F.Top view of a flower. G. Longitudinal section of a flower with petals and 4 stamens removed. H. Hypanthium. I. Longitudinal section of an old capsule, showing the horned placental column and thready placenta. Drawn by Mr. Yun-xi Zhu.

FIGURE 6. Holotype of Phyllagathis impressinervia.

FIGURE 7. Distribution of Phyllagathis impressinervia.