Phyllagathis stellata C.W. Lin & C.H. Lee, 2018

Lin, Che-Wei & Lee, Chi-Hung, 2018, Phyllagathis stellata (Sonerileae, Melastomataceae), a new species from southwestern Sarawak, Borneo, Phytotaxa 365 (3), pp. 295-300 : 295-299

Phyllagathis stellata C.W. Lin & C.H. Lee , sp. nov. ( Fig. 1 , 2 )

Type:— MALAYSIA. Borneo, Sarawak, Sri Aman Division, Batang Ai, ca. 100 m elev. Type specimens pressed from plants cultivated in a nursery in Taiwan, 5 Sep 2017, C. W. Lin 643 (holotype TAIF!, isotype HAST!).

Diagnosis: Phyllagathis stellata resembles P. jacobsiana (M.P. Nayar, 1965: 502) Cellinese (2003: 85) in its hairy leaves, pentamerous flowers and fleshy finger appendiculate sepals. The new species is different in its lamina with 11 or 13 basal veins (vs. 7 or 9-veins), inflorescence shorter (vs. longer) than petiole, hypanthium ribbed and densely verrucose (vs. smooth), stamens with a dorsal tuberculate appendage (vs. dorsally inappendiculate).

Caulescent herbs, ascending or creeping, terrestrial. Stems unbranched, rooting at nodes and creeping up soil slope, ascending or suberect upper part; olive green to reddish brown, to 15 cm or longer, 0.4–0.9 cm in diameter, terete, stout, slightly woody at base, covered with densely gland-tipped trichomes; internodes 0.5–2.8 cm long. Leaf blades 2–5, decussate, 10–18 × 9–18 cm ,, isophyllous, very widely to depressed ovate, base cordate, margins denticulate and sparsely incised, with rows of long gland-tipped trichomes up to 5 mm long, apex shortly acuminate; chartaceous; venation acrodromous, 11 or 13 veined, basal; veins slightly depressed on the adaxial surface and prominent on the abaxial surface, secondary and tertiary veins numerous and conspicuous, reticulate; adaxially emerald green, slightly bullate and long gland-tipped trichomes between veins; abaxially pale green, sparsely gland-tipped trichomes on all veins. Petioles 15–30 cm long, flat terete and slightly grooved adaxially, densely covered with gland-tipped trichomes and minutely translucent puberulous. Bracts inconspicuous, ca. 1 mm long, linear. Inflorescences in the upper leaf axils, very congested pleiochasium (umbelliform in young plants), peduncle 6–13 cm long, reddish brown, covered with gland-tipped trichomes, densely glandular and minutely translucent puberulous. Flowers pentamerous, pedicels ca. 0.5 cm long, densely glandular and minutely translucent puberulous. Hypanthium campanulate, ca. 3 mm long, 3 mm in diameter, covered with densely minutely translucent puberulous and gland-tipped trichomes <0.5 mm long; 10- ribbed, with undertint verrucose, giving hypanthium a rugose appearance. Sepals 5, persistent, very widely triangular, apex rounded, connate into a torus, each lobe with an acute-angled triangular external tooth; lobes alternating with fleshy finger appendages, appendage unbranched or multi-branched, tipped by a gland. Petals 5, oblique, glabrous, widely elliptic to oblong, 9–11 mm × 3.5–5 mm wide, white, sometimes pale pinkish, apex mucronate-apiculate. Stamens 10, isomorphic, filaments slightly flat, 4.5–6.5 mm long, white, pinkish toward apex, anthers subulate, apex attenuate, slightly curved ventrally, 4.5–6 mm long, purplish to bluish, pore 1, connective distinct, with one pair of ventral auricular appendages on the base, dorsal appendage ca. 0.3 mm, tuberculate. Style ca. 15 mm long, filiform, glabrous, stigma capitate. Ovary ca. 4/5 as long as the hypanthium, crown with fully connate lobes, margins denticulate with each tooth tipped by a glandular trichome, anther pockets shallow, placentae stalked. Capsules on pedicels 6–10 mm long, hypanthium cup-shaped, ca. 6 × 6 mm, placentae disintegrating after seed dehiscence.

Additional specimen examined:— MALAYSIA. Borneo, Sarawak, Sri Aman Division, Batang Ai, ca. 100 m elev. Type specimens pressed from plants cultivated in a nursery in Taiwan, 10 Sep 2017, C. W. Lin 646 ( TAIF).

Distribution and ecology: —This new species is endemic to Sarawak, currently only known from Batang Ai ( Fig. 3). Growing on riparian forest on soil steep slope in deeply shaded areas, at 100–200 m elevations.

Etymology: —The specific epithet refers to the resemblance of this new species capsule from apical view that appears star-like with radiating appendages.

Proposed IUCN Category: —DD-Data Deficient, according to IUCN (2016): the species is rare but possibly not threatened as it grows in an inaccessible location.

Note: Phyllagathis stellata belongs to a distinct group of Bornean Phyllagathis that have pentamerous flowers. Among this group that includes P. guttata (Stapf) Cellinese (2003: 83) , P. jacobsiana (Nayar) Cellinese (2003: 85) , P. osmantha (Nayar) Cellinese (2003: 88) , P. penrissenensis Cellinese (2003: 89) , P. rajah C.W.Lin, Chien F.Chen & T.Y.A.Yang (2015: 123) , P. rufa (Stapf) Cellinese (2003: 91) and P. subacaulis (Cogniaux) Cellinese (2003: 93) , it most resembles P. jacobsiana and P. guttata in its fleshy finger appendiculate sepals. However, in other aspects P. stellata is sharply distinct. A comparison of salient features of the three species is shown in Table 1.

Figures

FIGURE 1. Phyllagathis stellata C.W. Lin & C.H. Lee. A. Habit; B. Portion of leaf abaxial surface; C, C’. Flower, front and side views; D, D'. Petal, inside and side views; E, E', E''. Stamens, side, dorsal and ventral views; F. Hypanthium; G. Longitudinal section of ovary; H. Portion of crown lobe, showing margins denticulate with gland-trichomes; I. Capsules, side view. J. Infructescences.All from C.W. Lin 643 (TAIF).

FIGURE 2. Phyllagathis stellata C.W. Lin & C.H. Lee. A. Habit and habitats; B. Young plant; C. Portion of leaf adaxial surface; D. Portion of leaf abaxial surface; E. Immature inflorescence; F. Inflorescence; G. Flower, front view; H. Hypanthium; I. Anthers, dorsal, side and ventral views; J. Appendage of sepals; K. Vertical section of an ovary; L. Capsules, apical view; M. Old-age capsules.All from C.W. Lin 643 (TAIF).