Orophea phouphamarnensis D.Kong., Soulad. & Tagane, 2025

Kongxaisavath, Deuanta, Tagane, Shuichiro, Souvannakhoummane, Keooudone, Phengmala, Kajonesuk, Sengthong, Anousone, Dang, Van-Son, Nguyen, Quoc Bao, Yamamoto, Takenori, Tanaka, Nobuyuki, Takahashi, Kotaro T. & Souladeth, Phetlasy, 2025, Orophea phouphamarnensis (Annonaceae), a new species from limestone karst in central Laos, Phytotaxa 687 (1), pp. 15-20 : 16-19

Orophea phouphamarnensis D.Kong., Soulad. & Tagane , sp. nov. ( Figs 1 , 2 )

TYPE: — LAOS. Khammouane Province, Khounkham District, Nam Sanam-Phou Pha Marn PPA, The Rock Viewpoint walking trail, in evergreen forest, 18.17626°N, 104.48905°E, 423 m elev., 17 March 2024, fl., Tagane et al. Z994 (holotype FOF0005504 ; isotypes KAG187403 , KAG187404 , VNM) .

Orophea phouphamarnensis is most similar to O. laotica in leaf shape and size but distinguished by a number of morphological features, especially stamen and carpel numbers ( Table 1).

Evergreen trees, 20 m tall, d.b.h. 63.3 cm.Young twigs 2.0 mm in diam., densely covered with yellowish brown hairs, old twigs dark grey to dark brown, glabrous, lenticellate. Terminal buds 0.6–1.9 cm long, densely covered with dark brown hairs. Leaves alternate; blades oblong-elliptic to oblong-ovate, 9.2–16.0 × 2.6–5.2 cm, sometimes slightly falcate, dark greyish brown, glabrous adaxially, reddish brown, covered with yellowish brown hairs on midrib and secondary veins abaxially, apex acuminate, acumen to 18 mm long, margin entire, base broadly cuneate to acute, midrib prominent except shallowly sunken or flat near the base adaxially, prominent abaxially, secondary veins 6–8 pairs, prominent abaxially, tertiary veins scalariform-reticulate, prominent abaxially; petioles 2.0–6.0 mm long, covered with yellowish brown hairs. Inflorescences axillary or on old stems behind leaves, up to 7-flowered, dark to yellowish brown hairy, sessile; bracts ovate-elliptic, ovate-triangular, 2.3–4.1 × 2.0– 2.2 mm, glabrous adaxially, densely covered with dark brown hairs abaxially, margin ciliate, apex acute. Pedicel up to 2.0 mm long, densely covered with dark brown hairs, bracteoles narrowly triangular, 2.0 × 1.0 mm, margin ciliate, apex acute. Sepals 3, ovate-triangular, 1.0–1.2 × 1.0– 1.2 mm, glabrous adaxially, dark brown hairy abaxially, margin ciliate, apex acute. Outer petals 3, ovate-triangular, 2.7– 3.0 × 1.5–2.0 mm, glabrous adaxially, dark brown hairy abaxially, margin ciliate, apex acute. Inner petals 3, clawed, claw 3.0 mm long, lamina 2.0 mm long, tip protracted to 4.0 × 2.0 mm, broad, incurved, strongly recurved from bud to anthesis, warty, sparsely covered with hairs 4.0 × 2.0 mm. Nectary slits in paired. Stamens 12 in two whorls (6 + 6), 0.8 × 0.5 mm, anthers 0.5 mm long. Staminodes absent. Carpels 10–12, 0.5–0.8 mm long, 0.2–0.3 mm in diam., sparsely hairy, stigma globose, 0.2 mm in diam.; ovules 2 per ovary. Fruits not seen.

Distribution:— Laos, thus far known only from the type locality.

Habitat and Phenology:— Flowering in March in evergreen forest on limestone karst at 423 m elevation in forests dominated by Hopea pierrei Hance ( Dipterocarpaceae ), Diospyros brandisiana Kurz , D. retrofracta Bakh. ( Ebenaceae ), Cleidion javanicum Blume ( Euphorbiaceae ), Litsea lancifolia (Roxb. ex Nees) Fern.-Vill. ( Lauraceae ) and Saraca declinata (Jack) Miq. ( Fabaceae ).

Etymology:— Referring to the type locality, Phou Pha Marn.

Vernacular name:— Pha marn Inthy (ຜາມ່ານǥິນທີ; Lao), proposed here. Pha marn refers to an area, and Inthy refers to Inthy Deuansavanh, who established walking trails on the limestone karst that enabled access to the core area of Phou Pha Marn.

Preliminary conservation assessment:— Likely data deficient (DD; IUCN 2024). Currently Orophea phouphamarnensis is known only from a single locality. We confirmed a single flowering individual along the Rock Viewpoint walking trail. Since we could not find any additional specimens at the herbarium and online database as far as we surveyed, the species is considered to be narrowly endemic to the area of limestone karst in the Phou Pha Marn and adjacent areas. Further information on distribution and number of individuals/populations is needed to accurately assess the status and conserve this species.

Notes: — Orophea phouphamarnensis is closely related to O. laotica , endemic to Laos and shares many characteristics. However, it is clearly distinguished from O. laotica ( Table 1). Stamen and carpel numbers are known to be reliable and informative characters for the classification of Orophea ( Leonardía & Kessler 2001) , and indeed the two species are different in these.

Figures

FIGURE 1. Orophea phouphamarnensis (holotype, Tagane et al. Z994, FOF0005504).

FIGURE 2. Orophea phouphamarnensis. A. Flowering branch. B. Lower leaf surface. C. Inflorescence, top view and side view. D. Flower. E, F. Sepal (abaxial and adaxial). G, H. Outer petal (abaxial and adaxial). I, J. Inner petals (abaxial and adaxial). K. Stamen, L. Pistil. Photos A–C, K. Souvannakhoummane and D–J, L by D. Kongxaisavath of Tagane et al. Z994 (FOF).