Hiptage aptera M. T. X. Lam & T. V. Do 2025, sp. nov.

Hiptage aptera M. T. X. Lam & T. V. Do sp. nov. Type. Vietnam: • Ba Ria–Vung Tau Province, Dat Do District, 10.427317, 107.254949, 39 m elev., 16 May 2022, Nguyen Hoang Nam 08 _ 240118 _ VungTau (holotype: VNMN; isotype: VNMN). Diagnosis. This species shares similarities with H. lushuiensis, H. minor, H. bullata, H. subglabra and H. lucida such as leaf shape, basal leaf glands and petal colour. However, H. aptera differs from these related species in petal size and calyx gland presence. Its petals are significantly larger than those of H. lushuiensis, H. minor, H. bullata and H. subglabra and are erect to forward-curved with fimbriate margins, unlike the strongly reflexed petals in H. lushuiensis and the unfimbriate petals in H. lucida. Additionally, the absence of calyx glands distinguishes H. aptera from H. minor. This new species is distinctly different from H. benghalensis, one of the most studied species in the genus, which has extremely reflexed petals and a large calyx gland. A notable feature of H. aptera is its wingless, hemispherical mericarps (fruits), which are relatively large, measuring 2.4–4.5 cm in diameter. This unique fruit shape represents the first recorded occurrence within the Hiptage genus. Description. Woody shrubs or lianas, young branches densely red-brown pubescent, hairs appressed; older twigs glabrous, with white and small lenticels, rounded, coarse, stem wart-like structures. Leaves opposite; stipules present, linear, 1–2 mm, located at the base of the petiole, densely red-brown pubescent; petioles ca. 6 mm long, densely red-brown pubescent, adaxially canaliculate; leaf blade oblong, elliptic, ovate to lanceolate, 5.5–17.5 × 2–7 cm, coriaceous; young leaves usually red, white or red-brown pubescent on abaxial surface, densely so along mid-rib, adaxially glabrous; mature leaves green, glabrous on both surfaces, base cuneate, apex acuminate or retuse, margin entire, abaxially often with 1–3 pairs marginal gland near the base; lateral veins 5–7 pairs, prominent on both surfaces. Thyrses: terminal or axillary; main axis 2.5–20 cm long, red-brown pubescent; peduncle 2–17 mm long, covered red-brown pubescent; bracts lanceolate, 9–12 mm long, green; bracteoles lanceolate, 2–3 mm long, red-brown. Flowers: white to slightly pink; pedicels 16–22 mm long, spread red-brown pubescent. Calyx with five sepals basally connate, ovate to round, apex rounded to acute, ca. 3 × 15 mm, densely light brown pubescent abaxially, glabrous adaxially. Calyx glands: eight prominent, round, small, green, not decurrent to the pedicel, often connate at the junction between two sepals. Petals: five, suborbicular, 11–14 × 8–12 mm, white to light pink, erect to forward curved, apex rounded, margin fimbriate, claw short, ca. 0.2 mm length, ca. 0.3 mm width, basally yellow, yellow maculations, abaxially red brown pubescent, densely so near base, abaxially glabrous. Stamens ten, glabrous, unequal in size; filaments white, circinate, 9–11 mm long in the longest stamen and 2–5 mm long in the remaining nine; anthers oblong; pollen sacs yellow, rimose (longitudinal dehiscence). Ovary: ca. 25 mm, ovoid, densely light red pubescent; style 1, yellowish-green, 7.5–12 mm long, slightly curved upwards, deflected either to the left or right side, glabrous; stigma apical. Fruits: wingless, 1–3 mericarps, hemispherical, spread red brown pubescent, young fruit green, red-brown pubescent on both surfaces; mature fruit rusty to reddish-brown, glabrous, 2.4–4.5 cm in diam., adaxially with longitudinal groove, abaxially bulging. Seeds: ovoid, ca. 1.7 cm long, dark yellow or brown (Fig. 3). Phenology. Flowering in March to June and fruiting from May to August. Etymology. The specific epithet reflects the unusual fruit morphology compared to other Hiptage species. Vernacular name. Vietnamese: Dùi đ ục không cánh. “ Dùi đ ục ” is the popular Vietnamese name of Hiptage genus, “ không cánh ” is wingless. English name. Wingless Hiptage. Habitat and distribution. Hiptage aptera is found in two Provinces: Ba Ria – Vung Tau (southern Vietnam) and Quang Tri (central Vietnam). It grows in areas around the base of mountains, on slopes and along mountain paths under evergreen forests and near residential areas, at elevations of 28– 433 m. Conservation status (and study). Since its identification, we have found this species in various locations within Ba Ria – Vung Tau Province, where it maintains a relatively large population. It is commonly observed as shrubs or lianas covering certain areas, co-existing with other species in the same habitat. We propose that the new species H. aptera should be classified as Least Concern (LC) according to the current IUCN Red List Categories and Criteria (IUCN 2024). However, continuous monitoring of its population status and habitat conditions is crucial for making accurate assessments in the future. Additional specimens examined (paratypes). Vietnam: • Dat Do, Ba Ria–Vung Tau, 10.4064358, 107.2631240, 194 m elev., 8 Apr 2024, Lam Thi Xuan Mai, original ID 61 _ 240408 _ VungTau; • Dat Do, Ba Ria–Vung Tau, 10.406327, 107.263000, 190 m elev., 01 Jun 2024, Lam Thi Xuan Mai, original ID 62 _ 240601 _ VungTau; • Tan Thanh, Ba Ria–Vung Tau, 10.545323, 107.147117, 333 m elev., 23 Jun 2024, Nguyen Hoang Nam, original ID 64 _ 240623 _ VungTau; • Dat Do, Ba Ria–Vung Tau, 10.433306, 107.254722, 28 m elev., 23 Jun 2024, Nguyen Hoang Nam, original ID 65 _ 240623 _ Vung Tau; • Da Krong, Quang Tri, 16.328694, 106.997167, 433 m elev., 01 Dec 2022, Tran Dang Khoa, original ID 19 _ 221201 _ QuangTri.