Phanera mekongensis Mattapha, Suddee & Duangjai, 2022

Phanera mekongensis Mattapha, Suddee & Duangjai View in CoL , sp. nov. — Fig. 3 View Fig , 4 View Fig ; Map 1 View Map 1

Similar to Phanera hekouensis (T.Y.Tu & D.X.Zhang) Krishnaraj but differs by having shorter pedicels ( 8–11 mm in P. mekongensis vs 21–34 mm long in P. hekouensis ), oblong floral buds (vs spindle-shaped in P. hekouensis ), shorter hypanthium ( 9–11 mm long in P. mekongensis vs 17–21 mm long in P. hekouensis ), length of petal limb 7–8 mm long (vs 12–22 mm long in P. hekouensis ), anthers densely silky with hairs on the back (vs glabrous in P. hekouensis ), stipe of ovary c. 1 mm long (vs 8–15 mm long in P. hekouensis ) and a short style (less than 1 mm in P. mekongensis vs 12–19 mm long in P.hekouensis ). — Type: Suddee, Puudjaa, Hemrat & Kiewbang 5390 (holo BKF;iso BK,BKF,K, KKU,QBG), Thailand, Bueng Kan Province,Bung Khla District, Phu Wua Wildlife Sanctuary, cultivated in a medicinal garden, altitude c. 190 m, 5 Nov. 2018, fl. For paratypes see below.

Etymology. The epithet refers to the Mekong River, which runs close to the Phu Wua Wildlife Sanctuary.

Liana ; tendrils opposite, 4–8 cm long, hairy; young twigs densely whitish tomentose when young, becoming ferruginous at maturity. Leaves simple, bifid, spirally arranged, coriaceous; petioles 30–35 mm long, pubescent; lamina ovate, 6–13.5 by 5.5–12 cm, apically bifid to 1/4–1/3 of lamina length with a narrow sinus, midrib bristly between the lobes, lobes ovate to lanceolate, tip of lobes triangular-acute, margin tomentose, base deeply cordate, with 2 rounded to oblong alveoles at base of veins, 9–11-veined from base, tertiary veins reticulate-scalariform; upper surface sparsely pubescent; lower surface greyish velvety when young, densely brownish tomentose when fully grown; stipules ovate-lanceolate, 6–20 by 3–9 mm, apex acute, outer surface densely tomentose, inner surface glabrescent, caducous. Inflorescences terminal racemes, erect, elongated, slender, lax-flowered, 20 – 26 cm long, with 20 – 35 flowers, axis densely tomentose. Pedicels 8–11 mm long, densely pubescent; bracts caducous, ovate to lanceolate, 14–15 by 3–4 mm, apex acuminate, outer surface pubescent, inner surface tomentose; bracteoles caducous, linear to lanceolate, 8–9 by 2–3 mm, apex acuminate, outer surface pubescent, inner surface glabrous, inserted in lower part below the middle of pedicels. Buds oblong, 7–8 mm long, pubescent, apex acute. Hypanthium tubular, 9–11 mm long, densely pubescent. Calyx 5-lobed, splitting regularly at anthesis; lobes lanceolate, 7–8 by 2–3 mm, gradually separate from the base to completely separate at apex, equal, apex acute, margin pubescent, outer

cm

2 surface densely pubescent, inner surface glabrous, persistent in fruit. Petals 5, light yellow to slightly light pink, posterior one relatively larger than lateral petals, spathulate or obovate; limb of posterior petal 10–11 by 8–9 mm, limps of lateral petals 8–9 by c. 3.5 mm, apex rounded, margin undulate, crisped, inner surface glabrous, outer surface densely whitish pubescent along veins, more dense pubescent on claw, otherwise glabrous, claw of posterior petal 5 – 6 mm long, claw of lateral petals 6–7 mm long, flattened, pubescent outside and margins. Fertile stamens 3, included in the flowers; filaments 5–6 mm long; anthers brown, more or less flattened, oblong, c. 2.5 by 2 mm, dehiscing by longitudinal slits, versatile, densely silky on the back. Staminodes 0–2; filaments c. 1 mm long; anthers absent. Floral disc absent. Ovary shortly stipitate, densely pubescent all over, 7–9-ovuled; stipe c. 1 mm long; style very short, less than 1 mm long, glabrous at upper part; stigma peltate, c. 1 mm diam. Fruits oblong, flattened, 20–32 by 2.5–4 cm, dehiscent, woody, glabrous, 6–8-seeded; stipe 2–3 cm long. Seeds flattened, elliptic to rounded, 1.4–2 by 1.2–1.7 cm, hilum crescentic, glabrous, black.

Distribution — Seeds were originally collected from Phu Ngoen Village, Bueng Kan and subsequently cultivated in Phu Wua Wildlife Sanctuary medicinal garden ( Fig. 4 View Fig ). The precise habitat remains untraceable, and additional investigations are necessary to explore its distribution site in the natural habitat.

Habitat & Ecology — Cultivated in dry evergreen forest, elevation c. 190 m.

Phenology — Flowering: September–October; fruiting: November–February.

Vernacular name (in Thai) — Kam lang chang phueak (กำ�ลัง ช้�งเผือก).

Conservation status — Phanera mekongensis is currently known from a single population with a few individuals cultivated in Phu Wua Wildlife Sanctuary. A wild population in the area has not been found. In addition, we have no more information about the occurrence of the species in the areas of Nam Kading National Bio-Diversity Conservation Area, Lao PDR which is rich in endemic species ( Tagane et al. 2018). The species can probably be found in the Lao PDR’s area, opposite the Phu Wua Wildlife Sanctuary. Therefore, future intensive floristic investigations are necessary to explore the complete distribution range of the species. We assess it here as data deficient (DD) according to the IUCN Red List Categories ( IUCN 2019), due to inadequacy of the distribution information.

Additional specimens examined ( paratypes). CENTRAL, Bangkok, seeds were taken from Bueng Kan Province, but the exact location is unknown, and later cultivated in the Faculty of Forestry, Kasetsart University , 22 Oct. 2018, fl., Duangjai 2018 s.n. ( BKF) . – NORTHEASTERN, Bueng Kan, Bung Khla district, Phu Wua Wildlife Sanctuary, cultivated in Medicinal Garden , alt. 190 m, 10 Oct. 2007, fl., Kaewphoung 01 ( BKF) ; ibid., 8 Feb. 2018, fr., Suddee, Mattapha, Hemrat & Kiewbang 5343 ( BKF) ; ibid., 15 Sept. 2018, fl., Suddee, Puudjaa, Hemrat & Kiewbang 5378 ( BKF) ; ibid., 15 Oct. 2019, Suddee, Puudjaa, Tetsana, Thananthaisong, Hemrat, Kiewbang & Ue-aree 5568 ( BKF) .

Note — Phanera mekongensis is remarkable by its elongate laxly racemose inflorescences, flowers without a floral disc, anthers having a densely silky indumentum on the back and an ovary with a very short style and peltate stigma. Addition- ally, the morphological differences of the new species with its closely related species are shown in Table 2.