Phanera roseoalba Tk.Yamam., Tagane & Soulad.

Yamamoto, Takenori, Souladeth, Phetlasy, Soutakone, Khammon, Kongxaisavath, Deuanta & Tagane, Shuichiro, 2024, A new species and a new record of Phanera (Fabaceae) in Laos, with a lectotypification and a new combination for P. involucrans, Phytotaxa 640 (2), pp. 81-89 : 83-87

Phanera roseoalba Tk.Yamam., Tagane & Soulad. , sp. nov.

Type:— LAOS. Attapeu Province: Bolaven Plateau, Samakhixay District , Sox Village , in seasonal dry evergreen forest, 15°03′26.68′′N, 106°50′11.58′′E, 253 m elev., 19 December 2019, P. Souladeth, S. Tagane, D. Kongxaisavath, S. Rueangruea, S. Somran, Y. Suyama, E. Suzuki L3481 (holotype FOF0006810 !, isotypes BKF, KAG155843 !) . Figures 1 & 2 .

Phanera roseoalba is similar to P. involucellata distributed in Myanmar and Thailand, and P. involucrans endemic to southern Vietnam in having glabrous branches and leaves throughout, and conspicuous bracteoles (exceeding 1 cm long) situated just below the hypanthium enveloping young buds, but distinguished from the former by having lamina bifid 1/2–3/5 its length (vs. 1/3–1/ 2 in P. involucellata ), terminal inflorescences of compound corymbs (vs. mostly simple racemes, sometimes panicles composed of a few racemes), shorter pedicels at anthesis (3.2–5 cm long vs. (4–) 5.5–9 cm long), relatively smaller petals (claws 0.9–1.4 cm long, lamina 1.2–1.8 cm long vs. claws (1.5–) 1.8–2.5 cm long, lamina (1.3–) 1.5–2.8 cm long), and densely pubescent ovary and style (vs. glabrous); from the latter by having lamina bifid 1/2–3/5 to its length (vs. emarginate or bifid 1/10–1/3(–1/2) of its length in P. involucrans ), and pedicels, bracteoles, and buds covered with light brownish hairs (vs. densely ferruginous hairy) ( Table 1 ).

Description: —Woody liana, ca. 10 m tall. Branches glabrous throughout, young branches light green in vivo, dark brown in sicco; tendrils 7–9 cm long, glabrous. Stipules caducous, not seen. Leaves simple, alternate; petiole 2.4–3.7 cm long, sparsely puberulous when very young, soon glabrous; lamina broadly ovate, 6.2–11.4 × 5.9–9.3 cm, apex bifid 1/2–3/5 of lamina with a narrow sinus up to 6.5 mm, tips subacute to obtuse, base subcordate, 9-veined from base, prominent on abaxial surface, with 2 rounded alveoles at base of veins on adaxial side, mid vein ending with arista 2–2.5 mm long, abaxial surface of veins sparsely puberulous when very young, soon glabrous. Inflorescences terminal compound corymbs, composed of a few short corymbs, and axillary simple corymbs to racemes; peduncle slight greenish in vivo, dark brownish in sicco, glabrescent; rachises same in colour as peduncles, glabrescent near base, becoming puberulous acropetally. Pedicels 3.2–5 cm long, puberulous to pubescent with light brownish hairs; bracts often caducous, lanceolate to broadly elliptic, 0.8–1.2 × 0.2–0.8 cm, puberulous on both surfaces, margin entire, apex acute to acuminate; bracteoles ovate to broadly elliptic, 1.2–1.8 × 0.6–1.0 cm, puberulous on both surfaces, apex acute to acuminate, situated on upper part of pedicels near base of hypanthium, enveloping buds when young; short-stalked capitate hairs present at proximal area of adaxial surface of bracts and bracteoles, and adjoining area of pedicels. Floral buds fusiform, up to 1.5 cm long, 5-ribbed. Hypanthium tubular, 0.6–0.8 cm long, pubescent with light brownish hairs. Calyx (4–)5-lobed; lobes lanceolate to ovate, 0.7–0.8 × 0.3–0.5 cm, pubescent with light brownish hairs throughout, papillate glands present on proximal area adaxially. Petals 5, light pink, subequal, sparsely covered with wooly long hairs throughout, especially denser along margin and veins of lamina; claws 0.9–1.4 cm long; lamina broadly ovate to rhombic with crenulate margins, 1.2–1.8 × 0.9–1.4 cm, apex obtuse to rounded. Fertile stamens 3; filaments 2.8–3.0 cm long, covered with wooly long hairs; anthers 0.3–0.4 cm long, glabrescent to puberulous, light pinkish in vivo, dehiscing by longitudinal slits. Staminodes 7; filaments 1.3–2.0 cm long, glabrescent; reduced anthers puberulous. Floral disc absent. Pistils densely pubescent with light brownish hairs except stigmatic surface; ovary 0.7–0.9 cm long on a short stalk of 0.5–0.9 cm long; style 0.9–1.3 cm long; stigma small capitate, ca. 1 mm in diameter. Young fruits densely pubescent; mature fruits not seen.

Additional specimen examined: — LAOS. Sekong Province: La Mam District ["Nam man District"], Tan Village, Tattlie Waterfall, in secondary broad-leaved evergreen forest, 400–500 m elev., 5 December 2008, S. Wu WS-1906 [fl. buds, fl. & young fr.] (MO6146836 image!).

Distribution: — LAOS (so far known only from two provinces: Attapeu and Sekong, eastern side of the Bolaven Plateau).

Habitat and ecology: —This species was found in seasonal dry evergreen forest and secondary broad-leaved evergreen forest at 250–500 m elev. Flowering specimens were collected in December.

Etymology:— The specific epithet roseoalba is derived from the feature of its petals which are light pinkish in colour.

Vernacular name:— Siew Boua [“Siew” in Lao refers to Bauhinia or Phanera in general and “Boua” refers to the pinkish in colour of petals], suggested here.

Preliminary conservation assessment:— Data deficient (DD). Currently, Phanera roseoalba is known to occur at two localities in the vicinity of the Bolaven Plateau. From our observations by five field surveys on the Bolaven Plateau in 2018–2020 ( Souladeth et al. 2020, Tagane et al. 2020), the species was only found in a small area at eastern periphery of the Bolaven Plateau, Attapeu Province, and we estimate mature individuals less than 250 for this population. Another locality is known from northeast of the the Bolaven Plateau, La Mam District, Sekong Province, based on a single specimen collected in 2008, but the current condition of this population is unknown. Additional localities can be found in eastern region of the the Bolaven Plateau, and thus further floristic investigations are needed to elucidate the distribution range of the species. Given the inadequacy of the information of its distribution and number of individuals, we here propose Data deficient (DD) according to the IUCN Red List Categories ( IUCN 2012).

Notes: — Phanera roseoalba , P. involucellata and P. involucrans are likely to be closely related in that sharing a remarkable feature of bracteoles enveloping young buds, which is not found in any other Phanera species. The phylogenetic relationships among these taxa are yet to be clarified, and here we treat each of them as an independent species. Future molecular studies will be needed to understand their relationships.

New record

Phanera nervosa Benth. in Miq., Pl. Jungh. 2: 262 (1852). Type:— INDIA. Sillet Mont, N. Wallich 5777 (lectotype K000760781 image!, designated by Bandyopadhyay (2012); isolectotypes BM000958839 image!, CAL0000067903 image!, G00359968 image!, K001122106 image!). Figure 3 .

Specimens examined: — LAOS. Champasak Province: Bolaven Plateau, Paksong District, near Nong Luang Village, in wet evergreen forest, 15°04′44.53′′N, 106°12′27.06′′E, 1246 m elev., 3 July 2019, P. Souladeth, S. Tagane, N. Tanaka, K. Soutakone, Y. Suyama, K. Phengmala, N. Ishii L2798 (FOF0006129, KAG129087, TNS).

Distribution: — China, India, Myanmar, Laos, and Thailand.

Vernacular name: —Siew Dok-keo [“Siew” in Lao refers to Bauhinia or Phanera in general and “Dok-keo” refers to the white flowers], suggested here.

Notes 1: —Among Phanera species distributed in Laos, P.nervosa resembles P. coccinea de Loureiro (1790: 37–38) subsp. coccinea and P. rubra Lanorsavanh & Mattapha (in Mattapha et al. 2021: 545–546) in having lax inflorescences exceeding 3 cm in width, large flower buds exceeding 1.5 cm in length, calyx splitting into reflexed, lanceolate to oblong lobes, and densely pubescent pistils, but clearly distinguished from them by presence of ferruginous hairs on petioles and the abaxial surface of leaves even at maturity (vs. glabrous in both P. coccinea subsp. coccinea and P. rubra ) and white to greenish petals (vs. orange-reddish). It is distinguished from the other Phanera species in Laos by having a combination of following features: lamina bifid 1/3(–1/2) of its length; lax racemes of 3–10 cm wide; large obovoid flower buds 1.5–2 cm long; absence of floral disc; 3 fertile stamens per flower; densely pubescent pistils.

Notes 2: —Previously, Phanera nervosa has been known from northeastern India (Assam, Khasia, Sillet [type]), Myanmar (Kachin, Mandalay, Mon), southern China (Yunnan), and northern Thailand (Chiang Mai, Chiang Rai, Nan, Phitsanulok) ( Larsen & Larsen 1984, Chen et al. 2010, POWO 2023, also based on herbarium specimens cited in Appendix 1). The new locality in Laos is rather apart (ca. 600 km) from the proximate habitat in Thailand, representing the southern and eastern limit of the distribution range of this species, and thus important in the conservative perspectives.

Figures

FIGURE 1. Holotype of Phanera roseoalba Tk.Yamam., Tagane & Soulad. (Souladeth et al. L3481 (FOF0006810)). Photo: D. Kongxaisavath.

FIGURE 2. Phanera roseoalba Tk.Yamam., Tagane & Soulad. (Souladeth et al. L3481). A. Flowering branch; B. Portion of abaxial leaf surface; C. Young floral buds enveloped by two bracteoles; D. Floral bud just before anthesis, showing bracteoles, calyx splitting into lobes, and light pinkish petals; E. Flower (front view); F. Flower (diagonally backward view).Abbreviations: br, bracteole; cl, calyx lobe; pe, petal. Photos: S. Tagane.

FIGURE 3. Phanera nervosa Benth. (Souladethet al. L2798). A. Flowering branch; B. Adaxial leaf surface; C. Abaxial leaf surface; D. Flower (front view); E. Flower (side view). Photos: S. Tagane.