Phanera guangxiensis (D. X. Zhang & T. C. Chen) X. Peng, K. W. Jiang & T. Y. Tu

Peng, Xia, Jiang, Kai-Wen, Xie, Zhi, Gu, Shi-Ran, Wang, Xiang-Ping, Li, Shi-Jin, Shi, Miao-Miao, Tu, Tie-Yao & Zhang, Dian-Xiang, 2024, Rediscovery, amplified description, and taxonomic re-evaluation of Phanera erythropoda var. guangxiensis (Leguminosae, Cercidoideae), Phytotaxa 665 (1), pp. 55-62 : 56-61

Phanera guangxiensis (D. X. Zhang & T. C. Chen) X. Peng, K. W. Jiang & T. Y. Tu , comb. & stat. nov. Figs. 1A–M

& 2 .

≡ Bauhinia erythropoda Hayata (1913: 83) var. guangxiensis D. X. Zhang & T. C. Chen (1998: 145) .

≡ Phanera erythropoda (Hayata) Mackinder & R. Clark (2014: 54) var. guangxiensis (D. X. Zhang & T. C. Chen) Mackinder & R. Clark (2014: 54) .

Type:— CHINA. Guangxi: Longzhou, Jinlong, Shakao Hill , elev. 450–600m, 4 August 1957, S. H. Chun 13442 (holotype IBSC!; isotypes IBK00399065 !, KUN0157098 !, MO04158962 , image!) .

Description: —Woody lianas, main stem stout; branches green when young, sparsely sericeous with light-rusty hairs, glabrous when old. Tendrils slightly compressed at apex. Leaves unifoliolate, alternate but occasionally opposite; petioles 22–40 mm, slender, yellowish-green, indumentum similar to branches; leaflet blade hard coriaceous, adaxially dark green, abaxially pale green, glabrous on both surfaces, 3.5–10 × 3–8.5 cm, primary veins 7–9, cordate at base, bilobed at apex to 1/4 of the length, lobes slightly acute towards apex. Inflorescence a solitary raceme or several ones joined in a panicle, terminal or axillary, 3–7.5 cm; axis, pedicel, hypanthium, calyx, and corolla densely pubescent. Bracts and bracteoles not seen. Pedicel 14–24 mm, slender. Flower buds ellipsoid, ca. 4.2 × 3.1 mm; calyx mouth 5- toothed, not covering the corolla in buds, petals arranged in clasp pattern, folded at the adjacency to form 5 shallow longitudinal ribs. Open flowers ca. 14.3 mm in diam. Hypanthium funnelform, ca. 2–3 mm. Calyx lobs 5, triangular-ovate, green, not reflexed at anthesis, persistent. Petals 5, green, narrowly obovate, subequal, 7–9 × 2–3 mm, margins slightly inrolled, claw un-conspicuous, both surfaces densely pubescent with pale hairs. Floral disc fleshy, swollen, with orange-red edges and an orange-yellow center, gradually turns dark red or almost black as it wilts. Fertile stamens 3, mounted on lower parts of disc, filaments yellowish-green, equal to the length of petals, glabrous, curved; anthers elliptic, yellowish-green, longitudinally dehiscent; pollens white; staminodes 2–3, mounted on upper parts of disc. Gynoecium green; ovary oblique, densely pubescent with pale hairs, ovary shortly stipitate free from the inner wall of the hypanthium; style slender; stigma small. Pods lanceolate-oblong, densely pubescent with grey hairs.

Phenology: —Flowering March–May; fruiting June–August.

Distribution and habitat: — Phanera guangxiensis is currently known only from its type locality in Longzhou County, Guangxi, southwestern China, where it occurs at elevations of 450– 600 m. The species inhabits pristine evergreen broadleaf forests on limestone hills and cliffs, climbing up into the crowns of trees, shrubs, and bamboos. Its associated species include Ampelocalamus sinovietnamensis Y. H. Tong, Z. G. Xu, J. B. Ni & N. H. Xia. , Pterolobium punctatum Hemsl. ex F. B. Forbes & Hemsl. and Myrsine seguinii H. Lév.

Etymology: — Zhang & Chen (1998) did not provide the etymology when they established the variety, Bauhinia erythropoda var. guangxiensis , but it is obvious that the epithet of this taxon derives from its type locality, Guangxi Zhuang Autonomous Region.

Conservation Status: —From its first discovery in 1957 to the present, only a single population of Phanera guangxiensis has been recorded from the type locality, Shakao Hill in Longzhou County, Guangxi Zhuang Autonomous Region. Due to limited herbarium gatherings, the extent of occurrence (EOO) cannot be calculated. Shakao Hill is situated near the China-Vietnam border, part of the continuous Karst mountain range. The steep terrain and sparse soils have limited human encroachment, leaving mostly untouched primary forests, though flat areas between hills are cultivated as farmland. The gatherings XieZ2356, XieZ2362 and XieZ2696 were collected near the mountainside close to the 523 m summit, surrounded by well-preserved primary forest. We also observed the same species appearing to occur on other nearby hills. This unique terrain has likely contributed to preserving this population for nearly seventy years while also restricting access and spread of the species, explaining the extremely low number of collections. Based on the environmental stability of the area, we believe the habitat will continue to be maintained and the species, though rare, can persist. Therefore, we consider P. guangxiensis to be Data Deficient (DD).

Specimens examined:— CHINA. Guangxi: Chongzuo, Longzhou, Jinlong, Gaoshan Village, Banbi Tun to National Boundary Marker 872, on limestone mountain slopes and summits, elev. 530 m, 11 June 2021, Z. Xie & R. Wu XieZ2356 (IBSC). ibid., elev. 537 m, ead. die, coll. iid. XieZ2362 (IBSC, PE). Chongzuo, Longzhou, Jinlong, on the rocky cliffs of limestone mountainous terrain elev. 523 m, 11 May 2022, Z. Xie, H. Y. Li & L. X. Zhou XieZ2696 (CDBI, CSH, IBSC, NPH).

Taxonomic remarks: —The combination of densely hairy pods and smooth leaves led to the establishment of Phanera erythopoda var. guangxiensis . However, examination of the recently collected flowering specimens reveals floral characteristics that clearly distinguish it from P. erythropoda ( Figs. 1N–P & 3 ): inflorescences racemose or paniculate in P.guangxiensis (vs. racemose-corymbose in P.erythopoda ), pubescent with short grey hairs (vs. ferrigenous with long rusty hairs); calyx not covering the corolla in buds, top lobed (vs. calyx entirely covering the corolla in buds, closed); hypanthium funnelform (vs. cylindrical); calyx lobe 5, triangular-ovate, not reflexed at anthesis (vs. calyx lobes 5, splitting into 2 or 3, oblong-lanceolate, reflexed at anthesis); petals green, narrowly obovate with slightly inrolled margins (vs. white, broadly obovate and drastically rugose); floral disc fleshy (vs. not fleshy). This suite of morphological evidence supports recognizing P. guangxiensis as an independent species distinct from P. erythropoda . Moreover, P. guangxiensis exhibits short funnelform hypanthium, a fleshy floral disc, obliquely positioned ovary that is stipitate with the stalk free from the inner hypanthium wall, and a small stigma – characters that align well with the Lasiobema group within Phanera . These features further support recognizing P. guangxiensis as an independent species distinct from its previous varietal status under P. erythropoda .

Phanera guangxiensis is morphologically most similar to P. japonica ( Maximowicz 1873: 401) H. Ohashi (2014: 198) in having glabrous leaflet blades on both surfaces, pubescent inflorescences, a calyx not covering the corolla in bud, green petals, a hairy ovary, and hairy young pods. However, P. guangxiensis can be readily distinguished from P. japonica by its leaflet blades lacking a yellowish margin (vs. leaflet blades with a very narrow, thin, yellowish margin when dry in P. japonica ), calyx lobes not being reflexed at anthesis (vs. slightly reflexed), and the floral disc with orange-red edges and an orange-yellow center gradually turning dark red to nearly black as it wilts (vs. purple-reddish when young, turning black when old).

Phanera guangxiensis also resembles P. macrostachya Bentham in Miquel (1852: 262) to some extent in having leaflet blades glabrous on both surfaces, shallowly bilobed with broadly divergent lobes, a hairy ovary, and a calyx not covering the corolla in bud. However, P. guangxiensis can be distinguished by its leaflet lobes being slightly acute at the apex (vs. acuminate or obtuse in P. macrostachya ), ellipsoid flower buds (vs. obovoid), green petals (vs. orange-red), and 2–3 staminodes (vs. 7).

Figures

FIGURE 1. A–M. Phanera guangxiensis (D. X. Zhang & T. C. Chen) X. Peng, K. W. Jiang & T. Y. Tu, A. Habitat; B. Reproductive branches; C. Leaf (adaxial surface); D. Leaf (abaxial surface); E. Young branches; F. Paired tendrils; G. Flower buds, showing calyx not covering the corolla; H. Lateral view of pedicel and hypanthium, showing the pale pubescence; I. Flower; J. Flower when wilts, showing calyx not reflexed at anthesis; K. Inflorescence; L. Pods at an early stage, showing oblique ovaries; M. Immature pod. N–P. Phanera erythropoda (Hayata) Mackinder & R. Clark N. Inflorescence; O. Leaf (adaxial surface); P. Flower and its anatomy. Photographs by Zhi Xie (A–M) and Tie-Yao Tu (N–P).

FIGURE 2. Phanera guangxiensis (D. X. Zhang & T. C. Chen) X. Peng, K. W. Jiang & T.Y. Tu, A. Flowering branch; B. Leaf; C. Flower bud; D. Flower; E–F. Petals; G. Flower with petals removed; H. Stamen; I. Pod at an early stage. J. Pod. Line-drawing prepared by Ms. Yun-Xiao Liu.

FIGURE 3. Holotype of Bauhinia erythropoda Hayata [≡ Phanera erythropoda (Hayata) Mackinder & R. Clark]: CHINA. Hainan, 1910, Z. Katsumada s. n. (TI00082349).