Leptodermis hechiensis R.J.Wang, 2018

Guo, Xiao-Ming, Liao, Qi, Zhou, Shan & Wang, Rui-Jiang, 2018, Leptodermis hechiensis (Rubiaceae), a new species from Guangxi, China, Phytotaxa 349 (1), pp. 67-72 : 68-70

Leptodermis hechiensis R.J.Wang , sp. nov. ( Fig. 1 )

Type: — CHINA. Guangxi Zhuang Autonomous Region: Hechi city, Jinchengjiang district , 24°40’ N, 108°3’ E, 246m, 1 September 2013 (long-styled fl., fr.), R. J.Wang & Q.Liao 2500 (holotype, IBSC, Barcode number 0824856; isotype, IBSC, Barcode number 0824857) .

Diagnosis: — Leptodermis hechiensis is similar to L. yangshuoensis in slender branches, subcoriaceous leaf blade with pale green abaxial surface, and long corollas; the former differs from the latter by the triangular calyx lobes (vs. ovateoblong) and the 3-lobed style (vs. 5-lobed) ( Table 1).

Shrubs 0.3–2 m tall. Branches slender, pale gray, glabrous or sparsely pubescent, usually reddish and with soft hairs when young. Stipules rigid, triangular, 1–2.3 mm long, cuspidate, mucronate at apex, pubescent outside. Leaves opposite; petioles, (0–)2.5–4(–9) mm long, glabrous or sparsely pubescent; blades ovate to broadly lanceolate, 1.6–6.6 × 0.8–3.3 cm, subcoriaceous, adaxially dark green, abaxially pale green, glabrous on both surfaces, margins sparsely pubescent, attenuate or cuneate at base, acute or shortly acuminate at apex; midrib impressed adaxially, prominent abaxially, sparsely pubescent; secondary veins 3–4 on each side of midrib, distinct adaxially, indistinct or slightly prominent abaxially; tertiary veins usually indistinct. Inflorescences axillary or terminal, fascicled, 1–3(–6)-flowered. Flowers heterostylous, sessile or pedicellate; pedicels (when present) to 2(–3.5) mm long, sparsely pubescent; bracteoles in pairs, connate ca. 3/4 length, 1.6–1.9 mm long, membranous, usually transparent, subequal to or a little shorter than calyx at anthesis, distinctly veined, acuminate to acute at apex, mucronulate. Calyx 2.1–2.6 mm long; tube ca. 1.7 mm long; lobes 5, triangular, ca. 0.6 mm long, margins ciliate, acute at apex. Corollas salverform, purplish or white, (11–) 13–18 mm long, tubes densely hairy at throat; lobes 5, ovate-triangular, ca. 3 mm long, veined, hooked inward at apex. Stamens 5, introrse, filaments ca. 0.6 mm long, anthers ca. 2 mm long. Ovary 5-locular, one ovule per locule; style 3-lobed, lobes linear, slender, revolute, and hairy. Long-styled flowers: stamens inserted below the corolla mouth, not exserted; styles 11.5–14 mm long, style lobes 0.8–1.4 mm long. Short-styled flowers: stamens inserted at the corolla mouth, exserted; styles 6.0– 6.3 mm long, style lobes 0.3–1.0 mm long. Capsule ovoid, (2–)2.5–4(–5) mm long, septicidally dehiscing into 5 valves; valves persistent, with persistent calyx lobes. Seeds ca. 3.5 mm long, with reticulate aril free from testa.

Etymology: —The specific epithet is derived from the name of the type locality, Hechi City of Guangxi Zhuang Autonomous Region, China.

Geographical distribution: — Leptodermis hechiensis is known from Hechi City of Guangxi, China ( Fig. 2 ).

Habitat: — Leptodermis hechiensis often occurs on dry limestone slope or roadside, in sunny exposure, at low elevations (122–492 m).

IUCN Conservation assessment: —Eleven populations with more than 50 individuals in each have been found in Hechi area. There is no any significant or plausible threat to the habitat and the plant up to now. It is therefore evaluated as Least Concern (LC), according to IUCN Red List criteria ( IUCN 2017).

Phenology: —Flowering in August and September, fruiting from August to October.

Additional specimens examined (paratypes): — CHINA. Guangxi Zhuang Autonomous Region: Hechi city, Huanjiang county , elev. 335 m, 2 August 2012, R. J. Wang 2154 ( IBSC, short-styled fl.). Jinchengjiang district , elev. 255 m, 25 September 2013, R. J. Wang 2501 ( IBSC, short-styled fl.) ; Bawan village, elev. 423 m, 25 September 2013, R. J.Wang 2505, 2506 ( IBSC, short-styled fl.), R. J.Wang 2503, 2504 ( IBSC, short-styled fl.), R. J.Wang 2502 ( IBSC, long-styled fl.), 28 June 2017, X. M.Guo 505 ( IBSC). Luocheng county, Gumao village , elev. 287 m, 2 August 2012, R. J. Wang 2153 ( IBSC) ; Huaiqun town , elev. 284 m, 2 August 2012, R. J. Wang 2151 ( IBSC) ; Hualuo village , elev. 327

m, 24 August 2010, R. J. Wang 1429 ( IBSC, long-styled fl.) ; Luocheng garden, elev. 350 m, 24 August 2010, R. J. Wang 1430 ( IBSC, long-styled fl.) ; South of Luocheng , elev. 350 m, 2 August 2012, R. J. Wang 2149 ( IBSC, short-styled fl.) ; Xiaochang’an town , elev. 122 m, 1 August 2012, R. J.Wang 2147 ( IBSC, long-styled fl.), R. J. Wang 2148 ( IBSC, short-styled fl.). Tian’e county, Julongxia Forrest garden, elev. 492 m, 27 August 2010, R. J.Wang 1439 ( IBSC, long-styled fl.). Yizhou district, nearby Ziyun Temple, elev. 184 m, 25 August 2010, R. J. Wang 1433 ( IBSC, long-styled fl.), 24 September 2013, R. J. Wang 2491, 2492, 2496, 2497 ( IBSC, long-styled fl.), 27 June 2017, X. M. Guo 504 ( IBSC) .

Palynology: —Pollen grains of Leptodermis hechiensis are released in monads, and medium-sized (long-styled fl., diameter 29.4–42.6 μm; short-styled fl., diameter 31.2–46 μm), spheroidal, tetracolpate, and with a reticulate sexine. They show a remarkable dimorphism between pollen of long- and short-styled flowers, which is similar to the pollen grains of Damnacanthus C. F. Gaertner (1805: 18) species ( Akiyo & Hidetoshi 2003). Short-styled flowers always presented with larger pollen grains than those of the long-styled flowers. In pollen muri of long-styled flowers, the surface is psilate, whereas it is granula in muri of short-styled flowers ( Fig. 3 ).

Leaf epidermis: —In Leptodermis hechiensis , anticlinal walls arch adaxially and abaxially, the outline of the periclinal walls in adaxial epidermis is obscure, irregular abaxially. Leaf blades have abundant epicuticular wax on adaxial and abaxial surfaces. The adaxial epidermis is covered with a reticulum of buttressed ridges wax ornamentation, whereas the abaxial with long parallel striae. The paracytic stomata only appear on the abaxial surface ( Fig. 3 ).

The outline of the periclinal walls of the leaf adaxial epidermal cells are polygonal and the leaf abaxial epidermis is smooth in Leptodermis yangshuoensis and L. coriaceifolia . The leaf adaxial epidermis was covered with radiating striae wax ornamentation in L. yangshuoensis , and with short striae in L. coriaceifolia ( Fig. 3 ). In L. coriaceifolia , the leaf epidermis is covered with multicellular simple trichomes.

Notes: — Leptodermis hechiensis also resembles L. coriaceifolia in the number of style lobes; but differs from it in slender, sparsely hairy to glabrous branches (vs. robust, erect, hispid branches), subcoriaceous leaf blades with pale green surface abaxially (vs. coriaceous ones with whitish or pale yellow), bracteoles 1.6–1.9 mm long (vs. 2.7–4 mm long), corollas 13–18 mm long (vs. 8–12 mm long), and capsules 2.5–4 mm long (vs. 4–6.5 mm long) ( Table 1).

Figures

FIGURE 1. Morphology of Leptodermis hechiensis. A. Habitat, showing slender branches. B. Leaf, adaxial side. C. Leaves, abaxial side with pale green surface. D. Seed with reticulate aril. E. Inflorescence branches, showing pedicels. F. Calyx and membranous bracteoles. G. Detail of inflorescence, with long-styled flower with 3-lobed style, and immature fruits. H. Dissected long-styled flower, showing stamens insertion and pubescence at corolla mouth. I. Short-styled flower, top view. J. Inflorescence with short-styled flowers, side view. (A from R.J.Wang 2491, B from R.J.Wang, S.Zhou, S.J.Deng, Q.Liao 2153, C from R.J.Wang 1429, D from the type locality, E & I from R.J.Wang, S.Zhou, S.J.Deng, Q.Liao 2154, F–H from R.J.Wang & Q.Liao 2491, J from R.J.Wang & Q.Liao 2503). Photos by R.J.Wang

FIGURE 2. The allopatric geographical distribution of Leptodermis hechiensis (11 populations), L. coriaceifolia (29 populations) and L. yangshuoensis (five populations).

FIGURE 3. Leaf epidermis of the three species and pollen grains of Leptodermis hechiensis under SEM. A. adaxial epidermis of L. hechiensis, showing the reticulum of buttressed ridges wax ornamentation and the obscure outline of periclinal walls. B. abaxial epidermis of L. hechiensis, showing the long parallel striae. C. the paracytic stomata of L. hechiensis. D. adaxial epidermis of L. yangshuoensis, showing the radiating striae wax ornamentation and the polygonal outline of the periclinal walls. E. the smooth abaxial epidermis of L. yangshuoensis. F. the paracytic stomata of L. yangshuoensis. G. adaxial epidermis of L. coriaceifolia, showing the short striae wax ornamentation and the polygonal outline of the periclinal walls. H. the smooth abaxial epidermis of L. coriaceifolia. I. the paracytic stomata of L. coriaceifolia. J. long-styled flower pollen, showing the four apertures, polar view. K. long-styled flower pollen, equatorial view. L. short-styled flower pollen, showing the four apertures, polar view. M. short-styled flower pollen, equatorial view. N. aperture for long-styled flower pollen. O. long-styled flower pollen, showing the reticulate sexine with psilate surface. P. aperture for short-styled flower pollen. Q. short-styled flower pollen, showing the reticulate sexine with granula on pollen muri. (A–C, J, K, N, O, from R.J.Wang & Q.Liao 2500; D–F, from R.J.Wang & Q.Liao 2475; G–I, from R.J.Wang 2051; L, M, P, Q, from R.J.Wang & Q.Liao 2501).