Ceropegia tenuicaulis Kidyoo, 2014

Kidyoo, Manit, 2014, Two new species of Ceropegia (Apocynaceae, Asclepiadoideae) from eastern Thailand, Phytotaxa 162 (2), pp. 91-98 : 93-95

Ceropegia tenuicaulis Kidyoo , sp. nov. ( Fig. 2 )

Ceropegia tenuicaulis differs from C. thailandica by its slender stem to 50 cm tall, a tubular-urceolate c orolla tube, and dense non-glandular hairs on the corolla lobes.

Type:— THAILAND. Ubon Ratchathani: Pha Taem National Park , 230 m, 13 September 2010, M. Kidyoo 1508 (holotype, BCU! , isotype, BKF! ).

Herbs, perennial, erect, not twining, with clear latex in all parts. Rootstock tuberous; tubers subglobose, smooth, light brown, 1.5–2 cm in diam. Stem terete, usually solitary, glabrous, usually unbranched, 30–50 cm tall, 1–1.5 mm in diam., green when young and turning brown with age; internodes 2–8.5 cm long, usually shorter on upper part. Leaves opposite, sessile; blade linear to linear-lanceolate, 5–10.5 × 0.15–0.25 cm, slightly carinate in cross section, coriaceous, base attenuate, margins entire, slightly revolute, apex acute to acuminate; abaxial surface pale green, glabrous, adaxial surface green, glabrous; midrib greenish white, slightly convex; lateral veins obscure. Inflorescence 1–flowered cyme, axillary or extra-axillary; peduncle slender, erect, green, glabrous, 1–2.7 cm long, ca. 0.5 mm in diam.; pedicel white or pinkish white, 4–8 mm long, 0.8–1 mm in diam., glabrous; bract solitary, attached at base of pedicel, lanceolate, ca. 0.8 × 0.3 mm, pinkish white, apex acute. Calyx deeply 5-parted, lobes yellowish green or green, narrowly lanceolate, 1.4–1.7× 0.4–0.5 mm, glabrous, apex sharply acute, pink. Corolla tubular-urceolate, upright, straight; corolla tube purplish or reddish brown or basal part greenish brown and upper part reddish brown, glabrous, 1.6–1.8 cm long, slightly inflated at base (about 1/2 of tube length), 0.5–0.6 cm in diam., inflated above, tube becoming straight and gradually narrowing to an ascending cylindrical portion 2.5–3 mm in diam.; interior of inflated part purplish brown, covered with long white hairs; lobes linear, 3.7–4 × 0.17– 0.19 cm, long caudate, outside brown or purplish brown, inside green or greenish brown, basal part loosely twisted, 2.5–3 × 1.9–2.1 mm, margins slightly reflexed, auriculate, auricles green; upper parts overlapping and dextrorsely tightly twisted, margin except auricles covered with brown or purplish non-glandular hairs. Gynostegium stipitate, stipe 1–1.5 mm long, 1–1.1 mm in diam. Corona double, outer lobes 5, joined to form a shallow cup, 3.4–3.5 mm in diam., hairy inside, apex of lobes bifid, yellowish white; inner lobes 5, terete, 3.5–3.7 mm long, 0.2–0.3 mm in diam., lower part dark brown, incumbent on dorsal surface of anthers, apical part usually long connivent-erect, yellowish white or pinkish white, apex slightly recurved. Pollinaria 5, pollinium broadly ovoid, yellow, 0.53–0.57 × 0.41–0.42 mm, translators stout, hyaline, ca. 0.09× 0.1 mm, corpusculum spatulate, reddish brown, 0.40–0.41 × 0.19–0.21 mm. Ovaries 2, ovoid, ca. 2 mm long, 0.5 mm in diam., glabrous. Fruits follicles, usually 2, linearlanceolate in outline, green when young, turning reddish brown with age, 5–7.5 cm long, 2.5–3 mm in diam. Seeds ovate-oblong, 5–6 × 1.9–2 mm, with a single coma of hairs 1–1.2 cm long, silky white.

Distribution:— Thailand (Ubon Ratchathani Province).

Habitat & Ecology:—In sandy soil among tall grasses in open area of deciduous dipterocarp forest at about 230 m elevation. Flowering July–October.

Etymology:— The specific epithet, tenuicaulis , refers to the noticeable erect, slender stem.

Discussion:— Only a few species of Ceropegia , including C. acicularis and C. tenuicaulis are grass-like. Other examples of this type are C. antennifera Schlechter (46: 1895), C. attenuata Hooker (t. 867: 1852), C. spiralis Wight (t. 1267:1850) and C. thailandica Meve. These species have an erect stem arising from a tuber (subglobose or irregular in shape) with lanceolate to linear leaves and a 1-flowered inflorescences ( Hooker 1883, Huber 1957, Ansari 1984, Li et al. 1995, Meve 2009). The two new species, C. acicularis and C. tenuicaulis are mostly similar to C. thailandica in habit, habitat, vegetative characteristics, as well as in some reproductive traits, i.e. grass-like perennial herb with non-twining stem arising from subglobose tuber, having lanceolate to linear leaves and a single flower, growing in open sandy areas of deciduous dipterocarp forests.

Although these three species have features in common, they can be clearly distinguished on the basis of the following characters. Ceropegia tenuicaulis and C. thailandica usually produce an unbranched stem with 1- flowered inflorescences on slender peduncles. Their corolla lobes are linear and drawn out into long tails. They often grow among tall grasses where they are difficult to discern due to their grass-like appearance. In contrast, C. acicularis usually has a branched stem with a solitary flower and spatulate corolla lobes that apically unite into a cage-like structure ( Fig. 3 ). Moreover, C. acicularis is usually found in open places and does not grow intermingled with grasses.

Ceropegia tenuicaulis and C. thailandica are distinguished from each other by characters of stem and flower. Ceropegia tenuicaulis has a slender stem to 50 cm tall (inflorescence length not included). The corolla tube is slightly swollen at the base (swelling 1/2 length of corolla tube) and becomes narrowed distally. The corolla lobes are linear and drawn out into a long tail. The margin and inside of the lobes are covered with non-glandular hairs. In full bloom, the 5 lobes are loosely twisted and do not overlap. The basal part of the lobes is loosely twisted with slightly reflexed margins and green auricles. The stem of C. thailandica is stout, to only 15 cm tall (inflorescence length not included), the corolla tube is ovoid or urceolate and the corolla lobes are covered with glandular hairs. The basal part of the corolla lobes is dark purple with strongly reflexed auricles. Moreover, in full bloom, unlike in C. tenuicaulis , the five lobes of C. thailandica overlap and are dextrorsely tightly twisted and are usually inseparable because they are held together by the glandular hairs ( Table 1 , Fig. 3 ).

Thorough surveys in northeastern and eastern Thailand have revealed that C. thailandica occurs in the Phu Wua Wildlife Sanctuary and in Phu Langka National Park, areas not far from each other (only about 30 km). Ceropegia acicularis and C. tenuicaulis occur in Pha Taem National Park, far to the north (about 400 km) of the areas where C. thailandica is distributed ( Fig. 4 ).

In conclusion, all data from the present study, as well as field observations on geographical distribution and ecological preferences, strongly indicate that C. acicularis and C. tenuicaulis are distinct and new species. As a further aid to identification, a key to these three taxa is presented below.

Figures

FIGURE 2. Ceropegia tenuicaulis Kidyoo (a) habit, (b) leaf, (c) flower, (d) longitudinal section through corolla tube showing corona and gynostegium, (e) top view of gynostegium, (f) side view of gynostegium, (g) calyx, (h) pollinarium, (i) fruit, (j) seed. Drawn by Manit Kidyoo from M. Kidyoo 1508 (a–h) and M. Kidyoo 1530 (i–j).

FIGURE 3. Comparison of vegetative and reproductive parts between C. acicularis (a–b; a. habit, b. corolla lobe), C. tenuicaulis, (c– d; c. habit, d. basal part of corolla lobe), and C. thailandica (e–f; e. habit, f. basal part of corolla lobe). Photos by Manit Kidyoo.

FIGURE 4. Distribution map of C. acicularis (1), C. tenuicaulis (1), and C. thailandica (2–3). (1) Pha Taem National Park, Ubon Ratchathani Province, (2) Phu Langka National Park, Bungkan Province, (3) Phu Wua Wildlife Sanctuary, Bungkan Province.