Manihot luxurians M. J. Silva, 2015

Silva, Marcos José Da, 2015, Two new wild cassava species (Manihot, Euphorbiaceae) from the Brazilian Cerrado, Phytotaxa 213 (2), pp. 131-139 : 135-138

Manihot luxurians M. J. Silva , sp. nov. ( Figs. 3 , 4 )

This new species is characterized by an unique combination of characters: arborescent habit, glabrous vegetative and reproductive parts, bracts with their margins compressed up to the upper third of the calyx, ovate pistillate sepals, flowers in large panicle or typical racemes, flowers of both sexes yellowish, stigmatic branches patent, and glabrous and not winged fruit.

Type: — BRAZIL. Goiás: Colinas do Sul, Chapada dos Veadeiros, ca. 2 km a partir do final da fazenda do Sr. Marconi Perillo, Cerradão de encosta, 14º09’37.6”S, 47º57’2,3”W, 536 m elevation, 22 February 2014, (fl, fr), M. J. Silva & R. C. Sodré 5916 (holotype UFG!, isotypes K!, NY!, P!, UB!).

Shrubs to treelets 3–6.5 m tall, monoecious; stems unbranched or dichotomously branched near apex, erect, sometimes the stem being pendent in specimens taller than 4 m, branches green to bluish-green, waxy and glossy, including axis of inflorescences and petioles; latex yellow. Stipules almost caducous. Leaves in alternate spiral arrangement; lamina chartaceous to slightly coriaceous, 9–19.5 × 6.5–11 cm, glabrous on both surfaces, 5–7-lobed, or more rarely 3-lobed or unlobed near the inflorescence, lobes overlapping at sinus, oblong, oblong-obovate, or oblong-elliptic, margin entire, apex cuspidate, sometimes oblique; venation camptodromous-brochidodromous, primary and secondary veins pinkish or purplish, the primary ones prominent on both surfaces, the secondary ones arched in relation to the midrib and impressed on both surfaces, upper surface green and lustrous, lower surface glaucous to green-cinereous, with a smooth wax pattern; petiole 19–28 cm long, cylindrical to angulate, sulcate above, greenish to vinaceous or purplish. Racemes 5–15 cm long, solitary or in clusters of 2–5, with two pistillate flowers at the base and 5 to 18 terminal staminate flowers. Panicles 7–20 cm long, with basal axis similar to racemes. Both inflorescence types are terminal or located in the axil of dichotomous branches, erect or pendent. Staminate flowers: buds 11.1–11.9 × 6.5–7 mm, oblongoid to oblong-elliptic, yellowish without purplish pigmentation, glabrous to rarely glabrescent; bracts (at the base of the pedicels) 16–20 × 8–13 mm, elliptic, widely elliptic to ovate, base obtuse, apex acuminate, persistent or tardily caduceus, glabrous on both surfaces, 9–10-nerved; bracteoles 8–10 × 3–3.8 mm, elliptic to narrowly elliptic, base obtuse, acuminate at the apex, 3-nerved, glabrous to rarely glabrescent, persistent; pedicel 1.5–1.8 mm long, cylindrical; calyx 11–12 × 6.9–7 mm, campanulate, yellowish without purplish pigmentation, shortly pubescent internally, lobes widely triangular to obtuse, apex obtuse and shortly apiculate dorsally; disc 10-lobed, dark yellow, lobes rounded; stamens 10, in two whorls of five; filaments 5–11 mm long, pubescent near apex; anthers 4–4.1 mm long, lanceolate, yellowish. Pistillate flowers: buds 11–12 × 9–9.5 mm, ovoid, yellowish; bracts (at the base of the pedicels) 18–20 × 9–9.8 mm, widely ovate, entire, base obtuse, apex acuminate, glabrous or rarely glabrescent on both surfaces, caduceus; bracteoles 17–18.9 × 7–8 mm, ovate, base oblique or obtuse, apex acuminate, indumentum similar to that of bracts; pedicel 10–12 mm long, cylindrical to slightly obconical, glabrous, greenish; sepals 10–10.3 × 4–6 mm, ovate to widely ovate, yellowish, pubescent internally, apex obtuse and shortly apiculate dorsally, margins involute; disc discretely lobed, dark yellow to reddish; ovary 3.8–4.2 × 3.3–3.4 mm, ovoid, glabrous, conspicuously winged, green, styles 3, slightly united at the base, free portion 1.9–2 mm long, with a multifid apex. Capsules 19–22 × 18–28 mm, widely subglobose, smooth, glossy, conspicuously not winged, with septicidal and loculicidal dehiscence, light green, slightly waxy when immature, glabrous. Seeds 1.7–1.8 × 4.0– 4.2 mm, oblongoid, maculate; caruncle 2.3–2.4 mm, hat-shaped, cream to yellowish.

Additional specimens examined (paratypes): — BRAZIL. Goiás: Colinas do Sul, Chapada dos Veadeiros, ca. 2 km a partir do final da fazenda do Sr. Marconi Perillo, Cerradão de encosta, 14º09’37.6”S, 47º57’2,3”W, 536 m elevation, 22 February 2014, (fl, fr), M. J. Silva & R. C. Sodré 5914 ( UFG), M. J. Silva & R. C. Sodré 5915 ( UFG) ; Chapada dos Veadeiros, 4 km a partir do final da fazenda do Sr. Marconi Perillo, Cerradão de encosta, 29 January 2014, (fl), M. J. Silva & R. C. Sodré 5761 ( UFG), M. J. Silva & R. C. Sodré 5762 ( UFG), M. J. Silva & R. C. Sodré 5763 ( UFG), M. J. Silva & R. C. Sodré 5764 ( UFG), M. J. Silva & R. C. Sodré 5765 ( UFG), M. J. Silva & R. C. Sodré 5766 ( UFG) ; 500 m a partir da divisa dos municípios Colinas do Sul e Alto Paraíso de Goiás, 14º13’45.8”S, 47º54’46.2”W, 606 m elevation, 22 February 2014, (fl, fr), M. J. Silva, P. H. B. Santos & R. C. Sodré 5902 ( UFG) .

Distribution and ecology: — Manihot luxurians was found in Cerradão and Cerrado sensu stricto, growing on the edges of the vegetation in clayey soils, near streams or waterfalls, on slopes, or on the top of hills in Cerrado rupestre, at elevations of ca. 500– 606 m.

Phenology: —Collected with flowers and fruits from January to February.

Etymology: —The specific epithet “ luxurians ” alludes to the exuberant aspect and the beautiful foliage of the species.

Relationships: — Manihot luxurians shares with M. mossamedensis Taubert (1896: 442) the arborescent habit, leaves with 5–7 lobes or less, often 3-lobed or unlobed near the inflorescence, large bracts (up to 20 mm long), and the fruits conspicuously winged. However, the characteristics of the inflorescences, bracts, indumentum on the vegetative and reproductive parts, and orientation of the styles led to the conclusion that M. luxurians is a new species.

In M. mossamedensis the young branches, abaxial surface of the leaf, inflorescences, bracts and bracteoles of male and female flowers, and flowers of both sexes internally and externally, including androecium, gynoecium, and disc are densely and shortly tomentose (vs. glabrous in M. luxurians ). Also, in the former the bracts of male and female flowers present conspicuously revolute margin and cover both types of flowers at anthesis (vs. bracts with margin compressed up to the upper third of the calyx), the pistillate sepals are lanceolate (vs. widely ovate), staminate bracts are acuminate at apex (vs. obtuse), inflorescences are subspicate racemes (vs. panicles or typical racemes), flowers of both sexes are greenish (vs. yellowish), stigmatic branches are ascending (vs. patent), and fruits are tomentose and winged (vs. glabrous and not winged).

Manihot mossamedensis and M. luxurians are the only species of the genus in the state of Goiás with arborescent habit (up to 6.5 m tall) and the main stem with ramifications only near the apex. So far, these species are known only in the state of Goiás. Manihot mossamedensis has been reported in areas up to ca. 800 m above sea level in the central part of the state (Serra Dourada, in the municipality of Mossâmedes), whereas M. luxurians has been found in the northeastern part of the state (Chapada dos Veadeiros), in mountainous areas up to ca. 606 m above sea level. The two areas of occurrence of these species are more than 400 km apart.

Conservation status: —According to IUCN (2014), M. luxurians can be classified as critically endangered (CR) [B2 ab (ii)], since the species occurs in isolated populations in the municipality of Colinas do Sul, an area smaller than 100 km 2.

Figures

FIGURE 3. Manihot luxurians. A. Flowering branch. B. Staminate bract. C. Staminate bracteole. D. Staminate bud. E. Staminate flower. F. Staminate flower with calyx split and open. G. Detail of the lobe of the staminate calyx. H. Pistillate bract. I. Pistillate bracteole. J. Pistillate bud. K. Pistillate flower. L. Pistillate flower showing the gynoecium. M. Lobes of the pistillate calyx. N. Fruit. Drawn by Cristiano Gualberto from the holotype.

FIGURE 4. Manihot luxurians. A. Habit erect. B. Flowering branch pendent. C. Panicle. D. Staminate flower, lateral view. E. Staminate flowers, ventral view. F. Pistillate flower, ventral view. G. Pistillate flower open. H. Fruit. Photographs by the author.