Manihot macrocarpa P.Carvalho & M.Martins, 2017

Martins, Márcio Lacerda Lopes, Carvalho, Paulo Cezar Lemos De, Ledo, Carlos Alberto Da Silva & Amorim, André Márcio, 2017, Manihot macrocarpa (Euphorbiaceae), an unusual rain forest species from Brazil, Phytotaxa 309 (2), pp. 179-183 : 179-182

Manihot macrocarpa P.Carvalho & M.Martins , sp. nov. ( Figures 1–2 )

TYPE: — BRAZIL. Bahia: Mun. Ibirapitanga, administrative head office of Área de Proteção Ambiental do Pratigi, near the restaurant, 13º53’51.2” S, 39º27’25.9”W, 691 m, fl., fr., 27 March 2013, M. L. L. Martins & C. A. S. Ledo 1928 (holotype HURB!, isotypes CEN!, CEPEC!, HUEFS!, K!, SP!)

Manihot macrocarpa resembles M. compositifolia Allem (1989: 650) by its lianescent habit and indehiscent fruits. It differs by its simple, unlobed leaves and orbicular fruits (vs. compound, [3–]5[–7]-foliolate leaves and ellipsoid fruits in M. compositifolia ).

Monoecious climbing vine, up to 10 m tall. Roots not tuberous. Stems smooth, branches cylindrical with evident nodes along the basal portion, up to 4 cm diam., latex white, not abundant; glabrous. Stipules ca. 3 mm long, setaceous, caducous, margin entire. Leaves simple, (5–)10(–12) × 2–5 cm, chartaceous, elliptical to oval, base obtuse, margin entire, apex acute, venation camptodromous, petioles 1–8 cm long, cylindrical, basally inserted, clasping. Inflorescences paniculate or rarely racemose, 7–11(–15) cm long, erect to pendulous, bracts and bracteoles ca. 2 mm long, setaceous, blackened. Staminate buds 0.8–1.5 × 0.5–0.7 cm, ovoid, greenish yellow with purple inner spots; staminate flowers ca. 2 × 1 cm, pedicel 0.3–1.6(–2) cm long; staminal disc yellowish; sepals 5, fused for 2/3 of their length, stamens 10, in two whorls, glabrous, 0.8–1.2 cm long, filaments white, anthers yellow. Pistillate buds 2 at base of inflorescence, opposite to subopposite, ca. 2 × 0.5 cm, pyramidal, greenish yellow with purplish spots; pistillate flowers ca. 2 × 1 cm, pedicel 0.6–2(–2.5) cm long; sepals 5, greenish yellow, glabrous, free; ovary glabrous, disc nectariferous, light yellow, style up 3 mm long, stigmas 3, papillose. Fruits indehiscent, (3–)4–5(–5.3) cm diam., orbicular, glabrous, green, surface smooth, rarely ribbed, ribs ca. 1 mm long, tenuous. Seeds (2.5–)3.5–4 × 2–2.5 cm, ellipsoid to oblongoid, inner surface convex, dark brown, sometimes with small dark spots; caruncle ca. 1 × 5 mm, apical, yellowish white.

Etymology:— The epithet refers to the diameter of the fruit, which may be the largest known for Manihot .

Phenology:— Collected with flowers in March and October, and with fruits in March.

Conservation, distribution and habitat:— The species occurs in dense montane rain forest in the Serra do Papuã, in southern Bahia. Recently, taxonomic and floristic novelties in diverse groups of plants have been recorded for this region ( Zorzanelli et al. 2015, Marinho et al. 2016). Populations of Manihot macrocarpa are usually found on forest edges, and individuals can reach 10 m in height. To date there is only one occurrence record of this species, which includes it among the Critically Endangered species (CR B1abiii, B2abiii), according to criteria of the International Union for the Conservation of Nature ( IUCN 2012) reinforced by the expected decrease in area and quality of their habitat.

Paratypes:— BRAZIL. Bahia: Mun. Itacaré, road between Embratel Tower and highway BR-101/ Itacaré, fl., 21 December 1979, S. A. Mori & F. Benton 12851 ( CEPEC!). Mun. Ibirapitanga, Serra do Papuã , APA de Pratigi ; wood behind the bungalow 1, 13º53’53.002”S, 39º27’25.999”W, fr., 15 March 2013, L. Y. S. Aona et al. 2516 ( HURB!) .

Comments:— The species of Manihot that are vines and occur in rain forest usually have indehiscent fruits [e.g., M. baccata Allem (1999: 181) , M. compositifolia , M. quinquepartita Huber ex Rogers & Appan (1973: 196) ]. Although some authors consider them related to section Peruvianae Rogers & Appan (1973: 189) due to habit ( Rogers & Appan 1973), the species with indehiscent fruits have not been directly associated with any section of Manihot yet. Section Peruvianae includes only four lianescent species from Amazonia, and of these only M. quinquepartita has indehiscent fruits. Allem (1989) considered M. compositifolia related to section Peruvianae because of its habit. Allem (1999) later suggested that M. baccata was not related to this section because of its compound leaves and fruit type. A recent phylogeny of Manihot included the lianescent Amazonian species (including M. baccata ) in the same clade, while M. compositifolia appears in a clade of species from the caatinga [ Manihot section Glaziovianae Pax (1910: 23 , 89)] ( Duputié et al. 2011). The morphology of M. macrocarpa in combination with its distribution (distinct from the Amazonian species) suggests that it is closer to M. compositifolia . However, additional studies are needed before including it in one of the currently accepted sections of Manihot .

Figures

FIGURE 1. Manihot macrocarpa. A. Habit showing several branches covering the canopy of a tree. B. Detail of stem showing diameter. C. Clasping petiole. D. Leaves. E. Staminate buds F. Inflorescence G. Fruit. (A–G by M. Martins).

FIGURE 2. Manihot macrocarpa. A. Flowering branch. B. Pistillate bud with bract and bracteoles. C. Staminate bud. D. Pistillate flower. E. Fruit. F. Seed, frontal and lateral view (Martins & Ledo 1928, holotype; drawn by M. Martins).