A New Species of Jatropha (Euphorbiaceae) from Nicaragua

Abstract

ABSTRAcr A new species, Jatropha stevensii, is described from collections in Dept. Boaco in Nicaragua. It may be assigned to subg. Curcas and appears related to Jatropha fremontioides, a species from southern Mexico. Jatropha stevensii represents yet another extension of the Mexican xerophytic element into Central America, and the second record for Jatropha subg. Curcas. When Jatropha costaricensis Webster & Poveda was described from Guanacaste, Costa Rica, some years ago (Webster & Poveda, 1978), it was predicted that other xeric relict taxa might be discovered elsewhere in Central America. Recent botanical exploration in Nicaragua has disclosed not only a number of new populations of Jatropha podagrica Hook. in rocky areas in Dept. Esteli, but also on basaltic ridges in Dept. Boaco a species that appears to be undescribed. Unlike J. podagrica, which belongs to subg. Jatropha (Dehgan & Webster, 1979), the plant from Boaco clearly is referable to subg. Curcas. Jatropha stevensii Webster, sp. nov. TYPE: Nicaragua, Dept. Boaco, 1.6 km SW of Santa Cruz, low ridge of basaltic lava, 140-160 m, 12024'N, 85050'W, 7 June 1984, W. D. Stevens 22902 (MO, holotype; DAV, isotype; additional isotypes to be distributed). It should be noted that the type collection includes both glabrous and pubescent specimens and was apparently gathered from several individuals. Ab J. olivacea differt dichasio menor, minore stipulis obsoletis, fohiis integris marginibus non glanduligeris; ab J. alamanii foliis elobatis, sepalis minoribus, petalis tantum 1/3 longitudinis coalitis; ab J. fremontioide foihis acuminatis, dichasio non capituliforme. Deciduous shrub to 3 m high; twigs terete, greyish- or reddish-brown, glabrous or hispidulous, exuding cloudy latex when cut. Leaves alternate or clustered on spur shoots; stipules obsolete; petioles slender, 5-25 mm long; blades thinly chartaceous, ovate contracted to an acuminate tip, cordate at base, loosely tomentose to glabrous beneath, 2-4 cm long, 1-3 cm broad, palmately 5-veined at base, brochidodromous, beneath midrib and secondaries raised, veinlets prominent; margins entire, eglandular. Monoecious; dichasia terminal, often paired, with peduncle 1-2.5 cm long, branches hispidulous; bracts oblong-lanceolate to oblanceolate, glabrous or tomentulose, lower ones 4-5 mm long and 1.2-1.3 mm broad; pistillate flowers 0-2 per dichasium, at lower nodes; staminate flowers 1015, at upper dichotomies. Staminate flower: pedicel 0.5-0.8 mm long, articulated at base; sepals 5, lanceolate, obtuse or subacute, entire, glabrous or hirsutulous, 2.5-4.8 mm long, 1.2-2 mm broad; petals 5, pale green, oblong, glabrous abaxially, copiously hirsutulous adaxially in lower half, 5.5-6 mm long, coherent into a tube in lower 1/3, midrib with several sharply ascending laterals that dichotomize distally; disk glands 5, cubical, glabrous, 0.5-0.6 mm high; stamens 10, biverticellate, monadelphous below into a slender column 3-4 mm high, outer stamens on filaments ca. 1 mm long. Pistillate flower: pedicel glabrous or tomentulose, becoming 3-1 1 mm long in fruit; sepals 5, elliptic or lanceolate, obtuse or subacute, becoming in fruit 5.5-6.5 mm long, 2.5-3.8 mm broad; petals 5, ovate at base tapering to oblong obtuse tips, pale green, ca. 5.86 mm long, 4-4.2 mm broad, hirsutulous adaxially, coherent in lower 1/3; disk dissected into 5 lobes; ovary smooth, glabrous, sharply carinate, 3-locular; styles ca. 3 mm long, connate in lower 1/3, erect, scarcely bifid; stigmas dilated, elliptic, 0.7 mm long, 0.3 mm broad. Capsule smooth, 3-lobed, prominently 3-carinate on back of cocci, 1.5-1.6 mm in diameter; seeds ellipsoidal, ca. 9 mm long, smooth; caruncle brownish, deeply flabellately lobed, 2.5 mm long, 4 mm broad.