Monographs Details: Mapania insignis Sandwith
Authority: Maguire, Bassett. 1967. The botany of the Guayana Highland--Part VII. Mem. New York Bot. Gard. 17: 1-439.
Description:Distribution and Ecology - Endemic to British Guiana. BRITISH GUIANA. River Gorge at Amatuk Portage, occasional in marshy area, secondary scrub, Maguire & Fanshawe 23017; Amatuk, rainforest on bank of river, Harrison 1631; Potaro District, near Amatuk, moist part of secondary clearing, Whitton 182 in part (K); Potaro River, below Kaieteur Falls, Jenman 972 (K); Tukeit, Warratuk Portage, occasional in wet Dicymbe forest, Maguire & Fanshawe 23539; Potaro River, Melaratuk, Harrison 1636.The distribution range of M. insignis, which is confined to the Kaieteur Gorge of the lower Potaro River, is completely included within the large range of M. macrophylla covering eastern Guay ana, the entire Guianas and the adjoining Amapa of Brazil. In addition to the morphological data, the phytogeographical evidence that this intermediate plant occurs only within the limited range of M. insignis, where M. insignis and M. macrophylla coexist, strongly suggests the hybrid origin of the intermediate plant between the two related species. A collection, Harrison 1631, from Potaro River, consists of two variants; the sheet (NY) is typical M. insignis (Fig. 14 R-U), whereas the sheet (K) is an intermediate one. Mapania insignis X macrophylla (Fig. 14, P, Q) is probably a natural hybrid.BRITISH GUIANA. Upper Mazaruni River, Kurupung, H. Leng 281; Kuru-pung, Membaru line, A. C. Bor 278 (K) ; Potaro River, Amatuk Portage, Harrison 1631 (K).
Type. Potaro River, British Guiana, Jenman 7478 (K).
Mapania insignis is a distinct species readily separable from its nearest alternative, M. macrophylla, by the characters of fructifications, glumes, and involucral bracts as shown in the key to species. Three specimens out of some 30 different collections that I have examined are characteristically intermediate between M. insignis and M. macrophylla. In these three specimens the shape, texture, and size of fructifications and glumes lie exactly in the middle between those of the two related species, but some vegetative characters appear to be more closely related to the corresponding parts of one of the two species (Table III).
Characteristics in the probable hybrid between M. insignis and M. macrophylla
Characters closer to those of M. insignis Intermediate characters Characters closer to those of M. macrophylla
Fructification: size ranging from 2-2.5 the angles conspicu-
Glume: pale color mm long by 1.5-1.75 mm wide membranous, rather per- ously margined with a low ridge; dull surfaces
lnvolucral bract: Basal leaf sheath: the base broadly rounded, almost as wide as the head, not cuneate attenuate sistent, subabruptly acute at apex conspicuously dilated, lance-ovate in outline
Distribution:Guyana South America