Three New Brazilian Species in the Genus Marcetia (Melastomataceae, Melastomeae)

Abstract

Three new species of Marcetia are described and illustrated. Marcetia semiriana occurs only in Serra do Cip6, Minas Gerais. Marcetia shepherdii, collected in Marai1, at sea level, and M. lychnophoroides, from Chapada Diamantina, are both endemic to Bahia. The new species Marcetia shepherdii and M. lychnophoroides, together with M. luetzelburgii Markgraf, constitute a group of closely related species. They share in common subcoriaceous, fleshy, imbricate to subimbricate, revolute leaves. Marcetia shepherdii is distinguished by its rigid, erect branchlets, yellowish green leaves that are glabrous on the adaxial surface, unappendaged and broadly dilated connectives, linear-oblong thecae with a ventrally inclined pore, and a unique 2locular ovary. Marcetia lychnophoroides has velutinous to sublanate branchlets, cinereous-green leaves that are densely puberulous-sericeous on the abaxial surface, unprolonged and inconspicuously bilobulate connectives, and a 3or 4-locular ovary. Marcetia semiriana is very similar to M. taxifolia (A. Saint-Hilaire) DC., differing in the prostrate branches, long pedunculate flowers, and straight anthers. Marcetia is a neotropical genus of 27 species largely endemic to Brazil. Except for the widespread Marcetia taxifolia, which has a bicentric distribution in eastern Brazil and northwestern South America (Colombia, Venezuela, and Guyana), all other species of Marcetia have restricted distributions. Marcetia species are usually shrubs or subshrubs that occur in campo rupestre in the Serra do Espinhago, Minas Gerais, in the mountains of Goi s, and especially in the Chapada Diamantina, Bahia. Campo rupestre is an exclusively Brazilian complex mosaic of vegetation types characterized by extensive outcrops of highly acidic rocks, nutrient-poor soils, and local variations in topography, slope, aspect, and moisture regime. A few Marcetia species occur in both montane and littoral areas, such as M. ericoides (Sprengel) 0. Berg ex Cogniaux and M. canescens Naudin. Marcetia shepherdii is the only species in the genus that is endemic to coastal Bahia, where it occurs in the sandy vegetational formation commonly referred to as restinga. The genus Marcetia can be distinguished within the tribe Melastomeae mainly by the combination of tetramerous flowers and simple anthers that lack basally prolonged connectives (except in M. shepherdii) and, in some species, may have short ventral tuberculate appendages. Three of the species studied in my taxonomic revision of Marcetia (Martins, 1989) are new. They are described and illustrated here. Marcetia shepherdii A. B. Martins, sp. nov. TYPE: Brazil. Bahia: Maraui, 4 km de Mara6, 12 Mar. 1977 (fl, fr), G. J. Shepherd, L. S. Kinoshita, J. B. Andrade & N. Taroda 4550 (holotype, UEC). Figure 1. Haec species Marcetiae luetzelburgii affinis, sed ab ea foliis arcte adpressis sessilibus revolutis dense imbricatis internodia brevia occultantibus, ramis basin versus denudatis, conspicue annulis foliorum delapsorum praeditis, lamina foliari supra glabra in sicco flavovirescenti, staminum filamentis ter longioribus, antheris apice rotundato ventraliter minute dehiscenti atque ovario biloculari differt. Erect subshrub ca. 60 cm, compactly branched; branchlets rigid, subterete to inconspicuously quadrangular, moderately puberulous or nearly glabrous, at the base defoliating with age and with conspicuous leaf scars. Leaves opposite, sessile, appressed, densely imbricate and concealing the short internodes; blade lanceolate-ovate, 2.5-3 x 1 mm, fleshy-coriaceous, basally cordate, apically recurved and mucronulate, margins revolute, glabrous on the adaxial surface, glandular-pubescent abaxially, obscurely 1-nerved. Flowers 4-merous, subsessile, solitary in upper leaf axils resembling a terminal foliaceous spiciform inflorescence, becomNOVON 10: 224-229. 2000. This content downloaded from 157.55.39.45 on Fri, 02 Sep 2016 06:22:09 UTC All use subject to http://about.jstor.org/terms Volume 10, Number 3 2000 Luckow & Du Puy Gagnebina bakoliae from Madagascar 225