Simaba docensis, a New Brazilian Species of Simaroubaceae

Abstract

Simaba docensis, a new species of Simaroubaceae, is described and illustrated. Its geographical distribution seems to be restricted to semideciduous forest in the region of the Rio Doce basin, Minas Gerais, southeastern Brazil. Accordingly, it is likely to be a rare endemic and endangered species. It is very closely related to the only other Amazonian species of section Floribundae Engler, S. paraensis Ducke, from which it is basically distinguished by the number and shape of leaflets, leaf indument, and flower and fruit size. We describe here a new species of Simaba Aublet (Simaroubaceae), S. docensis. Its geographical distribution is apparently restricted to southeastern Minas Gerais, Brazil, in the semideciduous forest of the Rio Doce basin. The closest species to S. docensis is S. paraensis Ducke. The South American genus Simaba has 25 species, divided into three sections: Tenuiflorae, Floribundae, and Grandiflorae (Engler, 1874; Cronquist, 1944). They are trees or shrubs with pinnately compound leaves. The main diagnostic characters used to distinguish the three sections of Simaba are listed in Table 1. Section Tenuiflorae is an Amazonian taxon, whereas the other two sections are mostly extra-Amazonian. Simaba paraensis is noteworthy because it is the only Amazonian species of section Floribundae. Furthermore, it can have small flowers, as found in section Tenuiflorae, and it has stamen appendages as occur in section Grandiflorae. However, S. paraensis has large paniculate inflorescences and other flower characters similar to those found in Floribundae, which places it in this section. The new species resembles S. paraensis in its general appearance and because it has androecium characteristics of the section Grandiflorae. However, S. docensis fits better the characteristics of section Floribundae than S. paraensis because of its larger flowers. Couepia monteclarensis Prance, another endemic species of the Rio Doce basin, is also taxonomically very close to two Amazonian congeneric species: C. sandwithii Prance and C. bernardii Prance (Prance, 1989). Other field collectors (J. A. Lombardi & K. Yamamoto, pers. comm. 1999) have noticed the occurrence of Amazonian species affinities in the semideciduous forest of the Rio Doce basin. The conservation and detailed studies of this forest can help us to understand the evolution and history of the South American forests. Simaba docensis Franceschinelli & K. Yamamoto, sp. nov. TYPE: Brazil. Minas Gerais: Marli6ria, Parque Estadual do Rio Doce, on peninsula at Lake Helv~cio, 24 Nov. 1975 (fl), Heringer & Eiten 15182 (holotype, MO; isotype, US). Figure 1. Ad sectionem Floribundae Engler referenda, S. paraensis Ducke androecio similis, sed foliis 7-10 jugatis, foliolis subtus puberulis vel pilosis, floribus majoribus 8-10 mm longis differt. Tree 10-30 m tall. Branches glabrous with gray bark, strongly grooved and furrowed longitudinally, with prominent transversal scars due to leaf and bud abscissions. Leaves with 6-21 leaflets, usually 7-10 jugate, at apex of the branches; rachis 7.520 cm long, cylindric, puberulous. Leaflets sessile or subsessile, opposite or subopposite, interjuga 21.5 cm long. Leaflet 2.5-5 x 1.1-1.7 cm, blade oblong to obovate or elliptic, chartaceous, apex usually acute, sometimes obtuse to rounded, with gland at the tip, lateral leaflet base usually oblique and terminally cuneate, puberulent beneath with prominent central vein, glabrescent and slightly wrinkled above with prominent and puberulent central vein; lateral veins not visible. Inflorescence paniculate, 8-22 cm long, with ferrugineous tomentose axes, secondary axes 1.5-11 cm long, usually forming a right angle with the primary axis, subtended by bracts narrowly oblong to obovate with gland on the tip, 2.0-5.0 cm long, flowers at NovoN 9: 345-348. 1999. This content downloaded from 207.46.13.16 on Wed, 25 May 2016 06:45:37 UTC All use subject to http://about.jstor.org/terms