Native Euphorbiaceae of “cerrado” and “campo rupestre” of the São José Range, Minas Gerais, Brazil

Abstract

The São José Range (21o03-07’S; 44o06-13’W) is na Environmental Protection Area mostly composed by “campos rupestres”. A year of field work was done and ten species subordinated to three genera were found: Chamaesyce caecorum (Mart. ex Boiss.) Croizat, Croton antisyphiliticus Mart., C. arlineae D.Medeiros, Senna & Alves, C. campestris A.St.-Hil., C. floribundus Spreng., C. gnidiaceus Baill., C. timandroides (Didr.) Müll. Arg., C. urucurana Baill., C. vestitus Spreng. and Euphorbia chrysophylla Klotzsch ex Boiss. The taxon Croton section Medea (Klotzsch) Baill. sensu Webster was the richest group in number of species and specimens: C. arlineae, C. gnidiaceus, C. timandroides and C. vestitus, the later was the most spread taxon in the area. Euphorbia chrysophylla showed a sparse distribution, restricted to rocky outcrops, generally associated with temporary water courses. Analysis of foliar indument on both surfaces of Croton L. species through scanning electron microscopy (SEM) showed that only C. floribundus and C. urucurana present two distinct morphological types of trichomes depending on the surface. Simple type is restricted to adaxial surface of few species. Several development gradations of stellate type distal rays were observed, probably as a result of the transition from stellate trichome to simple one (derivated state). Identification key, morphological descriptions, illustrations, notes on habitat, geographic distribution, phenological, general comments and classification according to the Red List Categories of the International Union for Nature Conservation (IUCN/2001) of each taxon are provided.