Clearly distinct chromosome numbers allied to monophyly provide some support for a circumscription of the Bombacoideae and distinction within the Malvaceae. The phylogenetic signal for chromosome number supports the idea of an ancient WGD and further neopolyploidy events as important evolutionary trends for the Bombacoideae.

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With fi ve neotropical genera and ca. 220 species, Vochysieae is the largest tribe of Vochysiaceae, comprising more than 90 % of its species. Preliminary phylogenetic analyses with matK sequence data indicated that Vochysieae may be paraphyletic, separated into the clades QRC (Qualea, Ruizterania and Callisthene) and VS (Vochysia, Salvertia). Whether the genera and the infrageneric taxa are artifi cial is still controversial. In this study, we analyzed the distribution of chromosome numbers in mitotic or meiotic cells among 20 species belonging to the genera Callisthene, Qualea, Salvertia, and Vochysia, that are native and common in Central and Southeast Brazilian forests or savannas. Species of Callisthene and Qualea possessed 2n = 22, while species of Salvertia and Vochysia had 2n = 24 (or n = 12). Th ese chromosome numbers corroborate the recognition of two groups, and also suggest that chromosome evolution based on numerical variation is conservative in these lineages.

Hoff mannseggella viridifl ora Verola & Semir (Laeliinae, Orchidaceae) is a recently discovered species in the campos rupestres vegetation of the Espinha ç o Range, MG, Brazil, in synchronopatry with H. bradei (Pabst) V. P. Castro & Chiron. Both morphological and phenological studies indicate that these species are closely related. To substantiate the diff erentiation of these two species we examined their chromosome numbers and morphologies. Th e two species had diff erent chromosome numbers, with H. bradei having 2n ϭ 40 and H. viridifl ora having 2n ϭ 44 chromosomes, an aneuploid number not previously documented in the genus. Meiotic behavioral studies undertaken with H. bradei revealed many abnormalities related to bivalent numbers and chromosome migration, suggesting that meiotic abnormalities could generate aneuploid gametes and perhaps aneuploid zygotes. Karyotype formulas and chromosome morphologies are quite diff erent between the species, so H. viridifl ora was not directly derived from H. bradei through simple chromosome additions. Complementary analyses are necessary to understand the process and species involved in the origin of H. viridifl ora .