Caracterização e delimitação do genero Micranthocereus Backeb : (Cactaceae) baseadas em caracteres morfologicos e moleculares

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

Micranthocereus Backeb. is a genus of Cactaceae endemic to Brazil and inc1udes nine species distributed in the states of Minas Gerais, Bahia, Goiás and Tocantins. The goals of the present study were to investigate the monophyly of the genus based on morphological and macromolecular characters and its relationships to the members of the tribe Cereeae; to investigate the phylogenetic relationships between the species and to reevaluate the traditional morphological characters used to define taxa within the tribe Cereeae. The cladistics analysis was basead on morphological characters and sedan sequence data (of the region trnL-F of the chloroplastid) for 10 taxa representing four genera, including Cereus, Pilosocereus, Coleocephalocereus and Melocactus. One species of Cereus was inc1uded as outgroup in the cladistic analysis based on macromolecular characters while a species of Pilosocereus was used as outgroup for the morphological analysis. The matrixes were analysed using the maximum parsimony criterium. The results do not confirm the monophyly of the genus Micranthocereus due to constant inclusion of Coleocephalocereus within Micranthocereus. The c1ades obtained, however, are not strongly supported by the bootstrap analysis. The extreme variation of morphological characters within the genus, impedes its delimitation and the classification of its position within tribe Cereeae. Therefore it is not possible to propose any taxonomic change to Micranthocereus based on the present studies. Floral biology of two endemic species from Bahia, Micranthocereus streckeri and Micranthocereus f/iwiflorus, was also investigated. The flowers of these species vary from pinkish (M. flaviflorus) to deep pink (M.streckeri), their anthesis occurs during daytime, and each flower lasts around 36 hours. The nectar is produced and stored in the nectar chamber within the floral tube, and the sugar concentration varies between 18 and 24%. Both species present typical characters associated with bird pollinated flowers and are visited and pollinated by the same species of hummingbird, Clorostilbon aureoventris

ASSUNTO(S)

cacto

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