Taxonomia e filogenia e dimerostemma, e sua relação intergenerica na subtribo Ecliptinae (Asteraceae : Heliantheae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Sequence data for nine regions of the chloroplast genome have been obtained for 34 of the 49 genera of subtribe Ecliptinae of tribe Heliantheae. The analyzed regions include gene matK; introns petB, petD, trnL; and intergenic spacers ndhI-ndhG, rpl20-rps12, accD-rbcL, trnT-trnL, trnL-trnF. The bootstrap consensus tree reveals a monophyletic subtribe Ecliptinae with four major clades. The basal clade corresponds to taxa endemic to the Andes and the other clade are grouped in a trichotomy with each one strongly supported. One of these clades contains a heterogeneous array of genera including Dimerostemma, Eclipta, and Wedelia. The morphology of these taxa is discussed in the light of the results from the phylogenetic analyses and bio-geographical considerations are briefly addressed. A second phylogeny for a majority of the members of the mostly Neotropical Ecliptinae using the ITS and ETS of the nuclear DNA was constructed to elucidate the inter - and infrageneric relationships of Dimerostemma and Angelphytum. The strict consensus tree reveals a monophyletic subtribe Ecliptinae with seven major groups. The majority of the interior nodes has good bootstrap support, but not the basal ones. The clade containing the 18 species of Dimerostemma and Angelphytum sampled is strongly supported. It is sister to an assemblage of mostly North American Ecliptinae and has three main groups. The only annual species, Dimerostemma annuum, is basal and sister to the two other subclades, each containing a combination of species of both genera. The generic type, Angelphytum matogrossense is clustered with most species of Dimerostemma. This result indicated Angelphytum as synonym of Dimerostemma and the combinations under Dimerostemma were made. Nineteen species of Dimerostemma occur in Brazil. One new species, proposal of synonymies and a validation of a combination are proposed for Dimerostemma. All taxonomic novelties proposed here will be valid published in a near future somewhere else. Brazil, with approximately 80% of the current known species, is the principal focus of diversity for the genus. Dimerostemma is unified by its involucre with an outer series of leaf-like phyllaries, by an unconstricted coroniform pappus with awns mostly well developed, stout, and continuous with the margins of the cypsela. It is the only member of the subtribe differentiated by the extension of phytomelanin from the cypsela body to the base of the awns. The variation in the shape of the outer phyllaries, pales, disc cypsela and papus are all diagnostic in species identification. A key to the Brazilian members of Dimerostemma, synonymies, descriptions, commentaries and illustrations are provided, as well as notes on distribution, habitat, phenology and specimen citations

ASSUNTO(S)

filogenia compostas taxonomia

ACESSO AO ARTIGO

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