Revisão taxonômica e estudos filogenéticos de Mimosa L. sect. Calothamnos Barneby (Leguminosae-Mimosoideae) / Taxonomicrevision and phylogenetic studies of Mimosa L. sect Calothamnos Barneby

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

TAXONOMIC REVISION AND PHYLOGENETIC STUDIES OF Mimosa L. sect. Calothamnos Barneby (Leguminosae-Mimosoideae). Mimosa is the second largest genus of Mimosoideae, after Acacia s.l., with about 530 species, mainly distributed in the Neotropics in diferent types of vegetations, from forests to deserts. Traditionally, the genus was divided into five sections: Mimosa sect. Mimadenia, Mimosa sect. Batocaulon, Mimosa sect. Habbasia, Mimosa sect. Mimosa e Mimosa sect. Calothamnos, mainly based on the presence or absence of petiolar nectaries, on the kind of trichomes and on floral characteristics. Mimosa sect. Calothamnos is caracterized by the absence of petiolar nectaries, the presence of different types of branched trichomes covering vegetative and reproductive structures (except calyx and androecium) and by the tetramerous and isostemonous flowers with often yellow filaments (white or pink in some species). This group, with a high degree of endemism, is distributed mainly in the Southeastern (generally in Espinhaço Range, Minas Gerais) and South Brazilian regions, with some species extending into bordering countries, usually associated with open areas such as Campos Rupestres or Estepes, but with some species in Floresta Ombrófila Mista. The aims of the present study were to carry out a taxonomic revision and a phylogenetic approach of Mimosa sect. Calothamnos, in order to asnwer the following questions: 1) Is the number of taxa recognized in the section an overestimate?; 2) Is Mimosa sect. Calothamnos, as traditionally circunscribed, a monophyletic group? and 3) Are yellow stamen filaments and branched trichomes synapomorphic characthers of the section? The taxonomic revision was based on bibliographical survey, examination of about 2000 specimens from the Brazilian and foreign herbaria and on field expeditions. The phylogenetic reconstruction was carried out by parsinomy and bayesian analyses, based on molecular markers from cloroplast (trnH-psbA and rps16), nuclear (ITS) and morphological characters. Some modifications related to the traditional classification were proposed, such as infraspecific rearrangements, synonimizations and nomenclatural adequation. Besides this, seven lectotypes were designated and three new species were described, resulting in a larger number of the species, from 26 (34 taxons) to 32 (35 taxons). In the phylogenetics analyses based on combined data, Mimosa sect. Calothamnos is highly supported as monophyletic, with some morphological synapomorphies such as the presence of sessile stellate trichomes in the lower surface of the leaflets, corolla and fruits.

ASSUNTO(S)

mimosa sect. calothamnos mimosoideae revisão taxonomica leguminosae mimosa sect calothamnos filogenia phylogeny taxonomic revision

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