TOWARD A PHYLOGENY OF MIMOSA (LEGUMINOSAE: MIMOSOIDAE): A PRELIMINARY ANALYSIS OF SOUTHERN SOUTH AMERICAN SPECIES BASED ON CHLOROPLAST DNA SEQUENCE

BESSEGA, C.; HOPP, H. E.; FORTUNATO, R. H.

ANNALS OF THE MISSOURI BOTANICAL GARDEN

Missouri Botanical Garden

Lugar: Saint Louis; Año: 2008 vol. 95 p. 567 - 579

0026-6493

The pantropical and subpantropical genus Mimosa L. comprises more than 500 species of which nearly 480 are reported for the American Continent. Mimosa is subdivided into five sections, four of which are represented in southern South America: Batocaulon DC, Habbasia DC, Calothamnos Barneby, and Mimosa. Previous taxonomic studies of the species from the austral region have found classification conflicts among a) sects. Batocaulon and Habbasia, b) sects. Calothamnos and Mimosa, and c) series and sub series within sect. Mimosa. The present paper reports a preliminary phylogenetic analysis of chloroplast nucleotide sequences of the trnL intron and the trnL-trnF intergenic spacer from 34 species of Mimosa and related genera. Key morphological characters were mapped onto the phylogenetic hypothesis and discussed. Sequence analysis indicates that the genus Mimosa is monophyletic; it is derived from Piptadenia viridiflora. The four sections proposed by Barneby (1991) are not natural groups. The cladogram retrieved indicates that the representatives of Mimosa sect. Batocaulon are not clustered, the xerophylous representatives of this section are basal and the remaining species are related to those species of sect. Habbasia, suggesting that sect. Batocaulon ser. Stipellares is more recently derived. The species of Mimosa sect. Calothamnos that were analyzed are nested in sect. Mimosa. The results seem to support retention of this section within sect. Mimosa as was noted previously by Bentham (1875). The chloroplast sequence data suggest that the representatives from sections Calothamnos and Mimosa share a common ancestor with those from sect. Habbasia and sect. Batocaulon ser. Stipellares.