Testing the monophyly of infrageneric taxa within the genus Mimosa (Leguminosae, Mimosoideae) based on cpDNA sequence data.

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

Vancouver, BC

Congreso; Botany 2008; 2008

University of British Columbia

The genus Mimosa L. comprises more than 500 species with pantropical and subpantropical distribution. Mimosa is subdivided into five sections, four of which are represented in southern South America: Batocaulon DC, Habbasia DC, Calothamnos Barneby, and Mimosa. The aim of this study are: (1) examine the evolutionary relationships among Mimosa and other members of the Leguminosae, (2) test the monophyly of four sections of Mimosa (3) determine whether the phylogeny is congruent with the current classification. This phylogenetic analysis, based on trnL intron and the trnL-trnF intergenic spacer data, was carried out using NONA and Winclada; species of Mimosa (thirty-four) and one species each of Piptadenia, Parapiptadenia, Anadenanthera, Calliandra, and Mimosyganthus were studied. From sequences, a total of 1040 characters were scored and ten key morphological features were measured on herbaria specimens and mapped onto the phylogenetic hypothesis. Based on the representatives here included, our results indicates that Mimosa is monophyletic; it is derived from Piptadenia viridiflora. The four sections proposed by Barneby are not natural groups. The representatives of Mimosa sect. Batocaulon are not clustered, the xerophylous representatives are basal and the remaining species are related to those species of sect. Habbasia. The species of Mimosa sect. Calothamnos that were analysed are nested in sect. Mimosa. Our results suggest that the representatives from sections Calothamnos and Mimosa share a common ancestor with those from sect. Habbasia and sect. Batocaulon ser. Stipellares. In general terms, the most recent group exhibits the derived morphological features and the evolutionary sequence can be interpreted as a progressive reduction;  from diplostemonous and free filaments to haplostemonous and an androecium with monadelphous filaments; in leaf formula, in habit life form, and in pollen type.