No abstract

A study of nuclear DNA content was made in telophase nuclei (2C) of the root apex of germinating seed in nine populations of the following species and cytotypes of Larrea: L. nitida (2x), L. divaricata (2x), L. cuneifolia (4x) and L. tridentata (2x, 4x, 6x). There were no significant differences in DNA content per basic monoploid genome among the diploid taxa nor between the latter and the tetraploid, among tetraploids or between tetraploids and the hexaploid. On the other hand, the difference between means was significant when all diploids were compared with the hexaploid cytotype. These results would indicate: (I) Speciation at the diploid level in Larrea has not produced great differences in DNA content per basic genome. This is in contrast with the related genus Bulnesia.

Macroptilium (Benth.) Urban (Phaseoleae, Papilionoideae, Leguminosae) is an American genus of legumes, belonging to subtribe Phaseolinae along with other economically important genera, such as Vigna Savi and Phaseolus L. (the common bean genus). Cladistic analyses based on morphological, biochemical (storage seed proteins) and molecular (nuclear and plastid DNA sequences) data were performed on the 18 species currently ascribed to the genus, exploring several character weighting strategies. Equal weights, implied weighting and different transversion ⁄ transition costs were applied. The three data sets were first analyzed with separate partitions, and then combined into a single matrix. This study is the first one to analyze all the species of the genus from a cladistic point of view. In all the most parsimonious trees obtained, Macroptilium is monophyletic with excellent support values. Two monophyletic clades are recovered in almost all the analyses. Both are compound by nine species, and they constitute two sections of Macroptilium. Several interspecific relationships inside the genus are discussed.

Prosopis L. is a rather primitive genus within the Leguminosae-Mimosoideae. This genus has been divided into five sections on the basis especially of the vegetative diversification of the spines. Three of the sections, Algarobia, Monilicarpa and Strombocarpa, are distributed in America. In order to elucidate systematic relationships between the American sections of Prosopis, a morphological and biochemical phylogeny were obtained. Twenty-two morphological characters were scored for 27 species of Prosopis and the outgroup taxon following polyacrilamide gel electrophoresis of seed storage proteins. The results obtained clearly prove that the secction Strombocarpa is a natural taxon. The section Algarobia, on the other hand, seems to comprise an artificial grouping of species. Members of the series Denudantes appear isolated from the remaining species, therefore this taxon should be treated as a new section within Prosopis. The section Algarobia should be circumscribed to series Chilenses, Ruscifoliae and Pallidae, which are always united in a monophyletic clade. Finally, no evidence was found to confirm the existence of the section Monilicarpa.