Renée H. Fortunato

Chromosome and morphological studies in the Mimosa debilis complex (Mimosoideae, Leguminosae) from southern South America

Mimosa debilis Humb. & Bonpl. ex Willd. and M. nuda Benth. were grouped in specific and infraspecific complexes. Both taxa showed exomorphological similarities, with conflicts in their taxonomic circumscription and present different ploidy levels. The objective of the present contribution was to analyse chromosome numbers of different populations and to evaluate morphological characters of specimens from Paraguay, Argentina and boundary regions. Chromosome numbers of M. debilis var. debilis (2n = 2x = 26 and 2n = 4x = 52) confirmed previous reports, whereas those of M. nuda var. glaberrima (2x = 26, 4x = 52), M. nuda var. gracilipes (2x = 26, 4x = 52) and M. nuda var. nuda (4x = 52) are presented for the first time. Variation was observed in habit, foliar and floral morphology and was correlated with the chromosome number and the geographical distribution of the taxa. Groups with stable morphological characters and restricted geographic distribution were identified. Also, the results showed a pattern of hybrid swarms and polyploids of different origin that may explain the existence of taxonomic conflicts in the M. debilis–M. nuda species complex. On the basis of these results, M. nuda should be included in the synonymy of M. debilis.

Karyotype studies in Mimosa (Mimosoideae, Leguminosae) from Southern South America and ecological and taxonomic relationships

Abstract In this work we studied the chromosome number and karyotype formula of seven species of Mi- mosa L. (Mimosoideae, Leguminosae). The chromosome number 2n = 2x = 26 for M. detinens Benth., M. hex- andra M. Micheli, M. ostenii Speg. ex Burkart and M. xanthocentra Mart. var. mansii (Benth.) Barneby are new records, while the chromosome number 2n = 2x = 26 for M. debilis var. debilis, M. urugüensis Hook. and Arn. and M. uliginosa Chodat and Hassl. confirm previous records. Karyotype formulae revealed the existence of metacentric and submetacentric chromosomes, and the chromosomal asymmetry indexes did not show significant differences between taxa. The chromosome length of xerophilous and endemic M. detinens and M. ostenii differed from the rest of species, indicating that this parameter could have taxonomic value. In addition, the relationship between total chromosome length and climatic parameters showed that diploid species of marginal areas of distribution have a larger chromosome size, and that this could be related with mechanisms of ecologi- cal adaptation.

Genetic relationships in the Galactia–Camptosema–Collaea complex (Leguminosae) inferred from AFLP markers

Some species belonging to the genera Galactia, Camptosema and Collaea from southern Brazil, Paraguay, Argentina, and Uruguay are grouped into a complex based on exomorphological affinities. The diagnostic morphological features sometimes overlap among species of different genera and dissimilar criteria have been adopted to delimit them, thus generating great taxonomic uncertainty. The aim of this work was to clarify the genetic relationships of the species within the complex as well as to analyze the infraspecific variability by means of analysing the AFLP band patterns. We examined 378 AFLP markers generated after amplification using six primer combinations. The monophyly of Collaea was supported, corroborating the present morphological classification. On the other hand, the results are not congruent with the current circumscription of Galactia and Camptosema, in agreement with previous phylogenetic hypotheses based on morphological characters and karyological studies, as both genera are polyphyletic.

Four new diplostemonous species of Mimosa (Mimosaceae) from Paraguay and Eastern Bolivia

Four species of Mimosa, M. aureliana, M. chacoënsis, and M. tobatiensis known only from eastern Paraguay, and M. castanoclada known from northwestern Paraguay and eastern Bolivia, are described, figured, and compared with near kindred.

Cytogeography and morphological characterisation of a taxonomic, polyploid complex of Mimosa (Leguminosae) from subtropical South America

Abstract. Mimosa subseries Dolentes Barneby and Brevipedes Barneby are ecologically and morphologically high-diversified infrageneric taxa of this genus in southern South America. We performed a cytogenetical and morphological analysis of both subseries. Chromosome numbers from accessions throughout the area of distribution were studied. The chromosome numbers 2n = 8x = 104 for M. dolens subsp. callosa (Benth.) Barneby, M. dolens subsp. acerba varieties acerba (Benth.) Barneby, latifolia (Benth.) Barneby and rudis (Benth.) Barneby, M. dolens subsp. rigida var. rigescens (Benth.) Barneby, var. anisitsii (Lindm.) Barneby and var. foliolosa (Benth.) Barneby; and 2n = 4x = 52 for M. sceptrum Barneby, M. aff. custodis Barneby and M. dolens var. pangloea Barneby are presented for the first time. Their karyotypes were symmetric, with small chromosomes. There were several areas with taxa growing in sympatry, occasionally with intermediate forms. No diploids were found, which suggests the presence of either a declining polyploid complex or ancient polyploidy in the clade of southernmost representatives of M. series Mimosa, the most derived of the genus. Some vegetative, inflorescence and carpological characters seem to be associated with chromosome duplication. The distribution pattern of the cytotypes suggests events of chromosome duplication in centres of diversity and expansion of octoploids to the southernmost areas of distribution. Our findings support the importance of polyploidy in the morphological diversity, distribution and speciation of this complex.

The evolutionary history of Senna ser. Aphyllae (Leguminosae–Caesalpinioideae), an endemic clade of southern South America

In the legume genus Senna, series Aphyllae includes seven species of leafless shrubs and subshrubs from arid, semiarid and xerophilous areas of three different biogeographic subregions in southern South America. In this study, we investigated the evolutionary history of Aphyllae in a molecular phylogenetic framework. We reconstructed phylogenetic relationships among Aphyllae species based on DNA sequence data of four plastid (rpS16, rpL16,matK, trnL-F) and one nuclear (ITS) region from 23 accessions, analyzed with parsimony, Bayesian and maximum likelihood methods. We inferred the evolutionary and biogeographic history estimating divergence times and reconstructing ancestral character states and ancestral areas of distribution. Series Aphyllae was found to be monophyletic, and the taxa formed two main clades: Clade A gathering S. aphylla var. aphylla, S. crassiramea, S. rigidicaulis and S. spiniflora; and Clade B grouping S. acanthoclada, S. aphylla var. divaricata, S. aphylla var. pendula and S. pachyrrhiza. The morphologically complex S. aphylla appears thus polyphyletic. Molecular dating and ancestral area reconstructions suggest that the Aphyllae clade started to diversify in the South American Transition Zone in the Late Pliocene. Based on these results, we hypothesize that this diversification occurred during the last period of Andean uplift with the aridification in South America. The ancestral character state reconstructions suggest that, in addition to the loss of leaves in adult plants, series Aphyllae evolved various morphological features, such as fastigiate, thickened or decumbent–subdecumbent branches during the colonization and establishment in different arid and semiarid lands in South America.