Intrinsic reproductive barriers among the species of Petunia are weak and genetic isolation is obtained mainly by geographical separation and ecological diversification. The Serra do Sudeste region in the extreme south of Brazil is one of the centres of diversity of this genus and is characterized by the presence of species with different pollination syndromes. Petunia exserta is known only from four sandstone towers in a restricted area of this region (about 500 km(2)) and is characterized by its differentiated habitat (shelters in the sandstone towers) and by its floral characteristics adapted to ornithophily. In towers where this species is sympatric with the sphingophilous Petunia axillaris, phylogenetically close to P. exserta, we found plants with intermediate floral morphology, suggesting hybridization between them. To test this hypothesis and to better understand its consequences we analysed the sequences of the plastid trnH-psbA, trnS-trnG and psbB-psbH intergenic spacers in 121 individuals sampled all over the P. exserta distribution. The joint analysis of the three markers revealed 13 haplotypes and the network showed two main genetic clades, which probably represent the original gene pool of the two species in the region. In general, individuals of a given population presented the same haplotype, independently of phenotype, corroborating the hybridization hypothesis. Field observations suggest that hummingbirds are responsible for the interspecific gene flow. Analysis of molecular variance revealed high interpopulational diversity among the towers. The low gene flow between populations is possibly related to the autochoric seed dispersion system.

This difference might reflect the older age of the northern mangroves, which likely remained stable during the Quaternary glaciations. The lowest variability observed in the southern populations of the red mangrove most likely reflects their recent age, associated with allelic reduction, resulting from the consecutive founder events that followed subsequent colonization of estuaries during the gradual warming by the end of the last glacial period.

Passiflora, a genus with more than 400 species, exhibits a high diversity of floral and vegetative structures and a complex taxonomy, which includes 23 subgenera and many sections and series. To better understand Passiflora's variability and interspecific relationships, the phylogeny of 61 species, classified in 11 of 23 suggested subgenera, was investigated. Three molecular markers were used, the nuclear ribosomal internal transcribed spacers (nrITS), the plastid trnL-trnF spacer regions (∼1000 bp), and the rps4 plastid gene (∼570 bp). Three major clades were highly supported, independent of the marker and phylogenetic method used; one included the subgenera Distephana, Dysosmia, Dysosmioides, Passiflora, and Tacsonioides, a second, the subgenera Adopogyne, Decaloba, Murucuja, and Pseudomurucuja, and a third, the subgenus Astrophea. We call these the Passiflora, Decaloba, and Astrophea clades, respectively. The position of subgenus Deidamioides is undefined. The monophyly of Passiflora could not be statistically corroborated, and the relationships among the major clades and of these clades with the related genera remain unresolved. Our results indicate that a reevaluation of the monophyly of Passiflora and its infrageneric classification is necessary.

Representatives from 11 Petunia Jussieu species in south and southeast Brazil were compared with two Calibrachoa La Llave & Lex., one Bouchetia Dunal, and two Nierembergia Ruiz & Pav. taxa in relation to DNA molecular variability. A total of 4532 base pairs related to one nuclear, five plastidial and one mitochondrial systems was investigated. Petunia and Calibrachoa, although separated among themselves, clearly differentiate from the two other genera. Despite the fact that the Petunia species do not show marked molecular differences, they can be separated in two complexes, in good agreement with altitude data. Petunia + Calibrachoa should have diverged from other clades at about 25 million years before present.

As part of a long-term investigation on the evolution of Passiflora L., we investigated the divergence ages of the genus and diversification of its subgenera, relating them with biogeographical and/or historical events, and other characteristics of this taxon. The main aim of the present work was to evaluate the biogeographic distribution of this genus to better understand its evolutionary history. This is the first time that representatives from South American and Old World Passifloraceae genera have been studied as a group comprising a total of 106 widely distributed species, with representative samples of the four suggested subgenera. Seven DNA regions were studied, comprising 7,431 nucleotides from plastidial, mitochondrial and nuclear genomes. Divergence time estimates were obtained by using a Bayesian Markov Chain Monte Carlo method and a random local clock model for each partition. Three major subgenera have been shown to be monophyletic and here we are proposing to include another subgenus in the Passiflora infrageneric classification. In general, divergence among the four subgenera in Passiflora is very ancient, ranging from ∼32 to ∼38 Mya, and Passifloraceae seems to follow a biogeographic scenario proposed for several plant groups, originating in Africa, crossing to Europe/Asia and arriving in the New World by way of land bridges. Our results indicated that Passiflora ancestors arrived in Central America and diversified quickly from there, with many long distance dispersion events.