Phylogeny, biogeography and divergence times in Passiflora (Passifloraceae).

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.

Postglacial north-south expansion of populations of Rhizophora mangle (Rhizophoraceae) along the Brazilian coast revealed by microsatellite analysis.

PREMISE OF THE STUDY: Red mangrove (Rhizophora mangle) dominates tropical tidal areas along both sides of the Atlantic, yet little is known about its degree of population differentiation over large geographical scales. Information on the genetic variability of mangrove species along the Brazilian coast is important not only for understanding the recent gene flow dynamic between populations, but also to evaluate models of evolutionary diversification and develop effective strategies for conservation. We investigated the genetic variability of the red mangrove along the Brazilian coast. METHODS: Eight microsatellite loci were used to genotype 145 individuals across 10 populations spanning more than 4500 km of coast line. We estimated the genetic variability and structure of the populations and the historical gene flow between them. KEY RESULTS: The level of genetic variability was low, with only 27 different alleles being detected and allele richness between 1.25 and 2.75. On the other hand, there was substantial population differentiation (R(st) = 0.48; P < 0.001), especially between the northern and southern populations. The populations from Pará and Maranhão had significantly greater genetic variability than did the remaining locations. CONCLUSIONS: 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.

Phylogenetic position of Placozoa based on large subunit (LSU) and small subunit (SSU) rRNA genes

The phylum Placozoa, represented by its single species Trichoplax adhaerens, has always been considered one of the most basal animal clades due to its low morphological complexity. However, despite its importance, the phylogenetic position of the Placozoa remains uncertain, as does the relationships between the basal metazoans. We sequenced the nearly complete large subunit (LSU) of the T. adhaerens rRNA gene together with the small subunit (SSU) rRNA and used several methods to infer the phylogenetic position of Placozoa and the relationships between the basal animal phyla. The phylogenetic trees obtained from the LSU, SSU and SSU + LSU datasets support monophyly of all basal metazoan phyla, except the Porifera. However, the relationships between all these phyla were not consistently resolved due to a strong conflict between the LSU and SSU phylogenetic signals. The hypotheses that Placozoa is a derived Cnidaria or the most basal metazoan were not supported by our data. Moreover, our analyses suggests that Placozoa is most likely the sister group of Cnidaria and/or Bilateria.

Diversity and natural hybridization in a highly endemic species of Petunia (Solanaceae): a molecular and ecological analysis.

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.

Differential organellar inheritance in Passiflora's (Passifloraceae) subgenera.

Four chloroplast (cp), one mitochondrial (mt), and one ribosomal nuclear (ITS) DNA regions were studied in four artificial and one natural interspecific Passiflora hybrids. The ITS results confirmed their hybrid origin and all mtDNAs were maternally inherited. The same, however, was not true for cpDNA. The four hybrids (three artificial and one natural) derived from species of the Passiflora subgenus showed a cpDNA paternal inheritance, while the one involving taxa of the Decaloba subgenus gave evidence of maternal transmission. These results are of significance for the ongoing studies which are being performed on the molecular evolution of this genus and furnish important background for investigations aimed at clarifying the factors which determine cpDNA inheritance.

Molecular phylogenetic analysis of Petunia Juss. (Solanaceae).

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.

Molecular investigations of pathogenesis-related Bet v 1 homologues in Passiflora (Passifloraceae).

The major birch pollen allergen, Bet v 1, responsible for allergic reactions in many areas of the world, is homologous to a large number of pathogenesis-related proteins (PRs), identified as PR10. As part of a long-range investigation of these types of proteins and of evolution in Passiflora, DNA sequences from eight Bet v 1 homologue isoforms were obtained from five species of this genus in Brazil, and their sequences compared among themselves and with 30 others from 8 different species, classified in different taxonomic units. The objective was a first characterization of these PRs in wild passionflowers, and their use for evolutionary and applied investigations. High interspecific, but low intraspecific variability was observed, as expected from multigenic families subjected to concerted evolution. The relationships obtained both within Passiflora and between it and seven other genera probably best reflect functional similarities than evolutionary history.

Phylogeographic inferences concerning evolution of Brazilian Passiflora actinia and P. elegans (Passifloraceae) based on ITS (nrDNA) variation.

BACKGROUND AND AIMS: Passiflora actinia and P. elegans, two markedly parapatric species, have their southern and northern distribution limits, respectively, in the most southern part of the Brazilian Atlantic Rain Forest. Despite the fact that they are classified in different taxonomic series, previous phylogenetic studies of this genus revealed a high genetic similarity between them. The aim of the present work was to analyse in more detail their geographical range in this region of overlap, to investigate intraspecific genetic variability and phylogeographic structure, and to search for possible hybrids. METHODS: Eighty-two localities were searched for these species, and nuclear internal transcribed spacer (ITS) sequences were investigated for 32 individuals of P. actinia, 20 of P. elegans and one putative interspecific hybrid. Plastid trnL-trnF and psbA-trnH were examined for 12 plants of each species and the putative hybrid. KEY RESULTS: Both species showed a high level of intraspecific and intra-individual ITS variability. Network analysis revealed a north-south geographic gradient in their intra and interspecific relationships. Mismatch analyses suggested a recent population expansion of P. elegans. The plastid markers showed restricted variability but, together with the nuclear data, they contributed to the identification of an interspecific hybrid of intermediate morphology at the border of the distribution of these two species. Both genetic and morphological data indicate the absence of an extensive hybridization zone between these species. CONCLUSIONS: Gene flow between lineages is the possible cause for the presence of different ITS sequences within a given plant, the absence of homogenization being due to the high degree of vegetative reproduction in the two species. Differentiation of P. actinia into geographic groups and the origin of P. elegans may have been influenced by the Atlantic Forest migration towards southern Brazil. The genetic pattern of the interspecific hybrid indicates that plastid inheritance in these species is at least sometimes paternal.

A first molecular phylogenetic analysis of Passiflora (Passifloraceae).

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.