Abstract Phylogenetic niche conservatism can be investigated at multiple scales on an explicit geographical context. Haplotype-based comparative analyses of lineages occupying the same region, and thus subjected to similar environmental factors, allow decoupling shared evolutionary and ecological patterns, as well as multiple dimensions of adaptive diversification. Here we aimed to assess the role of environmental drivers on diversification of subtropical grassland, based on haplotypic diversity of two plant genera. We sampled two closely related and co-distributed grassland plant genera, Petunia and Calibrachoa, across their entire distribution area. Eigenvectors extracted from pairwise distances based on chloroplast DNA haplotypes were used to fit Phylogenetic Signal-Representation (PSR) curves to estimate evolutionary patterns in 19 bioclimatic variables and altitude. The PSR curves showed that altitude, precipitation, and temperature variables changed at different rates with haplotype differentiation. Altitude and temperature traits evolved under conditions closer to a neutral dynamics, whereas precipitation traits differentiated following more complex models. Our results indicated that the diversification in the two genera was more limited by precipitation conditions. Based on these novel findings, we suggest that future studies should test the possible impact of precipitation variables on the process of ecological differentiation in these genera.

Abstract Calibrachoa is a South-American genus comprising 27 species, several considered endemic or rare; few were subjects in genetic studies. We attempted to generate new data about the phylogenetically related and rare species C. eglandulata, C. sendtneriana, C. serrulata, and C. spathulata concerning their genetic diversity and population structure, which, coupled with their known restricted distribution, could help access their conservation status and contribute to the study of the Brazilian biodiversity. We sequenced 88 individuals for plastid intergenic spacers and genotyped 186 individuals for five microsatellite loci. Compared among each other, C. sendtneriana and C. serrulata presented the highest values of genetic diversity [π% (sd) = 0.23 (0.14) and 0.43 (0.25), respectively], followed by C. spathulata [π% (sd) = 0.19 (0.12)] and C. eglandulata [π% (sd) = 0.02 (0.03)]. Population differentiation was evident for these latter species, whereas it was not significant for C. sendtneriana and C. serrulata. Factors such as habitat specificity and fragmentation, pollination syndrome, and life history could explain the observed patterns. Based on the new genetic data and the species’ biology, a conservation status was assigned for C. sendtneriana and the status of the other three species was reviewed.

The association of cytogenetic and molecular techniques has contributed to the analysis of chromosome organization and phylogeny in plants. The fluorochrome GC-specific CMA3, fluorescent in situ hybridization (FISH) and RAPD (Random Amplified Polymorphic DNA) markers were used to investigate chromosome structure and genetic relationships in Hypochaeris (Asteraceae). Seven species native to South America, and two species introduced from Europe (H. glabra and Hypochaeris sp) were studied. FISH with rDNA probes identified one or two loci of 18S-5.8S-25S rDNA in the South American Hypochaeris species and one locus in the European species. Only one 5S rDNA locus was seen in all species studied. Blocks of GC-rich heterochromatin (CMA-positive bands) associated to 18S-5.8S-25SrDNA loci were detected in all species investigated. Co-location of 5S rDNA and CMA bands was also observed, except for three South American species and Hypochaeris sp. In two South American species, additional CMA bands not related to rDNA were observed on the long arm of chromosome 2, near to the centromere. Hypochaeris glabra exhibited additional CMA-positive signals distributed at pericentromeric regions, on the short arms of all chromosomes. A total of 122 RAPD markers were used to determine the genetic relationships among species. The level of polymorphism was very high, revealing two genetic groups comprising the South American and the European species, thus supporting a previous hypothesis of monophyly of the South American Hypochaeris species. The coefficients of genetic similarity between European and South American species were 0.35, on average. Polymorphism was also high within the two groups. The genetic associations observed with RAPD markers were consistent with chromosome characteristics. Species carrying similar distribution of 45S rDNA loci and CMA-positive signals were included in the same group revealed by RAPDs. Cytogenetic and molecular data support the view that not only chromosome rearrangements, but also changes in DNA sequence took place during the diversification of the South American Hypochaeris species.