HISTÓRIA EVOLUTIVA DE Baccharis crispa Spreng. NO SUL DO BRASIL

Abstract

The Atlantic Forest is among the most diverse biomes in the world. Much of the rich biodiversity of this biome is due to the wide range of latitude occupied by this. In the south of the Atlantic Forest there are vegetation formations that are typical of regions with a milder climate, such as the Araucaria Forest and the ancient grassy fields (Campos de Altitude). In these ancient grassy fields are species adapted to a colder and drier climate, with the presence of negative temperatures in the coldest months of the year. Numerous studies have been carried out on the evolutionary history of species occurring in the Atlantic Forest, helping to clarify the origin and diversification of this biome over time. However, these types of studies are scarce with plant species of greater abundance, or even endemic, from the cold regions of the southern Atlantic Forest. In this sense, this work aimed to study the evolutionary history of populations of Baccharis crispa Spreng Asteraceae from the South of the Atlantic Forest. For the study, sequences were obtained from the chloroplast (trnL-trnF and psbA-trnH) and nuclear (ITS) genome regions of individuals from six populations collected in the county of Guarapuava, in Paraná state, Joaçaba and Xanxerê, in Santa Catarina state, and Coxilha, Panambi and Herveiras, in Rio Grande do Sul. Of these populations, those from the states of PR and SC are located to the north of the Uruguay River valley and those from RS to the south of the valley. The results obtained showed high nucleotide and haplotype diversity when compared to other species of Asteraceae from the Atlantic Forest. The evaluation of the results of the neutrality tests, the Bayesian Skyline Plot, the mismatch distribution and the statistical significance of the SSD and HRAG indices showed a slight population expansion in the last 200 thousand years, with possible demographic expansion of populations from the north to the south of the valley of the Uruguay river. A high phylogeographic structure was observed for B. crispa and a high number of unique haplotypes and ribotypes in populations from north and south of the Uruguay river valley. The analysis of genetic groups showed that genetic diversity is better explained considering four genetic groups, two formed by populations north of the Uruguay River valley and two by populations south of the valley. The overall analysis of the data from this study corroborates that the Uruguay River valley may have acted as a geographic barrier limiting the gene flow between populations of B. crispa from the southern Atlantic Forest. Furthermore, the high diversity of populations and population stability over the last 200,000 years evidence the permanence of B. crispa in southern Brazil during the last glacial periods.