História evolutiva e distribuição de Adelphobates, gênero de sapos venenosos endêmico da Amazônia brasileira

Abstract

Distributions of species can be shaped by both climatic and structural features of the landscape, as well as biotic interactions. These factors can also influence current biodiversity patterns, promoting or interrupting gene flow between populations. Consider genetic information and biogeographical disruptions can result in the identification of potential Operational Taxonomic Units (OTUs) and, consequently, the revision of taxa distribution. Phylogeographic studies on dendrobatid from the Amazon plain are still very scarce, and some of the mechanisms listed to explain the diversification patterns were the influence of forest refugee and the riverine barriers hypothesis. Adelphobates species constitute an excellent model to understand different evolutionary mechanisms, as their distribution covers some of the main tributaries south of the Amazon River, in addition to being specialists in Terra Firme forests and sensitive to environmental changes. The objective of this thesis was to update information on the range limits of Adelphobates species both through occurrence records and distribution modeling, and to elucidate the main mechanisms responsible for intraspecific diversification, through mitochondrial DNA data. As results, no intraspecific UTOs were found and the distribution of the three species was confirmed to be limited by the right bank of the Amazon River at north, and the brazilian Cerrado at south. Adelphobates quinquevittatus and A. castaneoticus present the greatest differences when compared to the most widespread distributions on the literature. The first has a more eastern distribution, and the marginal areas, where there are specimens with phenotypic variation, were considered inappropriate by the distribution modeling. The second present a less fragmented distribution in the Tapajós-Xingu interfluve, and is apparently surrounded by the A. galactonotus distribution. This latter had its distribution expanded on the right bank of the Tapajós River, and towards Palmas, in Tocantins. A. quinquevittatus population genetic structure was identified partially related to the current configuration of the Madeira River during the Pleistocene. However, the upstream region does not represent a historical barrier, suggesting that the Madeira River may have reached its current configuration recently. This phylogeographic pattern supports the drainage dynamism and historical complexity of the upper Madeira River. A. castaneoticus showed no genetic population structure within the Tapajós-Xingu interfluve, while A. galactonotus exhibited three genetic clusters, but the Xingu River did not promote allopatric divergence between opposite banks. Intraspecific diversification events have been dated within the Pleistocene and demographic analyzes indicate a bottleneck effect followed by recent population expansion for both species, which may suggest an effect of Quaternary climate changes on the isolation of these clades. The drier periods may also have potentiated the competitive interactions within the forest refugee, eliminating one of the species locally. Sampling proved to be decisive for the interpretation of evolutionary processes in Adelphobates species, as the inclusion of few localities was able to change the interpretation of phylogeographic patterns. In A. quinquevittatus, the exclusion of localities on the left bank of the Jaci-Paraná River would indicate an effect of the Madeira River as a barrier, while the exclusion of sampling on the right bank of the same river would indicate an opposite pattern. In A. galactonotus, previous studies have indicated the effect of the Xingu River as a barrier to gene flow, but the inclusion of two localities within the Tapajós-Xingu interfluve resulted in a different pattern.