Filogeografia, hotspots evolutivos e conservação ao longo da diagonal de formações abertas da América do Sul

Abstract

One of the main goals of biogeography is to unveil the processes and mechanisms involved on the generation and maintenance of biodiversity over time and space. Accessing species’ genetic information, coupled with conceptual, methodological, and computational advances have revolutionized the comprehension of evolutionary process. These advances have enabled reconstructing the evolutionary history of species and testing diversification hypotheses (e.g. refugee, physical barriers, diversification time) in a refinement level that once was unfeasible. The diagonal of open formations stretches from northeast to southwest South America, encompassing three biomes: Caatinga, Cerrado, and Chaco. Historically considered speciespoor biomes with no evolutionary identity, these regions have witnessed a change in paradigm due to increase of research and, currently, are recognized as holding high levels of richness, endemism, and unique evolutionary histories. However, tempo and mode of fauna diversification throughout this region are still poorly known and the debate remains largely open. This dissertation is composed of two chapters. (i) In the first one, we used a phylogeography approach to test the effects of historical events on the diversification throughout the diagonal of open formations using the lizard Polychrus acutirostris as study model. In order to reach this goal, we inferred population structure, phylogenetic relationships between lineages, intraspecific genetic diversity, migration patterns, demography and the spatio-temporal diffusion history. Finally, we tested 12 diversification scenarios using approximate Bayesian computation (ABC). We recovered three non-overlapping lineages that are spatially structured in the Caatinga, northeastern Cerrado, and southwestern Cerrado. Diversification among lineages took place during the Neogene and was associated to a complex scenario involving simultaneous divergence, early stages of diffusion, symmetrical pattern of migration between neighbor lineages, distinct effects of physical and environmental barriers. (ii) The second chapter aimed to identify areas in the Caatinga biome where the genetic diversity is spatially restricted (Evolutionary Hotspots) and propose areas that should be protected in order to maintain the evolutionary history of those areas. For this purpose, we used available mitochondrial data for six animal species widely distributed in the Caatinga, including: three lizard species, one amphibian and one spider. We used an interpolation method to generate a genetic diversity surface for each species. Finally, we overlapped the genetic diversity surfaces of all species to determine areas that concentrate high genetic diversity. In general, southern, central and northwestern portions of Caatinga harbor the highest values of genetic diversity, despite being poorly represented within protected areas. Our results highlight the complex evolutionary history within the diagonal of open formations. Besides, we identified genetically diverse areas within the Caatinga that are of utmost importance for biodiversity conservation.