Efeito da variabilidade ambiental na história evolutiva das angiospermas do semiárido brasileiro

Abstract

The structuring of biological communities results from the dynamic interaction of multiple factors,such as speciation, dispersal, extinction, ecological interactions, and environmental filtering.However, most studies on these processes adopt isolated approaches, emphasizing either ecologicalmechanisms or historical processes. Integrating these perspectives remains a crucial challenge forunderstanding the factors shaping biodiversity. In this thesis, we aim to advance this understandingthrough two chapters that investigate the taxonomic and phylogenetic diversity patterns of woodyspecies in the Caatinga, analyzing how environmental variables, such as climate and soil, along withbiogeographic processes, influence the structuring of these communities. In the first chapter, weexplore the climatic and edaphic predictors that determine the diversity of woody species in thethree main geological substrates of the Caatinga (crystalline, karstic, and sedimentary). We alsoexamine the connections between these diversity patterns and adjacent areas of the Cerrado andAtlantic Forest, investigating the role of geomorphological landscapes in the diversification of theCaatinga’s woody flora. We calculated phylogenetic alpha diversity and taxonomic andphylogenetic beta diversity patterns for both woody and herbaceous species, considering theinfluence of climatic and edaphic variables. The results indicated that among the factors analyzed,only temperature significantly influenced the phylogenetic alpha diversity of herbaceous species. Incontrast, taxonomic and phylogenetic beta diversity were influenced by variables such as pH, cationexchange capacity, temperature, and precipitation. Furthermore, our findings revealed that diversityin the crystalline, karstic, and sedimentary substrates of the Caatinga is more similar among themthan to adjacent areas of the Cerrado and Atlantic Forest, highlighting the ecological uniqueness ofthe biome. In the second chapter, we adopted a phylogenetic approach to investigate how diversitypatterns relate to present and future projected climate conditions. Using different phylogeneticmetrics, we identified that both current and short-term future climate scenarios positively influencephylogenetic endemism. Additionally, we found that centers of neoendemism are associated withmilder conditions, such as lower temperatures and reduced precipitation seasonality, while centersof paleoendemism are linked to hotter and more seasonal conditions. These patterns suggest thathistorical events and long-term climatic variations have played a central role in the formation ofthese areas of endemism. The findings of this thesis emphasize the importance of integratinghistorical and ecological aspects to understand the mechanisms shaping the biodiversity of theCaatinga. Furthermore, they reinforce the potential of phylogenetic diversity as a tool for identifyingecologically significant areas and guiding conservation strategies, highlighting the need to preservekey regions for maintaining the biome’s biodiversity.