Evolution of Reptile Diversity in Tropical Savannas - A Study Across Scales and Continents

• Main Author: Fenker Antunes, Jessica
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2020
• Subjects: Biology; Ecology; Plant sciences
• ISBN: 9798691221910

What promotes biological diversity? Accurately recognising and describing patterns of diversity is fundamental to understanding the evolutionary and ecological processes underpinning diversification. The history of living organisms is expressed at multiple dimensions, ranging from speciation processes across various biogeographical scales, to variation in morphology, ecology and genetic diversity. Systems with highly heterogeneous habitats provide good models to investigate how landscape processes affect the observed patterns of ecological and genetic diversity, e.g. through speciation and local adaptation. Tropical savannas are environmentally heterogeneous biomes, covering one sixth of the Earth's terrestrial surface, in which a high number of species coexist, with high levels of endemism. My thesis compares pattern and process of savanna reptile diversity across two biogeographic realms - the Cerrado biome from South America and the Australian Monsoonal Tropics (AMT) of Australia. I investigate the principal factors that shape the adaptation and diversification of lizards (and sometimes snakes and amphisbaenians). This entails studies within in each of the Cerrado and AMT systems at landscape to regional scales. Comparing these two analogous but evolutionarily independent systems, I expect to identify common processes underpinning the high diversity of tropical savanna systems. A better understanding of the diversification process has three broad outcomes. First, the use of an integrative approach, including molecular, ecological and morphological datasets, provides a more complete view of the patterns of diversity that we see today. Second, the use of refined population-level and phylogeographic datasets improves our definition of species limits and overcome taxonomic shortfalls that preclude large-scale inferences. Third, the mapping of the distribution of this diversity, and a better understanding of the evolutionary processes involved, is essential to assess conservation priorities give rapid global change. The analyses include morphological, ecological and genomic diversity of squamates from both continents. The thesis is composed of four primary research chapters and two appendices. Each chapter has its own dataset and they collectively address different topics, at varying geographic and taxonomic scales. In chapter 1, I focus on a cross-continent comparison of morphological evolution, including all the snakes and lizards species found in the AMT and Cerrado. Then, focused only on Cerrado lizard species in chapter 2, I mapped spatial patterns of species richness, phylogeographic diversity and endemism to parallel a previous study for the AMT. Coming back to the AMT, I document the phylogeographic structure and demographic history of a diverse and highly structured group of agamid dragons (Diporiphora- Chapter 3). Finally, I explore whether dispersal limitation, environment and geographic barriers or habitat specialization at landscape scale predict differences in phylogeographic structure across co-distributed lizard taxa (Chapter 4). Collectively, these chapters provide new insights into the micro- and macro-evolutionary processes that have shaped the high and unique diversity of reptiles in these tropical savannas.