On the Emergence of Biodiversity: Mechanistically Bridging Ecology, Evolution and Paleo-Environments

Abstract

Understanding the origins of biodiversity has been an aspiration since the days of early naturalists such as Whewell, Lyell, Humboldt, Darwin and Wallace. These pioneers already acknowledged interactions between ecological and evolutionary processes, as well as the roles of continental movements, orogeny and climate variations in shaping biodiversity patterns. As science advanced, the complexity of ecological, evolutionary, geological and climatological processes became evident in an increasingly fragmented scientific landscape. Recent developments in computer modelling now enable the strengthening of interdisciplinary fields, opening unprecedented scientific pathways. In this thesis, a novel general engine for eco-evolutionary simulations (gen3sis) is presented. The engine consists of a spatially-explicit modelling framework that enables modular implementation of multiple macroecological and macroevolutionary processes interacting across representative spatio-temporally dynamic landscapes. Applications of gen3sis shed light into long-standing enigmas of global biodiversity patterns, such as: the latitudinal diversity gradient (LDG), the pantropical diversity gradient (PDG) and the life history of cold-adapted floras. Multiple reconstructed paleolandscapes and processes (e.g. environmental filtering, biotic interactions, energetic carrying capacities, dispersal, allopatric speciation, and the evolution of stress tolerance and competitive ability) were used to simulate emergent biodiversity patterns (e.g. ,  and  diversity, past and current species ranges, and phylogenies). Conclusions are based on comparisons of simulated patterns with literature reviews and empirical data (i.e. species ranges, phylogenies and fossils) of multiple faunas and floras. Bridging ecological and evolutionary mechanisms with paleo-environments shaped by plate-tectonic movements, mountain uplifts and deep-time climate changes using gen3sis is shown to be indispensable for reconstructing the formation of many global biodiversity patterns. Energetic carrying capacity was a significant process when concurrently simulating a realistic LDG, species range size frequencies, and phylogenetic tree balance of major tetrapod groups. Differences in paleo-environmental dynamics between continents (e.g. mountain and island formation and habitat fragmentation), combined with weak niche evolution, can explain the PDG by shaping spatial and temporal patterns of species origination and extinction. Simulations matched observed distribution and phylogenetic patterns of tropical plants and animals. Geological and climatological events, combined with species interactions and the evolution of competitive and temperature tolerance traits, provide a remarkable match with observed distributions, fossil records and the phylogenetic nestedness of cold-adapted plants. This thesis moves beyond correlational approaches and provides a novel framework for formalizing and exploring multiple hypotheses and reconstructions associated with the origin of biodiversity. Model comparison with empirical data serves hindcast, which might inform biodiversity trajectories. By advancing our numeric understanding of the physical and biological processes that shape biodiversity, new and interdisciplinary tools such as gen3sis support scientists to piece together key puzzles of the Earth’s astonishing biodiversity.