Girardi, Giorgia (2025) Temperature And Body Size Shaped Mammalian Biogeographic History. [Tesi di dottorato]

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Abstract

Macroevolution refers to evolutionary patterns and processes that occur at or above the species level over geological timescales (Raia, 2016) and includes the most significant trends in the history of life, including large-scale evolutionary radiations, mass extinctions, and ecological and morphological diversity. Species diversification is the net results of two opposite processes: speciation, which is the appearance of a new and distinct species, and extinction, which is the complete disappearance of a species. These processes, which vary widely between clades, among the different biomes, or geological times and settings, shape the patterns of biodiversity we observed today and unfolded in the past. The aim of my project is to analyse diversification in mammalian evolution during the Cenozoic. How did mammals respond to the major climate changes that occurred in the Cenozoic? What characteristics helped them cope with these major changes? How do these environmental changes modify mammalian biogeography? Besides these overarching issues, I will focus upon verifying the existence of macroevolutionary patterns such as Cope’s Rule (body size increase through time) and Bergmann’s Rule (body size increase with latitude) and to understand their role in mammalian diversification. To answer all these questions, I collected ~45,000 occurrence data of 2023 mammal species with a time span that covers the entire Cenozoic. Moreover, to evaluate if there were any factors that prompted or suppressed the diversification process, I also collected phenotypic data, substrate preferences, diet preferences and climatic data for all the analysed species, and developed a birth-death neural network (BDNN) model using the software Pyrate (Silvestro et al., 2014) to shed light on the factors controlling and the dynamics behind mammalian diversification.

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