Studies in biotic persistence and the taxonomic stability of traits over geological time

Abstract

It is increasingly recognized in evolutionary biology that biotic processes and pathways can be viewed as being under selection as well as organisms or populations. This view is particularly relevant when considering the history of the Earth’s biosphere over geological timescales, and the evolution of groups interacts with the evolution of processes in shaping the biosphere over time. This thesis considers a novel selection mechanism proposed to be operating on clades based on their age and tests its presence in marine animals over the Phanerozoic (Chapter 2); it also seeks to understand the interaction between some microbial traits and lineages over geological time as well as considering the implications of this interaction on the traits’ longevity. Chapter 3 considers the production of photoprotective pigment scytonemin, and Chapter 4 considers microbial iron oxidation. In these two chapters, I describe a metric called “clade fidelity” of a trait to describe its tendency to be associated with certain lineages and vertically inherited within them throughout the trait’s history, and I examine the relationship between a trait’s clade fidelity and its ecological context as well as evolutionary fate. The case studies in the thesis show that the proposed theoretical frameworks are applicable in practice and carry considerable explanatory power for the understanding of evolutionary processes on a scale of planetary history.