The evolutionary impact of resource availability

Evolution is the change in heritable characteristics in a population over successive generations that is driven by mutation, selection and random genetic drift. Understanding the factors affecting sequence evolution and the interactions between them is of fundamental importance and facilitated by the recent proliferation of genome data. One factor that is not well understood is the role that resource availability plays in determining sequence evolution. The aim of the research described in this thesis is to address this gap in our knowledge by presenting three papers on the theme of species and sequence evolution. First, I report the discovery of a new species of Phytomonas, a single-celled eukaryotic plant parasite. Second, using a comparative analysis of Phytomonas and other single-celled plant- and animal-infecting parasites, I reveal the importance of dietary nitrogen in determining biased patterns of nucleotide use in genome and transcript sequences. Third, I examine the interaction between codon biosynthetic cost and translational efficiency in a range of bacterial species. The new results reported in this thesis identify and quantify the impact of resource availability on sequence evolution. By elucidating the contribution of resource availability to sequence evolution, and investigating how selection acting on codon resource use interacts with selection acting on codon translational efficiency, the research presented in this thesis makes a significant contribution to our understanding of sequence evolution