XVI International Botanical Congess

Amino acid changes and genomic structure of chloroplast DNA can be related through the study of codons, revealing complex patterns of mutational change. When such data are placed in a phylogenetic framework, tests for causative processes are possible. We investigated codon usage bias via comparative studies of rps4 and rbcL cpDNA sequences across a phylogeny of land plants. In separate/combined analyses of these two genes we discovered differences in the codon preference and frequency among land plant lineages and between the genes in single lineages. Such variation appears correlated with protein functional constraint and phylogenetic inertia. These findings provide information usable not only for understanding the pattern of plant diversity, but also for understanding the evolutionary mechanisms responsible.