The Molecular Basis of Phenotypic Convergence

Understanding what aspects of evolution are predictable, and repeatable, is a central goal of biology. Studying phenotypic convergence (the independent evolution of similar traits in different organisms) provides an opportunity to address evolutionary predictability at different hierarchical levels. Here we focus on recent advances in understanding the molecular basis of convergence. Understanding when, and why, similar molecular solutions are used repeatedly provides insight into the constraints that shape biological diversity. We first distinguish between convergence as a phenotypic pattern and parallelism as a shared molecular basis for convergence. We then address the overarching question: What factors influence when parallel molecular mechanisms will underlie phenotypic convergence? We present four core determinants of convergence (natural selection, phylogenetic history, population demography, and genetic constraints) and explore specific factors that influence the probability of molecular parallelism. Finally, we address frontiers for future study, including integration across different systems, sub-fields, and hierarchical levels.