Abstract
In this paper, we propose a unified terminology of convergence, in which the phenomenon of convergent evolution is the set, and the types of convergent evolution are subsets of that phenomenon. The set of the convergence phenomenon contains all of the same or very similar traits that have evolved independently in different lineages of organisms. This set contains three subsets that specify the three pathways by which evolution may produce convergence: allo-convergent evolution, iso-convergent evolution, and retro-convergent evolution. Allo-convergent evolution is the independent evolution of the same or very similar new trait from different precursor traits in different lineages, iso-convergent evolution is the independent evolution of the same or very similar new trait from the same precursor trait in different lineages, and retro-convergent evolution is the independent re-evolution of the same or very similar trait to an ancestral trait in different lineages. This unified convergence terminology is proposed to replace the older and confusing terms parallel evolution, reverse evolution, and convergent evolution sensu stricto.