ABSTRACT
Two different but interdependent processes likely contribute to the majority of major evolutionary transitions and each will leave different signatures that are distinguishable in comparative analyses. Some components of novel traits have their mutational origins in duplication, subsequently followed by differential divergence in both form and function. Gene duplications are perhaps the best studied duplication events, but “duplication” (either by copying or by fi ssion) happens at other levels of biological organization, including protein domains, groups of interacting proteins, chromosomes,
Ecology Evolution and Marine Biology, University of California-Santa Barbara Santa Barbara. CA 93106; (805) 893-4715. E-mail: oakley@lifesci.ucsb.edu
genomes, cells, organs, castes, species, and ecosystems. Other novel traits originate as new combinations of existing traits, a process sometimes termed bricolage, or tinkering (Jacob 1977). As with duplication, recombinational novelties occur at multiple levels of biological organization: domains fuse to form new proteins, proteins gain new interactions with other proteins, cells/species merge as in the endosymbiotic origin of eukaryotes, and new ecological interactions emerge by dispersal of species. Recognizing and distinguishing duplication, and co-option requires a historical or phylogenetic perspective.
