Professor Juli Peretó
Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Departament de Bioquímica i Biologia Molecular, Universitat de València <email@example.com>
Over a hundred years after the classic debates on the individuality of lichens, the role of symbiosis in the emergence of innovations is a significant part of the canon of contemporary evolutionary biology. The theory of symbiogenesis, proposed by Boris Kozo-Polyansky (1890-1957) and deployed in all its explanatory power by Lynn Margulis (1938-2011), allows the study of the emergence of new structures, metabolisms and behaviors from the association of different species. Thus, we are convinced that mitochondria and chloroplasts have common ancestors with modern free-living bacteria and that eukaryotic complexity began out of prokaryotic consortia more than 1 billion years ago. But the link between symbiosis and evolution does not end here. Associations with prokaryotic organisms have been present and repeated throughout the evolutionary history of eukaryotes. One of the best studied cases are the metabolic symbiogenesis between insects and bacteria, which have occurred independently many times during the last 300 million years, producing numerous mergers of the branches of the tree of life. The vertically inherited endosymbionts and the intestinal microbiota have sculpted the metabolic capabilities of the largest animal group. If the association between prokaryotes was essential for the emergence of the eukaryotic cell, we must also recognize that the symbiotic associations with prokaryotes, explored during eukaryotic diversification, have been crucial in the evolution of eukaryotic metabolism. The eukaryotes are really metabolic mosaics.