title: Evolutionary transitions during RNA virus experimental evolution.
abstract: In their search to understand the evolution of biological complexity, John Maynard Smith and Eörs Szathmáry put forward the notion of major evolutionary transitions as those in which elementary units get together to generate something new, larger and more complex. The origins of chromosomes, eukaryotic cells, multicellular organisms, colonies and, more recently, language and technological societies are examples that clearly illustrate this notion. However, a transition may be considered as anecdotal or as major depending on the specific level of biological organization under study. In this contribution, I will argue that transitions may also be occurring at a much smaller scale of biological organization: the viral world. Not only that, but also that we can observe in real time how these major transitions take place during experimental evolution. I will review the outcome of recent evolution experiments with viruses that illustrate four major evolutionary transitions: (i) the origin of a new virus that infects an otherwise inaccessible host and completely changes the way it interacts with the host regulatory and metabolic networks, (ii) the incorporation and loss of genes, (iii) the origin of segmented genomes from a non-segmented one, and (iv) the evolution of cooperative behaviour and cheating between different viruses or strains during co-infection of the same host.This article is part of the themed issue 'The major synthetic evolutionary transitions'.
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, Campus UPV CPI 8E, Ingeniero Fausto Elio s/n, 46022 València, Spain Instituto de Biología Integrativa y de Sistemas, Consejo Superior de Investigaciones Científicas-Universitat de València, Parc Científic de la Universitat de València, Catedrático Agustín Escardino 9, 46980 Paterna, Valencia, Spain Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA santiago.elena@csic.es.
authors.forename: Santiago F
authors.identifier: 0000-0001-8249-5593
authors.initials: SF
authors.lastname: Elena
mesh_terms: D005075:Biological Evolution; D060085:Coinfection / Q000821:virology; D019143:Evolution, Molecular; D016679:Genome, Viral; D056265:Microbial Interactions; D012328:RNA Viruses / Q000235:genetics* / Q000502:physiology
keywords: emerging viruses; experimental evolution; genome complexity and evolution; virus evolution; virus sociology