title: Population genomics of eusocial insects: the costs of a vertebrate-like effective population size.
abstract: The evolution of reproductive division of labour and social life in social insects has lead to the emergence of several life-history traits and adaptations typical of larger organisms: social insect colonies can reach masses of several kilograms, they start reproducing only when they are several years old, and can live for decades. These features and the monopolization of reproduction by only one or few individuals in a colony should affect molecular evolution by reducing the effective population size. We tested this prediction by analysing genome-wide patterns of coding sequence polymorphism and divergence in eusocial vs. noneusocial insects based on newly generated RNA-seq data. We report very low amounts of genetic polymorphism and an elevated ratio of nonsynonymous to synonymous changes – a marker of the effective population size – in four distinct species of eusocial insects, which were more similar to vertebrates than to solitary insects regarding molecular evolutionary processes. Moreover, the ratio of nonsynonymous to synonymous substitutions was positively correlated with the level of social complexity across ant species. These results are fully consistent with the hypothesis of a reduced effective population size and an increased genetic load in eusocial insects, indicating that the evolution of social life has important consequences at both the genomic and population levels.
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, CNRS UMR 5554, Montpellier, France.
authors.forename: J
authors.initials: J
authors.lastname: Romiguier
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, CNRS UMR 5554, Montpellier, France.
authors.forename: J
authors.initials: J
authors.lastname: Lourenco
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, CNRS UMR 5554, Montpellier, France.|Institut de Recherches sur la Biologie de l'Insecte, CNRS UMR 7261, Université François-Rabelais, Tours, France.
authors.forename: P
authors.initials: P
authors.lastname: Gayral
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, CNRS UMR 5554, Montpellier, France.
authors.forename: N
authors.initials: N
authors.lastname: Faivre
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, CNRS UMR 5554, Montpellier, France.|Department of Veterinary Medicine, University of Cambridge, Cambridge, UK.
authors.forename: L A
authors.initials: LA
authors.lastname: Weinert
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, CNRS UMR 5554, Montpellier, France.
authors.forename: S
authors.initials: S
authors.lastname: Ravel
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, CNRS UMR 5554, Montpellier, France.
authors.forename: M
authors.initials: M
authors.lastname: Ballenghien
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, CNRS UMR 5554, Montpellier, France.
authors.forename: V
authors.initials: V
authors.lastname: Cahais
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, CNRS UMR 5554, Montpellier, France.
authors.forename: A
authors.initials: A
authors.lastname: Bernard
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, CNRS UMR 5554, Montpellier, France.
authors.forename: E
authors.initials: E
authors.lastname: Loire
authors.affiliation: Department of Ecology and Evolution, Biophore, University of Lausanne, Lausanne, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Keller
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, CNRS UMR 5554, Montpellier, France.
authors.forename: N
authors.initials: N
authors.lastname: Galtier
mesh_terms: D000818:Animals; D023281:Genomics; D007313:Insecta / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D011156:Population Density; D059467:Transcriptome
keywords: genomics; insects; life-history evolution; molecular evolution; population genetics