title: Widespread host-dependent hybrid unfitness in the pea aphid species complex.
abstract: Linking adaptive divergence to hybrid unfitness is necessary to understand the ecological factors contributing to reproductive isolation and speciation. To date, this link has been demonstrated in few model systems, most of which encompass ecotypes that occupy relatively early stages in the speciation process. Here we extend these studies by assessing how host-plant adaptation conditions hybrid fitness in the pea aphid, Acyrthosiphon pisum. We made crosses between and within five pea aphid biotypes adapted to different host plants and representing various stages of divergence within the complex. Performance of F1 hybrids and nonhybrids was assessed on a "universal" host that is favorable to all pea aphid biotypes in laboratory conditions. Although hybrids performed equally well as nonhybrids on the universal host, their performance was much lower than nonhybrids on the natural hosts of their parental populations. Hence, hybrids, rather than being intrinsically deficient, are maladapted to their parents' hosts. Interestingly, the impact of this maladaptation was stronger in certain hybrids from crosses involving the most divergent biotype, suggesting that host-dependent postzygotic isolation has continued to evolve late in divergence. Even though host-independent deficiencies are not excluded, hybrid maladaptation to parental hosts supports the hypothesis of ecological speciation in this complex.
authors: Institut National de la Recherche Agronomique INRA, Institut de Génétique, Environnement et Protection des Plantes (UMR 1349 IGEPP), Domaine de La Motte, BP, 35327, 35653 le Rheu Cedex, France.
authors: Jean
authors: J
authors: Peccoud
authors: Manon
authors: M
authors: de la Huerta
authors: Joël
authors: J
authors: Bonhomme
authors: Cindy
authors: C
authors: Laurence
authors: Yannick
authors: Y
authors: Outreman
authors: Carole M
authors: CM
authors: Smadja
authors: Jean-Christophe
authors: JC
authors: Simon
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000818:Animals; D001042:Aphids / Q000235:genetics*; D005075:Biological Evolution; D060146:Ecotype; D005260:Female; D056084:Genetic Fitness; D049810:Genetic Speciation; D006824:Hybridization, Genetic; D008297:Male; D015233:Models, Statistical; D018532:Pisum sativum
keywords: Ecological speciation; fitness trade-offs; hybridization; insect-plant interactions; postzygotic isolation; quantitative genetics