• Bates, D., M. Maechler, and B. Bolcker. 2009. Package lme4 – Linear mixed-effects models using S4 classes. Available at (accessed 2 August 2012).
  • Dion, E., S. E. Polin, J.-C. Simon, and Y. Outreman. 2011. Symbiont infection affects aphid defensive behaviours. Biol. Lett. 7:743746.
  • Ferrari, J., C. B. Müller, A. R. Kraaijeveld, and H. C. J. Godfray. 2001. Clonal variation and covariation in aphid resistance to parasitoids and a pathogen. Evolution 55:18051814.
  • Frantz, A., V. Calcagno, L. Mieuzet, M. Plantegenest, and J. C. Simon. 2009. Complex trait differentiation between host-populations of the pea aphid Acyrthosiphon pisum (Harris): implications for the evolution of ecological specialisation. Biol. J. Linn. Soc. 97:718727.
  • Guay, J.-F., S. Boudreault, D. Michaud, and C. Cloutier. 2009. Impact of environmental stress on aphid clonal resistance to parasitoids: role of Hamiltonella defensa bacterial symbiosis in association with a new facultative symbiont of the pea aphid. J. Insect Physiol. 55:919926.
  • Henry, L. M., J. Peccoud, J.-C. Simon, J. D. Hadfield, M. J. C. Maiden, J. Ferrari, et al. 2013. Horizontally transmitted symbionts and host colonization of ecological niches. Curr. Biol. 23:17131717.
  • Kraaijeveld, A. R., J. Ferrari, and H. C. Godfray. 2002. Costs of resistance in insect-parasite and insect-parasitoid interactions. Parasitology 125:7182.
  • Kwiatkowski, M., and C. Vorburger. 2012. Modeling the ecology of symbiont-mediated protection against parasites. Am. Nat. 179:595605.
  • Oliver, K. M., J. A. Russell, N. A. Moran, and M. S. Hunter. 2003. Facultative bacterial symbionts in aphids confer resistance to parasitic wasps. Proc. Natl Acad. Sci. U. S. A. 100:18031807.
  • Oliver, K. M., N. A. Moran, and M. S. Hunter. 2006. Costs and benefits of a superinfection of facultative symbionts in aphids. Proc. Biol. Sci. 273:12731280.
  • Oliver, K. M., P. H. Degnan, G. R. Burke, and N. A. Moran. 2010. Facultative symbionts in aphids and the horizontal transfer of ecologically important traits. Annu. Rev. Entomol. 55:247266.
  • Peccoud, J., A. Ollivier, M. Plantegenest, and J. C. Simon. 2009. A continuum of genetic divergence from sympatric host races to species in the pea aphid complex. Proc. Natl Acad. Sci. 106:74957500.
  • Peccoud, J., J. Bonhomme, F. Mahéo, M. de la Huerta, O. Cosson, and J.-C. Simon. 2013. Inheritance patterns of secondary symbionts during sexual reproduction of pea aphid biotypes. Insect Sci. online. doi: 10.1111/1744-7917.12083
  • R Development Core Team. 2013. R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN 3-900051-07-0, Available at (accessed 25 September 2013).
  • Simon, J.-C., S. Boutin, T. Tsuchida, R. Koga, J.-F. Le Gallic, A. Frantz, et al. 2011. Facultative symbiont infections affect aphid reproduction. PLoS ONE 6:e21831.
  • Strauss, S. Y., J. A. Rudgers, J. A. Lau, and R. E. Irwin. 2002. Direct and ecological costs of resistance to herbivory. Trends Ecol. Evol. 17:278285.
  • Vorburger, C., and A. Gouskov. 2011. Only helpful when required: a longevity cost of harbouring defensive symbionts. J. Evol. Biol. 24:16111617.