Male age is associated with extra-pair paternity, but not with extra-pair mating behaviour

Extra-pair paternity is the result of copulation between a female and a male other than her social partner. In socially monogamous birds, old males are most likely to sire extra-pair offspring. The male manipulation and female choice hypotheses predict that age-specific male mating behaviour could explain this old-over-young male advantage. These hypotheses have been difficult to test because copulations and the individuals involved are hard to observe. Here, we studied the mating behaviour and pairing contexts of captive house sparrows, Passer domesticus. Our set-up mimicked the complex social environment experienced by wild house sparrows. We found that middle-aged males, which would be considered old in natural populations, gained most extra-pair paternity. However, both, female solicitation behaviour and subsequent extra-pair matings were not associated with male age. Further, copulations were more likely when solicited by females than when initiated by males (i.e. unsolicited copulations). Male initiated within-pair copulations were more common than male initiated extra-pair copulations. To conclude, our results did not support either hypothesis regarding age-specific male mating behaviour. Instead, female choice, independent of male age, governed copulation success, especially in an extra-pair context. Post-copulatory mechanisms might determine why older males sire more extra-pair offspring

Genomics of Phenotypic plastity in Aphids

International audienceThis chapter aims at explaining how the understanding of a complex adaptive trait (phenotypic plasticity) of insect pests (aphids) can gain from genomics approaches. Aphids adapt their capacity of dispersal to escape natural enemies or poor plant quality, as well as they adapt capacity to produce eggs or viviparous larvae upon the seasons. Genomes of aphids are now available, and post-genomics strategies (including quantitative genetics) allow the community to identify key regulatory gene circuits that govern the phenotypic adaptation of these insects to their changing environment

Integrative Genomic Approaches to Studying Epigenetic Mechanisms of Phenotypic Plasticity in the Aphid

Phenotypic plasticity is the nongenic variation in phenotype due to environmental factors. It is a common phenomenon in the animal kingdom that is not well understood at the molecular level. A tenable form of phenotypic plasticity for molecular research is polyphenism, which is an extreme form of phenotypic plasticity that results in discrete, alternative morphs. Epigenetic mechanisms have been hypothesized as the molecular regulators of polyphenism, in particular DNA methylation and chromatin remodeling. The pea aphid exhibits multiple polyphenisms including winged and wingless females during summer (wing polyphenism) and asexual and sexual morphs during summer and fall, respectively (reproductive polyphenism). The aphid is ideally situated for research into the molecular basis of polyphenism, with a sequenced genome and multiple transcriptomic studies that have begun identifying key molecular regulators of these two polyphenisms. The aphid also possesses the genes necessary for DNA methylation and chromatin remodeling. The pea aphid system is thus primed for future research into the epigenetic regulation of polyphenism