title: Local mate competition mediates sexual conflict over sex ratio in a haplodiploid spider mite.
abstract: In haplodiploids, females pass their genes on to all their offspring, whereas a male's genes are only passed on to his daughters. Hence, males always benefit from female-biased sex ratios, whereas for females the optimal offspring sex ratio depends on the level of local mate competition (LMC), ranging from highly female-biased under strict LMC to unbiased in Panmixia. This generates a sexual conflict over sex ratio, the intensity of which depends on the LMC level, with most intense conflict in Panmixia. Such conflict might lead to an evolutionary arms race, with persistence traits evolving in males and resistance traits in females. Although this prediction is theoretically straightforward, it remains untested empirically. We addressed this by crossing spider mites that evolved under varying intensities of LMC (hence of sexual conflict), to mates from inbred lines. Under high levels of sexual conflict, both sexes evolved manipulative traits to shift the sex ratio to their own advantage. In females, this was partly achieved through changes in egg size. We thus show that (1) LMC levels modulate sexual conflict over sex ratio in haplodiploids, driving the evolution of manipulative traits, and (2) fathers can affect sex ratio, challenging conventional assumptions.
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, Place Eugène Bataillon, 34095 Montpellier cedex 05, France. Electronic address: emiliemacke@free.fr.
authors.forename: Emilie
authors.initials: E
authors.lastname: Macke
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, Place Eugène Bataillon, 34095 Montpellier cedex 05, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Olivieri
authors.affiliation: CE3C: Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciencias da Universidade de Lisboa, Edificio C2, 3° Piso Campo Grande, 1749016 Lisbon, Portugal. Electronic address: snmagalhaes@fc.ul.pt.
authors.forename: Sara
authors.initials: S
authors.lastname: Magalhães
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005260:Female; D008297:Male; D010063:Ovum; D012744:Sex Ratio; D012726:Sexual Behavior, Animal / Q000502:physiology*; D040102:Tetranychidae / Q000502:physiology*