Résumés
Résumé
Le déterminisme du sexe, par haplodiploïdie, que l’on rencontre chez les insectes hyménoptères, crée des asymétries de parenté entre les représentants des différentes castes de la fourmilière. Les valeurs des coefficients de parenté varient selon le nombre de reines ou le nombre de leurs accouplements. Le concept de sélection de parentèle qui en découle permet de mettre en évidence divers conflits plus ou moins discrets qui opposent les reines aux ouvrières et les ouvrières entre elles quant à la valeur du sex-ratio lors de l’élevage des futurs reproducteurs. Si les ouvrières, qui ont la maîtrise de l’élevage des larves, imposent souvent leur point de vue, les reines qui sont responsables du sexe des oeufs peuvent aussi manipuler le sex-ratio. Enfin, quand les reines sont absentes et remplacées par des ouvrières qui ont conservé la possibilité de s’accoupler, les conflits prennent un tour plus visible avec la mise en place d’une chaîne hiérarchique faisant intervenir interactions agonistiques et émissions phéromonales.
Summary
The haplodiploïd sex-determining system of Hymenoptera, whereby males usually develop from unfertilised eggs and females from fertilised eggs, results in relatedness coefficients that are not uniform among colony members. These asymmetries in relatedness are directly affected by the genetic architecture of the colony, which in turn depends on various factors such as queen number or queen mating frequency. Relatedness asymmetries induce different fitness returns per unit investment and, as a result, conflicts over brood composition may arise among colony members. Conflicts between the queen(s) and the workers over sex ratio represent one of the most frequent conflicts in eusocial Hymenoptera. Arrhenotoky allows queens great flexibility to control the sex of their progeny, by fertilizing or not the eggs; however because workers take care of the brood, they may influence the sex ratio by preferentially rearing one sex. Another salient conflict concerns the females over reproduction. In species where workers can mate and reproduce, physical aggressions or chemical communication may lead to dominance hierarchies for access to reproduction.
Parties annexes
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