Haplodiploidy and evolution of eusociality in insectsAplodiploidia ed evoluzione dell’eusocialità negli insetti

Hymenoptera is the order of insects where eusociality has arisen more frequently. The propensity of this order to evolve complex eusocial traits has been linked to their haplodiploidy (i.e. diploid females and haploid males). In this paper we propose a new theory explaining why eusocial traits evolve more frequently in haplodiploid than in diploid species. The probability to fix an allele(s) in haplodiploid systems may be orders of magnitude higher than in diploid species and the ratio of the two probabilities is inversely correlated with allele frequencies and with the number of genes involved. This property of the haplodiploid system should greatly facilitate the evolution of complex multigenic altruistic traits as those present in the eusocial systems. This theory is not incompatible with that proposed by Hamilton (1964), but foresees much higher advantages in the evolution of sociality both by kin and group selection.