Low enzyme gene variability in Hymenoptera as a consequence of haplodiploidy

Abstract

Enzyme gene variability in fifteen hymenopteran species, mainly bees, has been studied. The species were Apis mellifera L., six Bombus species, Macropis labiata F., Colletes succincta L., three Andrena species, Vespula vulgaris L., Mimesa equestris F. and Pontania vesicator Bremi. The hymenopteran species reproduce by arrhenotokous parthenogenesis so that the males are haploid and the females are diploid. The present results, as also the earlier studies, show that the number of polymorphic loci and the amount of heterozygosity are smaller in haplodiploid than in diploid insect populations. This is in accordance with theoretical expectations, as both deterministic selection models and the neutral hypothesis predict that genic variability is reduced in haplodiploid populations. The average heterozygosity per locus is lower in eusocial than in solitary species. The difference is not statistically significant, but it may indicate that either small effective population sizes or stable conditions in the nests of eusocial species affect genic variation.