Parent-of-origin effects, allele-specific expression, genomic imprinting and paternal manipulation in social insects

Haplo-diploidy and the relatedness asymmetries it generates mean that social insects are prime candidates for the evolution of genomic imprinting. In single-mating social insect species, some genes may be selected to evolve genomic mechanisms that enhance reproduction by workers when they are inherited from a female. This situation reverses in multiple mating species, where genes inherited from fathers can be under selection to enhance the reproductive success of daughters. Reciprocal crosses between subspecies of honeybees have shown strong parent-of-origin effects on worker reproductive phenotypes, and this could be evidence of such genomic imprinting affecting genes related to worker reproduction. It is also possible that social insect fathers directly affect gene expression in their daughters, for example, by placing small interfering RNA molecules in semen. Gene expression studies have repeatedly found evidence of parent-specific gene expression in social insects, but it is unclear at this time whether this arises from genomic imprinting, paternal manipulation, an artefact of cyto-nuclear interactions, or all of these. This article is part of the theme issue 'How does epigenetics influence the course of evolution?'