Hormone mediated dispersal and sexual maturation in males of the social paper wasp Polistes lanio

Abstract

Sex-biased dispersal is common in social species, though the dispersing sex may delay emigration if associated benefits are not immediately attainable. In the social Hymenoptera (ants, some bees and wasps), newly emerged males typically disperse from the natal nest whilst most females remain as philopatric helpers. The mechanisms regulating male dispersal, whether male dispersal is directly linked to sexual maturation and if such mechanisms are conserved across the Hymenoptera is relatively unknown. Through field observations and mark–recapture, we observed that males of the social paper wasp Polistes lanio emerge from pupation sexually immature, and delay dispersal from their natal nest for up to seven days whilst undergoing sexual maturation. Delayed dispersal may benefit males by allowing them to mature in the safety of the nest and thus be more competitive in mating. We also demonstrate that both male dispersal and maturation are associated with juvenile hormone (JH), a key regulator of insect reproductive physiology and behaviour, which also has derived functions regulating social organisation in female Hymenoptera. Males treated with methoprene (a JH analogue) dispersed earlier and possessed significantly larger accessory glands than their age-matched controls. These results highlight the wide role of JH in social hymenopteran behaviour, with parallel ancestral functions in males and females, and raise new questions on the nature of selection for sex-biased dispersal.