Convenience polyandry and the role of lone and reciprocal calls in a psyllid

Abstract

It is widely accepted that receptivity to mating may be asymmetrical between the sexes. While reproductive benefits for males are cumulative, females may not benefit equally from polyandry, especially in species where females can store sperm. Female psyllids (Hemiptera: Psylloidea) are reportedly polyandrous. However, the adaptive significance of this mating strategy has not been thoroughly investigated. Studies involving other insect species indicate that polyandry may be driven by benefits (direct or indirect) or by the need to minimize costs associated with male harassment. Drooping she-oak psyllids, Aacanthocnema dobsoni (Triozidae), use substrate-borne vibrations for mate attraction but they are not a prerequisite for mating. We suspected that polyandry in this species could be driven by male harassment because males exhibit indiscriminate mating behaviour (consistent with a scramble competition mating strategy), often mating with unresponsive (mated) females. We investigated relationships between calling, feeding and mating status to test whether females mate to minimize harassment by males and whether they gain any direct benefits from polyandry. We found that lone calls were commonly, but reciprocal calls were rarely followed by mating. As reciprocal calls should reflect female receptivity, copulations without them highlight the existence of sexual conflict over mating. Observations revealed that feeding females were less likely to resist mating than nonfeeding females. We did not find that females obtained any direct benefits from polyandry. Our results suggest that polyandry in this species may be a consequence of male harassment and that mated females, while feeding, may remate for convenience to minimize costs associated with stylet retraction/penetration and location of new feeding sites.