Resilience of haplodiploids to being exploited by sexually deceptive plants

Abstract

In species with obligate sexual reproduction, scarcity of males can occasionally limit female reproductive success. It is unclear, however, whether this impacts population-level persistence. Sexually deceptive orchids attract mate-searching male insects who lose time, mating opportunities and may even become sperm depleted by mating with flowers. These insects are almost exclusively haplodiploid, and able to reproduce regardless of sperm availability – which might mitigate costs of deception. We model the population dynamics of deceived diploid or haplodiploid pollinators. The model reveals that haplodiploidy can enhance prospects for coexistence. If ‘sperm theft' by orchids is severe enough to generate unmated females in the local pollinator pool, this enhances the production of sons, which are subsequently available to act as pollinators. The mechanism relies on female haplodiploids being able to reproduce with or without sperm; this is absent in many diploid insects – where unmated females do not reproduce. We show that this gives haplodiploids an ability to maintain higher population densities, and to persist up to higher orchid densities, than diploids. Our model identifies the enhanced resilience of haplodiploid pollinators against deceptive exploitation as a possible reason why these systems have persisted.