Male-killer dynamics in Danaus chrysippus (L.) (Lepidoptera: Nymphalidae) in East Africa.

摘要

Within certain regions in East Africa, the butterfly Danaus chrysippus (L.) shows female-biased population sex ratio, because of the production by some females of all-female broods, as a result of infection by maternally inherited, male-killing bacterium of the genus Spiroplasma. In this study, we describe a 3-year field survey for the population dynamics of the male-killing Spiroplasma in D. chrysippus in four independent localities, namely Uganda, Ghana, Sudan and Madagascar. The prevalence of the bacterium was found to show extensive variations at multiple scales among different sites, in various countries, seasons and years. A novel, selection-based hypothesis was suggested to explain the high variability of male-killer prevalence over space and time, based on the existence of an adaptive link between larval food-plant density and the magnitude of resource reallocation fitness advantage for the male-killer.