Facultative deuterotokous parthenogenesis in Callosobruchus maculatus

Abstract

The seed beetle, Callosobruchus maculatus (Coleoptera: Chrysomelidae), is a severe cosmopolitan pest of various stored legumes. Since no parthenogenesis has been reported in the genus Callosobruchus, here we report the evidence of a rare event of deuterotokous parthenogenesis in this species. Interestingly, 11.11% of females out of 600 tested virgin females were capable of reproducing by parthenogenesis. Unfertilized-eggs developed into viable adults with a sex ratio of 1:1. Parthenogenetically-produced males and females could successfully copulate and generate the next generation. They achieved statistically the same total immature development, adult longevity, egg number, and hatchability as sexually produced progeny. However, none of the 60 female offspring produced via parthenogenesis were capable of reproducing by parthenogenesis. Mating disruption and sterile insect technique for pest control could not be efficient in insects with parthenogenetic reproduction because parthenogenesis will compensate for males’ absence by producing viable male and female offspring, saving species from possible extinction in the future. Therefore, these findings are important not only for considering in the Integrated Pest Management programs but also from an evolutionary perspective. Biodiversity and genetic differentiation among the current worldwide distribution of C. maculatus could be the origin of this facultative deuterotokous parthenogenesis evolution.