The nutritional contribution of males affects the feeding behavior and spatial distribution of females in a bruchid beetle, Bruchidius dorsalis

Abstract

The relationship between the quality/quantity of male investment and the feeding behavior of females was investigated in a bruchid weevil, Bruchidius dorsalis (Fahraeus), whose males donate nutrition via seminal fluid to females. Experiments on the effect of feeding regimes of both sexes on the mating frequency of females showed that females mated at a higher frequency if given low-quality food or poor male investment. On the other hand, the experiment that examined the effect of male investment quality on female feeding behavior showed that females receiving the high-quality investment exhibited feeding behavior less often. These results suggest that male investment and feeding behavior play the same role for B. dorsalis females. These experiments also showed that there are sex-related asymmetries in mating and feeding behaviors: females mated more often but males fed more often. Moreover, a field census suggested that only males visited non-host flowers to feed on the pollen and nectar during the non-flowering period of the host plants; females always stayed on the host plants irrespective of the flowering phenology. These results suggest that in B. dorsalis courtship role reversal and sex-specific feeding modes are fairly fixed and obligatory, and that male investment, derived from sexual selection, could affect the feeding behavior and spatial distribution of both sexes, which may have far-reaching impact in various ecological contexts.