Courtship-role-reversal in the bean weevil, Bruchidius dorsalis (Coleoptera: Bruchidae): Interplay between male-male competition and cryptic female choice.

Abstract

Females of Bruchidius dorsalis, a wild bean weevil, exhibit courtship behavior actively, whereas the males are reluctant to mate but donate a large amount of seminal fluid, which eventually enhances female fecundity. This study examined the pre- and post-copulatory advantage of greater investing males: whether females choose greater investing males as their mates before copulation, and whether greater investing males attain larger reproductive success either by predominant sperm precedence or by prolonging the refractory period of the mating partner. B. dorsalis females did not preferably mate with greater investing or larger males, but refrained from mating for a longer period if they had obtained more investment. The sperm precedence of females mated with a sterilized and a normal male showed that the last mated male had precedence. Namely, B. dorsalis females did not choose greater investing males on a behavioral basis, but they preferentially used sperm of greater investing males by prolonging the mating interval according to the amount of the investment. The refractory period, approximately 20 h at the longest, was probably too short for the receiving females to assimilate the nutrients derived from the seminal fluid to the production of eggs that would be fertilized by the donating males. If this is the case, male investment in B. dorsalis is expressed as mating effort rather than paternal investment.