Prolonged mate guarding and sperm competition in the weevil Diaprepes abbreviatus (L.)

The hypothesis that prolonged copulatory mate guarding coexists with last male sperm precedence was tested for the sugarcane rootstalk borer weevil, Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae). Male D. abbreviatus showed a long copulatory guarding. Both males and females were less likely to remate when prolonged guarding occurred compared with terminating copulation early. Guarding was generally terminated by the struggling behavior of the female. Mating experiments using normal and sterile (X-ray irradiated) males revealed a similar value of last-male sperm precedence for both irradiated and normal males. The P-sub-2 values of normal and sterile males were similar when all oviposited eggs were counted over 30 days. These data made it possible to calculate the expected gain to a male from prolonged guarding compared with leaving a female early and seeking out an additional mate. We show that guarding has the higher fitness. Eggs were deposited in clutches in which normal fertilized eggs were grouped together and were attached to a group of sterile eggs. This, together with identifying the form of the cul-de-sac typespermatheca, allowed us to suggest a unique repositioning process, which has not been described elsewhere, as the likely mechanism by which last-male sperm precedence was achieved. Copyright 2003.