Sexual selection on male morphology-independent of male-mlale competition in the Mediterranean fruit flp (Diptera : Tephritidae)

Sexual selection on morphology was examined in the lek-mating ny Ceratitis capitata (Weidemann). Single-pair courtships were videotaped in small chamb ers for males from a laboratory strain (L males) and males from the laborat ory G(2) generation of a sample of wild flies (W males). Virgin females der ived from the wild population were used for all observations. The time spen t on each courtship behavior (pheromone calling, wing fanning, wing buzzing , copulation attempt [mounting], missed jump during attempted copulation, a nd stationary status) was scored. Behavior was uncorrelated with morphology , except for a negative correlation between scutellum width and missed jump in L males. A multivariate analysis revealed that copulatory success is in fluenced by intermale variation to attempt copulation. Stabilizing sexual s election was apparent on eye length in L males and head width in W males, b ut size-related traits of thorax and wings had no effect on mating success. Because this selection was independent of any possible male-male competiti on, intersexual selection on male morphology is implied. Sexual selection o n morphology was also substantial in a field cage experiment, where virgin flies were released into a cage containing a small host tree. The results o f this caged experiment were consistent with those of single-pair courtship s in that head morphology was suggested as a selection target, but directio nal selection (decreasing the trait mean) rather than stabilizing selection was apparent. Overall, male's head morphology was suggested to be at least one of the more probable direct target of mate choice of females once at a lek. The results are thus consistent with the predominant view that female mate choice is often significant in lek-mating systems.