Paternal investment in the seed beetle Callosobruchus maculatus (Coleoptera: Bruchidae): Variation among populations

Ejaculate size in seed beetles (Coleoptera: Bruchidae) is subject to both sexual and fecundity selection. We examined interpopulation variation and inheritance of ejaculate size in the seed beetle Callosobruchus maculatus (F.). There was significant variation among three populations in both body mass and the proportion of a male's body mass that was transferred to females during mating. The seed upon which beetles were raised had a small effect on male body size but not the size of their ejaculates. To investigate the inheritance of ejaculate size, we performed inter- and intrapopulation crosses with two of these populations. The progeny of interpopulation crosses were intermediate between the intrapopulation (parental) crosses, suggesting additive genetic autosomal inheritance. This result differs from an earlier study in which ejaculate size of a different population was maternally inherited. This study demonstrates that there is indeed genetic variation in ejaculate size, but that the loci exhibiting within-population variation may be different than the loci producing among-population variation.