In the present study the egg dumping behaviour in short (E)- and long (L)-lived lines of the seed beetle Acanthoscelides obtectus was analyzed. Females of the short-lived E line exhibited substantially higher egg dumping than long-lived L line females. We hypothesize that, since cessation of egg dumping enhances longevity, non-dumping females were selectively favoured in the L regime. Our study also produced evidence that the selection regime affected the male's ability to influence female egg-dumping behaviour. The females mated to males from the lines that were selected for extended longevity and of which the females exhibited little egg-dumping dumped fewer eggs. We suggest that in the L selection regime, where offspring produced at the end of the females' reproductive period were recruited to the next generation, selection operated against those males that stimulated female oviposition in the absence of seeds. This is the first study to provide evidence that selection for long-lived insects results in the reduced potency of male seminal products to stimulate female oviposition.
We studied the genetic architecture of the differences in the longevity between lines selected for postponed senescence and a control population of the seed beetle Acanthoscelides obtectus maintained on two hosts. By using lines with increased longevity, which were obtained by selection on natural variation in longevity, we showed that the genetic architecture of seed beetle longevity is complex, with sex-specific effects and variation attributable to many interacting genes, whose expression depend on the host on which the beetles were reared. The nonadditive genetic effects were more strongly expressed when reared on chickpeas, a novel host, than on beans. Outbreeding depression, with respect to longevity, was a consequence of both the intrinsic effect of interactions between genes from different parental sources (disruption of coadapted gene complexes) and the genotype × host interaction (loss of local adaptation).