INFECTION OF TRIBOLIUM BEETLES WITH A TAPEWORM - VARIATION IN SUSCEPTIBILITY WITHIN AND BETWEEN BEETLE SPECIES AND AMONG GENETIC STRAINS

Host susceptibility and resistance to parasites are often hypothesized to be genetically variable traits. We tested 2 species of Tribolium f lour beetles for among-strain variation in susceptibility to the rat t apeworm Hymenolepis diminuta. Twelve genetic strains of Tribolium conf usum and 11 strains of Tribolium castaneum were examined. We found T. castaneum was more susceptible to the tapeworm than T. confusum. There was significant among-strain and between-sex variation for both beetl e species in infection intensity and prevalence. Among-vial variation was marginally significant. These results add to evidence that host su sceptibility to a parasite is a genetically variable trait. We view th ese results as important findings for understanding natural selection on host-parasite interactions. Traits that are genetically variable ca n respond to natural selection. Thus, if a beetle's susceptibility to the tapeworm is correlated with fitness and heritable, susceptibility can evolve. Susceptibility is likely to be pleiotropic and have import ant consequences on issues ranging from parasite transmission to host species interactions and community structure.