GENETIC-VARIATION SEGREGATING IN NATURAL-POPULATIONS OF TRIBOLIUM-CASTANEUM AFFECTING TRAITS OBSERVED IN HYBRIDS WITH T-FREEMANI

We investigated patterns of within-species genetic variation for trait s observed in hybrids (hybrid numbers, hybrid sex ratios, and hybrid m ale deformities) between two species of flour beetles, Tribolium casta neum and T. freemani. We found genetic variation segregating among fou r natural populations of T. castaneum as well as within these populati ons. For some hybrid traits, we observed as much variation among popul ations 750 km apart as between populations on different continents, su ggesting genetic differentiation at a local scale. Within natural popu lations, the variation segregating among sires is greater than that fo und in an earlier study for an outbred laboratory population and compa rable to that observed between inbred lines derived from the outbred s tock by eight generations of brother-sister mating. When sires from T. castaneum are mated to conspecific and heterospecific females, we do not observe a significant correlation at the level of the family mean between the intraspecific and interspecific phenotypes, suggesting the independence of the hybrid traits from comparable traits within speci es. We discuss our findings in relation to the evolutionary genetics o f speciation and the expression of epistatic genetic variance in inter specific crosses.