Genetic differentiation among wild populations of Tribolium castaneum estimated using microsatellite markers.

We report our characterization of the genetic variation within and differentiation among wild-collected populations of the red flour beetle, Tribolium castaneum, using microsatellite loci identified from its genome sequence. We find that global differentiation, estimated as the average F(ST) across all loci and between all population pairs, is 0.180 (95% confidence intervals of 0.142 and 0.218). A majority of our pairwise population comparisons (>70%) were significant even though this species is considered an excellent colonizer by virtue of its pest status. Regional genetic variation between Tribolium populations is 2-3 times that observed in the fruit fly, Drosophila melanogaster. There was a weak positive correlation between genetic distance [F(ST)/(1 - F(ST))] and geographic distance [ln(km)]; pairs of populations with the highest degree of genetic differentiation (F(ST) > 0.29) have been shown to exhibit significant postzygotic reproductive isolation when crossed in previous studies. We discuss the possibility that local extinction and kin-structured colonization have increased the level of genetic differentiation between Tribolium populations.