Conspecific sperm precedence in flour beetles

Two related species may mate readily yet rarely form hybrid zygotes. Such cryptic reproductive isolation may occur as a result of conspecific sperm precedence, suggesting that postmating sexual selection is a key process in speciation. However, demonstrating conspecific sperm precedence is nontrivial, and several methodological problems may confound the results of such studies. By mating females to conspecific and heterospecific males of varying degree of relatedness, we established the existence of conspecific sperm precedence in flour beetles, Tribolium spp. Postmating incompatibilities seem to accumulate rapidly in this group of insects, and we discuss the implications of our findings for the influence of postmating sexual selection on speciation.