We propose a new speciation mechanism for hybridizing populations based on
frequency-dependent sexual selection theory. In contrast to previous reinforcement and
symmetric speciation models, this model does not require viability selection for male
sexual traits, selection against unfit hybrids or disruptive selection for ecological
traits. The model assumes that females exhibit mating preferences based on male secondary
sexual characters. Both female mating preferences and male secondary sexual traits are
independent quantitative genetic traits. Females choose using one of five tactics. All
individuals, including the hybrids, have the same ability to survive and reproduce. Two
populations that differ only in their average values of female preference and male sexual
traits are assumed to come into contact and hybridize. Most cases of the model frequently
result in complete prezygotic isolation. The likelihood of speciation decreases with the
degree of phenotypic overlap between the two merging populations. However, the probability
of speciation is not zero even when the two merging populations are identical.