The Cichlid Fishes of Lake Malawi, Africa

Abstract of Publication

Kawata, M. and J. Yoshimura. 2000. Speciation by sexual selection in hybridizing populations without viability selection. Evolutionary Ecology Research 2 (7): 897-909.  

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.




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