Microevolution Rate, Pattern, Process

Volume 8 of the series Contemporary Issues in Genetics and Evolution pp 435-443

Mechanisms of rapid sympatric speciation by sex reversal and sexual selection in cichlid fish

  • Russell LandeAffiliated withDivision of Biology 0116, University of CaliforniaInstitute of Evolutionary and Ecological Sciences, University of Leiden
  • , Ole SeehausenAffiliated withInstitute of Evolutionary and Ecological Sciences, University of LeidenDepartment of Biological Sciences, University of Hull
  • , Jacques J. M. van AlphenAffiliated withInstitute of Evolutionary and Ecological Sciences, University of Leiden

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Mechanisms of speciation in cichlid fish were investigated by analyzing population genetic models of sexual selection on sex-determining genes associated with color polymorphisms. The models are based on a combination of laboratory experiments and field observations on the ecology, male and female mating behavior, and inheritance of sex-determination and color polymorphisms. The models explain why sex-reversal genes that change males into females tend to be X-linked and associated with novel colors, using the hypothesis of restricted recombination on the sex chromosomes, as suggested by previous theory on the evolution of recombination. The models reveal multiple pathways for rapid sympatric speciation through the origin of novel color morphs with strong assortative mating that incorporate both sex-reversal and suppressor genes. Despite the lack of geographic isolation or ecological differentiation, the new species coexists with the ancestral species either temporarily or indefinitely. These results may help to explain different patterns and rates of speciation among groups of cichlids, in particular the explosive diversification of rock-dwelling haplochromine cichlids.

Key words

cichlid fish restricted recombination sex chromosomes sex ratio sex reversal sexual selection sympatric speciation