Field and experimental studies of fish in the genus Poeciliopsis (Cyprinodontiformes: Poecilidae) offer substantial insights into the origins, evolution, and ecology of clonal vertebrates. Recent molecular studies have clarified factors involved in the origins of diploid and triploid asexual lineages, and they provided evidence for a relatively ancient asexual lineage that has dispersed over great distances. The age of this lineage and perhaps other clones is sufficient for a ratchet-like mechanism to cause mutational deterioration. Recurrent origins of new clones from genetically variable sexual ancestors appears to be the driving force behind ecological diversification and the numerical success of unisexual populations. Genetic diversity also appears to play a role in the success of sexual populations. Discovery of a new sexual species that derived from a clonal lineage reveals an avenue of escape from the evolutionary dead end of asexuality.
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Robert C. Vrijenhoek (1993) studied this question.