Evolution of a Balanced Sex Ratio by Frequency-Dependent Selection in a Fish

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Science  14 Dec 1990:
Vol. 250, Issue 4987, pp. 1556-1558
DOI: 10.1126/science.250.4987.1556


Balanced (1 to 1) sex ratios are thought to evolve by a process known as frequency- dependent selection of the minority sex. Five populations of a fish with genetically based variation in temperature-dependent sex determination were maintained for 5 to 6 years in artificial constant-temperature environments that initially caused the sex ratio to be highly skewed. Increases in the proportion of the minority sex occurred in subsequent generations until a balanced sex ratio was established, thus confirming a central premise underlying the theory of sex-ratio evolution.

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