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Sex ratio variation in mammals
The Quarterly Review of Biology
|September 1, 1986
Summary
Parents can adapt offspring sex ratios to maximize reproductive success. While not all sex ratio variations are adaptive, some studies show species-specific adjustments based on the costs and benefits of producing males versus females.
Area of Science:
- Evolutionary biology
- Behavioral ecology
Background:
- Parents adjust progeny sex ratios to enhance fitness based on differential costs/benefits of sons and daughters.
- Variations in sex ratios are observed in non-human mammals, often cited as evidence of adaptive manipulation.
Purpose of the Study:
- To investigate the adaptive significance of sex ratio variation in non-human mammals.
- To determine if observed sex ratio trends align with adaptive theories or alternative mechanisms.
Main Methods:
- Review of existing studies on mammalian birth sex ratios.
- Analysis of sex ratio distributions and their correlation with parental fitness costs/benefits.
Main Results:
- Observed sex ratio trends do not consistently match predictions of single adaptive theories.
- Evidence suggests that within species, sex ratios vary with the costs or benefits of producing male or female offspring.
Conclusions:
- Not all mechanisms affecting birth sex ratio are adaptive.
- Adaptive sex ratio manipulation may occur within species, contingent on the relative fitness consequences of producing sons versus daughters.