SEX RATIO

Sex Ratio Elasticity Influences the Selection of Sex Ratio Strategy

There are three sex ratio strategies (SRS) in nature-male-biased sex ratio, female-biased sex ratio and, equal sex ratio. It was R. A. Fisher who first explained why most species in nature display a sex ratio of ½. Consequent SRS theories such as Hamilton's local mate competition (LMC) and Clark's local resource competition (LRC) separately explained the observed deviations from the seemingly u...

Sex ratio under conditional sex expression.

We present a model to show that, when sex depends on environment rather than genotype, the sex expressed under relatively unfavorable conditions will be more abundant. This result refers to numbers of males and females in the population. By contrast, no clear prediction can be made about the allocation of resources to the two sexes. The model is constructed to highlight the logical relationship...

Natural Selection: Sex Ratio

Natural selection acts strongly on the proportional numbers of male and female offspring among the progeny of adults. The equilibrium is often one at which males and females are produced in roughly equal numbers, but under certain ecological and genetic circumstances there may be dramatic population-wide biases, and even in populations with balanced sex ratios, parents are often selected to pro...

Sex-ratio evolution in sex changing animals.

Sex allocation theory is often able to make clear predictions about when individuals should facultatively adjust their offspring sex ratio (proportion male) in response to local conditions, but not the consequences for the overall population sex ratio. A notable exception to this is in sex changing organisms, where theory predicts that: (1) organisms should have a sex ratio biased toward the "f...

Sexuality: Sex Ratio and Sex Expression