The Cheaper Sex Hypothesis

Trivers suggested that females in relatively poor condition will produce predominately female offspring that will have higher mating success than their male brothers. Such sex ratio bias will evolve by natural selection when (1) the sizes of the offspring are positively correlated with the mother's condition and (2) the likelihood of successful mating of offspring is related to the condition of males but not of females. An alternative hypothesis states that under poor environmental conditions females should produce the sex that requires least investment ('cheaper sex') and thereby maximize the number of offspring. In a range of animal taxa, these two hypotheses predict the same outcome when male individuals are larger on average than females (as in some bird species, for example, blackbirds, grouse, and pheasants); a female-biased sex ratio is expected under poor environmental conditions and male-biased under favorable conditions. Nonetheless, there is little evidence for this hypothesis, especially among unisexual species, where sex is determined purely by genetic mechanism. Among plants, however, the label 'cheaper sex' almost invariably applies to male plants (in case of dioecy) or male functions (in case of hermaphroditism), since the production of pollen and the development of pollen tubes require little allocation of resources in comparison to the production of ovules and seeds.

Was this article helpful?

0 0
10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.

Get My Free Ebook

Post a comment