Sex Ratio Theory
The theory of sex ratio is a field of study concerned with the accurate prediction of sex ratios in all sexual species, based on a consideration of their natural history. The field continues to be heavily influenced by Eric Charnov's 1982 book, Sex Allocation. He defines five major questions, both for his book and the field in general (slightly abbreviated here):
- For a dioecious species, what is the equilibrium sex ratio maintained by natural selection?
- For a sequential hermaphrodite, what is the equilibrium sex order and time of sex change?
- For a simultaneous hermaphrodite, what is the equilibrium allocation of resources to male versus female function in each breeding season?
- Under what conditions are the various states of hermaphroditism or dioecy evolutionarily stable? When is a mixture of sexual types stable?
- When does selection favour the ability of an individual to alter its allocation to male versus female function, in response to particular environmental or life history situations?
Biological research mostly concerns itself with sex allocation rather than sex ratio, sex allocation denoting the allocation of energy to either sex. Common research themes are the effects of local mate and resource competition (often abbreviated LMC and LRC, respectively).
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