Optimal sex ratio as a function of EGG incubation temperature in the crocodilians |
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Authors: | F M Phelps IV |
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Institution: | (1) 290 Cedar Dr., 48858 Mt. Pleasant, MI, U.S.A. |
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Abstract: | Recently, there has been a growing consensus as to the adaptive significance of temperature-dependent sex determination in
the Crocodilia. The observationally and experimentally motivated hypotheses are that male fitness depends more strongly on
quality of incubation environment than female fitness, and that there is a strong correlation between a female's egg incubation
temperature choice and her own egg incubation temperature. A population genetics model based on these hypotheses is derived.
A method for finding the optimal sex ratio as a function of temperature, which is an evolutionary stable strategy (ESS), is
stated and applied under various assumptions. This extends ESS theory to thefunctional case. Cases where there is no ESS and the population sex ratio oscillates in evolutionary time are discovered. Numerical
computation is needed to solve the full problem and the resulting optimal sex ratio is compared to laboratory sex ratio data.
The general pattern of TSD in crocodilians (female-male-female with female biased overall sex ratio) agrees well with the
theory, but details of the pattern are problematic. |
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Keywords: | |
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