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Sexual selection theory evaluation


Calculations for quantifying the potential for sexual selection remain controversial. Many indices have been promoted in the literature, but each has unique sets of advantages and disadvantages.

We do not consciously (or...

Using marbled salamanders, I evaluated the performance of several measures by manipulating intensity of sexual selection in experimental breeding replicates of varying operational sex ratio.

Theory predicts that sexual selection among males will be higher when sex ratio is male-biased and lower when female-biased. I used microsatellite data to assign hatchling parentage, estimate adult fitness, and calculate several indices of inequality for quantifying sexual selection.

Opportunity for selection and Morisita index always conformed to Sexual selection theory evaluation expectations, which was not the case for index of resource monopolization, standardized Morisita index, or binomial skew Sexual selection theory evaluation. Although I conclude that opportunity for selection is advantageous in Sexual selection theory evaluation selection studies because of its link to formal theory, this should be tested against the null hypothesis of random variation in ambiguous cases.

In the present study, although variation in both reproductive and mating success was high when quantified using opportunities for selection, it was only significantly greater than random expectations for reproductive success. This study provides further empirical support for the continued use of opportunity for selection in sexual selection studies. Although sexual selection was first discussed over a century ago Darwin, and has been a major topic in the evolution literature for decades, there is still no consensus on how we should quantify its action.

Most often, people have used a calculation related to formal sexual selection theory opportunity for selection, I that grew out of what came to be known as Bateman's principles Arnold,as first discussed when Bateman published his descriptions of the mating system in Drosophila fruit flies Bateman, His ideas were based on the importance of fitness variance in determining the strength of sexual selection.

Darwin noted that sexual selection...

Specifically, Bateman's principles suggest that the sex that has higher variance in mating success number of mates and reproductive success number of progeny experiences more sexual selection. I has come under attack over the last few decades for three main reasons. First, it does not incorporate random variation that is expected to occur even in the absence of selection.

For example, Sutherland showed that Bateman's data can be explained by random chance alone and may not have reflected the action of sexual selection. Sexual selection theory evaluation further showed that differences in fitness variance between the sexes may result from simple randomness paired with sex differences in the time required for mating i. When mean fitness increases, I tends to decrease such that its expected value is the reciprocal of the mean.

This is expected for any random variable with a Poisson distribution for which mean and variance are equal. Indeed, the upper bound of I is equal to the number of individuals in the group. Several have suggested that we use other less biased measures to maximize the robustness Sexual selection theory evaluation these types of comparisons. Many indices of inequality have been derived, used in various studies, and promoted as the best options Ruzzante et al.

Generally, the new indices with the most support deal with these problems better than I. All express fitness variation relative to random expectations, some are restricted to values below one to ameliorate group size dependence, and mean dependence may not be as severe as in I.

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