Sex‐specific demography and generalization of the Trivers–Willard theory

Trivers and Willard proposed that offspring sex ratio should vary with maternal condition when condition, meant as maternal capacity to care, has different fitness consequences for sons and daughters. In polygynous and dimorphic species, mothers in good condition should preferentially produce sons, whereas mothers in poor condition should produce more daughters. Despite its logical appeal, support for this hypothesis has been inconsistent. Sex-ratio variation may be influenced by additional factors, such as environmental conditions and previous reproduction, which are often ignored in empirical studies. We analysed 39 years of data on bighorn sheep (Ovis canadensis) that fit all the assumptions of the Trivers-Willard hypothesis. Production of sons increased with maternal condition only for mothers that weaned a son the previous year. This relationship likely reflects a mother's ability to bear the higher reproductive costs of sons. The interaction between maternal condition and previous weaning success on the probability of producing a son was independent of the positive effect of paternal reproductive success. Maternal and paternal effects accounted for similar proportions of the variance in offspring sex. Maternal reproductive history should be considered in addition to current condition in studies of sex allocation.

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“…This species satisfies all the assumptions of the TWH but has repeatedly been found not to support its predictions [9][10][11].…”

Section: Introductionmentioning

confidence: 86%

Maternal condition and previous reproduction interact to affect offspring sex in a wild mammal

Douhard¹,

Festa‐Bianchet²,

Pelletier³

2016

Biol. Lett.

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“…We then extend this approach by developing dynamic models of the phenotype decomposed into its genetic and environmental components. We start with a two-sex IPM that captures all demographic processes that can contribute to the dynamics of phenotypes-survival, recruitment, development, inheritance, and mating patterns (Coulson et al 2011;Schindler et al 2013Schindler et al , 2015Traill et al 2014a)-and that iterates forward the distribution of the phenotype at time t: N(Z, t) ( fig. 1b).…”

Section: Modeling Approachmentioning

confidence: 99%

“…Some authors have queried the use of equation (3) as an approximation in IPMs to the inheritance convolution in equation (15) used in models of sexually reproducing species (Chevin et al 2010;Janeiro et al 2017). However, being able to construct inheritance functions for A that are of the form of equation (3) would be useful because it would permit methods developed for two-sex phenotypic IPMs to be applied to evolutionarily explicit IPMs (e.g., Schindler et al 2015). Given that Gaussian approximations frequently perform well in models of evolution (Turelli and Barton 1994), we hypothesize that Gaussian inheritance functions may perform well in evolutionarily explicit IPMs.…”

Section: ð1þmentioning

confidence: 99%

Modeling Adaptive and Nonadaptive Responses of Populations to Environmental Change

Coulson

Kendall

Barthold

et al. 2017

The American Naturalist

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113

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. abstract: Understanding how the natural world will be impacted by environmental change over the coming decades is one of the most pressing challenges facing humanity. Addressing this challenge is difficult because environmental change can generate both populationlevel plastic and evolutionary responses, with plastic responses being either adaptive or nonadaptive. We develop an approach that links quantitative genetic theory with data-driven structured models to allow prediction of population responses to environmental change via plasticity and adaptive evolution. After introducing general new theory, we construct a number of example models to demonstrate that evolutionary responses to environmental change over the short-term will be considerably slower than plastic responses and that the rate of adaptive evolution to a new environment depends on whether plastic responses are adaptive or nonadaptive. Parameterization of the models we develop requires information on genetic and phenotypic variation and demography that will not always be available, meaning that simpler models will often be required to predict responses to environmental change. We consequently develop a method to examine whether the full machinery of the evolutionarily explicit models we develop will be needed to predict responses to environmental change or whether simpler nonevolutionary models that are now widely constructed may be sufficient.

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“…Obviously, a more direct result following from the two assumptions is that sons of good-condition parents tend to have better reproductive prospects than their sisters, while daughters of poor-condition parents tend to have better reproductive prospects. Furthermore, in its generalized form, the TWH is sometimes stated as that natural selection should favor parents who bias offspring sex ratio toward the sex with better reproductive prospects (Schindler et al, 2015). …”

Section: Introductionmentioning

confidence: 99%

Socioeconomic status influences sex ratios in a Chinese rural population

Luo

Ding

Gao

et al. 2017

PeerJ

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According to the logic of the Trivers–Willard hypothesis, in a human population, if socioeconomic status is transmitted across generations to some extent, and if sons of high-status parents tend to have higher reproductive success than daughters, while daughters of low-status parents tend to have higher reproductive success than sons, then we should expect that offspring sex ratio is positively associated with socioeconomic status. This study examines whether the assumptions and prediction of this hypothesis apply to a rural population in northern China. Results show that (1) current family socioeconomic status is positively related to family head’s father’s socioeconomic status in around 1950, (2) low-status family heads have more grandchildren through their daughters than their sons, whereas high- or middle-status family heads have more grandchildren through sons, and (3) as family heads’ status increases, they tend to produce a higher offspring sex ratio. Therefore, the assumptions and prediction of the hypothesis are met in the study population. These results are discussed in reference to past studies on sex ratio manipulation among humans.

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Sex‐specific demography and generalization of the Trivers–Willard theory

Cited by 78 publications

References 35 publications

Maternal condition and previous reproduction interact to affect offspring sex in a wild mammal

Maternal condition and previous reproduction interact to affect offspring sex in a wild mammal

Modeling Adaptive and Nonadaptive Responses of Populations to Environmental Change

Socioeconomic status influences sex ratios in a Chinese rural population

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