Statistical analysis of sex ratios: an introduction

Wilson, Kenneth; Hardy, Ian C.W.

doi:10.1017/cbo9780511542053.004

Cited by 441 publications

(357 citation statements)

References 27 publications

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“…We used backward elimination procedures and aggregation of factor levels to obtain the parsimonious 'minimal adequate model' by model simplification (8,(23)(24)(25). We report the percentage of deviance explained (%Dev) as an approximate analogue of r 2 .…”

Section: Statistical Analysesmentioning

confidence: 99%

“…We report the percentage of deviance explained (%Dev) as an approximate analogue of r 2 . The assumption of quasi-binomially distributed errors (based on empirically estimated scale parameters) was adopted to reduce the probability of Type I errors occurring due to overdispersion (23,24). Because multiple successful cycles from the same mother (i.e.…”

Section: Statistical Analysesmentioning

confidence: 99%

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Effects of assisted reproductive technologies on human sex ratio at birth

Maalouf

Mincheva

Campbell

et al. 2014

Fertility and Sterility

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Section: Statistical Analysesmentioning

confidence: 99%

Section: Statistical Analysesmentioning

confidence: 99%

Effects of assisted reproductive technologies on human sex ratio at birth

Maalouf

Mincheva

Campbell

et al. 2014

Fertility and Sterility

Self Cite

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“…The effect of soil moisture on population female frequency was analysed using a generalized linear model on logit-transformed odds ratio data in S-PLUS (Mathsoft Inc. 1999). This analysis assumes binomially distributed errors and weights the logits from each population by the sample size (Wilson & Hardy 2002). 3. RESULTS (a) Manipulative water experiment LH soil moisture was ca.…”

Section: (B) Manipulative Water Experimentsmentioning

confidence: 99%

Soil moisture and sex ratio in a plant with nuclear–cytoplasmic sex inheritance

Barr

2004

Proc. R. Soc. Lond. B

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I investigated whether soil moisture affects relative fitness of females and hermaphrodites and sex ratio in a gynodioecious plant with nuclear-cytoplasmic sex inheritance. I contrast these results with those from species with strictly nuclear sex inheritance. I performed a manipulative watering experiment on seed fitness of the two sexes, and field studies measuring seed fitness and sex ratio as a function of soil moisture. In the dry site, watered hermaphrodites produced approximately twice as many seeds as unwatered hermaphrodites, with little treatment effect on female seed production. Over a natural soil moisture gradient, the ratio of female to hermaphrodite seed production was higher in dry than in wet sites. These data show that the seed fitness advantage of females is a function of soil moisture. Despite this, regression of soil moisture on the sex ratio of 23 populations was not significant. These results indicate a sex-dependent effect of soil moisture on resource allocation to seeds that does not translate into a strong effect on sex ratio. This is consistent with theory based on genomic conflict in which sex ratios are predicted to be only partly determined by fitness differences of the sexes.

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“…Proportion data such as sex ratio usually have nonnormally distributed error variance and unequal sample sizes. To avoid these problems, we analyzed the data with a generalized linear model analysis of deviance, assuming binomial errors, and a logit link function (Crawley 1993;Wilson and Hardy 2002). However, the data were highly overdispersed, with the residual deviance 174 to 252 times the residual degrees of freedom (this ratio is the heterogeneity factor), suggesting that a binomial error structure was not appropriate.…”

Section: Statistical Analysesmentioning

confidence: 99%

Sex-Ratio Evolution in Sex Changing Animals

Allsop

West

2004

Evolution

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Abstract. Sex allocation theory is often able to make clear predictions about when individuals should facultatively adjust their offspring sex ratio (proportion male) in response to local conditions, but not the consequences for the overall population sex ratio. A notable exception to this is in sex changing organisms, where theory predicts that: (1) organisms should have a sex ratio biased toward the ''first'' sex; (2) the bias should be less extreme in partially sex changing organisms, where a proportion of the ''second'' sex matures directly from the juvenile stage; and (3) the sex ratio should be more biased in protogynous (female first) than in protandrous (male first) species. We tested these predictions with a comparative study using data from 121 sex changing animal species spanning five phyla, covering fish, arthropods, echinoderms, molluscs, and annelid worms. We found support for the first and third predictions across all species. The second prediction was supported within the protogynous species (mainly fish), but not the protandrous species (mainly invertebrates).Key words. Comparative analysis, protandrous, protogynous, sequential hermaphrodite, sex allocation, sex ratio.Received October 16, 2003. Accepted January 8, 2004 Sex allocation theory describes how organisms should divide their resources between male and female reproduction (Charnov 1982). Some of the most striking successes of sex allocation theory have been in explaining cases in which individuals facultatively adjust their offspring sex ratios (proportion male) in response to local conditions (Charnov 1982;Hardy 2002;West et al. 2002a), as originally suggested by Trivers and Willard (1973). For example, numerous parasitic wasps have been shown to lay male eggs on relatively small hosts and female eggs on large hosts, because female offspring gain a greater fitness benefit from extra resources and larger body size (West and Sheldon 2002). In contrast, when such facultative sex ratio adjustment occurs, sex allocation theory has been much less successful in predicting and explaining variation in the overall population or breeding sex ratio (West et al. 2002a). The reason for this is that the population sex ratio is often predicted to depend upon biological details that are rarely known, such as the details of male and female life histories, and whether other behaviors such as clutch size are also facultatively adjusted (Frank 1987(Frank , 1990Weissing 2000, 2002;West and Sheldon 2002).Here we consider a case in which it is possible to make clear predictions for the overall population sex ratio. We are concerned with species in which sex change occurs, also termed sex reversal or sequential hermaphroditism. This has been documented in a variety of fish, invertebrates, and plants (Charnov 1982;Policansky 1982;Allsop and West 2003a). Sex allocation theory suggests that sex change is favored when the reproductive value of an individual varies with age or size, and the relationship is different for males and females. In this case natural select...

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Statistical analysis of sex ratios: an introduction

Cited by 441 publications

References 27 publications

Effects of assisted reproductive technologies on human sex ratio at birth

Effects of assisted reproductive technologies on human sex ratio at birth

Soil moisture and sex ratio in a plant with nuclear–cytoplasmic sex inheritance

Sex-Ratio Evolution in Sex Changing Animals

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