Temperature, age of mating and starvation determine the role of maternal effects on sex allocation in the mealybug Planococcus citri

A maternal effect is a causal influence of the maternal phenotype on the offspring phenotype over and above any direct effects of genes. There is abundant evidence that maternal effects can have a major impact on offspring fitness. Yet, no previous study has investigated the potential role of maternal effects in influencing the severity of inbreeding depression in the offspring. Inbreeding depression is a reduction in the fitness of inbred offspring relative to outbred offspring. Here, we tested whether maternal effects due to body size alter the magnitude of inbreeding depression in the burying beetle Nicrophorus vespilloides . We found that inbreeding depression in larval survival was more severe for offspring of large females than offspring of small females. This might be due to differences in how small and large females invest in an inbred brood because of their different prospects for future breeding opportunities. To our knowledge, this is the first evidence for a causal effect of the maternal phenotype on the severity of inbreeding depression in the offspring. In natural populations that are subject to inbreeding, maternal effects may drive variation in inbreeding depression and therefore contribute to variation in the strength and direction of selection for inbreeding avoidance.

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Translocation reverses birth sex ratio bias depending on its timing during gestation: evidence for the action of two sex-allocation mechanisms

Reproduction Fertility and Development ◽

10.1071/rd07027 ◽

2007 ◽

Vol 19 (7) ◽

pp. 831 ◽

Cited By ~ 21

Author(s):

W. L. Linklater

Keyword(s):

Glucose Metabolism ◽

Sex Ratio ◽

Sex Allocation ◽

Preimplantation Embryo ◽

Sex Ratio Bias ◽

In Captivity ◽

Developmental Asynchrony ◽

Adjustment Mechanisms ◽

Excess Glucose

Many sex allocation mechanisms are proposed but rarely have researchers considered and tested more than one at a time. Four facultative birth sex ratio (BSR) adjustment mechanisms are considered: (1) hormone-induced conception bias; (2) sex-differential embryo death from excess glucose metabolism; (3) sex-differential embryo death from embryo–uterine developmental asynchrony; and (4) pregnancy hormone suppression and resource deprivation. All mechanisms could be switched on by the corticoadrenal stress response. A total of 104 female rhinoceroses (Rhinocerotidae), translocated from 1961 to 2004 at different stages of gestation or conceived soon after arrival in captivity, were used to test for a reversal in BSR bias as evidence for the action of multiple sex-allocation mechanisms. Translocation induced a statistically significant BSR reversal between early gestation (86% male births from 0 to 0.19 gestation) and mid-gestation (38% male from 0.2 to 0.79 gestation). Captivity also induced a strongly male-biased (67% male) BSR for conceptions after arrival in captivity. The results indicate the action of at least two sex-allocation mechanisms operating in sequence, confirm the important role of sex-differential embryo death around implantation and of stress in sex allocation, and lend support to suggestions that sex-differential glucose metabolism by the preimplantation embryo likely plays a role in facultative BSR adjustment.

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Beyond sex allocation: the role of mating systems in sexual selection in parasitoid wasps

Biological Reviews ◽

10.1111/brv.12126 ◽

2014 ◽

Vol 90 (2) ◽

pp. 599-627 ◽

Cited By ~ 32

Author(s):

Rebecca A. Boulton ◽

Laura A. Collins ◽

David M. Shuker

Keyword(s):

Sexual Selection ◽

Sex Allocation ◽

Mating Systems ◽

Parasitoid Wasps

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Explaining discrepancies in the study of maternal effects: the role of context and embryo

Current Opinion in Behavioral Sciences ◽

10.1016/j.cobeha.2020.10.006 ◽

2020 ◽

Vol 36 ◽

pp. 185-192

Author(s):

Ton GG Groothuis ◽

Neeraj Kumar ◽

Bin-Yan Hsu

Keyword(s):

Maternal Effects

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Sperm sex ratio adjustment in a mammal: perceived male competition leads to elevated proportions of female-producing sperm

Biology Letters ◽

10.1098/rsbl.2019.0929 ◽

2020 ◽

Vol 16 (6) ◽

pp. 20190929

Author(s):

Renée C. Firman ◽

Jamie N. Tedeschi ◽

Francisco Garcia-Gonzalez

Keyword(s):

Sex Ratio ◽

Sex Allocation ◽

Sex Ratios ◽

Female Offspring ◽

Male Competition ◽

Offspring Sex ◽

Sex Ratio Adjustment ◽

Adaptive Adjustment ◽

Male House

Mammal sex allocation research has focused almost exclusively on maternal traits, but it is now apparent that fathers can also influence offspring sex ratios. Parents that produce female offspring under conditions of intense male–male competition can benefit with greater assurance of maximized grand-parentage. Adaptive adjustment in the sperm sex ratio, for example with an increase in the production of X-chromosome bearing sperm (CBS), is one potential paternal mechanism for achieving female-biased sex ratios. Here, we tested this mechanistic hypothesis by varying the risk of male–male competition that male house mice perceived during development, and quantifying sperm sex ratios at sexual maturity. Our analyses revealed that males exposed to a competitive ‘risk’ produced lower proportions of Y-CBS compared to males that matured under ‘no risk’ of competition. We also explored whether testosterone production was linked to sperm sex ratio variation, but found no evidence to support this. We discuss our findings in relation to the adaptive value of sperm sex ratio adjustments and the role of steroid hormones in socially induced sex allocation.

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