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Maternal effects obscure condition-dependent sex allocation in changing environments.

ABSTRACT: Climate change increases environmental fluctuations which thereby impact population demography. Species with temperature-dependent sex determination may experience more extreme sex ratio skews, but this has not been considered in species with chromosomally determined sex. However, anticipatory maternal effects cause lifelong physiological changes impacting sex ratios. Here we show, in mice, that more sons were born to mothers in good condition when their breeding environment matched their gestational environment, consistent with theoretical predictions, but mothers in mismatched environments have no condition-sex ratio relationship. Thus, the predicted effect of condition on sex ratio was obscured by maternal effects when the environment changed. This may explain extreme sex ratio skews in reintroduced or translocated populations, and sex ratio skews may become more common and less predictable with accelerating environmental change.

SUBMITTER: Edwards AM

PROVIDER: S-EPMC6502394 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Maternal effects obscure condition-dependent sex allocation in changing environments.

Edwards A M AM Cameron E Z EZ Wapstra E E McEvoy J J

Royal Society open science 20190403 4

Climate change increases environmental fluctuations which thereby impact population demography. Species with temperature-dependent sex determination may experience more extreme sex ratio skews, but this has not been considered in species with chromosomally determined sex. However, anticipatory maternal effects cause lifelong physiological changes impacting sex ratios. Here we show, in mice, that more sons were born to mothers in good condition when their breeding environment matched their gestat ...[more]

PMID: 31183124

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Project description:In promiscuous species, male reproductive success depends on their ability to mate with fertile females and on the fertilizing ability of their sperm. In such species, theory predicts that, owing to a trade-off between pre- and post-copulatory reproductive traits, males with lesser access to females should increase resource investment into those sperm traits that enhance fertilization success-usually referred to as ejaculate quality. This prediction has been validated in several taxa, yet studies on the physiological mechanisms modulating ejaculate quality are lacking. Sperm cells are highly vulnerable to oxidative stress, which impairs male fertility. Therefore, males that better protect their sperm from oxidative stress are expected to achieve higher ejaculate quality. Based on theoretical expectations, and since social dominance is a major determinant of mating opportunity, we predicted that subordinate males should invest more into the antioxidant protection of their sperm in order to achieve higher ejaculate quality. We maintained 60 male and 60 female wild-caught house sparrows Passer domesticus in outdoor aviaries, where we experimentally manipulated male social status to test our predictions. We measured cellular oxidative stress and enzymatic antioxidant activity in blood and sperm both before and after manipulating social ranks. Before manipulating the social status, we found that ejaculate viability correlated with oxidative stress level in sperm, with dominant males producing more oxidized and less viable ejaculates. Further, males at the lower end of the hierarchy produced ejaculates of similar quality to those of dominant males, suggesting that restricted access to resources might limit male reproductive strategies. After experimentally manipulating the social status, males matched their ejaculate quality to their new rank, while increases in antioxidant investment into ejaculates paralleled increases in ejaculate viability. Oxidative stress has been proposed as a general constraint to the evolution of life histories. Our results highlight oxidative stress and strategic antioxidant allocation as important proximate physiological mechanisms underlying male reproductive strategies.

Project description:Fire plays a key role in ecosystem dynamics worldwide, altering energy flows and species community structure and composition. However, the functional mechanisms underlying these effects are not well understood. Many ground-dwelling animal species can shelter themselves from exposure to heat and therefore rarely suffer direct mortality. However, fire-induced alterations to the environment may change a species' relative trophic level within a food web and its mode of foraging. We assessed how fire could affect ant resource utilization at different scales in a Mediterranean forest. First, we conducted isotopic analyses on entire ant species assemblages and their potential food resources, which included plants and other arthropods, in burned and unburned plots 1 year postfire. Second, we measured the production of males and females by nests of a fire-resilient species, Aphaenogaster gibbosa, and analyzed the differences in isotopic values among workers, males, and females to test whether fire constrained resource allocation. We found that, in spite of major modifications in biotic and abiotic conditions, fire had little impact on the relative trophic position of ant species. The studied assemblage was composed of species with a wide array of diets. They ranged from being mostly herbivorous to completely omnivorous, and a given species' trophic level was the same in burned and unburned plots. In A. gibbosa nests, sexuals had greater ?(15)N values than workers in both burned and unburned plots, which suggests that the former had a more protein-rich diet than the latter. Fire also appeared to have a major effect on A. gibbosa sex allocation: The proportion of nests that produced male brood was greater on burned zones, as was the mean number of males produced per nest with the same reproductive investment. Our results show that generalist ants with relatively broad diets maintained a constant trophic position, even following a major disturbance like fire. However, the dramatically reduced production of females on burned zones compared to unburned zones 1 year postfire may result in considerably reduced recruitment of new colonies in the mid to long term, which could yield genetic bottlenecks and founder effects. Our study paves the way for future functional analyses of fire-induced modifications in ant populations and communities.

Project description:Maternal high-fat diet consumption predisposes to metabolic and liver dysfunction in F1 male and female at young adulthood. Purpose: We used RNA-seq to determine the liver transcriptome of male and female F1 of MO and control fed mothers. Methods: Female Wistar rat mothers ate control (C) or obesogenic (MO) diet from the time they were weaned through breeding at postnatal day (PND) 120, delivery and lactation. After weaning all male and female F1 ate control diet. At PND 110 liver and fat were collected to analyze metabolites, histology and liver differentially expressed genes. To identify the functional F1 liver changes due to MO, we evaluated the differentially expressed genes (DEGs) between MO and C males and females with separate pairwise comparisons due to the marked differences between males and females. Genes were filtered based on ≥ 1.4 fold change (FC) and nominal P value <0.05 (Student´s t-test). Results: MOF1 males presented greater physiologic and histological NAFLD characteristics than MOF1 females. RNA-seq revealed 1,365 genes significantly changed in male MOF1 liver and only 70 genes in MOF1 female compared with controls. GO and KEGG analysis identified differentially expressed genes related to metabolic process. Male MOF1 liver showed the following altered pathways: insulin signaling (22 genes), phospholipase D signaling (14 genes), NAFLD (13 genes), and glycolysis/ gluconeogenesis (7 genes). In contrast, few genes were altered in these pathways in MOF1 females. Conclusions: These results improve understanding of the mechanism by which a maternal high fat diet affects their F1. In summary, MO programs sex-dependent F1 changes in insulin, glucose and lipid signaling pathways, leading to liver dysfunction and insulin resistance. Male adult MOF1 livers show global down-regulation of genes that are required for normal function of major liver metabolic pathways. This new knowledge is important for producing sex-specific interventions.

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Maternal effects obscure condition-dependent sex allocation in changing environments.

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Maternal effects obscure condition-dependent sex allocation in changing environments.

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