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Biology letters2007; 3(4); 395-397; doi: 10.1098/rsbl.2007.0089

Extreme sex ratio variation in relation to change in condition around conception.

Abstract: Adaptive theory predicts that mothers would be advantaged by adjusting the sex ratio of their offspring in relation to their offspring's future reproductive success. Studies investigating sex ratio variation in mammals have produced notoriously inconsistent results, although recent studies suggest more consistency if sex ratio variation is related to maternal condition at conception, potentially mediated by changes in circulating glucose level. Consequently, we hypothesized that change in condition might better predict sex ratio variation than condition per se. Here, we investigate sex ratio variation in feral horses (Equus caballus), where sex ratio variation was previously shown to be related to maternal condition at conception. We used condition measures before and after conception to measure the change in condition around conception in individual mothers. The relationship with sex ratio was substantially more extreme than previously reported: 3% of females losing condition gave birth to a son, whereas 80% of those females that were gaining condition gave birth to a son. Change in condition is more predictive of sex ratio than actual condition, supporting previous studies, and shows the most extreme variation in mammals ever reported.
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Publication Date: 2007-04-19 PubMed ID: 17439844PubMed Central: PMC2390657DOI: 10.1098/rsbl.2007.0089Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research paper evaluates how changes in a mother’s body condition around the time of conception impact the sex ratio of their offspring, using feral horses as a subject. Specifically, it shows that only 3% of the females who lost condition gave birth to a male, while 80% of those who were improving their condition gave birth to a male. The paper asserts that change in condition is a better predictor of offspring sex than the actual condition.

Adaptive Theory and Sex Ratios

  • In accordance with adaptive theory, it’s speculated that mothers could benefit by adjusting the sex ratio of their offspring based on their potential for future reproductive success.
  • This theory has been tested a lot in mammals, but the results have been inconsistent.
  • Recent studies, however, suggest that changes in a mother’s condition at the time of conception, possibly triggered by changes in circulating glucose levels, can consistently explain variations in sex ratios.

The Hypothesis of the Study

  • The researchers propose that sex ratio changes might be better predicted by changes in the mother’s condition rather than their condition at the time of conception.

Empirical Investigation using Feral Horses

  • The research records observations from feral horses, where previous studies have already found a relationship between maternal condition at conception and offspring sex ratio.
  • To test their hypothesis, the researchers measured the change in condition around the time of conception in individual mothers, using the difference in condition measurements taken before and after conception.

Key Findings of the Study

  • The sex ratio swings revealed by the research were even more extreme than previously documented: only 3% of females that lost condition gave birth to a son, whereas 80% of those that were gaining condition gave birth to a son.
  • The change in condition is a stronger predictor of sex ratio variation than actual condition, backing prior research, and shows the most extreme sex ratio variation ever recorded in mammals.

Cite This Article

APA
Cameron EZ, Linklater WL. (2007). Extreme sex ratio variation in relation to change in condition around conception. Biol Lett, 3(4), 395-397. https://doi.org/10.1098/rsbl.2007.0089

Publication

Biology letters
ISSN: 1744-9561
NlmUniqueID: 101247722
Country: England
Language: English
Volume: 3
Issue: 4
Pages: 395-397

Researcher Affiliations

Cameron, Elissa Z
  • Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ezcameron@zoology.up.ac.za
Linklater, Wayne L

    MeSH Terms

    • Adaptation, Biological
    • Animals
    • Animals, Wild / physiology
    • Body Constitution
    • Female
    • Fertilization
    • Horses / physiology
    • Male
    • Sex Ratio

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