Seasonal shifts in sex ratios are mediated by maternal effects and fluctuating incubation temperatures

Amanda W. Carter, Rachel M. Bowden, Ryan T. Paitz

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Sex-specific maternal effects can be adaptive sources of phenotypic plasticity. Reptiles with temperature-dependent sex determination (TSD) are a powerful system to investigate such maternal effects because offspring phenotype, including sex, can be sensitive to maternal influences such as oestrogens and incubation temperatures. In red-eared slider turtles (Trachemys scripta), concentrations of maternally derived oestrogens and incubation temperatures increase across the nesting season; we wanted to determine if sex ratios shift in a seasonally concordant manner, creating the potential for sex-specific maternal effects, and to define the sex ratio reaction norms under fluctuating temperatures across the nesting season. Eggs from early and late season clutches were incubated under a range of thermally fluctuating temperatures, maternally derived oestradiol concentrations were quantified via radioimmunoassay, and hatchling sex was identified. We found that late-season eggs had higher maternal oestrogen concentrations and were more likely to produce female hatchlings. The sex ratio reaction norm curves systematically varied with season, such that with even a slight increase in temperature (0·5 °C), late-season eggs produced up to 49% more females than early-season eggs. We found a seasonal shift in sex ratios which creates the potential for sex-specific phenotypic matches across the nesting season driven by maternal effects. We also describe, for the first time, systematic variation in the sex ratio reaction norm curve within a single population in a species with TSD. A lay summary is available for this article.

Original languageEnglish (US)
Pages (from-to)876-884
Number of pages9
JournalFunctional Ecology
Volume31
Issue number4
DOIs
StatePublished - Apr 1 2017
Externally publishedYes

Keywords

  • fluctuating temperature
  • maternal effect
  • oestrogen
  • season
  • sex ratio
  • temperature-dependent sex determination

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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