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SCIENCE

The Claim

Sexual dimorphism is energetically costly to produce and maintain, and these costs are expected to increase as environments become more thermally stressful.

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The Short Version

The central claim is supported, but it is broader than the strongest evidence. Many sexually dimorphic traits do carry energetic costs, and thermal stress generally increases metabolic strain in ways that can raise those costs. Still, the evidence is strongest for specific traits and species, and some studies show warming can reduce dimorphism through energy reallocation rather than only increasing trait-maintenance costs.

Caveats

  • The evidence does not show a universal, directly measured increase in dimorphism costs across all taxa; much of the support is mechanistic and species-specific.
  • Thermal stress can also suppress or attenuate sexually dimorphic traits, so higher stress does not always mean the same trait is maintained at a higher energetic cost.
  • The broad term 'sexual dimorphism' conflates different phenomena—body size, ornaments, weapons, physiology, and reproductive investment—which may respond differently to heat stress.

The Receipts

  1. The energy costs of sexual dimorphism in mole-rats are sex-specific

    PMC - NIH

  2. New research shows the true cost of reproduction across the animal kingdom

    Monash University

  3. Sex differences in the thermal acclimation and tolerance of Daphnia magna

    Proceedings of the Royal Society B

  4. The energy costs of sexual dimorphism in mole-rats are associated with sex-specific behavioural phenotypes

    Proceedings of the Royal Society B

  5. Quantifying Energetic Investment in Gamete Production by Males and Females

    PLOS ONE

  6. Thermal tolerance may cause sexual segregation in sexually size-dimorphic species

    Behavioral Ecology (Oxford Academic)

  7. Variation in Thermal Tolerance Plasticity and the Costs of Heat Hardening in an Intertidal Gastropod

    Frontiers in Marine Science (Chapman University repository)

  8. Facultative polyandry under heat stress and the evolutionary consequences of climate change

    Heredity (Nature)

  9. Sex shapes phenotype-linked metabolic signatures of stress exposure in the mouse hypothalamus and pituitary

    Canadian Journal of Physiology and Pharmacology (Elsevier/ScienceDirect)

  10. Effects of temperature, body size, and sex on the standard metabolic rates of a sexually dimorphic freshwater piscivore, walleye (Sander vitreus)

    Canadian Journal of Fisheries and Aquatic Sciences

+ 25 more sources — see the full list on Lenz

Filed Under

Sexual DimorphismThermal Stress

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