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Using life-histories to predict and interpret variability in yolk hormones
O P Love1, H G Gilchrist, J Bêty
1Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada. olovea@sfu.ca
General and Comparative Endocrinology
|October 28, 2008
Summary
Maternal yolk corticosterone varies with life history. Altricial and semi-precocial birds show clutch variation, potentially aiding offspring competition, unlike precocial species.
Area of Science:
- Evolutionary biology
- Animal reproductive strategies
- Endocrinology
Background:
- Maternal yolk hormones are thought to enhance offspring plasticity and maternal fitness.
- Hormone deposition patterns are expected to correlate with species-specific life histories.
- Yolk glucocorticoids can reduce offspring quality and modulate competition or brood reduction.
Purpose of the Study:
- To investigate the relationship between life history and intra-clutch variation in yolk corticosterone.
- To compare yolk corticosterone patterns across species with different developmental strategies (altricial, semi-precocial, precocial).
- To assess the adaptive significance of yolk hormone variation in maternal effects.
Main Methods:
- Quantification of intra-clutch yolk corticosterone levels in European starlings, black guillemots, and common eiders.
- Analysis of laying sequence effects on hormone deposition within clutches.
- Comparison of hormone variation patterns across species representing a developmental continuum.
Main Results:
- Yolk corticosterone increased with laying sequence in starlings and guillemots, but not in eiders.
- Starlings exhibited the greatest difference in yolk corticosterone between early and late eggs (94.6%).
- Individual females within species showed significant variation in hormone deposition patterns.
Conclusions:
- Intra-clutch yolk corticosterone variation may be an adaptive maternal effect in species where offspring competition modulation is beneficial (starlings, guillemots).
- In precocial species (eiders), intra-clutch yolk hormone variation likely has little adaptive role.
- Future research should integrate species-specific life-history hypotheses to understand the evolution of yolk hormone roles.
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