Offspring performance and the adaptive benefits of prolonged pregnancy: experimental tests in a viviparous lizard
The skink Egernia whitii is an ideal candidate species to examine the consequences of delayed parturition on the performance of offspring as it routinely gives birth asynchronously despite synchronous offspring development.
Using correlative data from a natural population and experimental manipulations of birthing asynchrony, we tested the prediction that, within litters, last born offspring have a better locomotor performance than first born offspring.
We show that prolonged pregnancy does significantly influence average offspring locomotor performance; however, contrary to predictions, the direction of this effect is dependent on gestation length and thus offspring date of birth. Last born offspring had significantly poorer performance than first born offspring in litters early in the season with this pattern reversed late in the season.
These results do not support the hypothesis that prolonged retention of fully formed offspring consistently increases offspring performance; however, they may help us understand the asymmetries in offspring competitive ability generated by birthing asynchrony.
- Biological Sciences
- ISSN: 1365-2435
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