Offspring size–number strategies: experimental manipulation of offspring size in a viviparous lizard (Lacerta vivipara)

1. Aspects of female ‘offspring size vs number’ strategies were studied in the viviparous Common Lizard, Lacerta vivipara Jacquin, by surgical yolk extraction from ovarian follicles and ovulated eggs in the oviduct (‘allometric engineering’). 2. This method has previously been applied exclusively to oviparous lizards but here it is applied to a viviparous taxon. 3. There was a strong negative relationship between the amount of yolk removed and the size of offspring at birth, and yolk-removed young were smaller and in poorer condition at birth than their control counterparts from within the same litters. 4. In yolk-removed young physiological performance was positively correlated with body mass. 5. Maternal resource provisioning thus influences offspring physiological performance, which suggests ongoing selection on female optimization of the offspring size–number trade-off