Effect of Energy Input on Variation in Clutch Size and Offspring Size in a Viviparous Reptile

1. We tested the effect of manipulating food intake on variance in clutch size and offspring size in a viviparous snake (Thamnophis marcianus). 2. We found that among-female variance in clutch size and offspring size was unaffected by changing food intake, whereas within-female variance in offspring size was higher in females receiving more food. 3. Our data support field studies of snakes which show that among-female variance in clutch size is unaffected by changing environmental conditions. Whether the higher levels of within-female variance in offspring size are adaptive is not known.