Variation in clutch size and offspring size relative to environmental conditions in the lizard Sceloporus virgatus

Fitness of female reptiles often depends on both the number and size of offspring. I examined clutch size (number of fertile eggs) and offspring size relative to maternal body size in the striped plateau lizard, Sceloporus virgatus, under conditions of natural and experimental variation in water and food availability. Under all environmental conditions, larger females produced more offspring. In the year with higher levels of precipitation, path analysis indicated a direct positive effect of maternal size on offspring size and a significant trade-off between offspring size and number. Similar nonsignificant trends were found in a year of severe drought During the drought, females of S. virgatus produced relatively small clutches of large offspring. Food supplementation during the period preceding and including ovulation removed the effect of drought on clutch size and offspring size. Food-supplemented females produced relatively large clutches of small offspring.