Factors Affecting Variation in Reproductive Traits within a Population of Wood Frogs (Rana sylvatica)

Abstract

Previous studies have demonstrated a great deal of geographic variation in reproductive traits of the wood frog Rana sylvatica. This paper demonstrates the existence of significant individual variation in reproductive traits within a single population in Maryland. Egg size, clutch size and total-egg-volume all varied positively with body size for each female age class. When adjusted for body size differences, clutch size and egg size had an inverse relationship to each other across age classes of females. One-year-old females had the largest clutches with the smallest eggs whereas 3 yr old females had the smallest clutches but the largest eggs. Two-year-olds were intermediate in both egg size and clutch size. Reproductive traits also showed year to year variation that was independent of body size and initial size at metamorphosis. The ecological and evolutionary implications of such variation are discussed relative to the potential effects of egg size on fitness.