Life History Variation in a Population of the Australian Frog Ranidella signifera: Egg Size and Early Development

Abstract

We examined the proposition that, in a population, large egg size confers greater fitness than small egg size. Within clutches of the frog Ranidella signifera from near Bridgewater, South Australia, larger eggs tended to hatch into larger tadpoles, but there was no consistent relationship between egg size and development time to hatching and to first feeding. Among clutches, those with larger mean egg size tended to have faster development times and to hatch into larger tadpoles. However, there was also a significant effect of clutch on these two parameters which was as great or greater than the effect of egg size. That is, two eggs of similar size could develop at quite different rates, and have quite different sizes as early stage tadpoles, if they came from different clutches. In certain environments, the fitness of free living tadpoles may be directly related to their size. Our data show that, after development to independent feeding, the largest tadpole need not have arisen from the largest egg.