Egg Mass and Size of Tadpoles at Hatching in the Midwife Toads Alytes obstetricans and Alytes cisternasii: Implications for Female Choice

Abstract

In Alytes obstetricans, the eggs of males carrying larger egg complements were smaller in mass and produced smaller tadpoles at hatching. In A. cisternasii, the total number of eggs in the male complement was not related to average egg mass or tadpole size. Alytes obstetricans males with large egg complements from several females could obtain their matings over a prolonged period. I tested the hypothesis that the negative correlation between progeny size and total number of eggs in the male complement could be a result of greater asynchrony in the development of the egg complement of male A. obstetricans. A simulation determined that the differences between species were not explained by differences in asynchrony in development between clutches of different females in a single male egg complement. Alytes obstetricans males with larger egg complements released their eggs later in the season and, hence, exposed their progeny to desiccation, whereas this did not occur in A. cisternasii in which the reproductive phenology was much more explosive. Therefore, in A. obstetricans, female preference for males that were already carrying eggs would be nonadaptive at the level of tadpole size at hatching.