Does body volume constrain reproductive output in lizards?

The numbers and sizes of eggs produced by adult females ultimately determine the viability of populations, as well as the evolutionary fitness of the females themselves. Despite an enormous amount of literature on the adaptive significance of fecundity variation within and among populations, simpler questions-such as the proximate mechanisms by which a female determines her clutch size-have attracted less attention. Our surgical manipulations show that the amount of space available to hold eggs within a female's abdomen influences her total reproductive allocation, enabling her to flexibly modify her reproductive output as she grows larger.