Follicle ablation increases offspring size in a lizard with a low clutch frequency

Abstract

Studies of lizards and snakes have shown that an experimental reduction of offspring number sometimes, but not always, results in an increase in offspring size. We applied the "follicle ablation" technique to an oviparous lacertid lizard (Eremias argus) to test the hypothesis that offspring size can be easily altered by manipulating clutch size in species with a low clutch frequency. Our manipulation of clutch size had the effect of inducing variation in egg size in the first post-surgical clutch, with follicle-ablated females producing fewer larger eggs than did controls. Follicle-ablated females produced a second post-surgical clutch as normally as did controls. The proportional amount of resources allocated to reproduction did not shift seasonally in E. argus, but females normally switched from producing a larger number of smaller eggs early in the breeding season to a smaller number of larger eggs later in the season. Females used in this study never produce more than two clutches per breeding season. Therefore, our data validate the hypothesis tested. Our data also provide an inference that maximization of reproductive success could be achieved in females of E. argus by diverting a larger enough, rather than an extraordinarily high, fraction of the available energy to individual offspring in single reproductive episodes. © 2009 Brill Academic Publishers.