EVOLUTIONARY CONSEQUENCES OF NONRANDOM MATING - DO LARGE MALES INCREASE OFFSPRING FITNESS IN THE ANURAN BUFO-BUFO

The purpose of my study was to determine whether male body size, a tra it known to be important to mating success, covaries with offspring pe rformance. I tested the effects of male body size on the performance o f Bufo bufo tadpoles reared at two food levels by mating large, small, and naturally-mated males to the same females. Survival of tadpoles i n the high-food environment was affected by male size class, but in th e opposite way to that expected. Tadpoles sired by large males had the lowest survival, and those sired by small males the highest. Neither body size at metamorphosis nor larval period were affected by male siz e class alone, but male size interacted with the female contribution: tadpoles sired by large males had short larval periods and large size at metamorphosis with some females,but long larval periods and small b ody sizes with others. Food level had a significant effect on both siz e at metamorphosis and larval period, and interacted with female contr ibution, but not male size class. This indicated that female contribut ion to tadpoles was dependent on food level, but that the effects of m ale size were not differentially expressed by tadpoles at the two food levels. My results indicate that traits with a direct effect on offsp ring fitness are not enhanced by large male body size, yet some males and females produced offspring with significantly better performance. I suggest that evolutionary change in this mating system is unlikely t o occur through the non-random mating of males based on body size alon e.