ESPINOZA, R.E.*; DEAN-BRADLEY, K.; TRACY, C.R.; California State Univ., Northridge; US Geological Survey, Ft. Collins, CO; Univ. Nevada, Reno: Herbivory imposes constraints on the life-history strategies of reptiles.

Extracting energy from plants is thought to be most challenging for small herbivores, especially neonates, because of their high energy needs and small guts. Herbivores could provide a digestive advantage to their offspring if they produced small clutches of large eggs. We tested this prediction for turtles (151 species) and lizards (176 species). Conventional analyses indicate that herbivorous reptiles produce smaller clutches of larger eggs relative to nonherbivores. Clutch mass is not different among trophic groups of turtles, but is larger in herbivorous lizards. Nonherbivorous turtles produce larger clutches of smaller eggs with increasing latitude, but no such relationship exists for herbivores. Phylogenetic analyses generally support the relationships between diet and reproductive traits for lizards, but not for turtles. This disparity is attributed to the larger eggs and smaller clutches produced by omnivorous turtles. Hence, producing small clutches of large eggs may evolve prior to strict herbivory in turtles. Herbivory has evolved infrequently in reptiles. Consequently, phylogenetic analyses are less likely to provide statistical support for trends observed in conventional analyses. Moreover, these life-history traits appear to be correlated with both phylogeny and diet, so phylogenetic analyses may conceal ecological trends. When considered concurrently, the relationships among these reproductive traits and herbivory from these two disparately related lineages of reptiles provide compelling evidence that diet affects the evolution of life-history traits. We offer explanations for why large-bodied neonates would have an advantage in digesting plants.