Meeting Abstract
Few studies of diet incorporate analyses of what an animal is digesting. Knowing what an animal actually digests allows us to understand if its physiology and morphology are optimized for its nutritional source. A population of Italian Wall Lizards (Podarcis sicula) in Croatia has become primarily herbivorous and morphologically distinct from its source population in ~30 generations, making it a compelling example of rapid evolution. To characterize the changes that occur on this short timescale, we have compared gut structure and enzyme activity across populations of males in a single season. Though the Adaptive Modulation Hypothesis predicts dietary specialization should lead to gut specialization, our previous work has documented few biochemical and histological changes in the herbivorous population’s guts from male lizards collected in the summer. Despite these similarities, the herbivorous population had a higher digestive efficiency of plant meals than their source counterparts. Using mixing models with stable isotope data, we reconstructed specific diets for each population. Stable isotope analyses indicate that dietary differences are seasonal, but that the “herbivorous” population consistently has elevated δ15N values in comparison to the source carnivorous population. Although we found no differences in gut length among males, we measured longer guts in females from the herbivorous population. Thus, we expect to find greater differences in gut enzyme activities across seasons and in females. We compared carbohydrases, proteases, and lipase, making this the most comprehensive study of lizard digestive enzymes to date.
