Meeting Abstract
A transplanted population of Italian Wall Lizards (Podarcis sicula) from an island in Croatia has become omnivorous and morphologically distinct from its source population in ~30 generations, making it a compelling example of rapid evolution. Vertebrates that eat plants often have longer guts to accommodate diets with low nutrient densities and recalcitrant components, such as fiber. However, this new P. sicula population does not have longer gut lengths than its source population. Still, sex differences in gut length were only apparent in the new population. Are these populations too recently diverged to find differences in gut length? Do females usually have longer guts? To more broadly understand the ecological drivers of gut length in natural systems, we surveyed other P. sicula populations, and their sister species, Podarcis melisellensis. We expect lizards that eat more plants will have longer guts, and that sex effects increase concomitantly with herbivory. We sampled P. sicula from 5 islands, P. melisellensis from 8 islands, and one mainland population of each species. From each site, we analyzed lizard stomach contents to determine ingested diet and measured gut lengths. Dietary analyses, including taxa and component consumed, are still underway, but preliminary data reveal only P. sicula populations consumed considerable proportions of plants. Intestine length will be analyzed in the context of diet data. Females had longer guts in half the populations, regardless of species. P. melisellensis generally had shorter guts than P. sicula, and their gut lengths differed among 1/3 of populations. However, P. sicula gut length only differed between two populations. This suggests P. sicula may have canalized longer gut lengths, giving them an advantage to make the transition to plant based diets.
