engleski

Testing the Adaptive Modulation Hypothesis: Physiological Changes in in a Newly Herbivorous Lizard

Few studies of diet incorporate analyses of what an animal is actually digesting. Knowing what an animal digests (as opposed to only what it ingests) allows us to understand if its physiology and morphology are optimized for its nutritional source. According to the Adaptive Modulation Hypothesis, dietary specialization should lead to gut specialization. We investigated potential digestive specializations in a lizard species that has shown rapid evolution of feeding and digestive tract morphology. A population of the Italian Wall Lizard (Podarcis sicula) in Croatia has become primarily herbivorous and morphologically distinct from its insectivorous source population in <30 generations. Though some morphological changes have been documented, it is unknown if gut function has shifted with this diet change. We compared the gross morphology of the intestines of both groups of lizards, compared their diets, and measured performances using digestive enzyme activities and concentrations of fermentation end products (short chain fatty acids, SCFAs). In a common garden experiment, we measured digestive efficiency of lizards from the herbivorous and source populations on different diets. Experiments are in progress, but we expected that the plant−eating population would have more plant material in their guts and a hindgut chamber in their distal intestines. Moreover, we expected to find differences in enzymatic activities among the populations, with the herbivores showing elevated carbohydrase activities. We also anticipated that the plant−eating population will have slower food transit times, increased microbial fermentation, and increased digestibility of a plant diet than the insectivorous population. Overall, this study will test whether rapidly evolving morphological features can translate into changes in animal performance.

Adaptive modulation hypothesis; plant digestion; Podarcis sicula

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