Irena Grbac

Rapid large-scale evolutionary divergence in morphology and performance associated with exploitation of a different dietary resource

Although rapid adaptive changes in morphology on ecological time scales are now well documented in natural populations, the effects of such changes on whole-organism performance capacity and the consequences on ecological dynamics at the population level are often unclear. Here we show how lizards have rapidly evolved differences in head morphology, bite strength, and digestive tract structure after experimental introduction into a novel environment. Despite the short time scale (≈36 years) since this introduction, these changes in morphology and performance parallel those typically documented among species and even families of lizards in both the type and extent of their specialization. Moreover, these changes have occurred side-by-side with dramatic changes in population density and social structure, providing a compelling example of how the invasion of a novel habitat can evolutionarily drive multiple aspects of the phenotype.

Fluctuating Asymmetry, Physiological Performance, and Stress in Island Populations of the Italian Wall Lizard (Podarcis sicula)

Abstract The use of fluctuating asymmetry (FA) as a measure of developmental instability, and its relationship to stress and fitness, is highly controversial. Here, we present results from a preliminary study comparing levels of asymmetry in various characteristics between two island populations of the Italian Wall Lizard (Podarcis sicula), one of which was recently founded. We relate individual asymmetry to several measures of physiological performance. Levels of FA varied clearly among the traits studied. Repeatability of FA estimates was high for meristic traits but low for metric traits. Levels of FA were on average higher in the newly founded population. We found a significant decrease in exertion (time until exhaustion by continuously chasing) with increasing levels of fluctuating asymmetry (i.e., more symmetric individuals had a higher exertion). Speed of locomotion showed a positive trend with increasing FA. No relationship was found between individual levels of FA and bite force. These results suggest that FA estimates, based on the accurate measurement of several traits, may be useful in explaining differences in developmental stability and physiological performance at the individual and population level.