Assessing factors involved in determining fluctuating asymmetry in four insular populations of the balearic lizard podarcis lilfordi

In animals, developmental stability is frequently assessed by the level of fluctuating asymmetry. Several environmental and genetic stress factors can increase the developmental instability in a population. Anyhow, the use of fluctuat-ing asymmetry as a measurement of developmental instability and its relationship to other measurements of genetic and environmental stress, remain controversial. We studied this subject in the Balearic lizard, Podarcis lilfordi, and examined four populations inhabiting different coastal islets of Minorca (Balearic Islands, Spain). These populations show clear ecological and genetic differences that allowed us to study factors potentially determining the level of fluctuating asymmetry. We examined the following predictions: (1) fluctuating asymmetry will increase on smaller islands; (2) fluctuating asymmetry will increase on islands with a higher lizard density; (3) fluctuating asymmetry will increase on islands with more heavily parasitized lizards; and (4) populations with higher inbreeding levels would be more susceptible to environmental stress. Our results would partially support the fourth prediction of a higher fluctuating asymmetry in populations with lower genetic variability and, consequently, a higher inbreeding level. Probably, other environmental factors modulate this relationship.