Asymmetry in Reptiles: What Do We Know So Far?

Abstract

Developmental disturbances in organisms may lead to subtle deviations from symmetry. Fluctuating asymmetry is the most commonly used measure of developmental instability, and it may be related to fitness. Knowledge of developmental instability in reptiles is incipient and with important gaps since there are few studies on asymmetry on this group. In this review, we quantified and analysed trends of reptiles’ asymmetry in the literature. We used keyword searches at Web of Science and Scopus to identify the available papers on asymmetry in reptiles published until 2012. After screening, 60 papers encompassing asymmetry investigations in reptiles were identified. The number of publications increased in the last two decades and lizards were the most studied group. There were no studies from South America and very few from Africa. Most studies involved the use of only meristic traits for asymmetry analysis and found evidence for fluctuating asymmetry. Some studies did not support the relationship between fluctuating asymmetry as the result of developmental instability and environmental and genetic stress, but most findings indicated that (a) females tend to select males with symmetrical sexual traits; (b) thermal instability during egg development produce individuals with a higher incidence of asymmetry; (c) occurrence of injuries is more frequent in asymmetrical individuals for a particular side; (d) there is a negative correlation between asymmetry and locomotor performance. A summary of the available information and a brief discussion about some asymmetric relationships are presented.