Diet of the Insular Lizard, Podarcis lilfordi (Günther, 1874): Complementary Morphological and Molecular Approaches

Abstract

The diets of insular lizards are extremely varied, depending on the different environmental characteristics of each island population. This is particularly evident in the case of the populations of small coastal islets of the Balearic Islands, where the Balearic lizard, Podarcis lilfordi, is found. The study of trophic ecology carried out by means of traditional tools, such as morphological analysis of feces, has made it possible to detect numerous prey and nutritional elements. However, these methods are clearly insufficient, as some rare groups are not detected. It is also difficult to identify remains of marine subsidies or of foods contributed to these small islands by other predators, such as seabirds. The current study demonstrates the advantages of combining morphological diet analysis with the molecular study of individual feces samples obtained from the same populations. We obtained a greater diversity of prey groups using the combined methodologies, with each method identifying prey items that were not detected using the other method. Particularly, the study of diets at the molecular level identified plant species consumed by lizards that were, occasionally, not identified in morphological analyses. Conversely, the traditional morphological study of an equivalent number of fecal samples allowed for the identification of several prey groups that had not been detected in the molecular study. From this viewpoint, the advantages and disadvantages of each methodology are discussed.

Effects of Anthropogenic Disturbance of Natural Habitats on the Feeding Ecology of Moorish Geckos

“…To minimize missing soft-body prey that might have been destroyed by the digestive process [ 40 ], we carefully searched for the body parts of soft-body prey that were less likely to be digested (e.g., head capsules of insect larvae, chelicerae and cephalic region of spiders). In lizards, diet composition based on the visual analysis of fecal pellet contents is highly comparable to diet analyses based on gastric contents of killed animals [ 41 ], and results are even very close to those obtained for the molecular analyses (DNA metabarcoding) of invertebrate prey presence in fecal pellets [ 42 ].…”