RESPONSES TO FOOD CHEMICALS BY TWO INSECTIVOROUS AND ONE OMNIVOROUS SPECIES OF LACERTID LIZARDS

Abstract

In snakes, many of which have fairly specialized diets, there is a correspondence between diet and chemosensory responsiveness to food cues not yet demonstrated in lizards, most of which are generalist insectivores. If such a correspondence exists for plants consumed by omnivorous species, we can make two predictions. Actively foraging insectivorous lizards such as most lacertids should exhibit prey chemical discrimination, but be unresponsive to chemicals from palatable plants. Omnivorous species derived from insectivores should discriminate both prey and plant chemicals from control substances. We show in experiments testing lingual and biting responses to food cues and control stimuli that the lacertid insectivores Podarcis hispanica and Lacerta perspicillata exhibit prey, but not plant, chemical discrimination and the omnivore P.sicula discriminates both prey and plant chemicals from control substances. The findings are consistent with the hypothesis that correlated evolution has occurred between plant consumption and plant chemical discrimination in lacertids, but data are needed for several more lineages of independently derived omnivores and for additional insectivores to test the hypothesis statistically.