Allometry and morphological integration shape the chemical detection system in Liolaemus lizards (Squamata, Iguania)

Abstract

The chemosensory system in tetrapods consists of glands that emit chemical signals and specialized organs that capture these signals. Lizards mostly depend on this chemosensory modality and different relationships have been suggested among components of their chemical detection systems; the vomeronasal organ (VNO), palatal openings (PO) and tongue morphology (TM), as well as epidermal glands and their secretions. In this study, we used phylogenetic geometric morphometrics to examine shape variation in the VNO, PO and TM of 20 species of Liolaemus lizards. First, we tested whether phylogeny, allometry or diet type influenced their shape. Second, we tested an integration hypothesis between the shapes of the VNO, palatal opening and tongue, as well as, their association with the number of precloacal epidermal glands (PEG). Third, we tested the relationship between the evolutionary change rates of trait shape. Results showed a weak phylogenetic effect on shapes and an allometry effect on the shape of PO. The diet type did not affect the shape of these traits as well as, the number of precloacal epidermal glands. The tongue shape showed significant integration patterns with both the shape of VNO and PO. A faster evolutionary rate change was observed for PEG; VNO and PO showed similar medium rates and TM showed the slowest evolutionary rate. Our results suggest that allometry and different morphological integration patterns may affect the chemosensory system in studied species. The integration patterns among the shapes of the tongue, the VNO and the PO support the assumed association of the chemical detection system components in Liolaemus lizards.