Morphological integration of cranium and postcranial skeleton during ontogeny of facultative paedomorphic European newts (Triturus vulgaris and Triturus alpestris)

Abstract

The patterns of ontogenetic and interspecific variation of morphological integration (the relationships and correlation patterns of functionally and developmentally related morphological traits) in facultative paedomorphic species of two European newts (Triturus vulgaris and T alpestris) were examined. The degree of morphological integration differed among ontogenetic stages. Variation in the level of morphological integration of cranium and postcranial skeleton during ontogeny of paedomorphic newts had the same pattern in both analysed species. The lowest level of cranium morphological integration characterises the larvae and the juveniles. Individuals that follow alternative life-history path (paedomorphs) remain at a relatively low level of morphological integration, while integration highly increased in metamorphosed adult individuals. Limb skeleton also showed a lower level of integration in paedomorphs in comparison with metamorphosed individuals. The hypothesis of morphological integration was confirmed for all stages of T vulgaris, while the same hypothesis was confirmed only for larval and paedomorphic stages of T alpestris. In T vulgaris, metamorphosis changes the pattern of correlation among the cranial traits, while in T alpestris, the patterns of phenotypic correlation among the cranial traits remain substantially similar for all analysed ontogenetic stages.