Paedomorphosis in the Alpine newt (Triturus alpestris): decoupling behavioural and morphological change

Paedomorphosis is a heterochronic pattern leading to morphological change, i.e. retention of larval characters in the adult phenotype. The aim of this study was to find out whether behaviour and morphology are decoupled in heterochronic phenotypes. To this end, I compared qualitative and quantitative aspects of courtship behaviour in syntopic metamorphic and paedomorphic Alpine newts, Triturus alpestris. Morphologically, the two morphs differ considerably (e.g. by the presence of gills only in paedomorphs), but their patterns of sexual behaviours are exhibited at similar frequencies and males use the same alternative reproductive tactics to attract unresponsive females. These results show that morphology and behaviour follow different ontogenetic pathways and are thus decoupled. Decoupling of the two traits offers the possibility of morphological evolution without alteration of sexual patterns.