Facultative paedomorphosis in a population of Lissotriton vulgaris (Amphibia: Salamandridae) from the Danube Delta Biosphere Reserve (Romania)

Paedomorphosis is an alternative ontogenetic pathway in which reproductive adults maintain larval traits. Sometimes both phenotypes (i.e. paedomorphic and metamorphic) can coexist within the same population and this phenomenon is referred to as facultative paedomorphosis. The mechanisms that trigger and maintain polymorphisms seem to be multiple, with both genetic and environmental components (Denoël et al., 2009), and they vary among species and populations (Semlitsch et al., 1990; Whiteman, 1994; Elinson and del Pino, 2012). Different environmental variables influence paedomorphosis and paedomorphic populations were reported from a diversity of habitats (Denoël et al., 2005b). Three main hypotheses were proposed to explain the maintenance of facultative paedomorphosis: “th