Surveys on populations of green frogs (Pelophylax) of Western Tuscany sites with molecular and morphometric methods

The water frogs of western Tuscany (Italy) belong to the L-E hybridogenetic system, and comprise one parental species and its hybrid. A stringent morphological approach for discriminating the Italian hybrids from non-hybrids has yet to be established. In this work, using the molecular marker RrS1, we have determined the hybrid versus non-hybrid status of 43 water frogs collected from two sampling sites (“Fiume Morto Vecchio” and “Padule di Bientina”). At “Fiume Morto Vecchio” we determined 25 non-hybrids and nine hybrids and in “Padule di Bientina” we determined eight hybrids and one non-hybrid individual. All individuals of these two frog populations were analyzed morphologically. We used the derived residuals from regression analysis of all normally distributed morphological parameters on callus internus length (snout to vent length, tibia length, head width, distance nostril eye, first toe length and body mass) to build sex independent variables in discriminant analysis providing a valid contribution to morphologically distinguish hybrids from non-hybrid green frogs in Italy.