A procedure for taxon assessment based on morphological variation in European water frogs (Pelophylax esculentus complex)

Methods for morphological identification of water frogs from the Pelophylax esculentus complex have changed over the decades. Still, without resort to genetic analyses, water frogs remain among the most difficult European amphibians to distinguish due to their hybrid nature. The aim of this study was to identify a reliable set of quantitative and qualitative morphological characters that objectively resolve species? identification in the Pelophylax esculentus complex and provide a rapid and robust procedure for taxon identification. Our results showed a substantial difference in morphological characteristics among taxa. The shape and size of the metatarsal tubercle along with the coloration of the hind limbs and flanks appear to be the most important diagnostic traits. Linear discriminant analysis with both quantitative and qualitative traits as a rapid method for the assessment of water frog taxa showed satisfactory accuracy and prediction classification for all 3 members of the complex.