Fluctuating Asymmetry in Pelophylax ridibundus (Anura: Ranidae) and Bufotes viridis (Anura: Bufonidae) Meristic Morphological Traits as Indicators of Ecological Stress and a Method for Assessing Environmental Quality of Their Habitats

This paper summarizes and presents the results from our years-long in situ analyses of the populations of the Marsh frog P. ridibundus and the Green toad B. viridis inhabiting freshwater ecosystems in South Bulgaria with different degrees of anthropogenic transformation. It covers the period 2009-2017 with tests of the application of fluctuating asymmetry in meristic morphological traits as a marker for deviation assessment of the developmental stability of individuals of both species as well as for parallel and independent from physicochemical analyses assessment of the quality of their living environment. The analyses held on the territory of South Bulgaria are divided into three phases: first (2009-2010), second (2011-2015) and third (2016-2017). The results of our investigations conducted over a period of 9 years, show that changes in asymmetry levels in meristic morphological traits in adult and sexually mature representatives of P. ridibundus and B. viridis are a very good bioindication method.