Application of Fluctuating Asymmetry Values in Pelophylax ridibundus (Amphibia: Anura: Ranidae) Meristic Traits as a Method for Assessing Environmental Quality of Areas with Different Degrees of Urbanization

In this paper, we assess the environmental impact of urbanization in three freshwater biotopes, using the levels of fluctuating asymmetry (FA) in 10 meristic morphological traits in the Marsh Frog (Pelophylax ridibundus (Pallas, 1771)). Two of the studied biotopes are located in the boundaries of the city of Plovdiv (one in the central part, the other in a suburban residential area), and the third is located in the vicinity of the village of Orizare. Our working hypothesis is based on the assumption that urban and suburban sites are more severely affected by human activities than rural sites. However, according to our results, the population of P. ridibundus inhabiting Maritsa River in the central part of Plovdiv City, and that in the suburban zone, have found relatively good living conditions. Contrary to our expectations, the worst environmental conditions were observed in the rural zone, where anthropogenic stress related to intensive pastoral animal husbandry and crop farming was present. The absence of adult individuals in the rural site is also an indicator of unfavorable living conditions.