Phenotypic structure of Pelophylax esculentus complex population in urbanized landscapes in the South Central Russian Upland

Background. Morphological features are one of the most important markers forbioindication. Among them, the polymorphism of phenotypic traits occupies a specialplace. In tailless amphibians, dorsal colouration variability is widespread: the presence orabsence of a light dorsomedial stripe or dark spots. The phenotypic composition is knownto change in the impacted areas. The purpose of the study was to analyze the phenotypicstructure of Pelophylax esculentus complex populations in the urbanized landscapes in theSouth Central Russian Upland. This study is a part of the comprehensive analysis of thepopulation structure of green frogs in the South Central Russian Upland. Materials andmethods. A total of 748 individuals were sampled from 35 localities in the South CentralRussian Upland. Collection points differed in the degree of anthropogenic pressure. Dorsalcoloration variations were analyzed according to the generally accepted grading. Analysisof phenotypes diversity was performed according to the indicators proposed by L.A. Zhivotovsky.Results. Four main phenotypes “Maculata” (M), “Striata” (S), “Punctata” (P),“Burnsi” (B), and their combinations SM, SP and SMP were registered in the study area.The highest phenotypic diversity was observed in natural or sparsely disturbed biotopes“Sazon” (6.815 ± 0.251), “Aidar” (6.527 ± 0.306), “Goluboi Dunai” (6.43 ± 0.418), whileunder anthropogenic pressure an increase in the proportion of rare phenotypes was observed.The principal component analysis has demonstrated the phenotypic similarity ofmost of the populations. At the same time, unique groups were found in both impact andnatural habitats, which may indicate an effective compensatory response of the green frogpopulations in the study area to anthropogenic pressures. Conclusions. The results obtainedconfirm the data of the previous studies on the phenotypic polymorphism of green frogs,according to which the phenotypic diversity declines and the proportion of rare phenotypesincreases under conditions of anthropogenic pressure. In addition, in a number of populations,both in urbanized and relatively clean biotopes, unique combinations of phenotypicfrequencies are observed, indicating active adaptation of green frogs to changing environmentalconditions.