Identification of cryptic forms of the hybridogenic complex of European water frogs (Pelophylax esculentus complex) in the conditions of transformed biotopes of the south of the Central Russian Upland based on DNA markers

AIM: The aim of the study was to carry out species identification of the hybridogenic complex of European water frogs (Pelophylax esculentus complex) in the conditions of transformed biotopes of the south of the Central Russian Upland based on molecular genetic markers 
MATERIALS AND METHODS: The study included 36 local populations (770 individuals) living in conditions of transformed biotopes of the south of the Central Russian Upland. Identification of cryptic forms was carried out by a Multiplex PCR. Two molecular genetic markers were used for amplification: intron 1 of the SAI-1 DNA serum albumin gene to determine hybrids and cryptic forms, and a fragment of the first subunit of the cytochrome oxidase COI mtDNA gene to determine maternal lines. 
RESULTS: According to the data obtained, pure R-type population systems predominate (58.33%) in the study region. Mixed RE-type population systems were identified in 14 localities, REL-type in the region is extremely rare and is noted only in one locality. No pure L-type, E-type, or mixed LE-type population systems have been identified. The study revealed a statistically significant (p 0.001) predominance of haplotypes of the Western form (Pelophylax ridibundus). 
CONCLUSIONS: The data obtained indicate active adaptive changes in the population structure of European water frogs in the study area. Degradation of water bodies caused by abiotic and anthropogenic factors forces amphibians to migrate to neighboring reservoirs in which hybridization of representatives of this complex occurs. Introgressive and hybrid forms of the marsh frog, as well as hybrid edible individuals with greater ecological plasticity and tolerance to anthropogenic pressure, displace populations of Pelophylax lessonae. Based on the above, we consider it necessary to include the pond frog (P. lessonae) in the Red Book of the Belgorod region.