Types of water frog populations (Rana esculenta complex) in Poland

Abstract

Poland is inhabited by the two water frog species Rana ridibunda (genotype RR) and Rana lessonae (LL) and their hybrido-genetic hybrid Rana esculenta. Besides diploid (RL) hybrids two triploid (RRL, RLL) forms were found. In most populations the hybrid occurs syntopically with only one of the parental species. Concerning their genotypic structure water frog populations can be subdivided into three systems: the L-E (lessonae-esculenta) system, the R-E (ridibunda-esculenta) system and the E-E (esculenta-esculenta) system. The composition of water frog populations in Poland is highly differentiated. Among 27 population types described from central Europe 18 types were found in Poland. The highest diversity of population types was seen in the R-E system (8 types). In the L-E system three and in the E-E system four different types were found. Among 11170 investigated adult water frogs 690 (6%) presumptive triploid R. esculenta individuals occurred. In western Poland the proportion of triploid individuals and the diversity of population types was higher (7.7% triploid individuals, 13 population types) than in the eastern parts of the country (0.2% triploid individuals, six population types). The distribution picture of triploid individuals in western Poland is similar to that seen in eastern Germany (as a rule a high proportion of triploids occurs) while in eastern Poland the distribution pattern of triploid genotypes resembles the situation observed in the territory of the former Soviet Union (nearly no triploids appear).