Preliminary genetic data suggest the occurrence of the Balkan water frog, Pelophylax kurtmuelleri, in southwestern Poland

Recent molecular studies have detected the occurrence of exotic water frog species (Pelophylaxsp.) in central and western European populations. Here, we report genetic evidence for the occurrence of the Balkan water frog,Pelophylax kurtmuelleri, in southwestern Poland. We found a high frequency of an allele of serum albumin intron-1 and a mitochondrial cytochromebhaplotype specific for this southern taxon in frogs from the Barycz river drainage system. We interpret this finding as evidence of admixture betweenP. kurtmuelleriand the localridibundus-esculentuswater frog population. The origin of the exoticP. kurtmuellerimitochondrial and nuclear alleles in southwestern Poland could be due to (i) hybridization after a human-mediated introduction ofP. kurtmuelleri, (ii) the persistence of ancestral polymorphism in central EuropeanP. ridibundus, or (iii) hybridization betweenP. kurtmuelleriandP. ridibundusin the Balkans followed by the northward expansion of admixedP. ridibundus. Identical mtDNA haplotypes found in southwestern Poland and localities on the borders between Greece, Albania and Macedonia suggest that this region harboured the source population ofP. kurtmuelleriat the studied site.</jats:p