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

<p>Recent molecular studies have detected the occurrence of exotic water frog species (<i>Pelophylax </i>sp.) in central and western European populations. Here, we report genetic evidence for the occurrence of the Balkan water frog, <i>Pelophylax kurtmuelleri</i>, in southwestern Poland. We found a high frequency of an allele of serum albumin intron-1 and a mitochondrial cytochrome <i>b </i>haplotype specific for this southern taxon in frogs from the Barycz river drainage system. We interpret this finding as evidence of admixture between <i>P. kurtmuelleri </i>and the local <i>ridibundus-esculentus </i>water frog population. The origin of the exotic <i>P. kurtmuelleri </i>mitochondrial and nuclear alleles in southwestern Poland could be due to (i) hybridization after a human-mediated introduction of <i>P. kurtmuelleri</i>, (ii) the persistence of ancestral polymorphism in central European <i>P. ridibundus</i>, or (iii) hybridization between <i>P. kurtmuelleri </i>and <i>P. ridibundus </i>in the Balkans followed by the northward expansion of admixed <i>P. ridibundus</i>. 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 of <i>P. kurtmuelleri </i>at the studied site.</p>