Pelophylax kurtmuelleri in Croatia: genetic evidence supports a native status in the Konavle Field and Neretva Delta

Recent genetic studies on Pelophylax examine regional distribution patterns and evolutionary processes and address taxonomy issues within the species. DNA analyses have been performed to monitor the prevalence of biological invasions. Although the presence of P. kurtmuelleri has been previously addressed, this species has never been included in the Croatian fauna, particularly as a native species. This study confirms the presence of Pelophylax kurtmuelleri in Croatia and suggests it to be a native species to the southern region of Dalmatia, specifically in the Konavle Field and Neretva River Delta. Genetic analyses using SAI-1 nuclear and COI and ND2 mitochondrial markers identified 34 P. kurtmuelleri individuals, without the detection of other Pelophylax species, hybrids, or hybridogenetic complexes. The obtained data complements previous studies based only on mitochondrial DNA, which indicated the distribution of P. kurtmuelleri in the Adriatic basin, including Croatia and neighbouring regions. Since P. kurtmuelleri is difficult to morphologically distinguish from Pelophylax ridibundus and is known to form hybrids with other Pelophylax species this study highlights the utility of combining nuclear and mitochondrial markers to resolve taxonomic ambiguity, providing thus evidence for the existence of pure P. kurtmuelleri populations in southern Croatia, where this species can be considered native. This study enhances the understanding of the biogeography of Balkan amphibians and underscores the significance of genetic methodologies in assessing amphibian diversity amid advancing biological invasions.