First record of North Italian roach, Leucos aula (Bonaparte, 1841) on the Pag Island, Croatia—relict of the last glacial maximum?

Croatian ichthyofauna is one of the most diverse and rich in freshwater and endemic fish species in the European continent. However, to date, the distribution and phylogenetic relationships of certain freshwater fish species in Croatia is still not well known. In this study, we present a phylogenetic analysis of the North Italian roach ( Leucos aula , Bonaparte, 1841) belonging to Croatian and Italian populations using nucleotide sequences of mitochondrial genes for cytochrome oxidase subunit I ( COI mtDNA). The results confirmed the occurrence of L. aula on Pag Island and showed its close phylogenetic relationship with Coratian populations of the species from Ravni kotari (Baštica and Jaruga streams, Zadar County), Pazinčica River (Istria), and Zrmanja River, and with samples from three different locations in Italy (Po, Arno, and Sardinia rivers). Our study contributed to a precise understanding of the distribution of L. aula in the Zadar County (Croatia) and confirmed the conspecificity of Croatian and Italian populations.