Svrha ovog rada bila je utvrditi genetsku strukturu te filogenetske odnose populacija obrvana, Aphanius fasciatus (Valenciennes, 1821) na lokalitetima koji do sada nisu bili uključeni u slična istraživanja. Sekvencirana su dva genetska biljega te su dobiveni slijedovi nukleotida gena za citokrom b duljine 1.140 parova baza te kontrolne regije mtDNK duljine 396-398 parova baza. Jedinke su prikupljene na osam lokaliteta u Sloveniji, Hrvatskoj, Crnoj Gori i Albaniji, a u analizu je uključeno više objavljenih sekvenci ove vrste, kao i drugih vrsta roda Aphanius. Uočena je niska intrapopulacijska te nešto viša interpopulacijska genetska ranolikost. Sve provedene analize ukazuju na to da istraživane populacije pripadaju nezavisnoj evolucijskoj liniji u odnosu na ostale vrste te da se međusobno genetski i prostorno mogu razdvojiti u dvije skupine. Prvoj skupini pripadaju populacije sjevernog i srednjeg, a drugoj lokaliteti južnog Jadrana.

The purpose of this thesis was to determine the genetic structure and phylogenetic relationships among mediterranean toothcarp, Aphanius fasciatus (Valenciennes, 1827) populations from sites not included in similar investigations to date. Two genetic markers were sequenced and a number of nucleotide sequences corresponding to the cytochrome b gene (1.140 base pairs) and mitochondrial region (396-398 base pairs) were obtained. Individuals were collected from eight different localities in Slovenia, Croatia, Monte Negro and Albania. A. fasciatus sequences available from previous investigations, as well as those from other species of the genus Aphanius, were also included. Low genetic diversity was observed within the populations and a higher genetic diversity between the populations. The molecular analyses show that the studied populations belong to an evolutionary line independent from the other species. They are genetically and spatially distinct and can be separated into a northern and a southern group of sites, corresponding to the northern and southern Adriatic.