153 ACTA ZOOLOGICA BULGARICA Acta zool. bulg., 70 (2), 2018: 153-164 * Corresponding author: pedja@bio.bg.ac.rs Systematics and Phylogenetics Research Article Introduction Banarescu (1964), Karaman (1971), Almaca (1981, 1984) and Economidis (1989) distinguished two groups of Barbus spp. based on their morpho- logical traits. One of them is the small-bodied rheo- philic group of species with non-serrated, weak (cyclolepis type) or very weak (meridionalis type) fourth dorsal ray. The members of this group inhabit montane streams and their monophyly has been a subject of controversy (Tsigenopoulos et al. 1999). Tsigenopoulos & Berrebi (2000) stated, on the basis of examination of the cytochrome b (cyt b), that “riverine species from the Balkans and eastern Europe constantly produced weakly supported as- sociations”. However, they agreed with the state- ment of Banarescu (1990) on the Quaternary dis- persal of riverine species from the middle Danube area of the former (late Myocene) Panonian basin of the Paratethys to northern Greece via the river catchments of the Južna Morava and Vardar (Axios) Rivers. Contrary to the expectations, that advance of the phylogeography of barbel taxa in the area of the Balkan Peninsula has not been followed by resolv- ing their taxonomic status. Tsigenopoulos & Berrebi (2000) considered rheophilic barbel from the Vardar River as B. pelo- ponnesius petenyi Heckel, 1848. In addition, they as- signed rheophilic barbel from the Struma River to B. cyclolepis strumicae Karaman, 1955, and that from the Danube River drainage area to B. petenyi Heckel, 1852. Machordom & Doadrio (2001) revealed, Morphological and Molecular Diferentiation between Rheophilic Barbels Barbus spp. (Cyprinidae) from Headwaters at the Divide between Drainage Areas of the Danube, Vardar and Struma Rivers, Central Balkans Predrag Simonović * , Saša Marić, Ana Tošić, Dubravka Škraba Jurlina & Vera Nikolić Faculty of Biology, University of Belgrade, Studentski trg. 16, 11000 Belgrade, Serbia Abstract: External morphology and cytochrome b structure of rheophilic barbels from headwaters of the Pčinja, Vrla (Barbus balcanicus) and Dragovištica (B. strumicae) Rivers in Southern Serbia at the watershed be- tween the drainage areas of the Vardar (Axios), Danube and Struma (Strymon) Rivers, respectively, were examined. Barbel specimens from the Pčinja River were clearly diferent from both congeners from the other two rivers in the shape of the head and the length of the caudal fn. They were closer in external mor- phology to B. strumicae from the Dragovištica River as compared to B. balcanicus from the Vrla River. On the contrary, their relationship inferred from the structure of cytohrome b revealed closer relationship between B. balcanicus and the rheophilic barbel from the Pčinja River. Despite of the diferentiation in morphology found between specimens of the rheophilic barbel, the divergence between them was insuf- fcient for sound taxonomic inferences. Their phylogenetic relationships shed some new light on their evolutionary history in the study area. Key words: Barbus, morphometry, cytochrome b, peninsular watershed divide, Balkan Peninsula