First look into the evolutionary history, phylogeographic and population genetic structure of the Danube barbel in Croatia

The Danube barbel, Barbus balcanicus is small rheophilic freshwater fish, belonging to the genus Barbus which includes 23 species native to Europe. In Croatian watercourses, three members of the genus Barbus are found, B. balcanicus, B. barbus and B. plebejus, each occupying a specific ecological niche. This study examined cytochrome b (cyt b), a common genetic marker used to describe the structure and origin of fish populations to perform a phylogenetic reconstruction of the Danube barbel. Two methods of phylogenetic inference were used: maximum parsimony (MP) and maximum likelihood (ML), which yielded well supported trees of similar topology. The Median joining network (MJ) was generated and corroborated to show the divergence of three lineages of Barbus balcanicus on the Balkan Peninsula: Croatian, Serbian and Macedonian lineages that separated at the beginning of the Pleistocene. Croatian lineage of B. balcanicus shows a uniform structure with many recently diverged haplotypes, which was further supported by the star-like shape of the MJ network. Effective size estimates were obtained for populations inhabiting separate river catchments and the results imply the good reproductive potential of Barbus balcanicus in Croatia, which is in positive correlation with the overall high genetic diversity calculated for its populations. Nevertheless, population sizes of several population seem to be reduced as a consequence of habitat degradation and fragmentation. Le barbeau du Danube, Barbus balcanicus, est un petit poisson d'eau douce rheophile, appartenant au genre Barbus qui comprend 23 especes indigenes d'Europe. Dans les cours d'eau croates, on trouve trois membres du genre Barbus, B. balcanicus, B. barbus et B. plebejus, chacun occupant une niche ecologique specifique. Cette etude a examine le cytochrome b (cyt b), un marqueur genetique commun utilise pour decrire la structure et l'origine des populations de poissons afin d'effectuer une reconstruction phylogenetique du barbeau du Danube. Deux methodes d'inference phylogenetique ont ete utilisees: la parcimonie maximale (MP) et la probabilite maximale (ML), qui ont permis d'obtenir des arbres bien etayes et de topologie similaire. Le reseau d'assemblage median (MJ) a ete genere et valide pour montrer la divergence de trois lignees de Barbus balcanicus dans la peninsule balkanique: les lignees croate, serbe et macedonienne qui se sont separees au debut du Pleistocene. La lignee croate de B. balcanicus presente une structure uniforme avec de nombreux haplotypes recemment divergents, qui a ete renforcee par la forme etoilee du reseau MJ. Des estimations de taille effective ont ete obtenues pour des populations vivant dans des bassins hydrographiques separes et les resultats impliquent le bon potentiel reproductif de Barbus balcanicus en Croatie, qui est en correlation positive avec la diversite genetique globale elevee calculee pour ses populations. Neanmoins, la taille de plusieurs populations semble etre reduite en raison de la degradation et de la fragmentation de l'habitat.

Automated summary

This study investigated the phylogenetic reconstruction of the Danube barbel using cytochrome b as a genetic marker, revealing the divergence of three Barbus balcanicus lineages in Croatian watercourses. The Croatian lineage displayed a high reproductive potential, but habitat degradation and fragmentation have led to reduced population sizes in some populations.