No abstract

In fish, species identity can be encoded by sounds, which have been thoroughly investigated in European gobiids (Gobiidae, Gobius lineage). Recent evolutionary studies suggest that deterministic and/or stochastic forces could generate acoustic differences among related animal species, though this has not been investigated in any teleost group to date. In the present comparative study, we analysed the sounds from nine soniferous gobiids and quantitatively assessed their acoustic variability. Our interspecific acoustic study, incorporating for the first time the representative acoustic signals from the majority of soniferous gobiids, suggested that their sounds are truly species-specific (92% of sounds correctly classified into exact species) and each taxon possesses a unique set of spectro-temporal variables. In addition, we reconstructed phylogenetic relationships from a concatenated molecular dataset consisting of multiple molecular markers to track the evolution of acoustic signals in soniferous gobiids. The results of this study indicated that the genus Padogobius is polyphyletic, since P. nigricans was nested within the Ponto-Caspian clade, while the congeneric P. bonelli turned out to be a sister taxon to the remaining investigated soniferous species. Lastly, by extracting the acoustic and genetic distance matrices, sound variability and genetic distance were correlated for the first time to assess whether sound evolution follows a similar phylogenetic pattern. The positive correlation between the sound variability and genetic distance obtained here emphasizes that certain acoustic features from representative sounds could carry the phylogenetic signal in soniferous gobiids. Our study was the first attempt to evaluate the mutual relationship between acoustic variation and genetic divergence in any teleost fish.

The Bednja River is the longest river flowing with its full course exclusively through Croatia and one of the largest right tributaries of the Drava River, which belongs to the Danube River basin. Due to the variety of habitats present within the course of the Bednja River, as well as older literature reports, it can be expected that this river harbors a high number of freshwater fish species and would likely benefit from conservation and preservation efforts. We compiled and analyzed the existing literature data on the Bednja River fish communities and performed field investigations at various localities on this river in order to describe the current structure of its freshwater fish fauna and monitor changes induced by human activities. Our results corroborate the presence of a rich and diverse fish community. Moreover, with 36 native species, the Bednja River harbors one of the richest fish communities in Croatia as well as in the Danube basin. Unfortunately, modifications of the native fish community were evident in the form of local extinctions, reductions in the population abundance of several native species and the presence of non-native species. Habitat degradation and fragmentation were identified as the most serious threats provoking negative effects on the native fish populations, followed by predatory and competitive effects of invasive species.

The genus Aulopyge, represented by a single species, the Dalmatian barbelgudgeon, Aulopyge huegelii, is an endemic genus with very restricted distribution range comprising several rivers in southern Croatia and Bosnia and Herzegovina. In this study, molecular genetic analyses based on three molecular markers (one nuclear and two mitochondrial) were performed to confirm the position of Aulopyge within Cyprinidae, obtain data on its evolutionary history, and describe its population genetic structure and diversity. Specimens of A. huegelii were obtained throughout the distribution range. Phylogenetic reconstruction corroborated the independent position of this species and its placement within the Barbinae subfamily. The evolutionary history of A. huegelii started already in the middle Oligocene, whereas intraspecific divergences that left a trace in its current genetic structure and diversity are of much younger origin, starting in the middle Pleistocene. Unlike in other cypriniform species and genera distributed in the Dinaric karst region, there is no significant structuring within A. huegelii, or distribution of haplotypes concordant with the geographic scale. Furthermore, low effective population sizes estimated for most populations and low genetic diversities within them raise strong concerns about the viability and future survival of this endemic species.