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Genetic and morphological differences among populations of Sabanejewia balcanica in Croatia

The genus Sabanejewia ranges from the Aral Sea to Italy and from Asia Minor to the Baltic Sea. This genus contains more than 20 species and subspecies and is highly diversified throughout Europe ; however the taxonomic positions and phylogenetic relationships between taxa have been disputed and remain uncertain. In fact, the phylogeny of the genus Sabanejewia remains one of the most interesting problems of the family Cobitidae. In Croatia, the golden loach (Sabanejewia balcanica) is widespread in the streams and rivers of the Danube drainage basin. Samples of Sabanejewia balcanica were collected from four streams in continental Croatia: the Drava, Voćinska, Rijeka and Petrinjčica Rivers. Voćinska River is a tributary of the Drava River, while the Rijeka and Petrinjčica flow into the Sava River. Taxonomic analysis of four Sabanejewia populations included morphological, morphometric, meristic and mitochondrial DNA analysis. Comparative analysis of 24 morphometric characters and 38 body ratios revealed some differences between populations. Specimens from the Drava River are significantly larger than specimens from other populations. The morphological characters of specimens from the Kupa and Petrinjčica Rivers are more similar than to those from the Voćinska River. Differences amnog fishes from different populations also exist in external morphology characters, such as spots on the caudal peduncle, the position of the suborbital spine and the form of pigmentation zones on the body sides. Mitochondrial DNA analysis of four Croatian Sabanejewia populations was performed to infer their phylogenetic placement within the genus Sabanejewia as well as to obtain insight into the level of genetic divergences among them. Phylogenetic analyses were based on the nucleotide sequence data obtained from three mitochondrial genes: cytochrom b (cytb, 1059 bp) and ATP synthase 8 and 6 (the total of 828 bp). Additionally, phylogenetic relationships within the “ S.montana— S.bulgarica— S.balcanica” (III) subclade of the Danubian-Balkan complex (as designated by Perdices et al. 2003) were investigated in greater detail using statistical parsimony analysis of the larger cytb data set (1048 bp). All Croatian samples clustered within the two sublineages of the Danubian-Balkan complex. Samples from the Voćinska River, as well as one sample from the Drava River were included in the “ S. balcanica” (VI) subclade. The remaining samples, including the two remaining haplotypes from the Drava River, were comprised within “ S.montana— S.bulgarica— S.balcanica” (III) subclade. While a single cytb haplotype was found in specimens from the Petrinjčica River, two quite different haplotype groups (maximal p-distance of 0.9%) were observed in the Rijeka River population.

Sabanejewia; mtDNA; phylogeny; morphology

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