Phylogeny and Genetic Variability of Rotifer’s Closest Relatives Acanthocephala: an Example from Croatia

The high intraspecific variability of the morphological characters of Acanthocephala can complicate their taxonomic classification. To solve this problem, molecular markers are used. Here, we present the identification and determination of genetic variability of four species of the Acanthocephala genera Pomphorhynchus , Acanthocephalus and Dentitruncus , obligate endoparasites of freshwater fishes. The DNA sequences of the three markers that evolve at different rates (18S rDNA, COI and ITS) were analysed. To put the genetic position of the Croatian Acanthocephala specimens in a broader context, the COI and ITS sequences of the other European specimens from the NCBI GenBank were used. Genetic structuring at the local level was minor or not visible at all, but in the context of European phylogeographic structuring, the Croatian P. laevis showed a clear grouping to the geographical subcluster Ponto-Caspian Balkans. Only two P. laevis Danubian haplotypes, which were not analysed morphologically, were assigned to the Ponto-Caspian Danube subclade together with the recently identified P. bosniacus from Austria. The haplotypes of P. tereticollis from Croatia were clustered within the two main European clades. In connection with the phylogeographic distribution of Acanthocephala and their hosts, we hypothesised possible phylogeographic patterns.