The Asian cyprinid Pseudorasbora parva is considered to be a major threat to native fish communities and listed as an invasive alien species of European Union concern. Our study aims to gain evidence-based knowledge on the impact of both P. parva and its parasite Sphaerothecum destruens on native fish populations by analysing fish assemblages and body condition of individuals of native fish species in floodplain water bodies that were invaded and uninvaded by P. parva. We explored the use of environmental DNA (eDNA) techniques to detect S. destruens. Prevalence of S. destruens in native fish species was assessed. Fish samplings showed significantly negative correlations between the abundance of P. parva and the native Leucaspius delineatus, and Pungitius pungitius and three biodiversity indices of the fish assemblages (Simpson's diversity index, Shannon-Wiener index and evenness). Contrastingly, the abundances of the native Gasterosteus aculeatus and P. parva were positively related. In nearly all isolated water bodies with P. parva, this species is outnumbering native fish species. No effect of P. parva presence was found on Electronic supplementary material The online version of this article (
For most if not all European herpetofauna, range-wide mtDNA phylogeographies have been published. This facilitates establishing the provenance of introduced populations. However, precision is contingent on the spatial genetic structure across the range of the taxon under study and, in particular, from where within that range the introduction was sourced. In the Netherlands, the common midwife toad, Alytes obstetricans, only naturally occurs in the extreme southeast and is on the decline there. Yet, introduced populations thrive elsewhere in the country. We use mtDNA analysis to try to determine the origin of two introduced populations along the Dutch coast, in the city of The Hague and the dune area Meijendel. We compiled a database of hundreds of individuals from throughout the distribution range and added over 130 individuals from both native and introduced populations from the Netherlands, Belgium and Germany. The mtDNA haplotypes found in the introduced populations are associated with postglacial expansion. The main haplotype predominates in the natural range in the Netherlands, but also occurs much more widely across western Europe, north of the Pyrenees. A closely related haplotype, newly identified from The Hague, was not found in the native Netherlands range, suggesting an origin from abroad. The combination of low phylogeographic resolution and low sampling density in the postglacially colonized part of the range hampers our ability to determine the provenance of the introduced A. obstetricans populations.
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