Abstract
Invasive alien species are a major driver of biodiversity loss, with their impacts potentially more intense when complexes of cryptic species are involved. In freshwaters, the anthropogenic manipulation of fish communities has resulted in altered fish communities, and in Europe has increased the complexity of Phoxinus species assemblages. Here, we investigated the Phoxinus communities of the westernmost part of the Po river basin, where adjacent freshwater ecosystems (Alpine high-altitude lakes and lowland streams) are representative of different management strategies (i.e. manipulated fish communities via stocking in Alpine lakes vs. natural populations in streams). We tested the genetic composition of the cryptic Phoxinus populations inhabiting these waters, as the species are morphologically indistinct. Sequences of the mitochondrial cytochrome oxidase I (COI) were obtained from 239 specimens, with the results indicating that 17 Alpine high-altitude lakes are now populated by a complex of Phoxinus species, comprising P. septimaniae (native to the Mediterranean area of France), P. csikii (native to the Central Balkans) and P. lumaireul (native to the North Adriatic Sea basins). Their introduction resulted from their use as angling live baits. Minnow populations in lowland streams were primarily comprised of native P. lumaireul, with only a single P. csikii specimen detected. While nuclear sequences of the recombination activating gene 1 (RAG1) marker were not useful for tracking the presence of alien alleles in these stream populations, the COI data emphasised the importance of using molecular tools to investigate cryptic species complexes that have been modified by anthropogenic activities.
Highlights
Invasive alien species are an important driver of biodiversity loss in aquatic ecosystems (Milardi et al 2018) and can result in serious economic impacts (Gallardo et al 2016)
Freshwater fish communities can be highly impacted by alien species, with invasions facilitated by the high connectivity of river habitats that enables rapid dispersal (Hermoso et al 2011)
A total of 52 haplotypes were identified in the 635 bp length multiple cytochrome oxidase subunit I (COI) alignment that was obtained from the 239 analysed minnows plus the 191 sequences retrieved from GenBank (Online resources Table ESM 5)
Summary
Invasive alien species are an important driver of biodiversity loss in aquatic ecosystems (Milardi et al 2018) and can result in serious economic impacts (Gallardo et al 2016). Detection usually results in fewer resources being required for eradication as the alien species is still of low abundance and spatially constrained (Britton et al 2011). This early detection can be hindered by the unresolved taxonomic status of species, or by the presence of cryptic species (Bickford et al 2007). While cryptic alien species are widespread across different taxa (Pfenninger and Schwenk2007; Adams et al 2014), many are assumed to remain undetected within communities of native species (Morais and Reichard 2018) Their detection is increasingly reliant on the application of molecular tools Their detection is increasingly reliant on the application of molecular tools (e.g. Smith et al 2012; Uchii et al 2016)
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