eDNA for detection of five highly invasive molluscs. A case study in urban rivers from the Iberian Peninsula.

Biological invasions are an important threat to biodiversity especially in aquatic ecosystems, and their frequency is generally higher near urban areas. Potentially invasive non-indigenous molluscs were deliberately introduced into European waters for food (Corbicula fluminea) and biocontrol (Melanoides tuberculata), and unintentionally introduced by ballast water (Mytilopsis leucophaeata, Corbicula fluminea), stock contamination (Sinanodonta woodiana), accidental escapes from aquaculture (Sinanodonta woodiana), aquarium trade releases (Melanoides tuberculata) and even attached to aquatic birds (Corbicula fluminea). Three rivers from the Iberian Peninsula were monitored near the three most populated inland cities to evaluate the presence of these invasive molluscs through PCR amplification using taxon-specific primers from eDNA. New primers were designed within 16S rRNA and cytochrome oxidase subunit I genes, tested in silico from BLAST methodology and experimentally in vitro before application in the field. C. fluminea was found in Ebro River (near Zaragoza); M. leucophaeata in Guadalquivir River (near Sevilla). M. tuberculata and S. woodiana were found from enclosed areas (lake and reservoir respectively) upstream, respectively, Zaragoza and Madrid. The new tools are ready to be used in other regions where these species are also invasive.