Phylogenetic Diversity of the Red Swamp Crayfish Procambarus clarkii and Its Dispersal Pattern in Northern and Central Italy

Simple Summary The red swamp crayfish Procambarus clarkii is one of the most threatening freshwater species in the world. Since 2016, it has been included in the Invasive Alien Species list of the European Union, and it is still actively colonizing new territories at the expense of native crayfish. The present study aimed to provide a genetic characterization for a better understanding of the invasion routes of this alien species in the Italian Peninsula. The analysis of the mitochondrial DNA of 153 P. clarkii samples collected from five Italian lakes and one river showed the presence of unique maternal lines in four of these basins, thus confirming the hypothesis of multiple introductions and strengthening the idea that knowledge of dispersion routes can be very useful to predict the invasiveness of this species and create control strategies to preserve biodiversity. The red swamp crayfish Procambarus clarkii is one of the most threatening freshwater species in the world. The aim of this study is to provide a better understanding of the phylogeography and the invasion routes of P. clarkii populations in the Italian Peninsula through the analysis of mitochondrial phylogeny. Mitochondrial control region and cytochrome c oxidase subunit I (COI) sequences of 153 samples collected from six Italian basins were analyzed and compared to worldwide data. Except for the lakes Bolsena and Posta Fibreno, a high genetic variability was found in the other basins. The mitochondrial DNA pattern of P. clarkii from the lakes Candia and Massaciuccoli confirmed the hypothesis of double introduction events. Another entry point could be represented by Lake Trasimeno, which shows haplotypes originating from Louisiana and not shared with other Italian basins. Moreover, unique lineages were also found in the Stella River, thus enhancing the hypothesis that multiple introductions of P. clarkii occurred in northern and Central Italy and strengthening the idea that knowledge about the dispersion routes of this alien species can be useful to predict its invasiveness and elaborate control strategies to preserve biodiversity.