Multiple sources implicated in the red swamp crayfish invasion in Michigan, USA

Reducing propagule pressure is critical for preventing the establishment and limiting the spread of invasive species. To reduce the risks associated with propagule pressure, the relative impacts of potential vectors contributing to invasions must be understood. In 2017, the red swamp crayfish (Procambarus clarkii) invasion expanded to include two new invasion fronts in Michigan, USA. To determine potential sources and make inferences about expansion dynamics among introduced populations, we developed genomic resources using restriction-site associated DNA (RAD) sequencing to genotype 175 red swamp crayfish at 1321 single nucleotide polymorphisms. Samples included potential wild and industry sources and collections within each Michigan invasion front. Results based on unsupervised clustering and multivariate analysis indicated that multiple, genetically distinct sources founded the Michigan invasions, which may include sources from the biological supply trade. Results support the recommendation that prevention strategies implement a multifaceted approach targeting diverse user groups associated with the live trades (e.g., biological supply, live food markets, and pet trade). In addition, regulatory frameworks that minimize the presence of a live invasive species should be adopted to reduce the risk of incidental introductions, geographic and demographic expansion, and establishment.