Genetic diversity of the invasive crayfish Procambarus clarkii in France

Procambarus clarkii is a widespread invasive species and its biological traits have often been used to explain its successful colonization of new areas. However, studies on the genetic features of invasive populations are still scarce, and the use of molecular markers could bring new insights about biological invasions. After being introduced in Spain in 1973, P. clarkii was introduced in France (approximate to 1976) and nowadays is widespread in its territory (61 departments) in wetlands which provide good conditions for a successful colonization. Here we ask whether the genetic diversity of invasive populations could help to understand the evolutionary history of its invasion. To investigate this issue, 227 individuals of P. clarkii from 27 French populations and 10 departments were collected, and a 553 bp COI fragment was amplified and sequenced using universal primers. For the analysis of genetic parameters, nucleotide diversity (pi), and haplotype diversity (Hd), the populations were organized into four major groups. The nucleotide diversifies (pi) were 0.000154, 0.00119, 0.00118, and 0.00123 for group 1, 2, 3, and 4, respectively. The genetic diversity of French populations (Hd = 0.350; pi = 0.00123) was lower than the native populations (Hd = 0.982; Tc = 0.00736). Nine haplotypes were found (H1-H9) in 230 sequences. Haplotype diversity (Hd) was 0.444, 0.239, 0.330, and 0.350 for groups 1, 2, 3, and 4, respectively. The haplotype network showed very similar haplotypes, differing by few mutational steps and showing some complex relationships. Three haplotypes related to the species' native region were found (H1, H2, and H3). Each of these haplotypes was also related to biogeographical regions. The most frequent haplotype (H2) was widespread throughout 10 departments. The other six haplotypes (H4, H5, H6, H7, H8, and H9) were not found in the native region but, in some cases, shared some French populations. Translocation by humans is the most plausible explanation of the observed haplotype relationships. We suggest that genetic information should play a larger role in the development of policies to manage invasive species.