Genetic diversity of the non-native crab Rhithropanopeus harrisii (Brachyura: Panopeidae) in the Polish coastal waters − an example of patchy genetic diversity at a small geographic scale

The American panopeid crab species Rhithropanopeus harrisii (Gould, 1841) is listed as an non-native species in European waters. In Poland, it occurred in the 1950s at two sites at the Baltic Sea coast, the Dead Vistula River (DVR) and the Vistula Lagoon (VL). Almost 50 years later, two additional populations were identified in the Gulf of Gdańsk (GG) and its inner part, Puck Bay (PB). In the present study, we sequenced and analyzed part of the mitochondrial cytochrome oxidase subunit I gene of the four Polish populations of R. harrisii in order to assess their genetic diversity and connectivity. The analyzed sequences of a length of 989 base pairs revealed eight different haplotypes. The highest number of haplotypes (n=6) was observed in the population from GG, whereas the lowest (n=3) in VL. The most common haplotype was recorded in 37% of the analyzed individuals. Pairwise Φ_ST values were mostly non-significant, with the exception of the comparison between DVR and VL (Φ_ST = 0.267; P < 0.05) and between PB and VL (Φ_ST = 0.194; P < 0.05), indicating a restricted gene flow or different sources of colonization.