Geographic distribution of COI haplotype frequencies of Chinese mitten crabs. The distribution is shown in the native range (A), the United States (B), Northern Germany (C) and Europe in general (D). Haplotypes only found in the native range are colored in blue tones, haplotypes only found in the introduced range are colored in green tones, and haplotypes found in both the native and introduced range are colored in yellow and orange tones. The smallest pie chart in each graphic represents a single individual. All populations with five or more sampled individuals are named. Additionally, in a we also point out the populations of Dalian City, Wuhu and Yangtze, as they contain the otherwise rare but invasive haplotype H2. Scale bars: 250 km (A, B, D). 25 km (c).