Population Genetic Structure of the Invasive Red Swamp Crayfish in China Revealed by ITS1 Variation

The invasive red swamp crayfish (Procambarus clarkii) provides a valuable opportunity for studying the population genetics of invasive species that disperse rapidly. We analyzed the population genetic structure among 12 populations of the crayfish in China based on the internal transcribed spacer 1 (ITS1) region. The ITS1 of 815 bp aligned across 34 haplotypes; the average GC content was 53.9%. AMOVA showed that intrapopulation variation (95.26%) was much higher than interpopulation variation (4.74%). Genetic differentiation between the Taiwan and mainland populations (F (st) = 0.160) was moderate, but the Chinese population (Taiwan and the mainland combined) and an American population were highly differentiated (0.682 and 0.977, respectively). Gene flow between the Chinese and American populations (N (m) = 0.006 and 0.117, respectively) was lower than that between Taiwan and the mainland (1.536). Phylogenetic trees showed that three major genealogical clusters matched the sample locations well, suggesting that genetic differentiation is created largely by geographic isolation.