The invasive red swamp crayfish, Procambarus clarkii, is native to southcentral United States and northeastern Mexico. Recently, it has been being spreading in the wild in South Korea. However, its primary sources, introduction routes, establishment, and expansion in South Korea remain unclear. Here, we analyzed genetic diversity and population genetic structures of its domestic natural populations during early invasion, commercial stock from local aquaria (a suspected introduction source), and original United States population using mitochondrial COI gene sequences for 267 individuals and eight microsatellite markers for 158 individuals. Natural and commercial populations of P. clarkii showed reduced genetic diversity (e.g., haplotype diversity and allelic richness). The highest genetic diversity was observed in one original source population based on both genetic markers. Despite a large number of individuals in commercial aquaria, we detected remarkably low genetic diversity and only three haplotypes among 226 individuals, suggesting an inbred population likely originating from a small founder group. Additionally, the low genetic diversity in the natural population indicates a small effective population size during early establishment of P. clarkii in South Korea. Interestingly, genetic differentiation between natural populations and the United States population was lower than that between natural populations and aquarium populations. This suggests that various genetic types from the United States likely have entered different domestic aquariums, leading to distinct natural populations through separate pathways. Results of our study will provide an insight on the level of genetic divergence and population differentiation during the initial stage of invasion of non-indigenous species into new environments.

줄똥풍뎅이속은 호흰개미성인 줄똥풍뎅이족에서 가장 많은 종수를 보유하고 있다. 국내에는 광양줄똥풍뎅이 한 종만이 기록되었으나 또 다 른 종인 Rhyparus helophoroides Fairmaire, 1893를 새로이 발견하여 보고한다. 본 종의 진단형질과 그 사진, 한국산 줄똥풍뎅이속의 검색표의 제 시와 함께 생태에 대한 간략한 정보를 제공한다.