Environmental DNA Haplotyping Reveals Dispersal Patterns of Invasive Bluegill Sunfish, Lepomis macrochirus, in Japan

Abstract

Biological invasions represent a significant threat to global biodiversity. Population genetics plays a crucial role in addressing the invasion history of invasive species, as information on the genetic structure of local populations of invasive species is useful in estimating their source and dispersal. This study aimed to demonstrate the potential of an environmental DNA (eDNA)-based approach for estimating the dispersal patterns of invasive species, using bluegill sunfish (Lepomis macrochirus), a freshwater fish introduced to Japan in 1960. We developed an eDNA haplotyping assay based on high-throughput sequencing and validated its ability to reproduce the haplotype distribution of bluegill sunfish in Japan, which had previously been determined through DNA analysis of individual fish. We also detected a negative relationship between the number of detected haplotypes and the geographic distance from Lake Biwa, one of the initial introduction sites, to each study site. This genetic pattern can occur in introduced species as a result of serial founder events during their range expansion. Our results suggested that Lake Biwa is the source of bluegill sunfish distribution in Japan, which is consistent with the invasion records of this species. We demonstrated the potential of the eDNA haplotyping assay for estimating the dispersal patterns of invasive species, which would aid the preparation of countermeasures against emerging biological invasions by simultaneously enabling the early detection and tracking of invasive species.