Abstract
Abstract: In Japan, Pallas’s squirrel (Callosciurus erythraeus) is an invasive species that was introduced from its native range in Southeast Asia through human activity. Using liver tissue samples obtained from C. erythraeus specimens collected from 2018 to 2022, we investigated the genetic structure of this invasive species in the cities of Kamakura, Yokohama and Yokosuka in Kanagawa Prefecture, Japan. Genomic DNA was extracted from each individual, and nucleotide sequences of the mitochondrial cytochrome b (cyt b) and D-loop regions were subjected to polymerase chain reaction and direct sequencing analyses. The cyt b sequence (1080 bp) analysis successfully identified 28 haplotypes (from 214 individuals) that were separated into three clades, all of which appear to have originated from Taiwanese populations. We subsequently identified the geographical origin of the three cyt b clades using D-loop sequences for which data were accumulated within their native range. For each cyt b clade, 38 representative individuals were selected and investigated their D-loop sequences (1079–1080 bp). The results showed that these representatives belonged to three native C. erythraeus populations in Taiwan: the eastern and western populations, and a population that was previously described as unknown, but sister to the eastern and southern populations. All haplotypes of this latter group were found in southern Taiwan. We classified all cyt b haplotypes from our sampling area into the three identified lineages and analysed their lineage distribution. In Kamakura, the eastern lineage and its sister group were mixed, suggesting two previously described introduction routes. In one pathway, pets escaped from a private owner in Kamakura prior to World War II; in the second pathway, individuals were introduced onto Izu Oshima, an island off Tokyo, and later transported to a botanical garden in Enoshima, from which they escaped in the 1950s. In Yokohama, the western lineage was intermixed with the eastern group and its sister group. In the eastern group and its sister group in Yokohama, however, haplotype composition was different from those in Kamakura, implying a complicated history of multiple introductions through different routes, other than those detected in Kamakura. Both lineages observed in Kamakura were also detected in Yokosuka; however, singleton haplotypes were more often observed in the latter city than former, suggesting a history of unrecorded introductions into Yokosuka. These findings will be useful for developing an effective control plan and preventing distribution expansions for this invasive mammal species.
