Biogeographical studies on the least weasel (Mustela nivalis) and the feral Japanese marten (Martes melampus)

To reveal the distribution and the dispersal history of the species is a basic concern of the biogeographical science. Among the carnivorans, Mustelidae has adapted to various habitat such as sea, river, forest, and high mountains. However, it is still unknown how they evolved and acquired their distribution and ecological niches for each species. In the present study, the dispersal history of the least weasel Mustela nivalis, distributed in Holarctic, was elucidated with phylogeographical analyses on the continental scale. Furthermore, the individual movements of the feral Japanese marten Mates melampus, in the local population, were revealed by the molecular ecological analyses.The least weasel is one of the most widely distributed mustelids. While previous studies have identified distinct western and eastern mtDNA lineages of the species in the western Palearctic, their broader distributions across the Palearctic have remained unknown. To address the broad-scale phylogeographical structure, the sampling locations were spread to populations in Eastern Europe, the Urals, and Japan, and analyzed the mtDNA control region and cytochrome b, the final intron of the zinc finger protein on Y chromosome (ZFY), and the autosomal agouti signaling protein gene (ASIP). The mtDNA data analysis exposed the previous western lineage (Clade I) but poorly supported assemblage extending across Palearctic, whereas the previous eastern lineage (Clade II) was reconfirmed and limited in the south western part of the Palearctic. The ZFY phylogeny showed a distinctive split that corresponding to the mtDNA lineage split, although less phylogeographical structure was seen in the ASIP variation. The present data concur with the previous inference of the Black Sea-Caspian Sea area having an ancestral character. The Urals region harbored high mitochondrial diversity, with an estimated coalescent time of around 100,000 years, suggesting this could have been a cryptic refugium for least weasels. Based on the coalescent-based demographic reconstructions, the expansion of Clade I across the Palearctic was remarkably rapid, while Clade II was relatively stable for a longer time. It seems that Clade II has maintained a constant population size in the temperate region, and the expansive Clade I represents adaptation to the cold regions. The Japanese marten is an omnivorous mustelid endemic to the mainlands of Japan. For fur production, this species was introduced to Hokkaido, around the 1940s. After the fur production was closed, fugitive individuals spread to southwestern Hokkaido, but little information on their ecological status make the management challenging. In the present study, the genetic population structure of the feral Japanese marten was assessed with a fecal DNA analysis, focusing on some local populations in Sapporo, Hokkaido. Surveys were carried out in a valley area and mountainous areas from 2016 to 2018. In total, 252 out of 317 fecal samples were assigned to the Japanese marten with mitochondrial DNA D-loop sequences, separating to two haplotypes. From 102 fecal samples, 36 Japanese martens were identified by genotyping of nine microsatellite loci. The genetic population structure in the valley was different from that in the mountainous areas: four full sibling sets were detected in the valley, whereas there was only one sibling set and small genetic variation in the mountainous areas. Similar to the populations from the mainlands of Japan, the feral Japanese marten increased its population size in autumn and preferred riparian forests. It was newly discovered that Japanese marten preferred the Sakhalin fir Abies sachalinensis, leading to a hypothesis that coniferous forests can be an important resource for the feral Japanese marten in Hokkaido. As a result, the least weasel had experienced rapid expansion to the northern Palearctic. This trend was also observed in the other species, such as stoat, red fox, Eurasian lynx, and brown bear. In addition, the present study showed a new northern cryptic refugia of least weasel, suggesting the adaptation to the cold regions. Furthermore, the multiple individuals’movements of the feral Japanese marten were revealed by the intensive surveys on the local population. This provoked their novel habitat preference to the coniferous forest and the occurrence of full sibling sets with male dispersal patterns. Thus, the present study showed the movement patterns of two mustelids on continental and local scales with phylogenetical and molecular ecological studies. These results will contribute to elucidate the complex Mustelidae evolutionary history.