Apodemus chejuensis Johnson and Jones, 1955 — Jeju Striped Field Mouse

Apodemus agrarius chejuensis Johnson and Jones, 1955a p.171; Type locality- 10 miles northeast Mosulpo, Jeju Island, Korea; Won, 1958 p.447; Jones & Johnson, 1965 p.382; Corbet, 1978 p.137; Han, 2004c p.126.

Micromys agrarius mantchuricus: Thomas, 1906 p.863 (Quelpart Island= Jeju Island).

A. chejuensis: Won & Smith, 1999 p.27; Jo et al., 2012 p.253.

Range: The Jeju striped field mouse is endemic to Jeju Island (Jo et al. 2012; Fig. 129).

Remarks: The striped field mice on Jeju Island was first considered a subspecies of A. agrarius . Koh (1986, 1987, 1991) and Koh and Yoo (1992) reported an apparent distinction in morphological characters and mtDNA restriction fragment length polymorphisms between chejuensis and agrarius coreae . Koh et al. (1997) compared morphometric characteristics and also reached the conclusion that among the eight subspecies ( agrarius, ningpoensis, pallidior, chevrieri, insulaemus, manchuricssssus, coreae, chejuensis) of the striped field mice in Asia, chejuensis had a distinct (largest body size) difference supporting its status of different species. Koh and Yoo (1992) suggested that chejuensis had distinct mtDNA haplotypes and elevated it to the species level as Apodemus chejuensis Johnson and Jones, 1955 . Oh and Mori (1998) showed post-mating isolation between chejuensis and agrarius, through very low reproductive success rate of the first crossbred generation notably linked to an anomalous reproductive organ in F 1 males.

Although striped field mice from Wan Island have been assigned to coreae, these mice have a large body size and cluster with chejuensis in morphometric analyses (Koh 1986, 1989) as in genetic analysis (Koh et al. 2000). It is possible that the mice from Wan Island were introduced to Jeju Island. Indeed, Koh et al. (2000) found that most Wan Island specimens clustered with the Jeju Island population; but other Wan Island specimens belonged to another subgroup from mainland Korea.