Origin ofCallosciurus erythraeusIntroduced into the Uto Peninsula, Kumamoto, Japan, Inferred from Mitochondrial DNA Analysis

Abstract

Alien squirrels cause severe damage to forests and commercial tree plantations (Rowe and Gill 1985; Dagnall et al. 1998). They also cause the progressive disappearance of native squirrel species (Reynolds 1985; Gurnell and Pepper 1993; Bertolino and Genovesi 2003). To prevent these serious effects by alien squirrels, it is important to ascertain how the species was introduced to the area. Even if the species has already been introduced, further introductions can be managed if the route of introduction is identified. The Pallas’s squirrel (Callosciurus erythraeus) is originally distributed in eastern India, Bhutan, southeast China, Taiwan, Indochina, and Malaya (Corbet and Hill 1992; Wilson and Reeder 2005). This squirrel is arboreal and inhabits lowland and montane forests, cultivated areas, and gardens (Nowak 1991; Francis 2008). It was exported to other countries as an exotic pet. As a result of this commercial activity, C. erythraeus now occurs in Argentina (e.g., Aprile and Chicco 1999), France (Jouanin 1986; Mitchel-Jones et al. 1999), and Japan (Ishii 2005; Tamura 2009). It is considered serious threat to forests and tree plantations (Jouanin 1986; Setoguchi 1990; Aprile and Chicco 1999). Callosciurus erythraeus is thought to have been introduced from Taiwan into central and southwestern parts of Japan (Tamura 2002). Study of Oshida et al. (2007) with mitochondrial DNA control region sequences shows that the C. erythraeus population of Japan is closely related to that of Taiwan. Several populations of C. erythraeus are reported in Japan (Ozaki 1986; Torii 1989, 1993; Tamura and Ohara 2005; Ishii 2005; Tamura 2009) (Fig. 1). In addition to C. erythraeus, Oshida et al. (2007) revealed that Finlayson’s squirrel, C. finlaysonii, had been introduced to the Shizuoka Prefecture, Honshu Island. It is difficult to distinguish this species from C. erythraeus based on external characteristics such as pelage patterns. As C. finlaysonii occurs in only the Indochina Peninsula (Corbet and Hill 1992), its presence in Japan is clear evidence of past introductions of Callosciurus squirrels from the Asian Continent. In 2008, a population of Callosciurus squirrel was found in the Uto Peninsula of Kumamoto, Kyushu Island (Yasuda 2010, Fig. 1). Under law number 78 of the ‘Invasive Alien Species Act’ (Ministry of the Environment, Government of Japan, 2004: http://www.env.go.jp/ nature/intro/index.html), import of Callosciurus squirrels to Japan is strictly prohibited. Therefore, it is important to identify how this population appeared in this area. With respect to the Kumamoto population, we propose three scenarios: 1) C. erythraeus was introduced from Taiwan or from any other area in Japan, 2) C. erythraeus was introduced from any original country other than Taiwan, and 3) C. finlaysonii was introduced from the Asian Continent or from any other area in Japan. To test these scenarios, we analyzed the mtDNA control region