New mtDNA Haplotypes of the Sika Deer (Cervus nippon) Found in Hokkaido, Japan Suggest Human-Mediated Immigration

Abstract

The sika deer (Cervus nippon Temminck, 1838) is widely distributed throughout eastern and northeastern Asia, from the Ussuri region of Siberia to northern Vietnam, Taiwan, and Japan (Ohtaishi 1986; Whitehead 1993), with the range extending from subarctic to tropical zones. Because of their high hunting value (e.g., beauty and taste), they have been introduced into at least 18 countries: Australia, Austria, the Czech Republic, Denmark, England, Estonia, France, Germany, Hungary, Ireland, Lithuania, Moldova, Morocco, New Zealand, the Philippines, Poland, Switzerland, and the United States (Pitra et al. 2005; Bartos 2009; Ohdachi et al. 2009). Although they have been highly valued as hunting animals, sika deer have also caused ecological problems in some introduced regions, including serious damage to the forests of British islands (Bartos 2009; Swanson and Putman 2009) and hybridization with native red deer (Cervus elaphus Linnaeus, 1758) in Europe (Whitehead 1972; Bartos 2009; Senn and Pemberton 2009). Such hybridization that introduces genetic pollution of native species poses a serious concern for conservation biology. Phylogenetic studies on Japanese sika deer show two distinct phylogroups: Northern and Southern lineages (Tamate et al. 1998; Nagata et al. 1999; Nagata 2009), which are thought to have diverged approximately 350,000 years ago. The genetic difference between these two groups is larger than the differences between sika deer in the Asian Continent and each lineage in Japan (Nagata 2009). Although hybridization within species may not be of serious concern, hybridization between deeply diverged lineages may ultimately reduce genetic diversity and cause genetic pollution. Relocation of the sika deer between the lineages should therefore be avoided. The Oshima region, the southernmost peninsula in Hokkaido, was the native habitat of sika deer until the 1870s. Drastic population decline due to overharvesting and heavy snow, however, brought on a local extinction of sika deer in the Oshima region. In order to restore the population for game hunting, administrative reintroductions were conducted (Kaji et al. 2000, 2010), in which six females and two males, and six females and three males from the eastern part of Hokkaido were released into the Oshima region in 1980 and in 1981, respectively. The most common mtDNA haplotype in the eastern part of Hokkaido was observed in individuals that were sampled in the 1990s and 2000s from the Oshima region (Nabata et al. 2007). Moreover, another unofficial introduction of sika deer of unknown origin has been suspected in the Oshima region; a hunter’s community has suggested that some deer might escape from captive bred sites which were privately managed. Therefore, we may find individuals that have different lineages from native one. In this study, we examined the mitochondrial DNA (mtDNA) haplotype composition of the sika deer population in the Oshima region to resolve the origin of sika deer in the region.