キタキツネ集団の形態学的および集団遺伝学的研究

In Chapter I , diversity of the red fox on Hokkaido Island was evaluated in morphological aspect. T o investigate the morphological variation in an island population of the red fox ( Vulpes vulpes ), 25 cranial and 24 dental characters were measured for 225 specimens (137 males and 88 females) from Hokkaido Island, Japan. A Bayesian principal component analysis found only small differences among three groups identified genetically in previous studies. Concretely, analyses of variance and post -hoc tests detected clear differences in two functionally important measurements: postorbital constriction and upper fourth premolar length. In the postorbital const riction, relating to size of the temporal muscle, a difference with a gradient of increase from west to east on Hokkaido Island was found in both sexes. In the upper fourth premolar length, relating to body size, a difference between the Southern and Centr al groups was found in both sexes. Additionally, in differences in four measurements of skull width, skull height, mastoid width, and occipital condyle width, relating to braincase, were detected in only male. Subsequently, a correlation analysis showed that the postorbital constriction might be related to climatic conditions (e.g., minimum mean monthly temperature and snowfall). Endemic climate conditions and food habits appeared to contribute to the observed geographical variation in skull morphology. In Chapter II , population genetic diversity of the red fox on Hokkaido Island was evaluated using the genotypes of the major histocompatibility complex (MHC ) gene as adaptive marker. To assess the genetic diversity of the population of the red foxes living on Hokkaido Island genotypes of the MHC class II DRB gene were examined for 232 individuals. As a result, 17 novel alleles of DRB exon 2 were identified from the fox es. In addition, it was found that the fox population of southern Hokkaido was genetically differentiated from those of central and eastern Hokkaido, possibly resulting from ecological and geographical isolation in southern Hokkaido. In addition, non- synony mous substitution rates exceeded synonymous substitution rate s in antigen binding sites (ABS) of DRB exon 2, indicat ing that the red fox DRB alleles have evolved under positive selection. The Bayesian phylogenetic analysis with alleles of other canids showed that most DRB alleles in the red fox were grouped into “ fox -like canids clade” , and t hat trans -species polymorphism was evident. This suggests that these alleles have evolved under balancing selection. In Chapter III , genetic structure and population dynamics were investigated for the fox population isolated on Mt. Hakodate . Microsatellite genotypes of fecal samples, which were noninvasively collected from Mt. Hakodate for three years (2009–2011) , were analyzed . Based on successfully obtained genotypes, 35 foxes we re identified as 16 males, 13 females and 6 unknowns . The estimated population sizes were 20 in 2009, 5 in 2010, and 44 in 2011. Fox density in each year was found to be larger than that in rural area s previous ly reported, and t hose in the urban fox of Zurich, Switzerland, which was internationally famous for hig h density. The comparison of genetic distance and structure showed that the Mt. Hakodate population was differentiated from the other Hokkaido populations and strictly isolated by the sea and rural area as geographical barrier . Even small home ranges were overlapped between foxes. The results suggest that the fox population on this mountain has been maintained by the food diversity and abundance of anthropogenic food resource.