Mosaic of various serai stages of vegetation in the Satoyama, the traditional rural landscape of Japan as an important habitat for butterflies

摘要

Assemblage structures of butterflies were studied by the transect count method in Farm and Coppice landscapes in a Satoyama, the traditional rural landscape of Japan, around Mt Mikusa in northern Osaka, central Japan from April to October, 2004. Transects in Farm and Coppice landscapes were classified into three and six landscape components, respectively, according to vegetation and landscape. To analyze characteristics of butterfly assemblage structures in the Satoyama, the serai rank of each butterfly was determined based on serai stages in which the main larval food plants occur, and compositions of each serai rank species were compared among landscapes and landscape components. A total of 1322 individuals belonging to 56 species from seven families were recorded throughout the whole study area. Both species richness and density of butterflies were higher in Coppice landscape (46 and 20.4 respectively) than in Farm landscape (39 and 13.1 respectively), while species diversity (1-A) and evenness(J') were higher in Farm landscape (0.91 and 0.75 respectively) than in Coppice landscape (0.85 and 0.66 respectively). Coppice landscape and the whole study area were characterized by the dominance of three dwarf bamboo feeders, Lethe diana, L. sicelisand Neope goschkevitschii. In addition, both species richness and densities of univoltine butterflies including grass, violet and deciduous oak tree feeders were abundant in Coppice landscape. Analysis based on the SR index revealed that species richnessand densities of butterflies dependent on plants occuring in young forests and deciduous broad-leaved forests as larval foods were high in Coppice landscape, whereas those dependent on plants occuring in short to tall grasslands were high in Farm landscape. On the other hand, some species of intermediate rank showed a wide range of distribution in Farm and Coppice landscapes in the study area. The results demonstrate that butterflies dependent on plants in wide ranges of serai stages of vegetation inhabit Satoyama. The mosaic structure of vegetation in terms of the serai stage is important for conservation of species diversities of butterflies in Satoyama.