Habitat specificity of butterflies along urban environmental gradients in Tama City, Tokyo

摘要

Butterfly assemblages were monitored by transect counts in a riverine area along Tamagawa River (RIV), a residential area on the plain (RES1), a residential area on the hill (RES2), the core area of the city (COR), the Tama Experimental Station of Forestry and Forest Products Research Institute (TES) and Tokyo Metropolitan Sakuragaoka Park (MSP) in Tama City, Tokyo, in 2005. The butterfly assemblages in forest-dominated TES and MSP were more species-rich than those in the other areas. The assemblage in the grassland-dominated RIV was characterized by the highest abundance of individuals. Species richness and abundance were lowest in COR. Ordination of the areas by detrended correspondence analysis placed RIV, MSP and TES in increasing order of scores along axis1, and RES1, RES2 and COR had higher scores along axis2 than RIV, TES and MSP. In axis1, grassland species had low scores and forest species high scores; the two groups were generally separated, coinciding with Tanaka's classification. However, the scores for two forest species, Papilio xuthus and Ypthima argus, were low and those for two grassland species, Potanthus flavus and Anthocharis scolymus, were high, challenging the validity of the classification. Most species recorded in this study were seminatural type, with relatively few natural type species, according to Sunose's classification. Most urban type species occurred in several different habitats and were not specific to highly human-dominated RES1, RES2 and COR.