A comparison of the diversity and structure of butterfly communities in semi-natural and human-modified grassland habitats at the foot of Mt. Fuji, central Japan

To examine the effects of human land use and disturbance on butterfly communities we compared the diversity and structure of communities in relatively undisturbed, semi-natural grassland habitats and highly disturbed, human-modified ones. Comparisons were based on transect counts conducted at 6 study sites at the foot of Mt. Fuji in the cool temperate zone of central Japan during 1995. Out of the six community parameters used in the analyses, the species richness, species diversities H' and 1/lambda, and dominance indices were significantly different between the two habitat types stated above. That is, butterfly communities in semi-natural habitats had higher species richness and diversity, and lower dominance indices than those in human-modified ones. This suggests that heavy land modification and disturbance to semi-natural habitats change greatly its butterfly community structure, which, indeed, leads to decreasing species richness and diversity mainly due to the loss of species that are confined to semi-natural habitats. Through the comparisons of various species' characteristics, it was found that the species confined to semi-natural habitats had lower population abundance, fewer generations per year, more restricted local distributions, and narrower geographic range size in Japan than the other component species. Based on our results, it is critical that the persistence of the species that are limited to semi-natural habitats be ensured in order to maintain high species richness and diversity in grassland butterfly communities. Thus, conservation plans that retain as much semi-natural habitat as possible within the process of human grassland use, development, and modification are needed.