Landscape versus local factors shaping butterfly communities in fragmented landscapes: Does host plant diversity matter?

Conversion of terrestrial land for the purposes of agriculture and urban development continues to result in loss and fragmentation of natural habitats. In this study, we focus on butterflies and investigate the relative importance of landscape-level habitat amount (the proportion of woodland area within a landscape), habitat fragmentation (length of woodland edges within a landscape), urbanization (the proportion of urban area within a landscape), and local host plant diversity for butterfly communities in a fragmented landscape in Hokkaido, northern Japan. Butterfly species observed in the field were grouped into woodland and open-land species. The results showed that both landscape and local factors shape the butterfly community. At a landscape-scale, woodland butterflies positively responded to woodland area and negatively to edge density, whereas open-land butterflies showed opposite responses. At a local-scale, positive influences of local host plant diversity on woodland butterflies were evident, but not for open-land species. These results suggest that negative influences of anthropogenic land-use changes on biodiversity could be mitigated by strategies aimed at stopping the spread of woodland edges and providing a wide variety of different host plant species in the landscape. Unfortunately, this study implies that further increases in habitat loss and fragmentation and decline in host plant diversity lead to a homogenization of local biological communities and functions.