A comparison of diversity and composition of carabid beetles between overpasses and underpasses in fragmented forest areas

Abstract

Wildlife crossing structures are important for increasing biodiversity of wildlife and other animals. Thus, the objective of this study was to compare the community structure of carabid beetles along environmental transects of forest–edge–crossing structures in fragmented forest areas. In addition, we also investigated whether there were differences in carabid beetle assemblages due to structural differences in crossing structures, i.e., overpass and underpass. A total of 3,737 carabid beetles belonging to 60 species were collected by pitfall trapping across environmental transects from June 6 to September 3, 2015. In crossing structures, environmental variables, such as soil texture, soil organic matters, and habitat structures were different from those in neighboring habitats. Abundance and species richness of carabid beetles in underpasses were significantly lower than those in neighboring habitats and overpasses. In particular, underpasses, especially those with more artificial structures in terms of soil properties and microhabitat, appeared to be less appropriate structures for movement of carabid beetles. Although less carabid beetle species were caught in crossing structures, species composition of carabid beetles were more similar to forest areas. In conclusion, efforts are needed to improve the connectivity of habitats and consider the needs of invertebrates by providing suitable microhabitats for wildlife crossing structures.