Effects of Crofton weed Ageratina adenophora on assemblages of Carabidae (Coleoptera) in the Yunnan Province, South China

Abstract Crofton weed ( Ageratina adenophora ) is a highly invasive weed that has spread into several provinces of southern China. This study compares carabid assemblages originating from native pastures with assemblages in Crofton weed dominated communities in the Lancang County, Yunnan Province, to assess how the invasion of this neophyte impacts the community structure of ground-dwelling arthropods. Over a period of 16 months, a total of 1574 carabid beetles representing 28 species were collected at two types of pasture, and 679 carabid beetles representing 34 species at stands of Crofton weed. The most common carabid species, Tetragonoderus arcuatus and Harpalus indicus , were mostly found in the pastures, while four of the five rarest species were present exclusively under Crofton weed. Alpha-diversity and evenness of carabid assemblages were greater under Crofton weed. Three distinct groups of carabid species were separated according to indicator values and a characterization of habitats: habitat generalists, Crofton weed specialists and native pasture specialists. The distribution of carabid species was related to environmental parameters such as depth of litter layer, total phosphorus, height of vegetation, amount of fresh biomass and pH of the soil. According to this study, the invasion of Crofton weed will alter the structure of carabid communities, but will not necessarily reduce the alpha-diversity of carabid assemblages.