Invertebrate community turnover following control of an invasive weed

Invasive plants are a significant threat to native biodiversity as they change community structure and ecosystem processes. However, little is known about the impact of invasive plant control on the terrestrial invertebrate community and the subsequent changes in habitat. We investigated the response of wetland invertebrates to the chemical control of an introduced tree, grey willow (Salix cinerea), in a before-after-control-impact (BACI) experiment within a New Zealand wetland over four years. Unexpectedly, our findings suggest that chemical control of grey willow resulted in significant increases in the abundance of invertebrates one- and two-years after herbicide application. More specific examination of the beetle communities revealed the abundance and species richness of herbivorous and predacious beetles, the abundance of introduced and unknown species, and the species richness of native and introduced species were all significantly higher in the herbicide treated plots than the unsprayed plots one and two-years after control. In addition, the composition of the beetle community separated into two clear groups – plots before spray/no spray and plots one- and two-years after herbicide application. These changes appear to be driven by changes in vegetation, associated with the death of grey willow trees and the influx of introduced plant species, predominantly weedy annuals and perennials, after willow control. Restoration via invasive plant control can promote the reestablishment of invertebrate communities typical of native wetlands but is likely to depend on the reinvasion of grey willow.