Arthropods and plant invasions: a systematic review, case study, and methods contrast

The primary objective of this program of study is to explore the relationship between invasive plants and arthropods and the importance of arthropods as bioindicators of environmental change. This thesis provides a systematic review of the literature on arthropod communities in association with invasive plants, then quantifies these effects with a case-study involving the plant invader Centaurea stoebe, and finally contrasts two arthropod sampling methods, sweep netting and pan trapping in a grassland system. The majority of arthropod-invasive plant literature is relatively simple, documenting the herbivore feeding guild in only the invaded region, as opposed to 2 or more trophic levels in both the invaded and native region. In grassland systems invaded by C. stoebe, overall arthropod abundance was reduced compared to uninvaded areas, though different trophic groups responded differently to invasion: native herbivores and omnivores negatively, and predators, detritivores, and biological control herbivores positively, likely through both direct and indirect mechanisms. For community-scale arthropod surveys in impacted grassland systems, a combination of sweep netting and pan trapping is recommended to adequately capture most arthropod groups, however, bees, which are important bioindicator organisms, are well represented in pan trap captures alone. Future studies of invasive plants would benefit from multi-trophic arthropod surveys to elucidate broad-scale patterns before finer resolution, taxon specific studies occur. Arthropods are key ecosystem components and quickly mirror the effects of environmental disturbance, making them valuable bioindicators.