Aliens in the Anthropocene: Invasive plants as a driver of global insect decline

Insect diversity is declining on a global scale with consequences for the resilience of ecosystem services and biodiversity at higher trophic levels. Although multiple factors contribute to global insects decline, biological invasions, particularly the introduction of non-native plants, are not so well documented. We provide a review of literature exploring the impacts of plant invasion on insects and other arthropods and how these mechanisms contribute to declines in both insects and related arthropods. We report that, generally, invasive plants have detrimental effects on native insect herbivores, as well as the predators and parasitoids that depend on them. Plant-feeding insects are particularly vulnerable if the species exhibit narrow diet breadth or lacks evolutionary experience with its novel host. Pollinator insects may exhibit similar patterns to herbivorous insects due to lack of evolutionary experience or phenological mismatch. Although predatory insect response is dependent on response of their prey, changes in plant structure associated with plant invasion may also impede movement, foraging, and predation success. Litter-feeding insects may be more variable in their response to plant invasion, either benefitting from a novel but abundant resource or declining as a result of changes in litter or soil chemistry. Insect and other arthropods fill diverse functional roles and changes resulting from invasive plants can have widespread and compounding effects at multiple scales. Improving our understanding about insect functional groups can guide restoration and management efforts to mitigate biodiversity loss, ecosystem function, and resources for both humans and wildlife.