The accumulation of novel Anthropocene insect communities on native and non-native plants

Human-mediated ecosystem alteration and the creation of novel habitats are defining features of the Anthropocene. Understanding more about the ecological and evolutionary ‘rules’ that govern the accumulation of native species in novel habitats is essential for conservation, whilst determining how non-native species associate with novel habitats is vital to prevent the spread of harmful invasive species across the globe. I propose that non-native plants introduced to Great Britain represent analogues of novel anthropogenic habitats for insects and mites. Non-native plants are an ideal model system as they are widespread, important ecologically, and it is possible to capture their distinctiveness (degree of novelty) effectively with a single quantifiable metric (phylogenetic isolation). I demonstrate that non-native plants typically host less rich and abundant insect communities, although richness and abundance are increased on plants with large geographic ranges, an increased time since introduction, and/or phylogenetic proximity to native plants. Non-native insects are strongly associated with non-native plants, particularly those that are phylogenetically distinctive, which may facilitate the spread of harmful invasive species. Importantly, some non-native plants have the potential to support native insects, as they are associated with similar or even higher levels of insect biodiversity than native plants, and host rare native insect species in the absence of their original native hosts. Thus, mixed plant communities (composed of both native and non-native plants) accumulate insect diversity at similar, or even increased, rates compared with native-only communities. This suggests that non-native plants may contribute to, and potentially maintain, broader-scale (assemblage) diversity in regions that contain mixtures of native and non-native plants. Overall, my work indicates that non-native plants/novel habitats have a real potential to support native biodiversity in an increasingly modified world, although we must be cautious of ecosystem disservices, such as the spread of invasive species and the loss of pre-existing habitats.