Host plant richness and abundance drive populations of a super‐generalist xylem‐feeding insect

Due to their wide diet breadth, generalist herbivores are often less sensitive tobottom-up forces compared to specialists. Despite this, some generalist insects canbe significantly affected by the diversity and structure of the plant communities.Here, we investigated the effect of habitat and plant richness on the abundance ofthe super-generalist meadow spittlebug, Philaenus spumarius (Hemiptera: Aphro-phoridae), at both juvenile and adult stages. We sampled 93 sites representing four habitat types (olive groves, vineyards,meadows and field margins) across eight heterogeneous agricultural landscapes incentral Italy. Nymphs were sampled by quadrat sampling in April along with the her-baceous vegetation community, while adults were sampled using a sweep net inJune, August and October. Nymph abundance was positively associated with plant species richness and vege-tation cover at a small scale (2 m 2), a scale consistent with the limited movementcapability of nymphs, while it did not differ between habitat types. A positive corre-lation between adult and juvenile densities was also observed. However, this effectweakened towards the end of the growing season. The findings indicate that bottom-up effects associated with plant community com-position can significantly influence the local abundance of a super-generalist xylem-feeding insect. The positive relationship between plant species richness and nymphabundance suggests that broad host use does not necessarily buffer P. spumariusagainst local vegetation effects. Furthermore, the marked weakening of the juvenile–adult abundance relationship is consistent with increased dispersal of adults in thefall. Given that P. spumarius exhibits variability in host use and population dynamicsacross its distribution range, the strength of these bottom-up effects, as well as itsdispersal patterns, is likely context dependent and may vary across environmentaland geographical gradients