Host plant richness and abundance drive populations of a super-generalist xylem-feeding insect - Raw data

Due to their wide diet breadth, generalist herbivores are often less
sensitive to bottom-up forces compared to specialists. Despite this, some
generalist insects can be significantly affected by the diversity and
structure of the plant communities. Here, we investigated the effect of
habitat and plant richness on the abundance of the super-generalist meadow
spittlebug, Philaenus spumarius (Hemiptera: Aphrophoridae). We sampled 93
sites representing four habitat types (olive groves, vineyards, meadows,
and field margins) across eight heterogeneous agricultural landscapes in
central Italy. Nymphs were sampled by quadrat sampling in April along with
the herbaceous vegetation community, while adults were sampled using a
sweep net in June, August, and October. Nymph abundance was positively
associated with plant richness and vegetation cover at a small scale (2
m2), a scale consistent with the limited movement capability of nymphs,
while it did not differ between habitat types. A positive correlation
between adult and juvenile densities was also observed. However, this
effect weakened towards the end of the growing season. The findings
indicate that bottom-up effects associated with plant community
composition can significantly influence the local abundance of a
super-generalist xylem-feeding insect. The positive relationship between
plant species richness and nymph abundance suggests that broad host use
does not necessarily buffer P. spumarius from local vegetation effects.
Furthermore, the marked weakening of the juvenile–adult abundance
relationship is consistent with increased dispersal activity happening in
the fall in our study area. Given that P. spumarius exhibits variation in
host use and population dynamics across its geographic range, the strength
of bottom-up effects in this species, as well as its dispersal patterns,
are likely context-dependent and may vary across environmental and
geographical settings.