Data from: How generalist herbivores exploit belowground plant diversity in temperate grasslands

Belowground herbivores impact plant performance, thereby inducing changes
in plant community composition, which potentially leads to cascading
effects onto higher trophic levels and ecosystem processes and
productivity. Amongst soil-living insects, external root-chewing
generalist herbivores have the strongest impact on plants. However, the
lack of knowledge on their feeding behaviour under field conditions
considerably hampers achieving a comprehensive understanding of how they
affect plant communities. Here, we address this gap of knowledge by
investigating the feeding behaviour of Agriotes click beetle larvae, which
are common generalist external root-chewers in temperate grassland soils.
Utilizing diagnostic multiplex PCR to assess the larval diet, we examined
the seasonal patterns in feeding activity, putative preferences for
specific plant taxa, and whether species identity and larval instar
affects food choices of the herbivores. Contrary to our hypothesis, most
of the larvae were feeding-active throughout the entire vegetation period,
indicating that the grassland plants are subjected to constant belowground
feeding pressure. Feeding was selective, with members of Plantaginaceae
and Asteraceae being preferred; Apiaceae were avoided. Poaceae, although
assumed to be most preferred, had an intermediate position. The food
preferences exhibited seasonal changes, indicating a fluctuation in plant
traits important for wireworm feeding choice. Species- and instar-specific
differences in dietary choice of the Agriotes larvae were small,
suggesting that species and larval instars occupy the same trophic niche.
According to the current findings, the food choice of these larvae is
primarily driven by plant identity, exhibiting seasonal changes. This
needs to be considered when analysing soil herbivore-plant interactions.