Data from: Intraspecific plant chemodiversity at plot level has contrasting effects on arthropod functional groups

Plant chemistry mediates interactions between plants and their
environment. While intraspecific chemodiversity at the individual plant
level is well-studied, the effects of chemodiversity at the plant
community level on arthropod interactions need more attention. We
conducted a field experiment to test how intraspecific chemodiversity
affects plant-arthropod interactions. We manipulated plots of Tanacetum
vulgare L., varying in chemotype richness and composition, and monitored
four arthropod functional groups (herbivores, flower visitors, predators,
and ants) over three seasons. We hypothesized that higher plot-level
chemotype richness would enhance occurrence across all studied arthropod
groups but have functional group-specific effects on abundance, resulting
in reduced herbivore and ant abundance and increased flower visitor and
predator abundance with increased chemotype richness. Using mixed models,
we found that increasing plot-level chemotype richness had a limited
effect on most arthropod group occurrences but led to significant changes
in abundance. Increasing chemotype richness decreased herbivore abundance,
while it increased flower visitor abundance. Predatory arthropods and ants
remained largely unaffected. Furthermore, we found that the presence of
specific plant chemotypes within a plot had variable effects for
herbivores across years, as some chemotypes initially promoted higher
abundances but were associated with lower abundances in the later years.
We also found that the presence of specific chemotypes had a positive
effect on the abundances of various flower visitor taxa. Predators and
ants, on the other hand, showed weaker and more variable responses to
specific chemotypes. Specifically, higher chemotype richness reduced the
abundance of herbivores such as Uroleucon tanaceti (2022 and 2023) and
Brachycaudus cardui (2023), while increasing visitation by flower
visitors. These results highlight the role of plant chemodiversity in
shaping insect communities and influencing ecosystem dynamics.