Supplementary Methods 1: Evaluate herbivore biomass in the field
survey
We used herbivore biomass to represent herbivore pressure (Allen et al.,
2021) as higher herbivore abundance may not always translate to greater
herbivore damage if feeding by particular herbivore species is
relatively minor (e.g., aphids and beetles) or extensive (e.g., larvae).
To determine whether the herbivore biomass correlated with leaf damage,
we checked all leaves and recorded the number of each herbivore species
on each non-native plant. We classified observed herbivores into five
orders (nine categories), including Lepidoptera (larvae), Orthopter,
Thysanoptera, Hemiptera (leafhoppers, stinkbugs, whiteflies, and
aphids), and Coleoptera (beetles and herbivorous ladybirds) since some
larvae were difficult to identify to species. A total of 20,723 insects
on non-native plants were counted (Native plants were not measured as
these measurements were primarily to correlate damage to insect
biomass). Then, we evaluated herbivore biomass on each plant by
multiplying abundance and mean herbivore biomass of each category and
then summing herbivore biomass of all categories. To obtain the mean
biomass of each herbivore category, we carried out a field survey at
eight sites in 2019. We collected all herbivores on non-native species,
stored them in plastic tubes with leaves of host plants and determined
the fresh weight of individual insects to the nearest 0.01g in the lab.
The mean biomass of each herbivore category was as follows: Lepidoptera,
0.25 g/ individual; Orthoptera, 0.45 g/ individual; Thysanoptera,
0.01g/30 individuals; leafhopper, 0.03g/ individual; stinkbug, 0.19 g/
individual; whitefly, 0.01 g/30 individuals; aphid, 0.01 g/5
individuals; leaf beetle, 0.05 g/ individual; ladybird, 0.04 g/
individual.