Plant size, latitude, and phylogeny explain within-population variability in herbivory

Interactions between plants and herbivores are central in most ecosystems,
but their strength is highly variable. The amount of variability within a
system is thought to influence most aspects of plant-herbivore biology,
from ecological stability to plant defense evolution. Our understanding of
what influences variability, however, is limited by sparse data. We
collected standardized surveys of herbivory for 503 plant species at 790
sites across 116° of latitude. With these data, we show that
within-population variability in herbivory increases with latitude,
decreases with plant size, and is phylogenetically structured. Differences
in the magnitude of variability are thus central to how plant-herbivore
biology varies across macroscale gradients. We argue that increased focus
on interaction variability will advance understanding of patterns of life
on Earth.