While top-down control plays an important role in shaping both natural and
agricultural food webs, we lack insights into how top-down control effects
vary across spatial scales. We used a multi-scale survey of top-down
control of coffee pests and diseases by arboreal ants to examine if colony
location creates a small-scale mosaic in top-down control around trees and
if the strength of that control varies between sites at the landscape
scale. We investigated pest and disease levels on coffee shrubs at
different distances from shade trees with and without a Crematogaster spp.
ant colony in 59 sites along a coffee management intensity
gradient in southwestern Ethiopia. Within sites, ants significantly
suppressed herbivory and coffee leaf rust at distances less than 10 meters
from nesting trees. Top-down control varied between sites, with stronger
top-down control of free-feeding herbivory near ant colonies at sites with
lower management intensity and stronger top-down control of a skeletonizer
at sites with higher canopy cover. We conclude that the strength of
top-down control by ants is highly heterogeneous across spatial scales, as
a consequence of the biology of the predator at the small scale and
herbivore density or changes in herbivore-ant interactions at the
landscape scale. See Stüber et al. See ReadMe_Stuber_etal_Ecology2021.docx