Abundance of sap-feeding generalist herbivores on mahogany (<i>Swietenia macrophylla</i>) plants with artificially reduced or ambient (control) ant abundances, across two levels of tree species diversity (mahogany monocultures and polycultures of four tree species, including mahogany), in a tree diversity experiment in southern Mexico.

<p>Values are means ± S.E. We found negative effects of ants on sap feeders at low diversity (F_{1, 17} = 5.7, P = 0.01), but not at high diversity (F_{1, 17} = 0.63, P = 0.42), whereas effects of diversity were significant under ambient (control) ant densities (F_{1, 17} = 10.23, P = 0.001) but not under ant-reduced conditions (F_{1, 17} = 1.52, P = 0.21). Statistics are based upon a posteriori contrasts.