direct effect

Reduced maternal fecundity of the high Andean perennial herb Alstroemeria umbellata (Alstroemeriaceae) by aphid herbivory

Assessments of the effects of invertebrate herbivores on high-altitude plants have seldom taken into account both mutualistic and antagonistic interactions. To evaluate the effect of herbivores (antagonists) and pollinators (mutualists) on the female reproductive success of the high-Andean perennial herb Alstroemeria umbellata, we separately and simultaneously excluded aphids (herbivores), and bees and bumblebees (pollinators) in a 2×2 factorial design. In flowers with pollinators excluded, aphids did not reduce seed set per flower (i.e., a direct effect).