A lot of plants produce nectar, either floral nectar or extrafloral nectar. Extrafloral nectar is notably supposed to have evolved as an plant indirect defense mechanism, that allows attracting "defenders" against pests, these defenders being predators, parasitoids, and/or ants. Extrafloral nectar presence has been successfully linked to enhanced natural enemy recruitment, reduced pest pressure, and increased plant fitness.
However, ants are also implied in mutualistic relationships with aphids and are known to defend them against their natural enemies such as predators or parasitoids.
So it seems that in the case of aphid-infested plants, nectar production could both attract "plant defenders" (predators, parasitoids), as well as "pest defenders" (ants). This could lead to opposite effects on plant fitness.
What are the ecological consequences of this multi-trophic interaction ? Do we have any clue about its outcome on the different trophic levels ?