Slide 1
Some ants exchange protection for aphid honeydew
Some ants collect honeydew produced by aphids. In return, the ants can defend aphids against predators or disturbances on the plant.
More to Read
Honeydew comes from the aphid's sap-feeding diet. Plant sap contains more sugar than aphids need compared with other nutrients, so aphids excrete a sweet liquid that other insects can use.
Slide 2
Driving predators away helps the aphids survive
An ant attending aphids may drive away an approaching predator. The aphids gain a benefit from an animal that is gathering food for itself.
More to Read
Mutualism is an interaction in which both species benefit, not a friendship or planned agreement. It can persist because each species' behaviour improves its own access to resources or its chance of survival.
Slide 3
The plant can bear the cost of this partnership
Aphids feed on a plant while ants protect them. A partnership beneficial to two animals can have costs for a third organism.
More to Read
More surviving sap feeders can increase pressure on the host plant. Describing an interaction as beneficial therefore requires naming whose outcome is being discussed rather than calling the whole arrangement good.
Slide 4
The association depends on species and conditions
Not all ants tend aphids, and not every aphid colony receives protection. Species and local conditions influence whether an association forms.
More to Read
The availability of alternative food can change an ant's interest in honeydew. Mutualistic outcomes depend on context, so observing attendance once does not establish a permanent obligation between species.
Slide 5
Plant sap, food and predation meet on one stem
An ant walking among aphids connects plant sap, insect nutrition and predation. Several ecological relationships meet on a single stem.
More to Read
Following the source and destination of resources reveals the network. The same ant may be a protector in one encounter and a predator in another without changing its species identity.
Sources
- Mutualism: Eight examples
Natural History Museum
- Paying Attention to Aphids
University of Cambridge