Ant-aphid mutualism

Definition

A facultative or obligate mutualistic interaction in which ants (Formicidae) tend colonies of aphids (Aphididae), receiving carbohydrate-rich honeydew excreted by the aphids in exchange for protection from predators, parasitoids, and fungal pathogens, plus sometimes transport to fresh host plants. The relationship ranges from loose facultative associations to highly specialized obligate partnerships with morphological and behavioral adaptations in both partners.

Etymology

From ant (Old English æmette) + aphid (from Latin aphis, coined by Linnaeus) + mutualism (from Latin mutuus, reciprocal)

Example

Lasius neoniger workers aggressively defend colonies of Aphis fabae on broad bean plants, consuming honeydew droplets as they are excreted and attacking approaching lacewing larvae and parasitoid wasps; in some populations, these ants also excavate soil to root-shoot aphids and carry them to uninfested leaves, effectively farming their partners.

Synonyms

• ant-aphid symbiosis
• trophobiosis (broader, includes other hemipterans)

Related Terms

• Trophobiosis
• myrmecophily
• honeydew
• extrafloral nectary
• mutualism
• facultative mutualism
• obligate mutualism
• herding behavior
• tending behavior

Usage Notes

Distinguished from trophobiosis, which encompasses ant-hemipteran mutualisms broadly (scale insects, mealybugs, treehoppers, etc.). The term is sometimes used loosely for any ant-aphid interaction, but specialists reserve 'mutualism' for demonstrably reciprocal fitness benefits; some ant-aphid associations are exploitative or parasitic rather than mutualistic. Ant species vary from generalist tenders to specialists that rely almost exclusively on honeydew and actively manipulate aphid colonies. The aphid partner may become less mobile, lose defensive cornicles, or alter honeydew composition under strong ant attendance.