The Elements of Evolution (43-15-10) Acacia & Ants

 Acacia & Ants

Bullthorn acacia trees in Central America produce large, swollen thorns at the base of their leaves. Acacia ants are stinging, wasp-like ants that hollow out the thorns and use them as nests.

The bullthorn caters to the ant’s nutritional needs: providing a sugary nectar for adults, and a high-protein liquid for growing larvae. The ants reciprocate by defending the tree.

A climbing vine will be met by vigorous chewing of its tendrils by the ants, defeating its advance. A competing plant near the acacia is dealt with similarly: its leaves nipped off by ant bites, hence hastening the plant’s demise.

The protective ants are alerted to nearby landing of any leaf-grazing insects by vibration. Their stings and bites persuade an intruder to graze elsewhere.

Vigilance is not the only benefit that bullthorns get from acacia ants. The ants’ microbiome includes bacteria that synthesize antifungal compounds.

The ants very presence on the trees keeps parasitic fungal growth in check. Thus, the ants act as an immune system agent for the bullthorn.