Symbiosis between ants and Acacia

The tree provides hollow spines to house the ants which defend it.
The tree provides hollow spines to house the ants which defend it.

In Carara National Park, Costa Rica, we found numerous Acacia trees with their Peudomyrmex ant defenders.  It is a classic model of mutualism, where species interaction over evolutionary time result in the interaction we see today. Each partner in this model provides benefits to its partner and obtains benefits in return. The ant’s have a nasty sting for any animals browsing on the Acacia leaves and so they defend their host. The acacias offer these large spines which new ant queens nibble into, lay eggs, and start new colonies.

Read more:
Janzen, D.H. 1966. Coevolution of mutualism between ants and acacias in Central America. Evolution 20(3):249–275.doi:10.2307/2406628.