Acacias are some of the most ubiquitous trees in the Neotropical dry forest. We have collected several acacia species at Las Baulas National Park, some of which exhibit remarkable plant-ant interactions. The trees provide the ants with room and board and the ants provide protection for the plant.

Acacia trees: A) yellow Beltian bodies on young leaflet tips; B) inflorescence; C) extrafloral nectaries on petiole, swollen thorn, and ant; D) swollen thorn and ant.

Ant acacias have swollen, hollow thorns in which the ants live. The queen drills a hole in the thorn to gain access. The acacia also provides the ants with two types of food: sugary nectar from extrafloral nectarines at the base of petiole and protein in the form of Beltian bodies that are produced at the tips of new leaflets. In exchange, the ants protect the tree from herbivores by attacking any animal that comes in contact with the plant. They also attack other plants that touch or grow too near their acacia. They trim encroaching branches from neighboring trees and shrubs and cut down any herbaceous plants or seedlings that grow under the acacia. This is one of the most intricate and well-studied mutualistic relationships in nature.