Ants on an Acacia in Uganda
Plant-animal interactions are very common, and a very obvious relationship in nature. Everybody, at some point or the other, would have seen insects pollinating flowers in return for the nectar, the most popular example of plant-animal interactions. There are many examples of symbiotic relationships between plant and animal, another common example being seed dispersal in forests. There is a strong possibility that most people would have seen ants crawling around tree trunks, scampering into holes they use as nests. It would seem that this would harm the tree as the ants would bore into the wood and cause damage to the plant. On the contrary, the numerous ants provide services to the tree in return for a place to raise their young and tend their queen and also in some cases, in return for food as well.Plants that harbor colonies of ants are called
myrmecophytes, and they have evolved hollow bulges, stems, roots or thorny structures that give ample room for a colony of ants to set up home. In return for the being allowed to live on a particular tree, ants provide security to the plant they live on. They keep away herbivores and other insects as well that would feed on the leaves and also cause extensive damage to neighboring plants trying to establish themselves that may be a competitor for the resources available, like soil nutrients and sunlight.
- Ants sipping Acacia nectar
There are many species of trees that are associated with their own guardian species of ant. The most common examples if ant-tree symbiosis is found between the Acacia trees and some species of ants. Some species of swollen thorn acacias do not have chemical defenses, like alkaloids, in their leaves and shoots to protect them from being grazed by insects and herbivores. The bullhorn acacia, found in Mexico and other part of Central America, houses a stinging ant (Pseudomyrmex ferruginea) that protects it and in return the tree provides the ants with protein-lipid Beltian bodies and carbohydrate rich nectar. The whistling thorn acacia of Kenya has bulbous thorns that harbor another stinging ant species of the genus Crematogaster. The ants hollow out the interior of the thorns to make room for living quarters. These ants deter any browsing by giraffes and other herbivores. Another type of tree that has mutualistic relationships with ants is the Cecropia tree, a member of mulberry family. The stems are usually soft and hollow allowing the Azteca ants to burrow in. The ants also feed on some of the insects that browse on the leaves of the Cercopia.Ants are known to be excellent engineers, they excavate the bulbs and thorns in such a way as to not leave scars called galls. But in the Amazonian rainforests, it has recently been discovered that if ants run out of room on the host tree, they are burrowing into neighboring non-myrmecophytes. By doing so, they are scarring the trees, leaving large galls or scars.
Posted in Ecology Tagged: Acacia, ant-tree symbiosis, ants, Cecropia, mutualism, plant-animal interactions
