Acacia Ants - Marietta College
The acacia tree (actually several species of Acacia) we saw at Santa Rosa National tree is its tendency to form symbiotic, mutualistic relationships with ants. Several species of acacia like Acacia cornigera, Acacia collinsii, and Acacia drepanolobium have a symbiotic relationship with the ants (like Pseudomyrmex. This month's mutualism is the relationship between the whistling-thorn Acacia drepanolobium and its body guard ants which protect it from the.
Acacias also bear formidable thorns to deter mammalian predators. Despite the thorns, herbivores such as giraffes feed routinely on acacias; in fact when giraffes were first brought to The Wilds in the 's I was struck by how quickly they began browsing on the locust trees locusts being a thorn-bearing Acacia relative.
One of the more interesting aspects of the Acacia tree is its tendency to form symbiotic, mutualistic relationships with ants. This happens in both the Americas and in Africa and perhaps in other areas as well. In Costa Rica, the association is usually with ants of the genus Pseudomyrmex. The Ants and the Symbiosis Left: The Acacia tree provides the ants with sugars, protein and a nesting site.
You can see two of those benefits in this picture.
The enlarged thorns are hollow - the ants need only chew an entrance hole to gain access to the hollow inside of the thorn, which they can then raise their young in. A colony of ants on a tree may occupy many such thorns. The other lure for the ants are nectaries; these glands have a little depression that fills with tree sap, a good source of sugar and water, something which should not be ignored in a tropical seasonal forest during the dry season.
Here is another view of a nectary. To fulfill the protein needs of the ants, the tree also provides protein-rich Beltian Bodies, particularly on the tips of newly developed leaves. These bodies serve no function for the plant, but they do help complete the nutritional needs of the ants which also derive nutrition from insects that they kill on the acacia. Some recent studies from Africa where the trees don't provide the Beltian bodies show an interesting effect.
The ants protect the tree from herbivores too. When the herbivores try to eat the leaves of the acacia, they cause the branches of the tree to move, this acts as a signal to the ants living in the domatia. The ants quickly reach the herbivore who is trying consume the leaves, and start stinging it.
Mutualistic Relationship Between Trees and Ants | Ask A Biologist
After some resistance, the herbivore gives up, and leaves the tree alone. In addition to this, the ants also eliminate any plants that try to grow on, or near the acacia, hence the acacia does not need to compete for resources.
Special Features of the Acacia-Ant Relationship The relationship between the acacia and the ant is characterized by the interesting features mentioned below: Possessiveness of the Ants The acacia and the ants share such a close bond that, as time goes by, the ants become very possessive about the tree on which they dwell.
They also attack other species of ants which try to occupy the tree. Distinct groups of ants usually compete for the acacia. Manipulation by the Acacia The ants attack all the insects which try to feed on the acacia, but it does not harm the pollinators. According to Wilmer and Stone, the young blossoms of the acacia make a repellent which does not allow the ants to patrol on them. It is believed that this repellent is ineffective once the pollination is over, and thus the ants can move freely on the flowers after the pollination is complete.
There are many examples of symbiosis in nature, but very few are as interesting as the relationship between acacia tree and ants. Scientists at the Max Planck Institute for Chemical Ecology have now looked more deeply into the insect-plant interaction, asking whether the tiny bodyguards also provide protection against microbial pathogens.
- Trees Get By with Ant Aides
- Ants protect acacia plants against pathogens
They compared the leaves of acacia plants which were inhabited by either mutualistic or parasitic ants to leaves from which ants had been removed.
Intriguingly, the leaves of acacia colonized by parasitic ants showed more leaf damage from herbivores and microbial pathogens than did the leaves that had mutualistic ants. Analysis of the surfaces of the leaves revealed that the number of plant pathogens as well as of necrotic plant tissues increased considerably when mutualistic Pseudomyrmex ferrugineus ants were absent. These plants also showed strong immune responses in the form of an increased concentration of salicylic acid, a plant hormone which regulates defence against pathogens.
Relationship Between Acacia Tree and Ants
Detailed analysis of the bacterial composition on the surfaces of the leaves suggested that the presence of mutualistic ants changed the bacterial populations and reduced harmful pathogens. Although far less pronounced, this effect could also be observed in parasitic ants.
Pseudomyrmex ferrugineus protects the Acacia with its bacteria from pathogens.