Ant–fungus mutualism - Wikipedia
The Mutualism between Leaf-Cutting Ants and their Fungus This symposium certainly succeeds in its aims and illustrates the many and. Leafcutter ants cultivate gardens of fungi and bacteria. community-level processes that underlie this important ant-fungus symbiosis. biomass is degraded as it moves through the strata of fungus gardens, the goal of this. The attine ant–fungus agricultural symbiosis evolved over tens of to the farming of fully domesticated cultivars and leaf-cutting, both arising.
One of the more distinguishing factors between these two subgroups is their respective cultivars and cultivar substrates.
Lower attines have less specialized cultivars that more closely resemble Leucocoprineae found in the wild and use "ancestral substrates" composed of plant, wood, arthropod, and flower detritus. The higher attines, on the other hand, use freshly cut grass, leaves, and flowers as their fungi substrate hence the common name "leafcutter ants" and cultivate highly derived fungi.
The fungus Escovopsis is a parasite in ant colonies, and the bacterium Pseudonocardia has a mutualistic relationship with ants. Pseudonocardia resides on the ants' integuments and assists in defending the ants from Escovopsis through the production of secondary metabolites.
The yeast has a negative effect on the bacteria that normally produce antibiotics to kill the parasitic fungus and so may affect the ants' health by allowing the parasite to spread. As she leaves, she takes with her a cluster of mycelium the vegetative portion of the fungus and actually begins a new fungal garden at her resting point using this mycelium.
This grows to become the new fungal farm complete with the genes of the original cultivar preserved for another generation of ants. The relationship between attine ants and the Lepiotaceae fungus is so specialized that in many cases the Lepiotaceae is not even found outside of ant colony nests. It is clear that evolutionary pressure has been exerted on these ants to develop such an organized system in which to feed the fungus and continue its reproduction.
Leaf-cutter ant fungus gardens transform during biomass degradation
Studies done with the concept of the prisoner's dilemma in mind to test what further drives partner fidelity among species have shown that external factors are an even greater driving force. The effects of cheating ants ants who did not bring plant biomass for fungal food had a much smaller effect on the fitness of the relationship than when the fungi cheated by not providing gongylidia.
Symbiotic Processes A worker ant harvesting the fungus who is covered with the powdery white bacteria that helps the fungus stay parasite free. The fungus, ant, bacteria relationship is so special because of the intertwined actions and benefits that they each have. The fungus and the ants depend on each other for survival and one can not live without the other. The ants cultivate the fungus in its colonies from chewed up leaves and at the same time the fungus acts as the main food source for the ants.
Biological Interactions The interaction begins when a queen attine ant leaves her original nest with a chunk of the Lepiotaceae fungus in her mouth, and colonizes a new nest. From there she can lay and the original piece of fungus can begin to be cultivated. To cultivate the fungus, the foraging ants go out and cut chunks out of leaves without ingesting any of the leave's toxic chemicals and bring them to the worker ants in the colony.
Those ants take the leaves, chew them up, and use the pulp as a substrate for the fungus to grow on.
- Leaf-cutter ant fungus gardens transform during biomass degradation
- Leaf Cutter Ants
- Ant–fungus mutualism
This fungus is their main food source. The fungus could not survive without the ants, and the ants cant survive without the fungus.
Leafcutter ants, fungi, and bacteria - microbewiki
But the ants have a special weapon in their arsenal for cultivating the fungi. They use the antibiotic producing actinomycete bacteria, that grows on the ants, as an antibiotic against outside sources of fungi and molds. This is how they keep their nest so clean and disease free. The antibiotic agent discourages the growth of fungi, except the specific fungi that the ants are growing.
This is one reason why this interaction is so interesting, the different partners work specifically with each other in order to form a balanced and well functioning system that has lasted a very long time. Fungi Growth The leaves in the rain forest have toxic qualities in them which is supposed to deter herbivory. But the harvesting ants cut the leaves without ingesting any of the toxins and are able to bring the leaves back to the nest.Where Are the Ants Carrying All Those Leaves? - Deep Look
There the leaves are given to worker ants which chew up the leaves in their mouths into a paste which becomes the food source for the fungus. The plant material is broken down through enzymes that break down the proteins and starches.
Depending on the colony, the enzymes used can be slightly different promoting a complete plant break down or only a plant wall digestion. Because of the symbiotic relationship, the toxins in the leaves are able to be broken down by through enzymes from the fungi into needed sugars and proteins safe for the ant to consume. Bacterial resistance to fungal parasites To maintain a clean and healthy fungus colony, the ants have a bacteria on their exoskeleton which they use when cultivating the fungus.
Some ants have this on their underbelly while ants that are in constant contact with the fungus are almost completely covered with the bacteria. This is an example of the complete evolutionary relationship bewteen the ant, the fungi, and the bacteria.
The ants are able to use the bacteria, Pseudonocardia, with antibiotic qualities to fight against any invasive molds or fungi. This bacteria is similar to the bacterium which produces half the antibiotics made today. The antibiotic qualities allow it to specifically work with the fungus to inhibit the parasitic mold. Unlike the ant, fungi, and bacteria symbiosis, present day antibiotics often produce resistant types of pathogens.
It is thought that the ant colonies do not produce antibiotic resistant molds because of the high diversity of the bacteria and as the two evolve together the parasitic mold will not evolve a resistance. Another method to cultivate only its native strain of Pseudonocardia is that the ant's feces contain incompatibility chemicals which select only for its resident fungus. There are also behavior cues which suggest that the ants physically pick out other types of fungus.
Environmental Implications The millions of ants in the forests have a huge effect on the ecosystem. For such a small organism, it has a huge effect.
Leafcutter ants, fungi, and bacteria
Nitrogen Fixation Like any other garden, the ant's fungus garden needs nitrogen in an available form fit to be used by the microorganisms. Research has showed that the fungus garden in the ants' nest fixes nitrogen. This means that the fungus is taking atmospheric nitrogen and reducing the nitrogen to produce ammonium. Even after the nest uses the nitrogen that it needs, there is still a large amount of available nitrogen that can be entered into the surrounding system.
This replenishes the nutrient poor tropical environment with an essential limiting nutrient Pinto-Tomas, Decomposition The ants cut and collect a huge amount of forest vegetation each year. Needless to say, this has a huge effect on the tropical forest system. The decomposition effect of the ant-fungal-bacterial relationship needs to be considered when assessing the environmental impact of the relationship.
When the plant material is brought to the nest, decomposition is aided by the ants chewing and initially breaking down the material, which can then be used as a substrate for the fungi. This speeds up decomposition in one place that would be spread out around the forest.
Decomposition could also be hindered by the toxic qualities of the leaves leaving them inedible to other macro or micro invertebrates. Decomposition is also aided by the previously mentioned nitrogen fixation process.
Bringing nitrogen into the system helps to decrease the carbon to nitrogen ratio which speeds up the decomposition processes. Niche This is a split side view of an underground chamber where the fungus and the queen is housed. Every new colony starts with a small room like this one,which starts with a queen moving to a new place carrying the fungus in her mouth.
Nest Characteristics Nests begin when a queen ant leaves one nest with a small amount of the fungus in her mouth and moves to a different area to start her own colony.