Cooperation, conflict, and coevolution in the attine ant-fungus symbiosis . Foundress queen mortality and early colony growth of the leafcutter ant, Atta texana. After establishing that staphylae size in leaf-cutting ant fungi has increased enzymes that the ants need for their functions in the mutualism. Leafcutter ants are in a symbiotic relationship with the fungus they farm. . Your Inner Fish, which unfortunately I don't have with me to quote.
The antibiotic qualities allow it to specifically work with the fungus to inhibit the parasitic mold.
Leafcutter ants, fungi, and bacteria
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.
- Leaf Cutter Ants
- Leafcutter ant
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.
Once a nest becomes established, the colonies can grow to have millions of ants in them. These subterranean nests vary in sizes. They can be small with a single fungus growing "room" or can be multiple feet below ground with many different rooms and complex tunnels.
Ants are also known as organized and clean insects. They have certain refuse dumps where the worker ants take the garbage and seclude it from the rest of the colony to decrease contamination.
Major Players There are a total of five major players that interact with the leafcutter ants. There are the attine ants, their cultivated Lepiotaceae fungi, the parasitic fungal escovopsis parasites that feed on the cultivated fungi, and the latest partner; the black yeast found on the ants to help rid the colony of antagonistic invaders.
Ants The group of ants that are LeafCutters belong to the tribe attini and their genera is Atta and acromyrmex These ants have been around for the better part of 50 million years. Interestingly, these ants are consume the largest amount of primary producers in the tropical rainforest areas which is not surprising considering their biomass is four times the amount of other invertebrates.
Leafcutter ant - Wikipedia
World wide, these insects take up a third of the total insect biomass. Fungi Playing the role of both a decomposer and the primary food source for the Leafcutters, the fungi from the family Lepiotaceae is grown underground in the nests chambers by the worker ants. Other types of fungi can creep into the system, but are taken care of by the ants and are not allowed to keep surviving in the system.
Bacteria Actinomycete bacteria are found in the underbellies of the worker ants. If the ants are in often close contact with the fungus, they tend to have more bacteria on them. This is because the bacteria has a special property that acts as antibiotic against other molds and fungi, except the ants' food source, the Lepiotaceae fungus.
Parasites Battling against the ant's seemingly clean fungis' agriculture are parasites that would quickly take over the colony's fungus growth if not carefully weeded against.
These can be competing molds or funguses that would come along and compete with the fungi for the delicious broken down vegetation.
The ant's fungi cant survive against the invaders. Some of these parasites are refered to as escovopsis, and would feed on the fungus Reynolds, Black Yeasts There has recently been research conducted on a fourth fungal partner. One of the most interesting and only recently discovered partners is the antibiotic producing fungi Ascomycota; Phialophora. This is a black yeast that can be found on the cuticle of the ant and is used in a similar fashion in discouraging parasitic growth.
This yeast has evolved with the ant-fungi symbiotic relationship and according to Little et al, the research into this partner shows how complicated and sophisticated this symbiotic partnership can be Little, The fungus is prevalent in different geographical areas with the attine ants, and therefore the researchers concluded that the fungus is indeed a fourth symbiotic partner within the fungus, ant, bacterial mutualistic relationship Little, Current Research Coevolution between attine ants and actinomycete bacteria It has been the thought that the close relationship between the ant and the bacteria has caused the two to evolve together.
But the study looks at if that is truly so. 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.
Ant–fungus mutualism - Wikipedia
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. 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.
Though external factors play a large role in maintaining fidelity between the mutualists, genetic evidence of vertical transmission of partner fidelity has been found among asexual, fungus cultivating ant species.