Biology of FUNgi. Last time...

Transcription

1 Biology of FUNgi Lecture 15 Happy together Fungus-animal symbioses Last time... Endophytes defined. Advantages of foliar endophytes. Advantages of root endophytes. How may endophytes control the composition of plant communities? 1

2 Fungus of the day - Taxonomy: Phylum (subphylum) Basidiomycota Order - Agaricales Family - Tricholomataceae A great example of a mutualistic symbiosis between animals and a fungus. is associated with leaf cutter ants (Acromyrmex and Atta) in tribe Attini and leaf cutter ant genera Acromyces and Atta in the tribe Attini. Acromyrmex is an example of fungus gardening attines Fungus of the day - Leaf cutter ants (here, Atta) appropriately for their name, harvest leaves......and drag them to their nests Nests are usually belowground to provide stable conditions for the residents and their gardens. 2

3 Fungus of the day - Simple on the surface... the nests are often monumental in size indicating the success of the mutualistic association. The nests may be impressive in size but they also have a beautiful infrastructure including the queen chambers and the fungus gardens. Fungus of the day - Some chambers are dedicated to serve a special area where the is grown. The special chambers are known as the fungus gardens, which... are meticulously tended by the leaf cutter ants. 3

4 Fungus of the day - Ants bring the harvested leaves into the fungus garden, which has fairly constant environmental conditions (temperature and humidity) for the growth of a saprobic T. myomyces. The ants then feed on the growing mycelium. There is more to this story, the ants do not only grow the fungus but they groom and keep their fungus farm clean. Special chambers are dedicated as the fungus gardens. Fungus of the day - The whole fungus-ant symbiosis is a complex web of interactions. In addition to providing the fungus a nice environment, the ants lick the surfaces of the nest and the new leaf material they bring in for substrate; they decontaminate the new substrate. is associated with leaf cutter ants in tribe Attini When contaminations occur, great number of workers dedicate their time and attention to picking contaminant spores out of the culture. If the contaminant spores germinate, the ants weed out the contaminated substrate. 4

5 Fungus of the day There is more to this story; it has been suggested that the ants have harnessed antibiotic bacteria to fight the contaminants. is associated with leaf cutter ants in tribe Attini The fungal gardens are the main habitat for a specialized parasitic ascomycete, Escovopsis. The attine ants carry about an actinomycete (Streptomyces) producing streptomycin-like antibiotic in their cuticles. The actinomycete is transmitted vertically (from parent to offspring) and promotes the growth of the garden fungus while suppressing the growth of Escovopsis. This symbiosis seems to have an ancient evolutionary origin. The ant and fungal topologies follow each other with few transversions which may be due to acquisition of a superior garden strain 5

6 Fungus of the day - Thricholoma myomyces is not the only mutualism of this kind. Termitomyces sp. is symbiotic with termites. Termitomyces sp. is associated with termites. Termitomyces sp. emerging from termite gardens. This time Fungus animal symbioses. Human fungus symbioses? Remember that symbiosis is not always mutualistic. 6

7 Human symbiosis with Agaricus The button mushrooms comprised 90% of the North American mushroom sales. Agaricus bisporus or A. Agaricus bisporus would not be this widely spread brunnescens - the common button mushroom - being grown on and doing this well unless humans had their fungus concrete blocks with a thin layer gardens. of straw and manure Human symbioses with other mushrooms Similarly to Agaricus bisporus, oyster mushroom and shiitake have gained global distribution and secured substrate and habitat as a result of human fungal gardening. Lentinus edodes or shiitake and Lentinus was traditionally produced on oak and elm was traditionally produced on logs. Nowadays, this practice is being replaced by hardwood logs. sterile bags like those we are using in our mushroom experiment. 7

8 Human symbioses with other mushrooms Log cultures have been given up and most lignicolous fungi are now commercially produced in sterile bags filled with saw dust or straw. Lentinus edodes or shiitake grown in spawn bags. This is how well the oyster mushroom Pleurotus ostreatus can produce when treated right and provided with more appropriate substrates. Other mammals can be more dependent on the fungi in their lives Long-nosed potoroo (Potorous sp.) Brown Bandicoot (Isoodon obesulus) Swamp wallaby (Wallabia sp.) 8

9 Other mammals were more dependent on the fungi in their lives California red back vole (Clethrionomys californicus) is exclusively dependent on fungi (truffles in particular) in its diet. The vole s dental structure does not allow it to eat anything but soft tissues, i.e. fungal tissues. Northern flying squirrel (Glaucomys sabrinius) is similarly dependent on truffles for dietary supplement, but not to the degree that California red back vole depends on them. Animals feed on fungi. What do fungi get in return? Most truffles emit odors that animals find attractive, this is necessary for the animals to find their food. Once ingested, the spores pass the digestive track unharmed and are deposited in poop-capsulated propagules. Chamonixia vittatispora smells like dog poop More rarely, the truffles mimic the food supply: Paurocystis pila and Weraroa erythrocephala mimic Podocarpus cones eaten by the kiwi-bird Paurocystis pila and Weraroa erythrocephala look like Podocarpus cones 9

10 Animals feed on fungi. What do fungi get in return? Animals that consume the truffles unknowingly stratify the fungal spores in their gut and disperse them with their feces. Predators can increase the dispersal capacity of the fungi. Some fungi do not pass the digestive track but are aerially dispersed once the outer layers of the sporocarps are eaten. Elaphomyces sp. disperses aerially once the sterile outer core is eaten Predators can disperse spores even longer distances Mesophelliaceae are even more clever than Elaphomyces spp.: animals need to get to the inner sterile tissue through the spore mass There is more to the story than that, though Many of the fungi eaten by the animals are also associated with the forest trees. We can talk about an interconnected food web on an ecosystem scale. Nutrients Water Protection from pathogens Carbon Energy Dispersal Carbon Energy Nutrients Protection Dispersal Carbon Energy Nutrients 10

11 Other fungus animal symbioses Recall, Laboulbeniales, the speciesspecific ascomycetes on the insect exosceleton with minuscule asci. A social disease of most of the insects. Laboulbenia is a social disease of insects colonizing the chitinous exosceleton. Other fungus animal symbioses Some insect symbionts (forming parasitic symbioses) have been considered for biocontrol. Entomophthorales (Zyg.) are omnipresent parasites of various insects. Beauveria bassiana (Asc.), for example is a common soilborne parasite of insects and several strains can level of peak insect populations. Similarly, Metarhizium anisopliae (Asc.) has been used against turf grass grubs. Entomophthora is a specialized parasite of insects, including flies. Wasps infected with the fungus Beauveria bassiana. Grass grubs infected with the fungus Metarhizium anisopliae. 11

12 Other fungus animal symbioses The specific parasitism a select insect resulted in great interest in Entomophthorales (Zyg.) as a potential biocontrol agent. Entomophaga maimaiga and control of gypsy moths serves as an example. Entomophaga maimaiga is a specialized parasite of gypsy moth which may cause extensive tree defoliation when E. maimaiga allows population densities are high. convenient dispersal. It has both resting diploid spores and haploid conidia. Summary Leaf cutter ant - Tricholoma symbiosis. Human fungus symbioses Small mammal - fungus food web Entomopathogenic fungi 12