Ant-fungus mutualism

Ant-fungus mutualism is a symbiosis seen in certain ant and fungal species, where ants actively cultivate fungus much like humans farm crops as a food source. Interestingly, in some species, the ants and fungi are dependent on each other for survival. The leafcutter ant is a well known example of this symbiosis. [cite book
author=B. Hölldobler & E.O. Wilson
year=1990
title=The Ants
location=Cambridge MA
publisher=Belknap] A mutualism with fungi is also noted in some species of termites in Africa. [cite book|last=Dawkins|first=Richard|authorlink=Richard Dawkins|title=The Selfish Gene|origyear=1976|edition=2nd edition|year=1989|publisher=Oxford University Press|location=Oxford| id=ISBN 0-19-286092-5, LCC|QH437.D38|pages=180|chapter=You scratch my back, I'll ride yours|quote=For example, several species of ants in the New World, and, quite independently, termites in Africa, cultivate 'fungus gardens'.]

General overview

This mutualism is thought to have originated in the basin of the Amazon rainforest some 50–65 million years ago. The attine ants actively propagate, nurture and defend the basidiomycete cultivar.cite journal
author=I.H. Chapela, S.A. Rehner, T.R. Schultz & U.G. Mueller
month=9 Dec.,
year=1994
title=Evolutionary history of the symbiosis between fungus-growing ants and their fungi
journal=Science
volume=266
issue=5191
pages=1691–1694
doi=10.1126/science.266.5191.1691] In return, the fungus provides nutrients for the ants, which may accumulate in specialized hyphal-tips known as "gongylidia". In some advanced genera the queen ant may take a pellet of the fungus with her when she leaves to start a new colony. [cite journal
author=N. Weber
year=1966
title=Gardening Ants: The Attines
journal=Science
volume=153
issue=1966
pages=584] This mutualism is further complicated by the introduction of two other factors, a fungal parasite "Escovopsis" and a bacterial species residing on the ants' integuments that assists in defending the fungus from this parasite through the production of secondary metabolites. [cite journal
author=Cameron R. Currie, Bess Wong, Alison E. Stuart, Ted R. Schultz, Stephen A. Rehner, Ulrich G. Mueller, Gi-Ho Sung, Joseph W. Spatafora, and Neil A. Straus
year=2003
title=Ancient Tripartite Coevolution in the Attine Ant-Microbe Symbiosis
journal=Science
volume=299
issue=5605
pages=386]

Whereas the ants are monophyletic, their symbionts are not. They fall roughly into three major groups, only G1 having evolved gongylidia. Some G2 species grow long hyphae that form a protective cover over the nest. Those in G3 are paraphyletic, the most heteregenous, and form the most loose relationships with their cultivators. Studies now show that the fungi themselves may not be completely dependent on the ants. The fungi were earlier thought to be propagated by ants purely through clonal (vegetative) means. However considerable genetic variation in the fungi suggests that this may not be the case. [cite journal
author=Mikheyev, S., U.G. Mueller, P. Abbott
year=2006
title=Cryptic sex and many-to-one co-evolution in the fungus-growing ant symbiosis
journal=Proc. Natl Acad. Sci.
volume=103
pages=10702–10706
url=http://www.biosci.utexas.edu/IB/faculty/mueller/pubs/mikheyev_PNAS06.pdf
doi=10.1073/pnas.0601441103]

References

External links

* [http://www.sciencemag.org/cgi/content/abstract/311/5757/81 Coevolved Crypts and Exocrine Glands Support Mutualistic Bacteria in Fungus-Growing Ants]