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Title: COLONY FOUNDATION, NEST ARCHITECTURE, AND DEMOGRAPHY OF THE FUNGUS-GROWING ANT, MYCOCEPURUS SMITHI (HYMENOPTERA, FORMICIDAE)

Author
item Fernandex-marin, H.
item Zimmerman, Jk
item Wcislo, Wt
item Rehner, Stephen

Submitted to: Journal of Natural History
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2004
Publication Date: 7/1/2005
Citation: Fernandex-Marin, H., Zimmerman, J., Wcislo, W., Rehner, S.A. 2005. Colony foundation, nest architecture, and demography of the fungus-growing ant, mycocepurus smithi (hymenoptera, formicidae). Journal of Natural History. 2005, 39(20):1735-1743

Interpretive Summary: The evolution of agriculture is rare and, besides humans, is practiced by only a few beetles, termites and ants. Mycocepurus smithi is a primitive member of the fungus-gardening ants, a group unique to the American tropics. We were interested in determining whether the biology of this ant could provide insight into the evolutionary origin and ancestral behaviors required for fungus agriculture. In Puerto Rico, fungus-gardening ants annually establish new colonies between July and August. Colonies are usually founded by single queens, which dig a small tunnel and chamber in the soil. The queens insert their discarded wings into the ceiling of the nest chamber and use it as a platform on which to establish the fungus garden. The physical isolation of the young garden on the ant wing is believed to facilitate garden sanitation, and represents a relatively simple solution by which competitors and parasites of the garden fungi may be successfully avoided. This information is useful to scientists interested in understanding the ecology and evolution of agriculture.

Technical Abstract: The genus Mycocepurus is a phylogenetically basal attine ant whose biology may provide insight into the evolutionary origin and ancestral behaviours associated with fungus-growing that uniquely characterizes this tribe. Mycocepurus smithi from Puerto Rico produces sexual females from July to September, but no males were observed in 2 years of observation. Colonies were founded between July and August and most nests were haplometrotic (85 % of 74 nests). After excavating a tunnel and small chamber, foundress queens inserted their forewings into the ceiling and used the wing surface as a platform on which the incipient fungal garden is grown. Foundresses foraged for substrate to grow the fungus garden. Growth of incipient colonies was slow: the first workers emerged two to five months after colony founding and, after eight months, colonies contained on average only a single worker. In a number of mature colonies, several sexual females with cut wings were observed remaining in the natal nests.