Volume 13, Part 2, May 1999

Mycological Dispatches

New world leaf-cutting ants of tropical andsubtropical America maintain fungalmonocultures' as their only food source", Themycosymbionts ' have been identified asLeucoagaritas gongylophorus (Moller) Singer(anamorph Attamyces bromatificus Kreisel,characterized by clumps of gongylidia"), Anevolutionary result of this symbiosis dated to theearly Tertiary (>50 million years ago"), has beenthe loss by the ants of their own digestiveenzymes and the consequent dependence on theenzymes of their fungi for the production of lowmolecular weight, absorbable nutrients'.

Greater insights into the phylogenetic rela-tionships among the more than 200 knownextant species of attine ants, their fungalmycobionts, and the free-living relatives of thelatter are provided by a recent Report" in Scienceand its anthropocentric Perspective', The fungiof most attine ants" are propagated asmycelium, except those maintained as yeasts, bya group of Cyphomyrmex ants. The greatmajority of these fungi, including the yeasts, aremembers of the tribe Leucocoprini (Lepiotaceae),a large, poorly known group of predominantlytropical mushrooms (the only exception is thecultivation of a nonlepiotaceous species by someApterostigma ants).

The phylogenetic origins of this symbiosishave been ambiguous because of the uncertaintyof the possible relationships within thesymbiosis". In their study Mueller and hisassociates' collected 309 wild basidiocarps (mostof those from Panama are undescribed) and 553isolates of mycosymbionts maintained by sevengenera of primitive attine ants (these are mostlikely to have retained the least modified forms

of the ancestral cultivation behaviour): 337 fromsympatric Panamanian colonies and 216 fromcolonies along a United States to Brazil transect.The evolution of this symbiosis was inferredfrom phylogenetic and population-geneticpatterns. A dendrogram of the rDNA analysessummarizes data for 57 mycobionts of the sevengenera of fungus-growing ants and 36 free-livingLepiotaceae and indicates the presence of atleast five clades of ant-fungi, suggesting at leastfive independent symbiont acquisition events. Aclose correlation between two of the unidentifiedmushroom species and two respective sets ofmycobionts, one of which is all the yeast forms,indicates two recent domestication events. Thethree additional lineages are statistically distinct

North1 also provides an excellent generaldiagram showing the interactions between theseants and the fungi they cultivate.

By the time you read this the Natural HistoryMuseum (London) should have its leafcutter antcolony established in the Insect gallery<www.nhm.ac.uk/museum/creepy/gallery.html>.It will be constantly monitored by ANTCAM, aweb-window which will bring pictures on the livesof the ants and allow you to see them tendingthe fungus they feed on, watch them carryingback leaves from their feeding area, and spot thesoldier ants that guard the workers.

'North, R. (1998) Biologist 45: 199-202.'Fisher, P. J. et aL 1994. Mycologist 8:128-131.'Hinkle. G. et aL (1994) Science 266: 1695-1697.'Diamond, J. (1998) Science 281: 1974-1975.'Mueller, G. et aL (1998) Science 281: 2034-2038.

Roy Moore

The next issue of the Mycologist will include articles on:

British Dermateaceae 3: Peziculoideae

Puccinia smyrnii and P vincae: a microscopical study

Teaching Techniques 7 - Zoospore discharge by Pythium and Phytophthora

Image analysis of mycelial systems

Profiles of Australian fungi

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