Adventures Among Ants - Mark W. Moffett [132]
Yet lower attines frequently shift to a new variety of fungus cultivar, and this happens from time to time with leafcutters also.38 When a shift is forced upon a colony experimentally by replacing its gardens with a fungus strain the workers would normally reject, the ants, having no alternative, come to adopt the new variety within days.
Given the ants’ diligence in keeping the family-fungus pedigree, how does such a shift come about in nature? On occasion, a nest must suffer a loss of fungus from famine, flood, contagion, or (with some lower attines) seizure by garden-eating ants that can’t rear their own fungus.39 Finding a replacement may be the only recourse. Robbery, a widespread practice among ants, is one option.40 Gardening ants are known to pillage fungi from each other, thus spreading cultivars, much as people do through trade or sometimes theft.41
The result of the leafcutter ants’ fussing over their gardens is that all but the subtlest genetic variations are bred out. The fungus flourishes only because the workers’ efforts relieve their cultivar of the burden of living in the real world.42 Without the ants’ intimate supervision, the unvarying leafcutter fungus, in monocultures of hundreds of kilograms in a nest, is particularly vulnerable to catastrophic destruction by the Escovopsis fungus—a problem more deadly than anything faced by the hearty fungus breeds of the lower attines.
We share with leafcutters a refined sense of what we like. We settle on certain favorite foods and then use artificial selection, inbreeding, and clonal propagation to heighten and maintain the characteristics in them that we prefer—consider the flavor difference we’ve come to expect from varieties of apples such as a Macintosh or Granny Smith. As a result, our crops, like the garden fungus, have lost the genetic diversity that their ancestors could draw on to survive disease and environmental change. Along with the ants, we must actively protect our cultivars. Controlling plagues has been part of the raising of inbred crops since ancient times, and risks remain grave for foods grown in monoculture—as, nowadays, most are. On this issue, we might once again heed the biblical injunction to “go to the ant” and consider her ways. Human agriculture began after the last ice age. Leafcutters have reared genetically uniform crops a thousand times as long. Why, then, haven’t leafcutter societies collapsed from their own version of the Irish potato famine? The answer lies in the fact that the ants keep their crops immaculately clean. Through an elaborate division of labor unmatched by that of any living creature besides people, ants sow those crops, weed them, cull them, manage their wastes, treat them with pesticides, and divide them among many chambers so that, when diseases do appear, the stricken gardens can be quarantined and killed.
In the Kaw Mountains of French Guiana, Cyphomyrmex rears fungus—in this case, a yeast—on caterpillar feces (alongside an incidental carapace). Unlike leafcutter ant gardens, those of lower attines are small, and their cultivar shows little sign of domestication.
Pests of human crops have been swift to evolve a resistance to our pesticides. The ant’s version of the potato blight, the Escovopsis fungus, must have done the same a staggering number of times over millions of years. Meanwhile, the ants must have countered each threat to their cultivar countless times over the eons with changes of their own. What can we