Life in the Ant Forest: Mutualism in Abundance
The ants of the myrmecophyte forest exist in a myriad of species in a diversity too expansive to come close to documenting in entirety, with a likely estimate being of upwards of 10,000 species of arboreal ants alone, of them approximately two thousand which live in obligate symbiosis with host trees and many others doing so opportunistically. Symbiotic ants differ in their behavior, appearance and dietary preferences and multiple species can coexist in a single tree by specializing in different diets. Some species are omnivores that consume plant and animal in equal measure, often doing so with different specialized castes, and will attempt to keep an entire host tree to themselves, attacking and killing other symbiote ants that threaten to encroach on their food supply. Other ants, however, have specialized into distinct carnivorous and herbivorous groups. Aggressive carnivores strip the tree branches of insect pests, protecting their host trees from harm, while herbivores trim the branches of neighboring trees and seedlings that grow too close to the base of the trunk, limiting their host's competition. Such different ant species usually tolerate one another, as they don't compete for food resources, and they may even share nests within the tree. When the tree is threatened all of them will respond in equal measure and defend their host collectively.
Of course, not all ants are tree-symbiotic. The majority live independently of sunflower trees, or nest in them only opportunistically without providing benefit to their host. Some are generalists, and many have highly varied diets and indiscriminate tastes, readily targeting any source of meat they can overwhelm with bites and stings, potentially making it very difficult for small animals with helpless nest-bound young to keep their offspring safe, since there is virtually no nest that can exclude such tiny and innumerable predators. This is where another example of mutualism occurs in the ant forest; while armies of defensive ants may make things difficult for herbivores, other creatures benefit from close association with the insects, welcoming benign species into their nests so that the harmful predatory species are excluded.
This arrangement works out because most symbiote ants, unlike free-living forms, are selective in their diets, and in whom they direct their defensive swarming against. They have nothing to gain from swarming unless absolutely necessary and so pay no attention to animals that pose no threat to them or their hosts, such as small birds or other creatures that move through the trees without nibbling them. Among the symbiotic ant families, even carnivorous species generally limit their sights to other invertebrates, and nesting birds utilize this passivity to their advantage. They choose to place their nests in trees containing a healthy population of insect-eating symbiotic ants, which will not only drive off less selective predatory ants that would attack their chicks but which will also clean their nests and nestlings of harmful mites and other parasites with remarkable efficiency, resulting in healthier chicks. As the adult birds incubate their eggs, these ants also climb into their plumage and remove any parasites they find there. By tolerating, even encouraging birds to nest in their host trees, these ants are also inadvertently hiring more help in keeping their homes clean and healthy, as many birds feed heavily on leaf-eating pest insects or on damaging wood-boring larvae, which the ants themselves cannot reach to keep in check. Many ants also collect the droppings left in the nests of birds and bring them into their nests inside the trees where in turn they are consumed and, after passing through the ants, provide an additional source of fertilizer to the tree; the end result is healthier birds, healthier ants, and a healthier host tree than would be the case if the birds did not breed there.
Molodonts, too, often raise their young in ant trees, and even though these species frequently feed heavily on the seeds of trees and are potentially quite damaging to their reproductive output, they too are often tolerated as the symbiote ants do not distinguish individual animal species as benign or harmful, instead only responding to pheromone signals released when the tree's soft tissues are damaged by feeding animals. To ensure their young are safe and that the insects don't turn on them, mothers feed a great distance from where they are hiding their young, in a different tree if possible, so that she does not induce a defensive swarm near her nest. So long as she avoids damaging the soft tissues of the tree near where she rears her pups, the ants that march along the branches pay her and her young no mind, entering the nest and removing parasites and waste products, promoting a healthier environment for her family.