The Ever Evolving Ant Forest

The Evolving Ant Forest

A Cooperative Ecology

Evolution often has a connotation of selfishness, of individuals fighting battles tooth and nail with predator and competitor. Consider such terms as "Darwinian", meaning ruthless or cutthroat in passing phrase. It can easily be construed that the evolutionary process is nothing more than a solo race to kill or be killed, everyone for themselves. Often forgotten, underestimated, or disregarded, however, is just how important cooperation can be in the game of life.

In truth, evolution is a much more complex process than one by which creatures fight red in tooth and claw and where only the strongest of the strong survive. Adaptation can be forged not only by the fight to adapt to an environment, avoid predators or compete with competitors, but also by the absence of harsh selective forces - and one of the most successful strategies for any living thing to reduce the intensity of selection is through cooperation. Organisms that work together to spot danger, find nourishment, fend off enemies or rear their young can gain much more than if they fought for survival independently and alone.

When life cooperates, the intensity of natural selection on an organism is reduced. Sharing resources instead of fighting over them, cooperating to find sparse food over a wider area, and sharing body warmth are all examples of situations that relax natural selection and allow chance mutations that improve genetic diversity to be given more opportunity to proliferate and succeed than when life exists alone and without a safety net. Simple laboratory studies with mice demonstrate this well; mice which are antisocial and do not share body warmth with other mice are less genetically diverse than their social counterparts, as their metabolisms must be more precisely efficient. They are less tolerant of temperature changes and must eat more, and forage more throughout the day and night to maintain their body heat, whereas the mice which differ initially in just one fundamental way - they like to huddle at night to conserve body heat - are largely free of these constraints. Individuals in such populations can survive more easily, and in this way accumulate new mutations that the loner mice would not be able to. In turn, this leaves the social mice with more beneficial genes available for if their conditions change suddenly, whereas the solitary mouse, living on a knife's edge, may simply perish. On a much broader scale, similar cooperation can allow wild species and indeed entire wild communities to thrive where solitary species would fail. On Earth, examples of cooperative systems surviving where solitary ones would not are everywhere, in a wide range of complexity from intraspecific to ecosystem-wide. They include emperor penguins, that only through total cooperation manage to incubate their eggs through the polar winter, and painted wolves which feed their wounded and in turn allow them to heal from injuries and continue to contribute to the gene pool in the future. Wider systems include coral reef ecosystems that support thriving communities of life in the veritable desert of the open sea, and almost all Earth plants, which can only survive thanks to symbiotic relationships with fungi that live among their roots or did among those of their ancestors, breaking down molecules in rock to provide plants with nutrients they cannot themselves obtain; indeed, without similar fungi first colonizing the land, land plants would never have been able to evolve into their modern forms at all.

As life in general evolved over time, it follows a tendency to become more complex. Individual animals are prone to develop larger brains and more complicated behavior, and ecosystems become ever more interdependent in turn. The pollination of plants by insects was an early social revolution, the emergence of a cooperative partnership that allowed each group an unprecedented level of success neither would have obtained alone. On Serina in the early Ultimocene this has been further expanded upon with the the continued success of the ant forests of temperate climates, now some of the the most interconnected, complex ecosystems ever to exist.

The animal/plant cooperative relationship that first evolved on Earth has, in this endemic ecosystem that now dominates Serina's land wherever enough water exists to allow the growth of trees (at this time, mostly broadleafed sunflower descendants), progressed from simple pollination to a complete and total reliance on one another. Insects in the form of thousands of specialist ant species now serve as an external immune system to their host trees, protecting from threats in return for housing and sustenance. The trees rely on the insects to distribute their offspring, planting the seedlings in suitable sites and tending to them as they grow, but the insects equally as much require the seedling to thrive for it will provide the home for their colonies for many years once established. Ants also collect organic matter around the tree to provide nutrition and remove weeds that would otherwise compete with their hosts. In every sense of the word, the ants are gardeners, though they do not dominate the relationship; theirs is one of true codependence, forged over many millions of years partnership.

Other larger animals became involved in the system over time. Interestingly, this is not always a cooperative process at every level. Often animals that eventually become cooperative partners in the system begin as parasites, at first actively harming the system before evolving to modify their behavior to benefit it. In the ant forest, the molodonts are the best example of a pest that has since become integrated as an important component of the forest community.

As the ant trees lost their fleshy, edible seeds in favor of bearing live seedlings to thwart early molodont predation, some molodonts in turn switched to feeding more heavily on vegetation; some of these moved to the ground and evolved into the circuagodonts, and they all persisted as a pest - perhaps a worse one - by now eating not just seedlings but chewing up the entire tree. Circuagodonts, as they adapted to forest environments from the grasslands, were veritably purpose-made tree-trimmers, with specialist jaws ideally adapted to to trim and clip branches, and proved highly destructive when they first returned to the forests from the plains they evolved on. Yet while at first the various herbivorous molodonts browsed indiscriminately and selfishly, damaging their food plants as most herbivores do, over time the aggressive defenses of the tree's ant colonies would have discouraged the most damaging feeding patterns and selected instead for light, all-over pruning of the edges of the plant where it caused little damage and could easily regrow, keeping the tree vigorous. Further, the powerful cutting jaws of the circuagodonts could perform a vital service that no smaller animal could: trimming dead and diseased woody branches. In doing so, these animals evolved to perform another role to maintain the health of the woodlands that they depended upon. From there, their feeding behavior was gradually shaped over hundreds of generations to include thinning healthy but crowded branches methodically as trees grow, in ways that allow light to reach lower branches as well as immature seedlings on the ground below, to produce a more vigorous, ultimately healthier tree and improve the odds of the younger trees' survival.

In the Ultimocene, these forests have become a marvel of interdependence and cooperation, with insects, plants and animals large and small working collectively for a common goal; the sustenance of the habitat each of them relies upon. In doing so cooperatively versus fighting for a living individually, the health and productivity of not only each individual but the ecosystem as a whole is improved. By thinning the trees' growth to maximize available light at all levels and removing diseased branches, the circuagodonts - which tens of millions of years ago evolved as seed-eating pests destructive to the tree and without redeeming quality, have become the arborists of the ant forest, not only ensuring the long term health of their food supply but improving the trees' welfare longterm in the process. For the first time, the dominant herbivores of the woodland community are not a threat existing outside the partnership, but rather an important contributing member to a large social system spanning many orders of life. Though the system is not an honor code and must still be maintained through boundaries and rules - symbiotic ants will swarm and discourage excessive, harmful browsing that an animal may still attempt if it can get away with it - the ultimate result is a more stable, less stressful, and healthier ecosystem than the forest would be without cooperation.

Ant forests of the early Ultimocene are now highly distinctive due to the changes the circuagodonts and the browsing molodonts have introduced to the ancient system as its first specialist, symbiotic browsers. Arboreal molodonts thin the canopies of the trees they feed on in a way that doesn't compromise height but maximizes the penetration of sunlight and air flow into the foliage; they trim branches toward a layered, open canopy with open spaces between clusters of foliage. Circuagodonts, being unable to climb, tend to groom the trees in a way that maximizes clumps of available foliage to browse from the ground, encouraging abundant short, new shoots instead of long woody branches with regular trimming, and so in forests where circuagodonts are the dominant browsers the trees tend to be kept compact in size, with branches starting close to the ground.

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Some forest circuagodonts adapt to digest wood as a primary diet, their stomachs supporting symbiotic microbes that process cellulose, and become deadfall specialists that eat predominately ailing or crowded branches which they cut from the trees as well as any fallen wood, which has the secondary effect of changing understory ecology; normally rotting wood is an important food source for countless small decomposing invertebrates, but in forests with a circuagodont presence, this food source is comparatively absent and the forest floor unusually clean of any refuse. What was once available to feed detritivores and in turn to feed small carnivores is now accumulated in the bodies of large herbivores and then deposited as dung. While dung is, theoretically, also a source of nutrition for invertebrates, in this system even this is often recycled directly into the trees by other ants which gather it and bring it down into their nests to nourish fungal gardens upon which they feed; ultimately, in the modern ant forest, almost all organic matter produced by the trees is recycled back into the trees with few organisms outside the partnership benefiting.

above: an antlear circuagodont about to clip a stray, dying branch off of an ant tree. Removing this diseased portion will keep the tree healthy and encourage the tree to put out a cluster of new, healthy foliage.

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This makes the ant forests highly productive and efficient for those species which have involved themselves into the system, but has resulted in a decline in the populations of animal species that relied on the deadfall for food and shelter, such as other insects, tribbets, worms and snails, and for birds that fed upon them, and demonstrates that there is no system that is ultimately perfectly efficient for all life involved. Even the ant forest, though cooperative, is ultimately selfish for its own collective goals.

The interconnected nature of the ant forest is most visible in the growing season, yet additional checks exist to maintain balance which do not show themselves until the trees shed their leaves in the autumn. As the cold comes, the trees go barren, the ants go dormant, and the herbivores are left seemingly without boundaries as to what they can or cannot eat. Yet they do not overbrowse the forest nearly to the extent that would be expected without the ants to control the degree of their feeding, for the trees have developed subsequent adaptations to control the browsers by themselves at this trying time; the young trees merely continue an ages-old successful tactic and simply start out life unpalatable; they may sport large spines or fill their tissues with bitter or otherwise unpalatable chemicals to discourage feeding before they are mature enough to tolerate pruning. The mature trees, however, which have been pruned and maintained all summer and go into winter dormancy healthy and strong, do the reverse. Partly to protect the vulnerable young trees from the browsers, and partly to ensure the survival of the browsers that they have come to depend on in the summer, they have evolved to fill their own youngest shoots with nutritious, sugar-rich sap that animals find highly nutritious. This encourages selective browsing so as to not only protect their less replaceable, older woody branches but also to protect their immature offspring - effectively, the winter is a time where the mature trees return some of their own resources, gathered all summer long, back into the forest to maintain the health of the browsers and protect their young. Through winter, the browsers feed upon these sacrificial shoots that ensure the damage is confined to the most replaceable parts of the tree, so that they quickly return to their full vigor in the spring as the cycle renews. As the weather warms, the nutrients they lent out during the winter are steadily cycled back into them as the various symbiotic ants re-awaken. Some gather the dung produced all winter, bringing it back to their fungal gardens to ultimately nourish the trees and return the bulk of the nutrients they lent out all winter, while the defensive species return to their role of keeping the browsers in line to ensure the trees can recover their losses from the winter season and enough of a reserve to ensure the survival of the community through the following winter.