Symbiotic Relationships 

Symbiotic Relationships in the Rainforests, by Maggie Eisenberger 

Mutualism (Good for you, good for me) 

Capuchin monkeys lap nectar from flowers in trees as part of their varied diet.  In the process they get pollen on their faces and pollinate the flowers.

Bacteria and protozoans inhabit the guts of termites and sloths, breaking down the plant cellulose which would otherwise be indigestible to the larger animal.

Sloth hairs are grooved, which allows algae to easily take hold and grow on the sloth's fur.  This camouflages the sloth and allows the algae to get closer to the sunlight.

Bromeliads can contain a large amount of water, up to twelve gallons in a large tank bromeliad.  This water is for the use of the bromeliad, because as an epiphyte it has no roots in the soil, but it is used by many other animals as well.  Researchers have identified over 250 species of animals, mostly invertebrates, which inhabit bromeliad pools and/or use the pools as a hunting ground for food such as insect larvae.  A few creatures, such as mosquito and frogs, use the pools for a nursery for their developing young.  At first glance it may seem that the bromeliad would not benefit from this relationship, but the waste products of the animals living in the water are a necessary source of nutrients for the ephiphyte.

The Brazil nut is an important source of food for the agouti.  The agouti bits open the tough outer shell and eats the nuts inside.  Sometimes it buries some of the seeds for later use, and forgets where they all are, so some will have the chance to germinate.  Without the gnawing of the agouti, the Brazil nut would be unable to germinate through the extremely hard shell.

Gongora orchids produce no nectar, but they still perform a service for the bees they manage to attract.  They produce a strong scent to which the euglossine, or carpenter, bees come.  The bees receive no nectar in return for their pollination services, but the scent which they pick up is essential to their own breeding process.  The highly scented males gather together and fly in a swarm, which attracts females for mating.

The flower of the largest water lily in the Amazon opens at night with a bright white color.  This attracts beetles, who crawl around in the flower lapping the nectar it produces.  At dawn the flower closes, imprisoning the beetles.  This ensures that they will be well-coated with pollen when they are released the following night.  To prevent the beetle from pollinating the same flower, the flower changes to a beautiful pink, which does not tempt the beetle to return.

The calvaria tree on the island of Madagascar mysteriously failed to produce new saplings for so long that the trees were all at least 300 years old.  After much lab research, scientists realized that the seeds needed to pass through the digestive tract of the dodo bird in order to germinate; hence, no seeds had germinated since the dodo went extinct.  Turkeys were imported to perform the service, and the tree species was saved.

Fig fruit is a keystone species, a basic source of food for very many rain forest animals, but the fruits contains a laxative which causes the seed to be rapidly passed, to avoid being damaged by the acidic environment in the animal's gut.  Thus, the animals serve as seed dispersers.

Orchid seeds are nearly microscopic, carrying no nutrients for embryonic plant growth.  A fungus must invade the seed for it to successfully germinate, the hyphae bringing nutrients to the embryo in much the same way mycorrhizal fungi feed tree roots with soil nutrients. 

Commensalism (Good for me, doesn't bother you) 

Epihytes usually fall in this category.  They grow on the sides of tall trees in an attempt to be closer to the sunlight.  They have no roots, and collect water and nutrients from the air.  However, in some cases, it is not a benign relationship for the host tree.  In seasonal rain forests, the tree may grow fine rootlets into the bromeliad to tap into its store of water.  In this case it becomes good for both partners.  When the epiphyte becomes part of an extensive epiphyte mat capable of absorbing a great deal of water, the weight can cause a limb to break off the tree, or even bring down the tree in a high wind.  This is not a good relationship for the tree.

At least nine species of moths, mites and beetles live on sloths, eating the algae on their fur.  The arthropods lay their eggs on the dung of the sloths, which provides food for the growing larvae.  This relationship does not hurt of the sloth, but provides no benefit either.

Balonophora look like fruiting bodies of fungi, like strawberry shaped mushrooms on stalks.  They are actually parasitic plants which root into roots of trees and draw out food and water, although not enough to hurt the host plant.  Therefore, they lack leaves and chlorophyll of their own and cannot perform photosynthesis.  Rafflesia similarly parasitizes vines, but also does not seem to do serious damage to the host plant.

Antbirds travel with army ants, eating the small vertebrates and insects which are flushed out by the advancing army.  The ants still get plenty to eat and the birds never eat the army ants themselves, but the birds do no good for the ants, either.

Flower mites which feed on pollen hitchhike from one flower to a fresher one by climbing into the nasal passages of hummingbirds and disembarking when carried to a better flower. 

Parasitism (Good for me, bad for you) 

There is no wind on the forest floor.  For a fungus to disperse spores by the wind, it has to have a way to rise above the forest floor.  Many kinds of decomposers and scavengers of the insect world will incidentally ingest a spore of a certain fungus.  As the hyphae grow through the animal's tissues they drive it insane, the insect climbs a tall plant and walks out to the tip of a leaf, and dies as the fruiting body bursts through its back, dispersing its spores in the breeze from its new, exposed position.

 The leaf cutter ant parasitic fly lays its eggs only on the backs of leaf-cutter ants targeting porters who are carrying leaves.  The larvae burrow into the ant's body after hatching and feed on it, killing it.  For this reason, sometimes a smaller morph of leaf-cutter can be observed riding shotgun on a leaf piece to protect the porter ant, which fails to defend itself because it will not put down its leaf.

A parasitic wasp preys on fig wasps, drilling a small hole into the fig and using her long ovipositor to inject an egg near a developing fig wasp larva, which will be consumed by the parasitic larva after it hatches. 

Long stories that have many relationships. 

Heliconia butterfly larvae feed on the leaves of passionflower vines.  The vines produce a poisonous substance to deter leaf predation, but this particular caterpillar is capable of incorporating the poison into its own tissues, becoming poisonous itself to any predator that might consider eating it.  Other defenses evolved by the plant include the presence of a variety of shapes of leaves, which may fool the butterfly into not recognizing at least a few of the leaves, and the growth of small pale dots on the leaves, which may look like previously laid eggs to the butterfly.  This would dissuade her from leaving yet another egg, as the caterpillars are cannibalistic and the first to hatch would eat the others.   The butterfly could still lay an egg on a new tendril at the growing tip of the vine, where poison has not yet accumulated and false egg spots have not had time to grow. But the plant in that case will drop the tendril like a lizard drops its tail, leaving the hatched caterpillar with very little to eat.

Oropendolas are birds that build large bag-nests that hang down from tree branches, an adaptation that usually protects the nestlings from predatory tree snakes like the emerald tree boa.  They feed mainly on insects and fruits.  Chestnut-headed oropendolas build their nests in close proximity to colonies of stinging trigonid bees.  These bees are fierce when aroused, defending not only their nests, but also large areas in the trees around their nests from intruders.  They defend the area, day and night, from all potential predators such as toucans, which can pluck nestlings out of hanging nests.  The oropendolas are not bothered by the bees, which seem to recognize their smell, and it is not known if the bees derive any benefit from the birds.  The bees are preyed upon by carnivorous wasps and ants, so they often build their nests inside the nests of tree-living termites where they are protected by the termite soldiers.  It is possible the birds also would eat these predators and protect the bees.  The termites tolerate the bees since they help protect the nest against tamanduas and other anteaters.  In addition, trogons actually build their nests inside a bee nest located inside a termite nest!  The cowbird lays its eggs inside oropendola nests, where the large cowbird chick out competes or even kicks out the oropendola chicks.  Sometimes the bees' presence discourages the cowbird from attempting to lay her egg.  Even if the egg is laid, the cowbird can actually end up protecting the oropendola chicks from predation by botflies. Which are also driven away by the bees, but some do get through.  The cowbird chick may eat botfly larvae from the skin of the smaller chicks