There are many dynamic relationships in the rainforests of the world. Which is expected as they are home to up to 40 percent of known plant and animal species. Within the forest there are a widely variety of symbiotic relationships, which means there are interactions between two species. For some species the relationship is beneficial for both parties, this is call mutualism. For example the Brazil nut trees (Bertholletia excelsa) produces a nut that is an only be cracked by a few species, one of which is various agouti (Dasyprocta sp.) which is a small rat like animal. The tree benefits as it’s seeds are dispersed and the agouti receives a free meal.
English: A Central American Agouti (Dasyprocta punctata) in Panama experimenting with a western diet.
In some cases one species is unaffected and the other benefits, this is commensalism. A example of this would be a frog sheltering itself from a storm event under the leaves of a plant. The plant is un effected but the frog benefits. Lastly, parasitism is when one species is harmed and the other benefits. Bot flies are a common tropical parasite that lay their eggs on a mammal host. The eggs then hatch and the larva develop in the skin of the host animal.
A frog in the rain in Belize. Image by Lauren Schramm
Competition is a symbiotic relationship in while two species use the same resources. Because it requires an energy investment both species are harmed, but the harm may be unequal. Many rainforest plants are animal pollinated or their seeds are dispersed by animals. Resource partitioning occurs when a resource is divided among species in some way like time or place. One way plants reduce their competition against each other is by targeting different animal groups. For example flowers pollinated by bats are often white making them easier to see at night, while flower pollinated by other animals are red, orange, and yellow. Bat pollinated flowers also contain a musky smells, while flower pollinated by moths, bees, and other insects have a strong fragrance. Plants also reduce competition by flowering and fruiting at different times. This is one reason there are always flowers and fruits available in the rainforest at any given time.
Ocotillo (Fouquieria splendens) is a desert plant that is found in the Sonoran Desert and Chihuahuan Deserts of North America. Although there are other ocotillo species that are found further south. The plant is made up of long thin individual stacks and when it is in bloom those stacks are tipped with a cone of bright red flowers. In fact, they are named for these flowers as ocotillo is Spanish for little torch. This flowering actually is timed to happen when the hummingbirds are migrating through the desert.
The following has been modified from my field notes from when I took tropical ecology and did a field session in Belize.
In the rainforest ecosystem, the number of symbiotic relationships between organisms is astounding. For example, the relationship between leafcutter ants and the fungus is highly observable in Belize. There is such a great number of these ants that paths are created by them. Leafcutter ant is a generic term for one of 47 species, in the orders Atta and Acromyrmex. They take leaves from plants and chew them up, this plant material is then fed to a fungus, which they eat. In a sense they are farmers. Since the fungus receives a habitat and the ant receive food, this symbiotic relationship is mutualism. There is a dark side to this relationship though. If a plant is highly desirable by ants they will highly predate on said plant. Because of this, they are seen as pests by farmers, whose crops they can destroy.
We saw a wide variety of epiphytes growing on a wide range of trees. Epiphytes are plants that live on the bark and the branches of other trees. This feature allows the plant to gain access to light with a limited energy investment. Most plant growth is limited by sunlight, water availability, and temperature. They are not parasitic but their weight can damage trees. This is an example of commensal as the trees are not harmed but the epiphyte benefits from the relationship. At the Mayan ruins, we saw one plant that has adapted to solve this issue by shedding its bark, so the epiphytes fall off with the bark. This worked fairly well for the tree but in one area a plant had managed to survive on the tree. The most commonly recognized epiphytes are pitcher plants, “air plants”, and mistletoe (Santalales).