epiphytes

The rainforest is teeming with dynamic relationships!

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.

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Description
English: A Central American Agouti (Dasyprocta punctata) in Panama experimenting with a western diet.
Source BirdPhotos.com
Author Tomfriedel

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.

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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.

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Belize ecosystems

Belize is found within the tropics. The tropic is the region between the tropic of cancer and the tropic of Capricorn. More specifically Belize is found in the Neotropics which are the new world tropics (Central America, South America and the Caribbean). Between 80-90 percent of known species live within the tropics. Belize also has a wide diversity of habitats including savanna, rainforest, mangroves, and coral reefs. See the below photos, taken by yours truely, that show just some of the diversity Belize has to offer. It has one of the largest reefs in the world which is able to support a large number of species.

Within tropical forests, there are many ways in which a species can specialize. This is because a large number of nutrients and space resources are available. This type of environment can create endemic species which are species whose range is limited to a certain geographic area. When there is a high number of endemic species there is a high level of biodiversity.

In comparison to other nearby areas Belize has a high number of native forests, 65-70 percent of the country is covered by the native forest. In part this is because some areas are too remote to sustain development. Native forests are found to have greater diversity than secondary forests. A large area of the country is a part of reserves, about 26 percent of the land and sea, and 33 percent of the land. The average percent for land conserved across Latin America is 20 percent.

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A savannah in Belize, captured by Lauren Schramm

Belize contains 4000 species of flowering plants, 730 tree species, and 280 orchids. Its biodiversity is high compared to the surrounding regions because of the island biogeography theory. Basically what this means is that the level of species on a landmass is contrast (but not necessarily the same species) and species richness is positively correlated with landmass size. So the greater the landmass the more species there will be. Since the Caribbean is made up of islands then there cannot be as many species as a place on the mainland like Belize.

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The black orchid (Encyclia Cochleatum), the national flower of Belize, captured by Lauren Schramm

Indicator species are species that are heavily influenced by the quality of the environment in which they live. Because of this, they are often used to gauge the health of the ecosystem. Because amphibians breath through their skin they are considered an indicator species. In Belize, there are 37 species, in 10 families. In contrast, Bermuda only has 3 species of amphibians, in 2 families. This can be explained by the latitudinal diversity gradient. Belize is much closer to the equator than Bermuda and other Caribbean nations. The theory says that species richness declines the further away from the equator you move. Because there are many species in the tropics the species are often found in low abundances.

There are many theories on why diversity is high in the tropics including high speciation rate, low extinction rate, more net primary productivity, structurally complex ecosystems, and stable climate over time. In addition, there is lots of rain in the tropics which means that lots of water is available. Species like epiphytes greatly benefit from this. The environment has been stable over time so likely the species there today are similar to those in the past. However because there are a large number of species, none dominates. This means that each occurs in a low number. In areas with fewer species, there are often dominant species.

Forest ecosystem types of Belize

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.

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Leafcutter Ants. Captured by Lauren Schramm, Belize City, Belize

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).

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