Symbiosis of Orchids & Spanish Moss

Spanish moss lives in commensalistic symbiosis on trees.

A biological relationship where one species interacts with another for a long period of time is called symbiotic. In symbiosis, one member is benefiting from the relationship. If the other member is injured, the relationship is called parasitism. Mutualism is when both parties benefit. If the other species remains relatively unaffected, the relationship is called commensalism. This is the type of symbiosis demonstrated by both orchids and Spanish moss.

Commensalism

Commensalism is a symbiotic relationship between two species in which one species receives benefits while the other does not appear to receive any benefit, nor is it tangibly harmed. In a commensalistic relationship, the host species provides food, a home, protection or transportation for the other species. An example of this is the remora, a small fish, which lives in close association with manta rays. The remora attaches itself to the manta ray using its sucker-like dorsal fin. In so doing, the remora does not injure the manta ray. The remora benefits by eating scraps of food that escape the mantra ray's mouth.

Epiphytes

Encyclopedia Britannica online defines an epiphyte as "any plant that grows upon or is in some way attached to another plant or object for physical support." Approximately 70 percent of all orchids grow on other plants and are categorized as epiphytes. Other epiphytes include bromeliads, ferns, airplants, lichens and mosses. Spanish moss is classified as a bromeliad and is, therefore, an epiphytic plant. Epiphytes live in commensalastic relationships with their hosts as they do not rely on the host plant for nutrients.

Orchids

Orchids thrive in lightly shaded conditions.

Epiphytic orchids tend to grow in the inner branches, midway up mature trees as this provides them the lightly shaded conditions that they prefer. These orchids have succulent stems and highly efficient root systems that quickly absorb moisture and nutrients. They gain an enormous ecological benefit from living on larger plants: gaining more sunlight than if they were on the ground.

Spanish Moss

Spanish moss is commonly known as Florida moss, long moss or graybeard.

Almost all bromeliads are native to the Americas. Spanish moss is found growing on trees in the southern, coastal states as well as in the tropics. Spanish moss does not have a root system but has long, thin stems that wrap around the host tree and hang down from the branches. Its leaves are cup-like with permeable scales that allow the plant to capture moisture and nutrients from the air.

Detrimental Effects on Hosts

For the most part, orchids and Spanish moss grow in commensalistic symbiosis with their hosts. Sometimes the weight of epiphytic orchids or Spanish moss combined with the weight of accumulated organic debris can cause the limbs of the host tree to break off. Though Spanish moss does not directly harm trees, it can block sunlight and thereby, slow the growth of its host tree.

Interesting Facts

Spanish moss is not really a moss; it's a flowering member of the bromeliad family related to the pineapple. There is a species of orchid native to Southeast Asia which produces growths up to 20 feet long, and clumps weigh in excess of 2 tons.

References

• National Center for Biotechnology Information: PubMedCentral: Evolving Together: The Biology of Symbiosis
• PBS.org: Evolution: Coral Reef Connections
• Encyclopedia Britannica Online: Epiphyte
• Brooklyn Botanic Garden: Orchids and How They Grow
• School of Forest Resources and Conservation: Florida Forest Plants--Spanish-moss (Tillandsia usneoides)