What characterizes commensalism?

Commensalism is characterized by a specific type of interaction between two different species in which one species benefits while the other species is neither helped nor harmed. This relationship often occurs in nature where one organism uses another for a habitat or as a means of transportation without affecting the host in any significant way.

For example, epiphytic plants, such as orchids, can grow on trees; they benefit from the height and increased exposure to sunlight without taking nutrients from the tree or negatively impacting it. In this way, the commensal organism gains a beneficial advantage for its growth and reproduction, while the host remains unaffected. This contrasts sharply with mutualism, where both species benefit, or parasitism, where one species benefits at the expense of the other. In commensalism, the key point is that the host species remains neutral in the interaction, highlighting the unique nature of this ecological relationship.