International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 229-239 http://ecoevopublisher.com/index.php/ijmec 22 9 Research Insights Open Access Commensal Relationships in Forests: The Ecological Role of Epiphytes Xianliang Xu Horticulture & Landscape Center, Hainan Institute of Tropical Agricultural Resouces, Sanya, 572025, Hainan, China Corresponding email: xianliang.xu@hitar.org International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5 doi: 10.5376/ijmec.2025.15.0023 Received: 06 Aug., 2025 Accepted: 15 Sep., 2025 Published: 28 Sep., 2025 Copyright © 2025 Xu, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Xu X.L., 2025, Commensal relationships in forests: the ecological Role of epiphytes, International Journal of Molecular Ecology and Conservation, 15(5): 229-239 (doi: 10.5376/ijmec.2025.15.0023) Abstract This study introduces the diversity pattern, functional adaptation and ecological role of epiphytes in forest ecosystems. Research has found that there are various symbiotic relationships in forest ecosystems, with epiphytes being typical representatives. It forms a symbiotic relationship with the host tree: Epiphytes utilize the support and space provided by the host tree, but generally do not directly absorb nutrients or water from the host. Epiphytic plants are rich in species, including ferns, mosses, lichens, orchids and bromeliads, etc., and are widely distributed in tropical, subtropical and even temperate forests. Epiphytes play a significant role in maintaining forest biodiversity, regulating the microclimate of the forest canopy, and participating in nutrient and water cycling. However, deforestation, climate change and air pollution pose threats to epiphytes, and the decline in their diversity will weaken the above-mentioned ecological functions. The recovery and conservation of epiphytic plants can be promoted through conservation strategies such as strengthening corridor connections and artificial breeding and reintroduction. Epiphytes, as a crucial yet easily overlooked component in forests, their research and protection are of vital importance for maintaining the integrity of forest ecosystems. Keywords Epiphytic plants; Symbiotic relationship; Forest diversity; Functional adaptation; Ecological function 1 Introduction In forest ecosystems, there exist complex interrelationships among organisms, and commensalism is one of the common types. In a symbiotic relationship, one party benefits while the other remains largely unaffected. In canopy ecosystems, epiphytes and the host trees to which they attach are usually regarded as symbiotic relationships (Garcia-Garcia et al., 2025). This kind of symbiotic relationship is very important in forests because it creates opportunities for many plants to survive in the vertical space of the forest, greatly enriching the structure and biodiversity of the forest (Kromer and Batke, 2025). For instance, in the canopy layer of tropical rainforests, a large number of epiphytic plants "live at high altitudes", together with the ground vegetation, forming a multi-level forest structure. Symbiotic relationships enable species in different niches to coexist, promoting energy flow and material cycling at multiple levels (Amici et al., 2020). Epiphytes are generally defined as "plants that can germinate and grow on the surface of other plants (mainly trees) throughout their entire life cycle but do not obtain nutrients from their hosts" (Kromer and Batke, 2025). It is estimated that 20% to 39% of the vascular plants in the Tropical Plant Diversity Center are epiphytes, and in some specific tropical regions, the number of epiphyte species in the flora even exceeds half. The main epiphytic vascular plant groups include: Ferns (such as epiphytic ferns of the Polypodiaceae family), Orchidaceae (Orchidaceae, which accounts for a particularly prominent proportion of epiphytic flowering plants, approximately 75% of epiphytic angiosperms), and Bromeliaceae It includes many epiphytic species such as the genus Airweed, plants of the Araceae family (such as some epiphytic plants of the genus Peperomia), and the genus Peperomia, etc. The non-vascular epiphytes are mainly mosses (including moss, lichen, etc.) and lichens. These groups each have their own adaptability, forming diverse epiphytic types. Epiphytic plant groups are rich, and different groups occupy different positions in the vertical stratification of the forest, constituting unique and significant components of the forest ecosystem. Epiphytes also include some special life forms, such as hemiepiphytes, whose life cycle is in an epiphytic state for part of the time and extends long roots to penetrate the soil at another stage. For instance, some Ficus plants are epiphytic on trees when they
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