International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 229-239 http://ecoevopublisher.com/index.php/ijmec 23 4 shading), and at the same time has a strong adaptability to arid environments (Figure 2) (Mitchell et al., 2021). The water retention capacity of the bark is also very important: tree species with spongy bark (such as cotton trees and mahogany) often have a higher coverage of epiphytic moss and mosses. The chemical composition of bark can affect the distribution of lichens, mosses and mycorrhizal appendages. Figure 2 Ecological characteristics of the epiphytic orchid Prosthechea karwinskii in mountain dry forests (Adopted from Santos-Escamilla et al., 2021) Image caption: (A) Habitat of Prosthechea karwinskii, an oak forest in San Pedro y San Pablo Teposcolula, Oaxaca. (B) Prosthechea karwinskii growing in situ as a hanging epiphyte on Quercus sp. in Santo Domingo Yanhuitlan, Oaxaca. Photographs by R. Solano (Adopted from Santos-Escamilla et al., 2021) The chemical composition of bark can affect the distribution of lichens, mosses and mycorrhizal appendages. Some barks are rich in tannins, resins and other substances, which may inhibit the germination of certain epiphytic lichen spores, resulting in fewer epiphytic lichen species of this tree species (Paoli et al., 2020). The age and size of the host tree affect the space and time occupied by epiphytes. Studies have shown that the several old trees with the largest diameters at breast height in a forest often carry a much greater diversity of epiphytes than other trees and are called "key hosts" (Shen et al., 2022; Siaz Torres et al., 2024). The transmission mechanism also shapes the "selection" of hosts by epiphytes. The vectors (wind, birds, etc.) and behaviors of many epiphytic plant seeds can cause them to tend to land on certain tree species. In addition, the requirements of epiphytes themselves for the microenvironment lead to their rooting in specific forest structures. For instance, some epiphytes require a shaded environment. Their spores germinate on the trunks of relatively shady tree species and do not survive on tree species with sparse canopies and direct sunlight (Dias-Pereira et al., 2022). 5 Ecological Functions of Epiphytes 5.1 Promoting role of biodiversity Epiphytic plants have significantly enhanced the biodiversity and ecological complexity of forests with their unique lifestyles. The presence of epiphytes effectively expands the forest ecological space, creating vertical habitats beyond the two-dimensional ground, thereby increasing β diversity (inter-habitat heterogeneity) (Svahnstrom et al., 2025). Just as some people refer to epiphytes as "the aerial gardens of the forest", this garden attracts and nourishes a host of flora and fauna residents in the forest canopy (Kromer and Batke, 2025). The significant contribution of epiphytes to the biodiversity of forests is also reflected in species conservation: many endangered plants such as orchids and ferns are epiphytes. Protecting epiphytes in forests is protecting these endemic species (Santos-Escamilla et al., 2024). In addition, at the landscape scale, different forest lands have enhanced regional diversity due to the diversity of epiphytic plant communities. For instance, in landscapes with remnants of primary forests and those with only secondary forests, the primary forests significantly increase the regional plant list due to the greater number of epiphytic species (Werner and Homeier, 2024).
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