Neglected epiphytism: Accidental epiphytes dominate epiphytic communities on tree ferns in the Atlantic Forest

Vascular epiphytes and tree ferns constitute an important part of the Atlantic Forest structure. We characterized vascular epiphyte communities on two tree fern species (Alsophila setosa Kaulf. and Cyathea phalerata Mart.) including accidental epiphytes (i.e., species that are usually terrestrial, without necessarily completing their life cycle as an epiphyte), which have been overlooked in many previous studies. We aimed to understand epiphytism in terms of distribution, diversity, community composition, and host attributes that affect the richness and abundance of accidental epiphytes. Despite the great species richness of accidental epiphytes, they were-in contrast to true epiphytes-generally low in abundance and heavily represented by singletons and doubletons. We did not identify a difference in accidental epiphytic diversity and composition between host species, implying that both host species provide similar habitats for accidental epiphytes-although some epiphytic species showed a preference for a specific host species and/or stratum. Epiphyte richness and abundance were positively associated with a codependence of host surface area and moisture content, but only for accidental epiphytes. Our study illustrates the importance of two tree fern species as epiphyte hosts in the rainforest understory. It also shows that, although frequently overlooked, accidental epiphytism can be common in the understory of tropical forests and a phenomenon that merits further study in this region. Abstract in Portuguese is available with online material.

Automated summary

The study characterizes the vascular epiphyte communities on two tree fern species and highlights the significance of accidental epiphytes in the ecosystem. It emphasizes the importance of understanding epiphytism in terms of distribution, diversity, community composition, and host attributes, especially in tropical forests.