In forest ecosystems, epiphytes, as secondary foundation species, enhance both the quality and quantity of habitats for arthropods by providing plant structures and suspended soil on trees, which serve as primary foundation species. Since ants, which dominate the tree canopy, utilize epiphytes as nesting and foraging sites, the presence and abundance of epiphytes may contribute to the diversity of the tree canopy community. In this study, we proposed two hypotheses to clarify the effects of epiphytes on arboreal ant communities: 1) Epiphytes are more likely to be inhabited by ants than other habitats in the forest canopy, and this effect is size-dependent. 2) The presence and abundance of epiphytes influence arboreal ant communities.
This survey was conducted in a subtropical wetland forest on Iriomote Island. Ten 150 m² quadrats were established, and the number and size of epiphytes were recorded. Ants in the forest canopy, on tree trunks, and on epiphytes were collected using three methods:
i) Bait traps were placed on epiphytes and tree trunks (1.5 m above ground) outside the quadrats.
ii) The Winkler extraction method was used to collect ants from suspended soil on epiphytes.
iii) Bait traps were set in the forest canopy (5–8 m) within each quadrat, targeting three trees with epiphytes and three trees without epiphytes.
A total of 16 ant species were recorded using these three methods. Up to three species were found in any given trap. Ants were more frequently observed on epiphytes than on tree trunks, and the size of the epiphytes positively influenced the likelihood of ant occurrence. Colony collections obtained through the Winkler extraction method confirmed that ants were nesting within epiphytes. Additionally, two ant species were exclusively dominant in the canopy. However, the diversity index of canopy ants was not significantly related to the presence or abundance of epiphytes. These results suggest that epiphytes contribute to local scale ant diversity in the canopy. However, when a few dominant species monopolize the entire canopy, the effect of epiphytes on overall canopy diversity appears to be limited.