Epiphyll specialization for leaf and forest successional stages in a tropical lowland rainforest

Prepared by Anna Mežaka, Maaike Y. Bader, Noris Salazar Allen & Glenda Mendieta-Leiva

Lichen, liverwort, algae and fungi patches on an old leaf of Xylopia macrantha. Barro Colorado Island, Panama. Photo credit: Anna Mežaka.

Forest gaps in tropical rainforests contribute to habitat heterogeneity and vascular plant diversity. However, the role of forest gaps in maintaining the diversity of other organisms, such as that of epiphylls, is unclear. Epiphylls are organisms that grow on the leaves of vascular plants, mostly in tropical wet forests. Bryophytes and lichens represent two major epiphyll groups. For epiphylls, new communities start forming continuously as new leaves appear in the forest. Epiphyll succession thus does not depend on gaps being formed. However, as the microclimate in gaps differs from that in closed forest, succession paths in epiphyll communities may differ between these habitat types, so that forest gaps can still increase epiphyll diversity. To determine leaf- and forest-level specialisation of epiphyll communities for successional stages, we studied how epiphyll communities change with leaf age in gaps and closed forest sites.

After identifying and analysing the epiphyll communities on leaves of three age classes, we found that succession is mostly driven by species accumulation in both gap and closed forest sites. Both groups contained species that specialised for either gap or closed-forest environment.

Zetek gap site on Barro Colorado Island, Panama. Photo credit: Anna Mežaka.

Our study shows that miniature epiphyll communities on leaves are highly diverse and shaped by heterogeneity at both the leaf and forest scale. Forest gaps thus indeed contribute to epiphyll diversity maintenance. For a more detailed analysis of epiphyll community development, future research could follow single leaves through time, although the identification of the species in situ will be highly challenging, to say the least.

This is a plain language summary for the paper of Mežaka et al. published in the Journal of Vegetation Science (https://doi.org/10.1111/jvs.12830).