How diverse are epiphyte assemblages in plantations and secondary forests in tropical lowlands?

The on-going destruction of old-growth forests puts tropical forest species under great pressure because of the resulting loss of habitat. An important biotic component of these forests are vascular epiphytes, which structurally depend on trees. In human-modified landscapes potential hosts may still be present, e.g. in the form of isolated remnant trees, small groups of planted trees, in patches of secondary forests, or in plantations. For this study, we assessed the potential of timber monocultures and secondary forest patches to function as refuges for vascular epiphytes. We studied epiphyte assemblages in teak and pine plantations and secondary forest patches of unknown age along a rainfall gradient (1100 – 4200 mm) at the Pacific coast of western Panama and also in a few oil palm plantations. Invariably, rainfall had the expected positive influence on epiphyte diversity and abundance. Individual-based rarefaction curves showed that species richness was significantly lower in timber and oil palm plantations compared to secondary forest patches, which in turn hosted less species-rich epiphyte assemblages than (cultivated and wild grown) pasture trees from the same study region. Our results suggest that the value of timber and oil palm plantations as refuges for vascular epiphytes in human-modified landscapes is limited. Secondary forest patches were more promising in that regard.