Several studies of hurricane damage on epiphyte communities implied that epiphytes might be in danger of being blown off their host when subjected to strong wind. There is very limited knowledge about the mechanical impact that wind may have on epiphytes. Using a wind-triggered camera set-up, we observed how epiphytic tank bromeliads are affected by wind. Despite offering a relatively large area of ‘attack’ to the airflow, bromeliads moved relatively little themselves. Rather than being directly moved by wind, the bromeliads in the upper crown of tall trees moved with the sway of the branches. Only when the substrate did not move, bromeliads with long broad leaves showed considerable disturbance due to wind. Our observations underline the complexity of the system and emphasise that our current understanding of the mechanical aspects of the epiphyte–host system is still very limited.

We investigated the effects of host tree on epiphyte diversity, controlling for microclimate. We measured the light profiles of the lower trunks of 20 individuals, each from three host groups (tree ferns, dicots, palms) occupying the understorey in a tropical montane forest in Panama. The per cent cover and species richness of vascular and non-vascular epiphytes were surveyed on the lower trunks of each understorey host. Light varied considerably between trees (5–21% total transmitted light) but mean light level did not vary between types of host. Light was not significant as a covariate with host in any model. Tree ferns had higher covers than dicots and palms of filmy ferns (15%, 0.02% and 0.2%), other ferns (7%, 0% and 0.5%) and other vascular epiphytes (16%, 3% and 3.4%), and greater species richness of vascular epiphytes (filmy ferns: 3, 0.4 and 0.5; other ferns: 2, 0.2 and 0; other vascular: 7, 2 and 2). Dicots had a higher cover of liverworts (53%) than palms (18%) and tree ferns (27%). Palms and tree ferns were the compositional extremes. We conclude that the differences in species composition and cover between the three host groups relate better to physical differences between hosts than differences in light climate.

Almost 50% of the estimated 2500 species in the Bromeliaceae grow epiphytically in a remarkably wide range of habitats from inhospitable deserts to tropical rain forests (Benzing 2000). The degree of dependence on the host varies (Benzing 1990, Laube & Zotz 2006), and in some cases, epiphytic bromeliads may dispense completely with living hosts, and may thrive on artificial substrates such as electrical cables. This is not entirely surprising because this family provides examples of particularly remarkable adaptations to the epiphytic habitat like water-impounding leaf bases and water- and nutrient-absorbing scales (Benzing 2000). The so-called atmospheric forms in this family (e.g. Tillandsia recurvata) possess a dense covering of these scales, and use roots entirely as holdfasts, while leaves perform photosynthesis and take up water and nutrients. Although quite regularly mentioned in the literature (Benzing 1990, 2000; Brighigna et al. 1997, Lüttge 1989), we are not aware of any study investigating the vigour of plants growing on cables compared with plants growing on trees. The only functional aspects that have already been studied are related to nutrients, i.e. presence of nitrogen-fixing endophytes in Tillandsia recurvata plants from natural hosts and from electrical cables in Mexico (Puente & Bashan 1994) and differences in chemical composition of plant tissues and nutrient retention by leaves in Tillandsia capillaris growing on cables and trees in Argentina (Abril & Bucher 2009). Intermittent water supply, but also low nutrient supply, play an important role in epiphyte ecology (Zotz & Hietz 2001), which leads to the following alternative hypotheses: (1) Plants on electrical cables are usually close to roads.

The abundance of epiphytes has been assumed to be important in explaining the high diversity of tropical canopy arthropods. In this study we assessed the possible role that the presence of epiphytes may have on the diversity and abundance of canopy insects in an experimental study conducted in a coffee plantation in Coatepec, Veracruz, Mexico. Epiphytes were removed from trees in one of two plots in two sites of the coffee plantation. In each plot we collected insects from three Inga jinicuil trees by knockdown insecticide fogging. Insects were sorted to morphospecies, counted and measured. Trees with epiphytes had significantly higher numbers of species and individuals and insects larger than 5 mm were also more species-rich and abundant in trees with epiphytes. The magnitude of the enhancement was surprisingly large with the epiphyte plot samples having on average 90% more individuals and 22% more species than plots without epiphytes. These differences were even greater for large (>5 mm) insects (184% and 113% respectively). Our results support the tenet that epiphytes provide valuable resources to arthropods, which we have illustrated for canopy insects in shade trees of coffee plantations.

We conducted a survey of the epiphyte flora growing on the stilt palm Socratea exorrhiza in a primary lowland rain forest in Panama by means of a canopy crane. For each palm in a 0.9-ha plot, we determined diameter at breast height, tree height, per cent bryophyte cover and the number, identity and attachment site of all vascular epiphytes. The 118 palm trees hosted a total of 701 epiphytes and hemi-epiphytes, belonging to 66 species. Trees were estimated to be c. 20 y old before colonization with vascular epiphytes began. Epiphyte species were highly clumped and segregated along the vertical axis of the trunk. Sequential colonization led to an increased number of species and individuals as the tree grows. Epiphytes were associated with bryophyte patches much more than expected by chance, but no species seemed to depend upon them for establishment. The influence of tree size, age and bryophyte cover on the composition of the epiphyte community are discussed.