Vascular epiphytes are a diverse and conspicuous component of biodiversity in tropical and subtropical forests. Yet, the patterns and drivers of epiphyte assemblages are poorly studied in comparison with soil-rooted plants. Current knowledge about diversity patterns of epiphytes mainly stems from local studies or floristic inventories, but this information has not yet been integrated to allow a better understanding of large-scale distribution patterns. EpIG-DB, the first database on epiphyte assemblages at the continental scale, resulted from an exhaustive compilation of published and unpublished inventory data from the Neotropics. The current version of EpIG-DB consists of 463,196 individual epiphytes from 3,005 species, which were collected from a total of 18,148 relevés (host trees and 'understory' plots). EpIG-DB reports the occurrence of 'true' epiphytes, hemiepiphytes and nomadic vines, including information on their cover, abundance, frequency and biomass. Most records (97%) correspond to sampled host trees, 76% of them aggregated in forest plots. The data is stored in a TURBOVEG database using the most up-to-date checklist of vascular epiphytes. A total of 18 additional fields were created for the standardization of associated data commonly used in epiphyte ecology (e.g. by considering different sampling methods). EpIG-DB currently covers six major biomes across the whole latitudinal range of epiphytes in the Neotropics but welcomes data globally. This novel database provides, for the first time, unique biodiversity data on epiphytes for the Neotropics and unified guidelines for future collection of epiphyte data. EpIG-DB will allow exploration of new ways to study the community ecology and biogeography of vascular epiphytes. K E Y W O R D S biodiversity, community ecology, database, forest plot, hemiepiphytes, Neotropics, nomadic vines, taxonomic diversity, vascular epiphytes, vegetation relevé 520 |

In tropical montane forests epiphytes represent a substantial proportion of biodiversity and green biomass, particularly where fog occurs almost daily. Epiphytes play important ecological roles in these ecosystems, for example, in forest hydrology and in amplifying arthropod biodiversity, but quantitative assessments of epiphytic biomass and species diversity are rare. Such data are important, however, for a better understanding on their ecological roles and as a baseline for detecting ecological change due to climate or land-use changes. In a tropical lower montane cloud forest (c. 1,150 m above sea level) in Panama, we identified and weighed all epiphytic matter, which includes vascular plants, bryophytes, lichens, and dead organic matter from the trunks of 22 trees varying in diameters at breast height and 28 canopy branches. Additionally, we collected epiphytic matter in the understory in 22 plots of 2 Â 2 m. A total of 155 species of vascular epiphytes, hemiepiphytes, and nomadic vines were found. Orchidaceae were by far the most species-rich family, followed by Araceae and Bromeliaceae. The vertical distribution of these species in the forest showed species-specific vertical preferences, but species numbers varied little in undergrowth, trunks, and tree crowns. Epiphytic matter was positively related to tree size, and we used tree-size data inventory data from a nearby 1-ha plot to extrapolate our findings to the plot level. The resulting estimate of 16,439 kg ha À1 for total epiphytic matter and 6,214 kg ha À1 for living plants, the latter representing about 2% of aboveground forest biomass.

Ongoing destruction of tropical forests makes isolated pasture trees potentially important for the persistence of original forest dwellers such as many vascular epiphytes. We studied epiphyte assemblages on 100 isolated trees at ten pasture sites in southwest Panama along an elevational gradient ranging from 140 to 1240 m a.s.l. We analysed epiphyte species composition (richness, similarity) and registered climate and host trait variables of potential influence on their occurrence. We found a total of 5876 epiphyte individuals belonging to 148 species. Epiphyte abundance, species richness and diversity all varied about 4-fold among the 10 sites, with a high similarity of epiphyte assemblages among sites. Two sites at 870 and 1050 m a.s.l. did not fit into the overall elevational trend of increased abundance, species richness and diversity. However, all three measures were significantly correlated with humidity as the independent variable. This highlights that a gradient in humidity, and not elevation as such, is responsible for the typical elevational changes in epiphyte assemblages, so that special local conditions may lead to deviations from expected patterns. Our documentation of current elevational diversity patterns also provides a baseline for the study of long-term changes in epiphyte assemblages in anthropogenically modified landscapes.

Velamen radicum, a dead tissue at maturity, characterizes the roots of many epiphytes. Apart from a role in water and nutrient uptake, protection against excessive radiation in the upper forest canopy has also been suggested, but this function has never been critically assessed. To test this notion, we studied the roots of 18 species of Orchidaceae and Araceae. We defined thermal insulation traits of velamina by monitoring the temperature on the velamen surface and just below the velamen while exposing it to infrared radiation. We investigated velamen’s functionality-correlating morphological and thermal insulation traits. In addition, we investigated the viability of the living root tissue after heat exposure. The maximal surface temperatures ranged from 37–51 °C, while the temperature difference between the upper and lower velamen surface (i.e., ∆Tmax) ranged from 0.6–3.2 °C. We found a relationship of velamen thickness with ∆Tmax. Tissue viability was strongly affected by temperatures >42 °C, and no significant recovery after heat exposure was found. Thus, there is only limited support for an insulating function of velamen, but the data suggest considerable species-specific differences in heat tolerance. The latter could be a crucial determinant of the vertical distribution of epiphytes.