The arthropod fauna inhabiting 90 individuals of three different species of epiphyte was investigated in the moist lowland forest of the Barro Colorado National Monument in Panama. In total, 3694 arthropods belonging to 89 morphospecies and 19 orders were collected. While arthropod abundance was primarily a function of host plant biomass irrespective of epiphyte species, there were pronounced differences in species richness, species composition and guild structure of the arthropod faunas of the three epiphyte species. Although all study plants were growing in close proximity on the same host tree species, there was remarkably little overlap in the species assemblages across epiphyte taxa. The inhabitant species also differed dramatically in their ecological functions, as feeding guild and hunting guild analyses indicated. The influence of plant size, structure and impounded leaf litter on arthropod diversity is discussed. We conclude that epiphytes are microhabitats for a diverse and numerous fauna, and that different species of epiphytes foster both taxonomically and ecologically very distinct arthropod assemblages.

Growth and survival of plants of eight species of epiphytic bromeliad were studied over a period of 5 y in a humid montane forest in eastern Mexico using repeated photographs of branches. Growth was calculated from annual size increment and used to predict the time taken to reach fertility. Most intermediate-sized plants grew at a rate of 2–3 cm y−1, with the exception of Tillandsia deppeana, which does not invest in offshoots and grew about twice as fast. Tillandsia deppeana and two Catopsis spp. were predicted to become fertile after 11 and 9 y, respectively, T. multicaulis and T. punctulata after 13 y and T. juncea after 18 y. Individuals growing closer to the tree top tended to grow slightly faster. Relative growth rate calculated as biomass increase of the leading shoot was highest in T. deppeana and lowest in T. juncea. These differences are related to the proportion of biomass invested in offshoots, which are most numerous in T. juncea and mostly absent in T. deppeana. Fast maturation is particularly important for species growing on small and exposed branches, which experience higher mortalities caused by the breakage of their supporting branches.

The spatial organization of epiphytes has come under increasing attention. This kind of information is necessary for the general understanding of their ecology and for the design of sustainable harvesting methods. In this study, the small-scale (local) distribution of epiphytic bromeliads was studied using correlograms and permutational regression on distance matrices. Fieldwork was carried out in a young secondary forest stand in the central cordillera of Colombia at 3150 m asl. A complete census of the bromeliads in this plot was made, using a lattice with 400 quadrats. Six species of bromeliad were found (1008 individuals). All of these except one showed an aggregated spatial pattern. This pattern was independent of the position of the trees in the sampled plot. The distribution of the bromeliads was determined by the availability of substrate (branch surface area per quadrat), the proximity of conspecifics and the geomorphology of the terrain. The structure of the forest surrounding an epiphyte had an influence on the position of the epiphyte in the tree (height measured as distance from the canopy). The use of two-dimensional, lattice-based sampling strategies is discussed as a possible method for comprehensive surveys of epiphyte populations in natural forests.

We examined the effects of the 1997–98 El Niño drought on nine rain forests of Mount Kinabalu, Borneo, at four altitudes (700, 1700, 2700 and 3100 m) on contrasting geological substrata (ultrabasic versus non-ultrabasic). Measurements of rainfall and atmospheric aridity indicated that the departure from normal conditions during the drought became greater with increasing altitude. During 1997–99 (drought period) compared to 1995–97 (pre-drought period), median growth rates of stem diameter of trees decreased for both smaller (4.8–10 cm) and larger (≥ 10 cm) diameter classes in the six upland forests (≥ 2700 m on ultrabasic substrata and ≥ 1700 m on non-ultrabasic substrata), but for neither diameter class in the other forests. The majority of species decreased or did not change growth rates during 1997–99, whereas some did increase. Tree mortality increased during 1997–99, at the larger diameter class in the two lowland forests (700 m) on both substrata, and at least at the smaller diameter class in the four upland forests (≥ 1700 m) on non-ultrabasic substrata. In two of these upland forests, mortality was restricted to particular understorey species. Mortality did not significantly increase in the three upland forests (≥ 1700 m) on ultrabasic substrata; this suggests that the adaptation to nutrient-poor soils might have provided the resistance to drought.

How do animals respond to an unpredictably heterogeneous environment? Ants foraging in the leaf litter of tropical wet forests experience unpredictably fluctuating food resources. To study how an ant species responds to these changes, foragers were tracked to determine home ranges of 51 colonies of Aphaenogaster araneoides, in three sites in a Costa Rican tropical wet forest. Of these colonies 16 were excavated to measure colony size, colony growth, and reproductive investment. These demographic variables were compared with two measures of home range quality: leaf litter dry weight and mass of arthropods. Home range areas of colonies were highly correlated with colony size, and moderately correlated with resource abundance. Colony growth was independent of colony size, as is found in other ants in unpredictable environments. The growth of colonies was closely associated with resource abundance. Production of the male reproductive caste was closely tied to the size of a colony rather than growth, but male production in slow-growing colonies was limited. Colonies foraging within high-quality environments grew at a faster rate, but reproduction was mainly correlated with colony size. Furthermore, it was found that the frequency of foragers in long-term treatment plots with supplemental food and reduced leaf-litter quality was not significantly different from the frequency of foragers in control plots. This rain-forest ant does not modify its home range areas in response to poor environments, and as a result, small-scale environmental heterogeneity strongly determines growth and reproduction.

The allometry of crown shape and trunk diameter with tree height were analysed for four tree species in a tropical lowland rain forest, southeast Brazil. The dimensional relationships of a subcanopy species (Garcinia gardneriana) were contrasted with those of two canopy (Chrysophyllum flexuosum and Swartzia simplex) and one emergent species (Sloanea guianensis). For all trees ≥ 1 cm dbh, we recorded dbh, total height, branching height, crown area, crown width and crown length. Observed allometric relationships indicated interspecific variation in trunk diameter and crown shape with height. All species conformed to the elastic similarity model, except the emergent one that showed thicker trunks and a scaling exponent conforming to the constant stress model. The general allometric function used to describe the overall relationship (all sizes combined) did not specify exceptional variation in crown shape between species of contrasting adult stature (emergent vs. subcanopy species). However, when allometric relationships through ontogeny were considered, different strategies of growth, maintenance and expansion of crown became evident. Crown shapes were much more variable in canopy and emergent species than in the subcanopy one, suggesting that larger-statured species might be more flexible in the relative allocation of energy to height, diameter, and crown growth than smaller-statured ones. Notwithstanding, it is suggested that it is not possible adequately to predict allometric relationships only by adult stature/canopy position. Allometric variation may be also related to size-dependent changes in demographic traits and/or different responses to light availability among tree species.

Seed removal was evaluated at the macro- and micro-habitat level in areas differing in successional stage in the Bolivian Amazon. The successional stages consisted of secondary forests of 2, 10 and 20 years old and primary forest. Seeds of nine tree species were artificially dispersed and the number of seeds removed was evaluated over 7 weeks. Several stand characteristics were measured at the sites where seeds were dispersed. Seed removal at the end of the experiment varied from 50 to 100% depending on the species, and from 74 to 90% depending on successional stage. In general, the removal rate decreased with an increase in age of successional stage. The seed removal rate was related to liana density and not to litter thickness. Different microhabitat characteristics explained the seed removal rate of four species but microhabitat characteristics did not explain the decrease in seed removal rate with an increase in forest age. The results support the idea that post-dispersal seed removal reduces the number of seeds available for germination, consequently playing an important role in the regeneration of abandoned agricultural areas.

Palm seeds of the genus Astrocaryum are known to attract a wide range of seed predators, including insects, rodents and peccaries. We investigated the removal of seeds of Astrocaryum murumuru var. macrocalyx in dense groves and under solitary palms, both within and outside of peccary exclosures. We set out arrays of 40 seeds at each of 40 sites representing four treatments: in the open and in peccary exclosures, in groves and under solitary palms. Seed removal from each site was monitored daily for 55 d. Infra-red-triggered cameras were installed to identify the species that removed seeds. From the known and hypothesized behaviour of vertebrate seed predators under various circumstances, we predicted that (1) overall seed loss should be higher under solitary trees, (2) peccaries should forage preferentially in groves, (3) the variance in the rate of seed removal should be higher in groves, (4) a greater fraction of the seeds removed from solitary palms should be scatterhoarded, and consequently, (5) greater numbers of seedlings should recruit near solitary palms than in groves. The first four of these predictions were confirmed and the last was rejected by the results. Peccaries preferred to forage in groves, and small rodents preferred to forage under solitary palms. Whether in groves or under solitary palms, peccaries preferentially removed seeds from large arrays (21–40 seeds), and mostly ignored small arrays (≤ 20 seeds). Camera trapping demonstrated that the most frequent visitors to seed arrays were Myoprocta pratti and Proechimys spp. There was no significant difference in the numbers of seedlings around trees in groves versus solitary trees.

The high predation pressure in aquatic environments is generally assumed to be the ultimate cause of terrestrial breeding in anurans (Downie 1993, Magnusson & Hero 1991, Poynton 1964, Yorke 1983). It has evolved multiple times and is presently found in most anuran families (Bogart 1981, Duellman 1992). It is often associated with higher humidity and thus lower desiccation risk in tropical forests (Duellman & Trueb 1986). Most clutches that are oviposited terrestrially are either hidden in subterranean refuges or attached more or less exposed to vegetation (Duellman & Trueb 1986, Lamotte & Lescure 1977). Exposed clutches however, face the risk of desiccation, even in rain-forest environments (Rödel pers. obs.) and are still vulnerable to predation. Such disparate groups as various arthropods (Villa 1977, 1980; Villa & Townsend 1983, Vonesh 2000), frogs (Crump 1974), snakes (Roberts 1994, Scott & Starrett 1974, Warkentin 1995) and birds (Brosset 1967), have been reported to feed on these clutches. The foam nests,which occur in at least six tropical anuran families, seem to provide better protection. Their drying surface and their more or less liquid interior offers the tadpoles an aquatic environment that is well protected against desiccation and predation (Duellman & Trueb 1986, Seymour & Loveridge 1994). In addition the bubbles of the foam facilitate oxygen diffusion within the nest and may even provide a capacious oxygen store for eggs and hatched tadpoles (Seymour & Loveridge 1994). Few predators have been reported to feed on foam nests, one of which,paradoxically, is a frog (Drewes & Altig 1996). In the Taï National Park, Ivory Coast, we discovered a quite unexpected group of predators preying on foam nests and frog clutches exposed on leaves: monkeys.

An important property of plant communities is the Leaf Area Index (LAI), which is the vertically integrated surface of leaves per unit of ground area. Leaves are the primary sites of photosynthesis and transpiration, thus the LAI, which conditions the light interception by the canopy, is directly related to carbon and water exchange with the atmosphere at the stand scale (McNaughton & Jarvis 1983). LAI also has an impact on tree growth through the interception of light. Light availability below canopies is the principal limiting factor of tree recruitment and growth in forests (Denslow et al. 1990). Several methodologies have been used for measuring LAI in the field. These can be classiffed in four categories (Marshall & Waring 1986): (1) direct measurements by litterfall collection or destructive sampling, (2) allometric correlations with variables such as tree height or tree diameter, (3) gap-fraction assessment (e.g. with hemispherical photographs), (4) measurement of light transmittance with optical sensors.

The integrity of ecological interactions, such as pollination and seed dispersal, has been recognized as important for long-term conservation of biodiversity (Asquith et al. 1999, Buchmann & Nabhan 1997, Howe 1984, Pizo 1997). This is illustrated by the fact that the loss of large-bodied animals like birds and mammals after habitat fragmentation can result in population changes or even extinction of many plant species (Silva & Tabarelli 2000). In the absence of primary seed dispersers (vertebrates), the importance of invertebrates such as ants, that can carry or clean seeds, probably increases.

During the redrawing of Figure 1 some of the bars within Exp. 1 were omitted, plus the incorrect species name was introduced on two of the graphs. The publishers would like to apologise to the authors and their readers for these errors. The corrected figure appears below.