Studying species turnover along gradients is a key topic in tropical ecology. Crucial drivers, among others, are fog deposition and soil properties. In northern Peru, a fog-dependent vegetation formation develops on mountains along the hyper-arid coast. Despite their uniqueness, these fog oases are largely uninvestigated. This study addresses the influence of environmental factors on the vegetation of these unique fog oases. Accordingly, vegetation and soil properties were recorded on 66 4 × 4-m plots along an altitudinal gradient ranging from 200 to 950 m asl. Ordination and modelling techniques were used to study altitudinal vegetation belts and floristic composition. Four vegetation belts were identified: a low-elevation Tillandsia belt, a herbaceous belt, a bromeliad belt showing highest species richness and an uppermost succulent belt. Different altitudinal levels might reflect water availability, which is highest below the temperature inversion at around 700 m asl. Altitude alone explained 96% of the floristic composition. Soil texture and salinity accounted for 88%. This is in contrast with more humid tropical ecosystems where soil nutrients appear to be more important. Concluding, this study advances the understanding of tropical gradients in fog-dependent and ENSO-affected ecosystems.

Dipterocarpaceae, a dominant family of trees in South-East Asian tropical forests, are remarkable in that they exhibit supra-annual mass-flowering events. The flowering patterns are related to the El Niño Southern Oscillation, but the mechanism that precipitates mass-flowering is still debated. Here, we test if a cumulative-trigger model that tracks resource availability, specifically light, may better explain dipterocarp phenology than a direct-environmental-trigger mechanism. Using 11 flowering time series with an average length of 29 y and variety of candidate predictor variables (precipitation, cloud cover, minimum temperature and El Niño indices) we could not find a plausible direct-environmental-trigger (median AUCs across regions from 0.53 to 0.57 indicating near random predictions). The cumulative-trigger model based on El Niño indices showed better predictive results (AUC 0.67), which could further be improved by resetting the resource at known flowering events (AUC 0.76). Additional support for a cumulative-trigger model comes from the observation that regional differences in the time of year of peak flowering correspond to where El Niño effects are strongest. We conclude that cumulative resource tracking is an evolutionary plausible trigger mechanism that has other primary evolutionary advantages, such as predator satiation.

To understand how fruit tree characteristics and microhabitats shape the assemblage of birds on fig trees and the pattern of fig–bird interactions, we observed and recorded, over 96 d and 816 h, the frugivorous birds visiting 32 individual trees belonging to 14 species of Ficus that were distributed across four different sites. A total of 30 bird species were recorded as eating figs, comprising 66.7% of the total number of frugivorous bird species recorded at the four sites. Small passerine birds such as bulbuls were the dominant frugivores for fig species. The number of bird species visiting different fig trees was significantly influenced by the crop size and canopy volume. Fruit colour and fruit size did not significantly influence the number of bird species, whereas habitats appeared to influence the composition of visiting birds. The fig–frugivorous bird interaction was asymmetrically structured, and the degree of nestedness appeared to be influenced by the forest type and degree of disturbance: the degree of nestedness in non-limestone forest tended to be higher than limestone forest; forest with less disturbance tend to be more nested compared with the open forest with high disturbance.

Competitive interactions among pioneer species may have a significant impact on the course of secondary succession in tropical rain forests. We predicted that the outcome of competitive interactions in early succession would vary with soil nutrient availability. To test this hypothesis we grew seven pioneer tree species alone and in dense competitive mixtures, with four nutrient treatments: no nutrient addition, and N, P, and N plus P addition. Performance of plants grown alone and in mixtures was strongly nutrient limited. However, contrary to expectation, the competitive hierarchy among the seven species was almost identical among the four nutrient treatments. The dominant species, Melastoma malabathricum, accounted for > 70% of total stand biomass in all nutrient treatments. Seedlings of this species had higher rates of gas exchange and initial growth, and lower root allocation than the other species. Profiles of light availability within the competitive stands indicated that light levels at ground level were well above levels at which pioneer species can successfully survive and grow, yet seedlings of species other than Melastoma remained stunted. Leaf N concentrations in all stands were 25–55% reduced by competitive interactions, and N addition increased relative competitive performance in only Melastoma suggesting that Melastoma was particularly effective at N acquisition, limiting nutrient uptake by the other species. Toward the end of the experiment individuals of Melastoma began to reproduce, suggesting that the competitive hierarchy would have changed in a longer-duration experiment.

The mechanisms that maintain palm species diversity in tropical rain forests are still debated. Spatial variation in forest structure produces small-scale environmental heterogeneity, which in turn can affect plant survival and reproductive performance. An understanding of how palms respond to variation in forest heterogeneity may help to explain the diversity and structure of their assemblages. We used multivariate ordination statistics and multiple linear models to analyse how palm assemblages are affected by forest structure and landscape features in central Amazonia. In 72 (250×4 m) forest plots distributed over an area of 64 km2, we recorded all seedling and adult palms, and measured topographic and soil variables, and components of forest structure and tree abundance. We found 16976 adults and 18935 seedlings of 46 palm species and five varieties including two morphological forms making a total of 50 botanical entities. Results show that landscape features (altitude, slope, proportions of soil sand and clay) and various components of forest structure (such as degree of forest openness, abundance of forest trees, logs and snags, and leaf litter mass), influence spatial variation in richness, abundance and species composition of palms, creating ecological gradients in palm community composition. Despite the statistically significant effects of environmental variables, most species occurred throughout the full range of the ecological gradients we studied, indicating that there is either relatively weak niche specialization in the palms, or that the competition between the species is mediated by diffuse demographic processes that cannot be evaluated only through studies of species distributions.

Dioecious plants often exhibit male-biased sex ratios and sexual differences in life history traits such as plant size, growth rate and frequency of flowering, which arise from the different costs of reproduction for male and female plants. In tropical dioecious species sexual differences in reproductive costs have been demonstrated for several subcanopy species, but few canopy dioecious trees have been studied. We recorded the sexual expression of c. 2600 trees of Cecropia schreberiana and Dacryodes excelsa, two canopy dioecious species, during several censuses over 2 y in a 16-ha plot located in ‘subtropical wet forest’ in the Luquillo Mountains, Puerto Rico. There were similar numbers of male and female trees of C. schreberiana but D. excelsa had a female-biased population. Cecropia schreberiana showed no differences in male and female diameter distributions or growth rates, suggesting that reproductive maturation and longevity are similar for both sexes. This lack of differences in size and growth rate in C. schreberiana may result from mechanisms to compensate for the higher cost of reproduction in females, no resource limitation related to its pioneer life-history, or similar male and female reproductive costs. In contrast, D. excelsa males were larger than females, probably because males grow slightly faster than females. This sexual difference in D. excelsa may reflect a higher cost of reproduction in females than in males. Spatial segregation of males and females into different habitats is not common in tropical forest and neither C. schreberiana nor D. excelsa males and females exhibited significant spatial segregation. The contrasting results for these two canopy species reflect their different life history strategies in this hurricane-affected forest.

A modified Kempson apparatus is described, the extraction procedure for arthropods in neotropical soils is given, and an example from Central Amazonia is presented.

Patterns of buttress formation in tropical trees vary greatly within and among species. In Kibale National Park, Uganda, some form of a buttres was found on 23% of the 78 species (1785 trees) sampled from a variety of distantly related families. Large differences in buttress formation were documented within a single family and even within the same genus. Previous studies have suggested that buttresses are mechanical adaptations to counter asymmetric loads experienced during brief critical phases in a tree’s development and these persist after the need for a mechanical support has disappeared. As a tree grows from the understorey, up to the canopy, or emerges from the canopy, the potential number of occasions that a tree will experience directional stress increases. Many canopy level trees will probably have been in the vicinity of a treefall gap during their development, while emergent trees may experience gap exposure in addition to wind stresses associated with canopy emergence. Therefore, it is predicted that understorey trees should have fewer and less developed buttresses (after correcting for overall tree size) than canopy trees, which should have fewer and less developed buttresses than emergent trees. Detailed measurements of buttresses from 194 trees of eight species support this prediction. There was no evidence that trees thought to have experienced directional stress associated with selective logging almost 30 y ago had increased the number or size of existing buttresses. The pattern of buttressing in Kibale generally supports the idea that buttresses are mechanical adaptations to counter episodic asymmetric loads, and that buttresses persist after the need for a mechanical support has disappeared.

Amazonian white-sand vegetation has unique tree communities tolerant to nutrient-poor soils of interest for interpreting processes of adaptation in neotropical forests. Part of this phytophysionomy is confined to Late Quaternary megafan palaeo-landforms, thus we posit that sedimentary disturbance is the main ecological factor controlling tree distribution and structuring in this environment. In this study, we characterize the topographic trend of one megafan palaeo-landform using a digital elevation model and verify its relationship to the forest by modelling the canopy height with remote sensing data. We also compare the composition and structure (i.e. canopy height and diameter at breast height) of tree groups from the outer and inner megafan environments based on the integration of remote sensing and floristic data. The latter consist of field inventories of trees ≥ 10 cm dbh using six (500 × 20 m) plots in várzea, terra firme and igapó from the outer megafan and 20 (50 × 20 m) plots in woodlands and forests from the inner megafan. The unweighted pair group method with arithmetic mean (UPGMA) and the non-metric multidimensional scaling (NMDS) were applied for clustering and dissimilarity analyses, respectively. The megafan is a sand-dominated triangular wetland with a topographic gradient of < 15 cm km−1, being more elevated along its axis. The outer megafan has a higher number of tree species (367), taller canopy height (mean of 14.1 m) and higher diameter at breast height (mean of 18.2 cm) than the white-sand forest. The latter records 89 tree species, mean canopy height of 8.4 cm and mean diameter at breast height of 15.3 cm. Trees increase in frequency closer to channels and toward the megafan's axis. The flooded and nutrient-poor sandy megafan substrate favoured the establishment of white-sand vegetation according to the overall megafan topography and morphological heterogeneities inherent to megafan sub-environments.

The assemblages of root-feeding chrysomelid larvae from 21 locally common tree species were studied in a secondary tropical forest in New Guinea and compared with confamilial larvae and adults feeding on the foliage. Larval host plants were inferred from adults emerging from the soil containing the roots of known tree species. In total, 2495 chrysomelids from 100 species were reared from the roots. Almost 90% of adults in the forest canopy recruited from the species with root-feeding larvae, while species with leaf-feeding larvae represented 1% of individuals (the feeding guild for the remaining 9% was unknown). The root-feeding larvae were thus more important in tropical than temperate forests, possibly because of predation pressure by ants on tropical vegetation. The number of chrysomelids emerging annually from the soil in 1 ha of the forest was approximately 0.2 million. Root-feeding larvae were polyphagous as their modal host range included three or four from the six plant families studied. The lack of correlation between the phylogenetic distance of tree species and the similarity of their chrysomelid assemblages indicated that host choice was not constrained by plant phylogeny. The host range of larvae feeding on roots was as wide as that of the conspecific adults feeding on the foliage. The density and species composition of larval and adult assemblages on the studied trees were not correlated. These results suggest that even studies restricted to adult assemblages, which represent a majority of chrysomelid studies, can be informative, as the composition of adult assemblages is not necessarily constrained by larval host-plant selection.

Recruitment success of individual plants is limited by an array of biotic and abiotic factors. Seedling survival may experience high mortality due to negative density dependence or altered microclimatic conditions. This study reports regeneration of Poulsenia armata (Moraceae), in the fragmented landscape of the Los Tuxtlas region in south-eastern Mexico. Density, survival and growth of seedlings (<1 y) and juveniles (<150 cm height) of P. armata were predicted to be significantly lower in forest fragments compared with extensive continuous forest. Contrary to expectation, density did not vary between habitats; however, we found twice the number of seedlings (n = 82) in forest fragments than in the continuous forest (n = 35). Forest fragments were associated with higher seedling densities close to adult trees. Unexpectedly, we found no evidence for negative density dependence in plant survival or growth. Survival and growth of P. armata were negatively impacted in forest fragments, with desiccation by warmer daily temperatures likely the cause of mortality, independent of density. Of the 111 individuals recorded in 2010 in forest fragments, 38% died over 2 y of census (n = 42), while 9% (n = 12) of the 127 individuals from the continuous forest died. Higher rates of mortality suggest that conditions in forest fragments are detrimental to seedling cohorts over time. Low juvenile recruitment jeopardizes persistence of P. armata, in fragmented populations of this rain-forest tree.

Relative densities of mahogany species vary across tropical Africa and correspond with changes in soil fertility and moisture status. Seedling growth of four co-occurring African mahoganies (Entandrophragma spp.) was studied in relation to soil nutrient and moisture status in a shade-house experiment. On naturally occurring forest soils, E. cylindricum and E. utile exhibited increased relative growth rate (RGR) and decreased root mass ratio (RMR) with an increase in soil fertility while E. angolense and E. candollei did not. Changes in leaf morphology with fertility did not correspond to changes in species performance. On moist, fertile soils, E. angolense outperformed congeners but E. candollei performed equally well on moist infertile soils. Entandrophragma cylindricum performed as well as E. angolense and E. candollei on two of three soil moisture stress treatments but E. utile consistently performed poorly. Comparative seedling performance fitted well with limited available data on the distribution of Entandrophragma spp. in relation to soil fertility and moisture gradients and suggests that within-forest microsite heterogeneity may help explain the distribution of Entandrophragma species within the Dzanga-Sangha Dense Forest Reserve, Central African Republic.

Most butterfly species forage for nectar, which provides them with carbohydrates and to some degree other nutrients, such as lipids and amino acids (Boggs 1987). A small number of genera feed exclusively on rotting fruits and plant sap (DeVries et al. 1999). Some 40 passion vine butterfly species, belonging to the genus Heliconius Kluk and a closely related monospecific genus Laparus Billberg gather nutrients from pollen feeding (Brown 1981, Gilbert 1972). Although common in bees, wasps, flies and beetles (Roulston & Cane 2000, Thorpe 2000), pollen feeding is rare among lepidopterans. In order to collect pollen, adults scrape anthers with the proboscis and gather the grains. The pollen is then incubated in solution and the amino acid-rich solution is ingested. The empty pollen grains are eventually discarded (Gilbert 1972, Krenn & Penz 1998). Pollen feeding provides amino acids that are used for egg production and somatic maintenance in adult Heliconius (Dunlap-Pianka 1979, Gilbert 1972, 1991). The most common sources of pollen are flowers of species in the genera Psiguria Neck. ex Arn. and Gurania (Schltdl.) Cogn. (Cucurbitaceae). The home range of an individual Heliconius will encompass one to many pollen plants (Murawski & Gilbert 1986).

Seed-consuming rodents are increasingly recognized for their roles in the maintenance of tree species diversity, by acting on crucial post seed-dispersal processes. Yet, studies examining the extent to which rodents may act as secondary seed dispersers and/or predators in Madagascar's forests are limited. Thread-marking seed experiments were run to address this, using the seeds of two native large-seeded, frugivore-dispersed tree species (Abrahamia thouvenotii and Cryptocarya crassifolia), in disturbed and less-disturbed habitats in the rain forests of Ranomafana National Park, during the dry season. Data show that post-dispersal handling of seeds by rodents (predation and removal) was significantly lower in disturbed than in less-disturbed habitats (1.31–3.78 times lower; n = 2200). Also, seeds were more likely to be predated or left on the forest ground after removal than being larder- or scatter-hoarded: 27–78% of the removed seeds were found on the ground, <12% found in burrows and there was no evidence of scatter-hoarding (n = 132). Based on pictures from camera traps, the native rodent species, Nesomys rufus, was potentially responsible for seed predation and/or removal in the less-disturbed habitat; but no indication of the rodent species active in the disturbed habitat was obtained. The lack of scatter-hoarding suggests a limited role of rodents in secondary seed dispersal in this system. These findings form a preliminary account of the potential roles of rodents in post seed-dispersal processes in Madagascar's forests, but this warrants further study.

Nanophyes shoreae (Coleoptera, Apionidae) is a pre-dispersal fruit-predator of dipterocarp trees in South east Asian rain forest These trees frequently abort a large part of their fruitcrop soon after anthesis, coincident with N shoreae oviposition Fruit parameters, related to the incidence of weevil attack, were investigated by examination of fruit collected from host trees and through observations made in the canopy Fruit size and the incidence of prior oviposition determined whether beetles initiated attacks However, many fruits were attacked without oviposition occurring and this is discussed with respect to chemical stimuli

Dormancy and germination ecology of two Harpagophytum species (Pedaliaceae) from an open Acacia savanna in Botswana were investigated. The maintenance of dormancy is governed partly by the seed coat but mainly by the endosperm and the embryo itself, as demonstrated by removal of the endosperm. Dissemination of the seed from the fruit can be delayed for several years without affecting the viability of the embryo, due to very low respiration rates.

Germination can be enhanced slightly by high temperatures under natural conditions, and by gibberellic acid or removal of the endosperm under laboratory conditions. Relative growth rates for both Harpagophytum species are lower than for subtropical grasses and legumes, due to a strong investment in root and tuber biomass. Germination and seedling growth is discussed in relation to the drought avoidance syndrome and the animal disperser syndrome.

In the Cerrado of Itirapina, Brazil, 34% of the shrubs of Didymopanax vinosum (Araliaceae) were colonized by the honeydew-producing homopteran Aconophora teligera (Membracidae) which was found exclusively on this species of plant. Correlations were made between membracid density and ant frequency, as well as between these parameters and plant damage. We found that: (1) ant frequency was higher on branches with membracids and both were more frequently found near apical meristems; (2) herbivore damage was lower on apical meristems where the membracids concentrate than on ones where they are absent; (3) the presence of membracids on the plant was correlated with a reduction in the occurrence of other potential herbivores, especially on the branches housing membracids; (4) plants with more tillers tended to have a larger number of membracids. The data suggest that the presence of A. teligera and associated ants probably reduce herbivory on apical meristems of D. vinosum.

Small mammal live-trapping was carried out in a dry tropical forest mosaic in Huai Kha Khaeng Wildlife Sanctuary, central Thailand. Trapping was done in two forest types in three seasons. Maxomys surijer was the dominant species in both plots. The three most abundant species in each plot accounted for > 90% of all captures. Community structure, density, relative abundance, biomass, age structure of populations, and habitat usage of some small mammal species varied by forest type and season. The dry evergreen/mixed deciduous forest type supported a greater abundance and biomass of small mammals than the mixed deciduous/dry dipterocarp forest type in all seasons, although species richness was the same. The greatest density, biomass, and home-range size for Maxomys surijer occurred in the rainy season in both forest types. Seasonal changes in ratios of adults and subadulls of several species suggested a breeding peak at the end of the dry season or beginning of the rainy season. The mixed deciduous/dry dipterocarp forest showed a drastic drop in numbers, density, and biomass of small mammals six weeks after a fire burned through it.