Predators of herbivorous insects play important roles in tropical ecosystems as herbivory may affect structure and diversity of plant populations. Although insectivorous bats are particularly abundant and diverse in the tropics, their impact on herbivorous insects is little understood. To assess prey consumption, we observed the gleaning bat Micronycteris microtis (Phyllostomidae) continuously for 3 mo including 16 full nights at a nightly feeding roost on Barro Colorado Island in Panama using infrared videotaping combined with collection of prey remains. Individual bats consumed about 61–84% of their body mass in arthropods per night. Diet analysis revealed a high percentage of herbivorous insects, constituting more than half (51%) of all prey and over 70% of prey biomass. Dominant prey were caterpillars (33% of prey biomass), and other herbivores including crickets, katydids, scarab beetles and phasmids. Furthermore, a novel feeding behaviour was observed as M. microtis selectively discarded parts of intestines of phytophagous insects before consumption, probably to avoid intake of plant material either for ballast reduction and/or for protection from secondary plant compounds. Combined with estimated feeding rates of insects in sympatric bat species, our data suggest that gleaning bats are important predators of herbivorous insects and might be under-estimated reducers of herbivory in the tropics.

The ‘aggregation model of coexistence’ predicts that a strong and independent aggregation of species across ephemeral resource patches promotes species coexistence and maintains diversity. This study examines the role of aggregation in maintaining tropical dung beetle diversity and the effects of deforestation on aggregation patterns and diversity loss. Using clusters of pitfall traps, dung beetle aggregation was quantified in natural and disturbed habitat at nested temporal and spatial scales in central Peru. The results indicate that dung was colonized by a greater number of species, many of which were large, leading to a higher total beetle biomass in forest habitat than in deforested, farm habitat. Beetles were intraspecifically aggregated at each spatial scale examined. Habitat-type (forest/deforested) had no effect on the intensity of intra- or interspecific aggregation. Analyses of aggregation patterns revealed that dung beetle assemblages in forest habitat were generally saturated whereas in deforested habitat they were unsaturated. In general, interspecific aggregation was too weak relative to intraspecific aggregation to explain the high diversity of species in forest habitat. Other mechanisms, including resource partitioning are likely to play a greater role in maintaining the diversity of dung beetle assemblages in the region. These results also indicate that the loss of species from disturbed habitat has not been due to a breakdown in the aggregation mechanism.

Co-evolutionary processes have moulded interactions between hummingbirds (Trochilidae) and ornithophilous flowers. Generally, long corollas exclude short-billed trochilids, whereas short corollas allow access for both long- and short-billed species. At La Mucuy, Sierra Nevada National Park, Mérida, Venezuela, we studied interactions between Aphelandra runcinata (Acanthaceae) and its avian pollinators. Of 13 trochilid species reported from this site, only two, Coeligena torquata and C. eos, have bills long enough to allow legitimate access to the nectar of A. runcinata flowers. However, we observed that hummingbirds with much shorter bills were also able to extract nectar and pollinate the flowers. This is due to a reversible compression mechanism in A. runcinata, caused by the pressure exerted by the bird in flight and the physical opposition of the inflorescence. The compression mechanism observed in A. runcinata flowers is a morphological characteristic that provides mutualistic advantages for both the plant and its avian visitors. The spectrum of potential pollinators is increased by giving access to nectar even to species with short or medium-long bills. Moreover, nectar-robbing, a foraging strategy that does not result in pollen transfer common among short-billed trochilids, seems to be reduced.

Although the potential contribution to tropical tree species coexistence of niche differentiation along light gradients has received much attention, the degree to which species perform differentially along soil resource gradients remains unclear. To examine differential growth response to soil resources, we grew seedlings of nine tropical tree species at 6.0% of full sun for 12 mo in a factorial design of two soil types (clay and white sand), two phosphate fertilization treatments (control and addition of 100 mg P kg−1) and two watering treatments (field capacity and water limitation to one-third field capacity). Species differed markedly in biomass growth rate, but this hierarchy was almost completely conserved across all eight treatments. All species grew more slowly in sand than clay soils, and no species grew faster with phosphate additions. Only Eperua grandiflora and E. falcata showed significant growth increases in the absence of water limitation. Faster-growing species were characterized by high specific leaf area, high leaf allocation and high net assimilation rate but not lower root allocation. Slower-growing species exhibited greater plasticity in net assimilation rate, suggesting that tolerance of edaphic stress in these species is related more to stomatal control than to whole-plant carbon allocation. Although relative growth rate for biomass was correlated with both its physiological and morphological components, interspecific differences were best explained by differences in net assimilation rate across six of the eight treatments. A suite of traits including high assimilation and high specific leaf area maintains rapid growth rate of faster-growing species across a wide gradient of soil resources, but the lack of plasticity they exhibit may compromise their survival in the poorest soil environments.

Large-scale natural disturbances, such as hurricanes, can have profound effects on animal populations. Nonetheless, generalizations about the effects of disturbance are elusive, and few studies consider long-term responses of a single population or community to multiple large-scale disturbance events. In the last 20 y, two major hurricanes (Hugo and Georges) have struck the island of Puerto Rico. Long-term population trends of 17 species of terrestrial gastropod were evaluated to determine whether gastropods respond to hurricane disturbances in a consistent fashion. Some species increased, some decreased, and some exhibited no simple trend in density or spatial variability following disturbance. In addition, some species responded differently to the two hurricanes with respect to population density, absolute spatial variability, or relative spatial variability. Population responses probably hinge on trade-offs between sensitivity to microclimatic changes and resource availability resulting from the relocation of biomass from the canopy to the forest floor. The historical context within which a hurricane occurs may be as important, or more so, than the intensity of the storm, per se.

Seed dispersal by frugivores is thought to play an important role in the maintenance of tropical forest diversity. Spider monkeys (Ateles spp.) are amongst the most frugivorous primates known, and they incorporate a diverse array of fruit species in their diets. In a 1-y study in lowland Ecuador, 670 h of focal observations and data on 916 faecal depositions were collected, and these data are used to describe the seed dispersal patterns of one group of wild spider monkeys (Ateles belzebuth) in terms of both the quantity of seeds dispersed and the primary seed shadows generated. Spider monkeys fed on the fruits of at least 152 plant species and swallowed seeds from more than 98% of these. Collected faecal samples contained seeds from at least 133 different plant species, with an average of 1.9 species (range: 0–7) per defecation. Individual spider monkeys dispersed a minimum of ∼195 000 seeds >1 mm in diameter per year, ∼35 000 of which were >3 mm in diameter. Mean retention time for seeds was 4.5 h. Seed dispersal distances averaged 443 m, but some seeds were moved >1250 m away from parental sources. These results suggest that declines in populations of spider monkeys might have a direct effect on forest dynamics, especially if other disperser species cannot compensate for their lost ecological services.

Tree recruitment is determined in part by the survivorship and growth of seedlings. Two seedling cohorts of the three most abundant caesalpiniaceous species forming groves at Korup, Cameroon, were followed from 1995/1997 to 2002, to investigate why Microberlinia bisulcata, the most abundant species, currently has very few recruits compared with Tetraberlinia korupensis and T. bifoliolata. Numbers of seedlings dying, and the heights and leaf numbers of survivors, were recorded on 30 occasions. Survivorship after 2.5 y was 30% for M. bisulcata and 59% for the similar Tetraberlinia spp. together. After 7 y the corresponding values were 4 and 21%. Growth of all species was slow for the first 4 y; but survivors of T. korupensis became 63% taller, as the other species stagnated, by 7 y. The poor recruitment of M. bisulcata was the result of its very low seedling survival. Within species, the tallest seedlings of M. bisulcata and T. bifoliolata, but medium-height ones of T. korupensis, survived longest. This was likely due to higher root allocation in T. korupensis. Seedling dynamics of M. bisulcata and T. korupensis over 7 y accorded well with relative abundances of adult trees; T. bifoliolata is predicted to recruit later.

Cerberiopsis candelabra is a long-lived monocarpic rain-forest tree endemic to New Caledonia that shows mass flowering across a substantial proportion of a population, and across a substantial number of populations. We investigated the relationship between tree size and flowering (and subsequent dying) across 18 populations from the flowering event of 2003 in order to understand the role of possible size thresholds for flowering in the life history and regeneration ecology of this monocarpic species. There was a strong positive correlation between trunk diameter and the incidence of flowering when population data were combined. However, the relationship between size and flowering was complex in that flowering occurred across a wide range of tree sizes, with almost complete overlap in size between flowering (5–79 cm dbh) and non-flowering trees (5–64 cm dbh), and with large trees in both the flowering and non-flowering state in the same population. In about half the populations studied there was no significant difference in mean trunk diameter of flowering and non-flowering trees. Nonetheless, we suggest that tree size may play a fundamental role in the life history and regeneration ecology of this species. The seedlings appear to be relatively shade-intolerant and dependent on large canopy gaps for recruitment. A significant effect of mass flowering and subsequent death of multiple large trees is the potential to form large canopy gaps and enhance seedling survival, as the gap is temporally linked with seed germination. However, it is unclear why there is such a large size range of flowering trees, i.e. whether this is just a consequence of the proximate cue, or whether the optimal size for flowering does indeed vary among individuals.

We examined the relationship between giraffes (Giraffa camelopardalis) and Acacia nigrescens in Kruger National Park, South Africa, to determine whether these tall ungulates may be providing a pollination service for the trees, or are simply flower predators. We quantified florivory and subsequent fruit set in the presence and absence of giraffes. Acacia nigrescens flowers are clearly a substantial dietary component for giraffes. Although A. nigrescens flowers contain almost three times as much condensed tannin as leaves, giraffes consume large quantities of flowers (∼85% of flowers within reach), resulting in distinct browse lines on the trees. This substantial florivory is detrimental to the overall fecundity of A. nigrescens, with significantly reduced fruit set at heights on trees that are accessible to giraffes. Fruit set increased above the reach of giraffes, suggesting successful pollination by insects. Giraffes were effectively flower predators of A. nigrescens in the season we examined.

Maximum height was assessed for tree species from seven temperate deciduous forests, one subtropical forest and one tropical forest and combined with published tree heights for three other tropical forests. The temperate deciduous forests showed a strong concentration of canopy species and a dearth of subcanopy species. In contrast, the four tropical forests showed more uniform distributions of maximum heights, while the subtropical forest had an intermediate distribution. The tropical and subtropical sites had greater densities of small trees than did the temperate sites and most of these small trees were members of small-to medium-sized species. Sapling recruitment per unit stem basal area increased with declining maximum height in Panama, which is consistent with the criterion for coexistence of species of differing stature derived from Kohyama's forest architecture hypothesis. Greater penetration of light into gaps and favourable conditions for growth over most of the year may allow more smaller-statured species to coexist with canopy trees in tropical vs. temperate forests.

This study provides a community-level analysis of how regeneration requirement and adult stature are related to tree allometry (diameter, height and crown size) throughout post-seedling ontogeny on Barro Colorado Island, Panama. Comparing 65 species, gap species are taller, have higher diameter growth rates and occupy more low-canopy sites (≤10 m canopy height) than shade species at small diameters (≤10 cm dbh). For trees >10 cm dbh, diameter-height relationships and growth rates no longer differ between gap and shade species, but shade species have larger, particularly deeper, crowns than gap species. Species with tall adult stature have more slender stems with larger crowns compared with treelet and mid-canopy species starting at 5 cm dbh. From 10 to 40 cm dbh, diameter growth rate is also significantly greater for tall species. The consistent allometric differences between functional groups on a community level will, in part, determine vertical and horizontal stand structure.

Forest structure and species distribution patterns were examined among eight topographically defined habitats for the 205 species with stems ≥ 1 cm dbh inhabiting a 25-ha plot in the Sinharaja rain forest, Sri Lanka. The habitats were steep spurs, less-steep spurs, steep gullies and less-steep gullies, all at either lower or upper elevations. Mean stem density was significantly greater on the upper spurs than in the lower, less-steep gullies. Stem density was also higher on spurs than in gullies within each elevation category and in each upper-elevation habitat than in its corresponding lower-elevation habitat. Basal area varied less among habitats, but followed similar trends to stem density. Species richness and Fisher's alpha were lower in the upper-elevation habitats than in the lower-elevation habitats. These differences appeared to be related to the abundances of the dominant species. Of the 125 species subjected to torus-translation tests, 99 species (abundant and less abundant and those in different strata) showed at least one positive or negative association to one or more of the habitats. Species associations were relatively more frequent with the lower-elevation gullies. These and the previous findings on seedling ecophysiology, morphology and anatomy of some of the habitat specialists suggest that edaphic and hydrological variation related to topography, accompanied by canopy disturbances of varying intensity, type and extent along the catenal landscape, plays a major role in habitat partitioning in this forest.

Spatial and seasonal patterns of seed removal by rodents, ants and birds were evaluated using seed-dish experiments in a Trachypogon savanna in Venezuela. Four-day experiments were conducted on three dates and at four different sites. Seeds from 10 native plant species representing a broad mass range were offered at densities equivalent to 3145 seeds m−2. We found that total seed removal and relative importance of granivorous groups varied widely among sites and dates. Rodents were the major seed predators in all the habitats, except for the savanna/forest border where birds dominated. Ants removed more seeds than birds, but since they preferred the smallest seeds, ants ranked last in mass removed. We found a temporally variable relationship between seed removal rates and seed rain or seed bank. We inferred monthly seed predation from seed-dish experiments as well as through the decline of the seed bank in the environment during the dry season, and compared both estimations to evaluate the suitability of the seed-dish technique for estimating granivory. We initially hypothesized that seed-dish experiments that emulate seed availability more closely may yield a better estimate of seed predation, but in fact, they may still overestimate granivory intensity.

This study examined the foraging behaviour of a resident bird species, the rufous-capped warbler (RCWA, Basileuterus rufifrons), in a shaded-coffee farm in Chiapas, Mexico. Unlike many resident species that use shaded-coffee agroecosystems seasonally, RCWAs do not move to other habitats when migrants are present. RCWA foraging was compared when migrant birds were present (dry season) and absent (wet season). It was hypothesized that RCWAs would exhibit a seasonal foraging niche shift because of resource competition with migrants. Observations from both the canopy and coffee understorey show that RCWAs foraged almost equally in both vegetative layers during the wet season although they were more successful foraging in the canopy. In the dry season, migrants foraged primarily in the canopy and RCWAs shifted so that 80% of RCWA foraging manoeuvres were in the understorey. At that time RCWAs foraged less successfully in both vegetative layers. Avian predation in the dry season was found to reduce densities of arthropods by 47–79% in the canopy, as opposed to 4–5% in the understorey. In the canopy, availability of large (>5 mm in length) arthropods decreased by 58% from the wet to dry season. Such resource reductions could have caused the RCWA foraging niche shift yet other alternative or additional hypotheses are discussed. Shifts in foraging niche may be a widespread mechanism for some small insectivorous residents to avoid seasonal competition with abundant migrant species.

Seedlings of five species in the Dipterocarpaceae were grown in experimental plots in Sabah, Malaysia. These were sited both in gaps and understorey and on alluvial and sandstone soils. Half of all seedlings were provided with a complete fertilizer. Herbivore damage levels were recorded on over 25 000 individual leaves in four surveys over the course of 2 y. Rates of herbivory were lower on mature leaves (0.07–0.8% leaf area mo−1 among species) than new leaves (2.1–4.4% leaf area mo−1). There were no overall effects of light conditions, soil type, fertilizer treatment or time on rates of herbivory. The only consistent source of variation was that between species, with the three alluvial-specialist species suffering higher rates of damage than the two sandstone-specialists. Mature leaves of alluvial species received greater damage in sandstone soils, whereas sandstone species were damaged at equivalent rates on both soil types. New leaves were more damaged on their native soil type. Published herbivory rates vary in the timescales and methods of measurement. Nevertheless, the few comparable studies confirm that herbivory rates on seedlings in tropical rain forests are remarkably constant over time and across experimental treatments.

Tropical rain forests are well known as centres of insect diversity and much effort has focused on the role of larval host plant specificity in generating and maintaining this diversity, but fewer studies have examined the exploitation of different food resources by adults in this context. Tropical butterflies feed as adults on a wide range of resources and we examined the diversity and ecology of species feeding on rotting fruit and carrion in a tropical lowland rain forest in Sabah, Borneo. We found that species richness and diversity were significantly higher on carrion than on fruit, and that this pattern was repeated at genus and family level. There was little similarity in species assemblages on the two substrates and β-diversity between carrion and fruit comprised 33% of the total diversity of butterflies feeding on decaying matter. β-diversity between canopy gap and shade microhabitats comprised 21% of total species diversity on carrion but only 7% of the total on fruit, indicating greater functional diversity on carrion in terms of light preferences. Captures were strongly male-biased on carrion but not on fruit, and recapture rates were much lower on carrion than on fruit. Species from two subfamilies (Nymphalinae and Charaxinae) exploited both substrates and for Charaxinae, there was evidence from adult flight morphology that species on carrion were capable of faster more-powerful flight. These results support the notion of a distinctive carrion-feeding fauna comprising more mobile species, which may use carrion to meet additional nitrogen requirements resulting from greater musculature. However there was no relationship between flight morphology and substrate choice in the Nymphalinae, and carrion-feeding may not have a unitary explanation.

Fig pollinators (Agaonidae, Chalcioidea) lay their eggs in fig inflorescences (Ficus, Moraceae). Reproductive success for both partners is thus largely dependent on the dispersal of these tiny wasps. Some are known to cover substantial distances (> 10 km) using wind above the canopy. However, fig ecology is extremely varied, and hence one might also expect a diversity of pollinator dispersal strategies. We studied fig pollinator dispersal in Sarawak (2001 and 2004) and Peninsular Malaysia (2003). The results indicate substantial differences in dispersal ecology between the pollinators of monoecious and dioecious figs. Monoecious-fig pollinators were common, and species composition and rank abundances were similar between years despite short sampling periods. Substantial temporal and spatial variation in their production is thus smoothed out by long-distance dispersal. Some species whose hosts do not occur at our Sarawak site and are rare throughout Borneo were caught, suggesting exceptionally long-distance dispersal in these species. Conversely, few dioecious-fig pollinators were caught and species overlap between years was low. Dispersal range in many dioecious-fig pollinators may be more restricted. At a finer scale, among genera pollinating monoecious figs we found marked differences in flight behaviour (height and time-of-dispersal). We relate these findings to the ecology of their hosts, and discuss the implications for fig–fig-pollinator coevolution.

We investigated the dispersal of a large-seeded tree species, Canarium euphyllum (Burseraceae), in the moist evergreen forests of the Khao Yai National Park in Thailand. By combining direct observations of fruit consumption in tree canopies (543 h) and the camera-trapping observations of fallen fruit consumption on the forest floor (175 camera-days), we identified the frugivore assemblage that foraged on the fruits of C. euphyllum and assessed their role in seed dispersal and seed predation. In the canopy, our results showed that seeds were dispersed by a limited set of frugivores, one pigeon and four hornbill species, and predated by two species of squirrel. On the forest floor, seven mammal species consumed fallen fruits. A combination of high rates of fruit removal and short visiting times of mountain imperial pigeons (Ducula badia) and hornbills (Buceros bicornis, Aceros undulatus, Anorrhinus austeni and Anthracoceros albirostris) led us to conclude that these large frugivorous birds provide effective seed dispersal for this tree species, in terms of quantity. These frugivorous species often have low tolerance to negative human impacts and loss of these dispersers would have severe deleterious consequences for the successful regeneration of C. euphyllum.

Stick insects (Phasmida) are important herbivores in tropical ecosystems, but have been poorly investigated in their natural environment. We studied phasmids and their food plants in a tropical lowland rain forest in Borneo (Danum Valley, Sabah, Malaysia). Thirty species of phasmid were collected from 49 plant species during nocturnal surveys in the forest understorey. In most cases (35 plant species), experiments confirmed that these phasmids fed on those plant species from which they were collected. Partitioning of phasmid species among food plant species was highly significant. Two common species had a largely restricted diet: Asceles margaritatus occurred mainly on Mallotus spp. (Euphorbiaceae) and Dinophasma ruficornis on Leea indica (Leeaceae). Other phasmids fed on a broad spectrum of plant families and can be considered polyphagous (e.g. Haaniella echinata, Lonchodes hosei herberti). Feeding experiments were performed on captive phasmids using leaves from eight plant species. Asceles margaritatus showed a significantly higher consumption rate for Mallotus miquelianus leaves than for other plants, while H. echinata showed the opposite trend and the lowest consumption for M. miquelianus. However, A. margaritatus readily accepted foliage from several plant families, particularly when Mallotus was not offered at the same time. Therefore, studies on host specialisation by herbivores need to include their distribution in the natural vegetation.

A prediction of the hypothesis that niche processes control plant species distributions across edaphic gradients is that pairwise comparisons of related species on contrasting soils should show consistent patterns of trait divergence. This hypothesis was tested in lowland Bornean rain forest by combining measurements of leaf traits, soil nutrients and the distribution of tree species in the Dipterocarpaceae across a nutrient gradient. Nine species were studied, comprising four related pairs in Shorea (phylogenetic independent contrasts; PICs) and one habitat generalist (Dipterocarpus sublamellatus). Lamina area, specific leaf area (SLA), leaf nitrogen (N) and phosphorus (P) were measured for ∼10 saplings of each species; habitat associations were defined as a continuous function of soil nutrients and categorically in relation to substrate. Species distributions and traits varied significantly with soil nutrients. When all species were pooled, SLA and leaf P increased significantly with species' distribution across the nutrient gradient; leaf N showed the same trend. Trait shifts with habitat were stronger and more pervasive when habitat was defined categorically – in all four PICs, rich-soil specialists had larger leaves, higher SLA, leaf N and P, and lower N:P ratios. Trait shifts with habitat at least partly reflect intrinsic differences between species. Within Shorea, variation in lamina area and N:P ratio were more strongly related to phylogeny than habitat, whereas the reverse held for SLA and leaf P. Phylogeny also influenced the extent of trait divergence between related species on different soils, and patterns of trait correlation within lineages. Results support the hypothesis that niche processes influence the distribution of species and traits in lowland tropical tree communities, and highlight the value of phylogenetic information for increasing the power of comparative studies.