Spatial distributions of many tropical trees are skewed to specific habitats, i.e. habitat specialization. However, habitats of specialist species must be divergent, i.e. habitat divergence, to coexist in a local community. When a pair of species specialize in the same habitat, i.e. habitat convergence, they could not coexist by way of habitat specialization. Thus, analyses of habitat divergence, in addition to habitat specialization, are necessary to discuss coexistence mechanisms of sympatric species. In this study, the habitat specialization and habitat divergence along topographic gradients of eight sympatric tree species of the Fagaceae were studied in a 15-ha study plot in a tropical lower montane forest in northern Thailand. A statistical test with torus shift randomizations for 9673 trees of Fagaceae revealed significantly biased distributions for all of the species, for at least one of the four topographic variables used: elevation, slope inclination, aspect and convexity. Slope convexity was the most critical topographic variable, along which all but one species had significantly skewed distributions. Out of 112 possible combinations of species pairs and topographic variables, 18 (16%) and two pairs (1.8%) showed significant habitat divergence and habitat convergence, respectively. The observed habitat divergence alone could not completely explain the coexistence of the eight species. There was a gradation in the habitat position of each species, with relatively large overlaps between species distributed in similar habitats, and small overlaps between species associated with contrasting habitats, respectively. The gradual changes in the habitats of the species suggested that dividing the species into a small number of distinct habitat groups, such as ridge and valley specialists, would not be straightforward.

Nitrogenase activity in the surface soil and litter layers from a tropical lowland rain forest and an adjacent fernland in Sri Lanka was measured by the acetylene reduction method. The total amount of acetylene reduced, a measure of biological nitrogen fixation, was greater in the fernland (38.4 µmol m−2 h−1) than in the forest (15.3–29.2 µmol m−2 h−1). In both ecosystems the nitrogenase activity was greater (59–85%) in the soil than in the litter layer. The rates of acetylene reduction in soil and litter showed an inverse relationship with the decay constants of mixed litter and a positive relationship was found between the rate of acetylene reduction and the C:extractable nitrogen ratio of the soil. The relatively greater rate of nitro genase activity coupled with the slower rate of litter decomposition in the fernland indicates that accumulation of nitrogen may result in the soil and litter layers of the deforested areas during their aggrading phases.

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.

Plant productivity, distribution and diversity in tropical rain forests correlate with water availability. Water availability is determined by rainfall and also by the available water capacity of the soil. However, while rainfall is recognized as important, linkages between plant distribution and differences among soils in available water capacity have not been demonstrated. One reason for this may be that measurements of soil moisture, such as gravimetric water content, may be overly simplistic. To investigate this, we compared two sites in Panama, Allee and Rio Paja, which have similar rainfall but different plant communities. Soil water release curves were obtained from about −0.1 MPa to −9 MPa, permitting us to calculate available water capacity. The Rio Paja site had 17% greater available water capacity (between −0.1 MPa to −3 MPa), whereas the gravimetric water content at Rio Paja was lower by 16% in rainy season and by 41% at the end of the dry season. Hence soil gravimetric water content and soil available water capacity did not correspond. The results suggest that available water capacity may better predict plant distributions. Hence, whenever possible, available water capacity should be determined in addition to gravimetric water content.

Abandoned plantations of coffee, tea and other commercial crops offer opportunities for understanding ecological processes in modified forest ecosystems. Unlike tree plantations tea is maintained as a shrub with a continuous dense short canopy that precludes large-frugivore activity thereby limiting dispersal of forest species to such areas. In this study we determine how location and density of Grevillea robusta a shade tree in tea plantations and proximity of plantations to forests influences seed arrival from forests into the plantations. We also estimate the importance of dispersal modes in the colonization processes. We laid 10 × 10-m plots at three distance intervals from the forest edge in three different plantation types with varying shade tree densities. Within the plots we laid four 1× 1-m subplots at the corners of the plot. We estimated species richness, abundance and categorized the seeds into dispersal modes in these plots. Grevillea robusta increased species richness of seeds by three times and abundance of seeds by 3–30 times compared with plantations without them. Higher density of G. robusta increased seed input changed species composition and altered species dominance in the plantations. Distance to forests influenced seed arrival in plantations without G. robusta trees and plots 95 m from the forest did not have any seeds in them. No such effect was seen in plantations with G. robusta trees. Seeds dispersed by birds or a combination of birds and mammals contribute 30% of the seeds reaching the plantations with G. robusta and this was not influenced by distance from the forest. In plantations without G. robusta bird dispersal is restricted to 25 m from the forest edge. In general density of shade trees has a strong influence on seed arrival which can negate the forest proximity effect and enhance natural forest colonization.

New leaf production in seasonal tropical forests may result from changes in water or light availability. In this study, the relationship between leaf flushing, photosynthetically active radiation (PAR) and rainfall was examined for understorey saplings in a moist tropical forest over one year. During the wet season, weeks with greater PAR were correlated with a greater proportion of saplings flushing new leaves during subsequent weeks in nine out of ten species. Rainfall was negatively correlated with subsequent leafing during the wet season for six of ten species. However, during the dry season, rainfall was positively correlated with leafing during the following weeks for six species, but the relationship was much weaker. PAR in the dry season was negatively correlated with flushing in eight species. These results support the hypothesis that under well-watered conditions, light limits leaf production, and peaks in insolation result in greater leaf production.

Whereas broad-scale Amazonian forest types have been shown to influence the structure of the communities of medium- to large-bodied vertebrates, their natural heterogeneity at smaller scale or within the terra firme forests remains poorly described and understood. Diversity indices of such communities and the relative abundance of the 21 most commonly observed species were compared from standardized line-transect data across 25 study sites distributed in undisturbed forests in French Guiana. We first assessed the relevance of a forest typology based on geomorphological landscapes to explain the observed heterogeneity. As previously found for tree beta-diversity patterns, this new typology proved to be a non-negligible factor underlying the beta diversity of the communities of medium- to large bodied vertebrates in French Guianan terra firme forests. Although the species studied are almost ubiquitous across the region, they exhibited habitat preferences through significant variation in abundance and in their association index with the different landscape types. As terra firme forests represent more than 90% of the Amazon basin, characterizing their heterogeneity – including faunal communities – is a major challenge in neotropical forest ecology.

Of all feeding guilds, understorey insectivores are thought to be most sensitive to disturbance and forest conversion. We compared the composition of bird feeding guilds in tropical forest fragments with adjacent agro-ecosystems in a montane region of south-west Ethiopia. We used a series of point counts to survey birds in 19 agriculture and 19 forest sites and recorded tree species within each farm across an area of 40 × 35 km. Insectivores (~17 spp. per plot), frugivores (~3 spp. per plot) and omnivores (~5 spp. per plot) maintained species density across habitats, while granivores and nectarivores increased in the agricultural sites by factors of 7 and 3 respectively. Species accumulation curves of each guild were equal or steeper in agriculture, suggesting that agricultural and forest landscapes were equally heterogeneous for all bird guilds. Counter to most published studies, we found no decline in insectivore species richness with forest conversion. However, species composition differed between the two habitats, with certain forest specialists replaced by other species within each feeding guild. We suggest that the lack of difference in insectivorous species numbers between forest and agriculture in this region is due to the benign nature of the agricultural habitat, but also due to a regional species pool which contains many bird species which are adapted to open habitats.

Figs (Ficus species) are an important resource for a diverse array of organisms in most tropical forests (Janzen 1979 but see Gautier-Hion & Michaloud 1989). The inflorescence of Ficus, hereafter referred to as the ‘fig’, is an enclosed receptacle lined with unisexual flowers. The flowers of Ficus species are pollinated by wasps that feed on galled fig ovules as larvae and that lay eggs in fig flowers as adults (Weiblen 2002). Ripe figs are consumed by vertebrate frugivores, which are the primary dispersers of fig seeds (Shanahan et al. 2001). The interaction between figs, pollinators and frugivores introduces the potential for conflict between the roles of raising fig wasps and dispersing seeds. Specifically, the pollination mutualism could be compromised if frugivores consumed figs containing pollinator larvae. This conflict is resolved in very different ways according to the breeding system of the fig.

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.

We studied the breeding success and distribution of three species of eagles, four species of vultures and one species of eagle owl on two areas of differing primary productivity from 1973 to 1984. Densities of all species were lower in areas with lower productivity. Breed-ing success on both biomes was similar, the lower densities of birds on the least productive biome apparently compensating for the lower productivity. Eagles produced more one-egg clutches, laid later and reared fewer young in the period of poor rainfall, probably as a result of reduced productivity. Vulture data were difficult to interpret because abundant food at breed-ing time was created by ungulate population management throughout the entire study period. Concentrations of all species on the more productive biome, and solitary breeding on the least productive biome by a normally colonially breeding species, suggests that primary production also influences vulture densities and perhaps breeding success.

Logged forests form an increasingly large proportion of tropical landscapes but disproportionately few studies have studied the impact of forest disturbance, e.g. lightly vs. heavily logged, on tree and seedling communities simultaneously. We sampled all trees (on 1 ha) and all recently germinated seedlings (on 90 m2) in three lightly and three heavily logged sites in each of the following three East African tropical forests: Budongo Forest and Mabira Forest in Uganda and Kakamega Forest in Kenya. We analysed species richness, diversity, abundance and community composition of late- and early-successional trees and seedlings. We recorded no difference in species richness or diversity of late-successional or early-successional trees between lightly and heavily logged sites. However, the abundance of late-successional species was lower in heavily than lightly logged sites. Moreover, there was no difference in species richness or diversity of trees among the three forests. Yet, abundances of late-successional trees were higher in Budongo Forest than in Mabira Forest and Kakamega Forest. Species richness, diversity and abundance of seedlings did not differ between lightly and heavily logged sites. Only the abundance of seedlings of late-successional species differed among the forests with more individuals in Budongo Forest than in Mabira Forest. This was corroborated by non-metric multidimensional scaling (NMDS) showing clear differences in composition of tree and seedling communities among the three forests. Thus, both, the tree and seedling communities differed significantly among the three forests but not between lightly and heavily logged sites.

The population dynamics of the liana Machaerium cuspidatum (Fabaceae) were studied in an Amazonian forest in Ecuador using a stage-classified matrix model. Growth, mortality and number of new seedlings were recorded over two 1.5-y periods in eight 20 × 250-m transects. The population growth rate (λ) was 1.032, which was significantly higher than 1. The dynamics of the species were most influenced by survival of large plants, which is typical for slow-growing woody species. λ varied little among years or transects in spite of the high seedling production in one period. The importance of canopy openness and crown height for population growth was studied using bootstraps on λ for different subsets of the whole population. The results suggest that the population growth rate was lower in tall forest (height > 10 m) than in the population in general. The population growth rates in areas with shaded understorey and in low forest (≤ 20 m) were the same as for the whole population. A life table response experiment (LTRE) revealed that the lower λ in tall forest resulted from lower growth and survival of large plants in tall forest. These results indicate that the species is shade-tolerant but that it is sensitive to variations in forest dynamics. The dominance of the species and the increasing population size suggest that the forest has had a low disturbance rate for a long time.

In mid-elevation areas of Mesoamerica, Acacia pennatula commonly occurs in mixed woods with various species of oak. During a 1-y study in Nicaragua, we found the abundance of birds in acacia was far higher than the representation of this species in the mix of trees, whether this is estimated by number of individual trees, canopy cover or foliage cover. This higher abundance was probably related to the fact that acacias supported approximately three to four times the abundance of arthropods that were found in oaks and twice the biomass. Although oak foliage supported fewer arthropods, relatively more of them were large (>1 cm). The greater preponderance of small arthropods in acacias versus oaks was probably related to the small leaflet size of acacias. However, it is likely that the higher abundance of arthropods in acacias, particularly herbivorous species, was related to the higher nutritional content of the acacia foliage (crude protein, minerals, non-structural carbohydrates) and lower content of digestion-inhibiting compounds (structural carbohydrates, total phenolics, condensed tannins). The major defensive mechanisms of acacia are mechanical (thorns) or qualitative-defence chemicals (cyanogenic glucosides) that are apparently more effective against vertebrate than invertebrate herbivores. These observations support the hypothesis that the anti-herbivore defences of acacia are primarily directed against large mammalian herbivores, rendering the foliage highly palatable to arthropods.

Tropical montane systems are characterized by a high plant species diversity and complex environmental gradients. Climate warming may force species to track suitable climatic conditions and shift their distribution upward, which may be particularly problematic for species with narrow elevational ranges. To better understand the fate of montane plant species in the face of climate change, we evaluated a) which environmental factors best predict the distribution of 277 plant species along the Himalayan elevational gradient in Nepal, and b) whether species elevational ranges increase with increasing elevation. To this end, we developed ecological niche models using MaxEnt by combining species survey and presence data with 19 environmental predictors. Key environmental factors that best predicted the distribution of Himalayan plant species were mean annual temperature (for 54.5% of the species) followed by soil clay content (10.2%) and slope (9.4%). Although temperature is the best predictor, it is associated with many other covariates that may explain species distribution, such as irradiance and potential evapotranspiration. Species at both ends of the Himalayan elevational gradient had narrower elevational ranges than species in the middle. Our results suggest that with further global warming, most Himalayan plant species have to migrate upward, which is especially critical for upland species with narrow distribution ranges.

We investigate the effect of patch size on liana diversity and distribution in 19 patches of montane evergreen forest in the Nilgiri hills, Western Ghats, southern India. Additionally, we examined how liana species richness and community assemblage in both edge (within 10 m of the forest edge) and interior regions of forest patches respond to patch size, in order to infer the impact of forest expansion or reduction on the liana communities. A total of 1276 woody liana individuals of 15 species were identified, belonging to 10 genera and nine families. Total species richness of lianas was significantly positively related to forest-patch area, both when analysed for the entire patch, in addition to both core and edge regions when examined separately. Species richness of larger lianas also showed a significant positive relationship with increasing forest patch area. Community assemblage varied with respect to forest edge, with shade-dependent species only occurring in interior patch regions, shade-averse species in edge regions, and shade-tolerant species occurring throughout. Disturbance also played a role in determining the response of liana diversity to patch size, with heavily disturbed patches showing no relationship between patch size and diversity, whereas positive relationships exist in low to moderately disturbed patches. The most significant result is the change in liana community composition between small and larger fragments. Many species present in smaller patches are also present in edge zones of larger fragments. This suggests that lianas are important structural components of montane forest ecosystems, and their compositional patterns are possibly driven by succession. Moreover, this study reveals the importance of edge effect and patch size in influencing liana species richness and compositional patterns.

Tropical cyclonic storms with sustained winds above 120 km h−1 are called hurricanes, typhoons or cyclones depending on their geographic location. They can cause considerable damage to forests. This damage may be in the form of pruned and fallen trees from intense winds (Boucher et al. 1990, Walker et al. 1992), defoliation from a combination of winds and torrential rains (Vandermeer et al. 1997), or mortality from marine inundation of low-lying land (Gardner et al. 1991). Occasionally, extensive defoliation of forests can also occur from wind-driven saltwater when winds are onshore and precipitation is insufficient to dilute the seaspray (Chen & Horng 1993). Below I report the dramatic consequences of an unusual seaspray-laden typhoon on the vegetation of the western Micronesian island of Guam.

Stable isotopes are commonly used in ecological studies to infer food resources (Ambrose & DeNiro 1986, Bocherens et al. 1990,1991,1994;Yoshinaga et al. 1991) since isotopic composition is conserved during the feeding process. Moreover,for herbivorous (sensu lato) species, it is often possible to identify the main resource because different photosynthetic pathways generate different values of carbon isotope ratios (Park & Epstein 1961, Sternberg et al. 1984). This allows the characterization of broad biota such as savannas or forest and discrimination of grazers from sympatric folivorous species (DeNiro & Epstein 1978).

In tropical forests, most individual fruit-bearing trees depend on frugivores for seed dispersal (Howe & Smallwood 1982, Wilson 1992). Seed dispersal enhances germination potential, provides an opportunity for seeds to escape predation under the parent plants, and reduces seedling numbers under parent trees (Şekercioğlu et al. 2004). The way frugivores handle seeds and process them may influence the seed fate of many plants (Janzen 1971). The quantity of seeds dispersed and the quality of dispersal provided by frugivores impact plant fitness (Herrera & Jordano 1981). Schupp (1993) defined the effectiveness of seed dispersal by frugivores as an empirical measure of quantity of seeds dispersed and quality of dispersal from the parent plant to a suitable microsite. Seed dispersal by frugivores increases the chances for seedling survival away from the vicinity of the parent plant because in tropical forests seed predation is concentrated under adult trees that prevent seedlings from establishing near parent trees (Howe & Miriti 2004).