All mature individuals of Aglaia aff. flavida (Meliaceae) were mapped in a 260 ha study area at the Crater Mountain Biological Research Station in Papua New Guinea. Sixty-four reproductively mature trees were found in an aggregated distribution with a mean inter-tree distance of 88.9 m. The sample consisted of 35 female and 29 male trees with a mean shortest distance between sexes of 232 m. Seed production and seed removal of 22 female trees was monitored throughout the 1992 fruiting season. Female trees with in 200 m of male trees generally produced large seeds crops (> 100 seeds) whereas trees farther than 200 m from the nearest male had small seed crops (< 100 seeds) regardless of female size (DBH). Most seeds (63.2%, n = 3312) produced in a sub-sample of 22 trees came from the five most fecund trees, which also produced 74.1% of the seeds that were removed by vertebrate dispersers. Where a minority of a population of rare tropical trees produce the majority of progeny, sustainable harvest practices would be most effective where highly fecund individuals are identified and conserved.

Strangler fig density varied considerably in the evergreen forest of Karian Shola National Park, southern India, with 11 individuals ha−1 in an open trail area and 5.6 individuals ha−1 within the primary forest area. The index of light level was assessed by estimating the percentage of upper canopy cover along the longitudinal centre of ten, 500-m × 20-m plots in each of the two areas of the evergreen forest. However, the increase in strangler fig density was not correlated to light levels but was significantly correlated to the numbers of their main host species in the two areas. In Karian Shola National Park, strangler figs occurred predominantly on a few host species with 20 and 50% of strangler figs growing on Vitex altissima, Diospyros bourdilloni and Eugenia/Syzygium spp. in the primary forest and trail areas respectively. Both young and established strangler figs were recorded mainly on larger individuals of their host trees indicating that older host trees are likely to be more suitable for the germination and establishment of strangler figs. The reason for the above could be the higher incidence of humus-filled and decaying regions in the older host trees which would provide an assured supply of nutrients for the establishing strangler fig.

Patterns in above-ground biomass of tropical forests over short altitudinal gradients are poorly known. The aim of this study was to investigate the variation of above-ground biomass with altitude in old-growth forests and determine the importance of changes in floristic composition as a cause of this variation. We used a dataset from 15 1-ha permanent plots established from lowland (200 m asl) to submontane forests (900 m asl) in the Ngovayang Massif, south-western Cameroon. We analysed variation over altitude in two specific functional traits, the potential maximum tree height and the wood density. Forest above-ground biomass decreased from 500–600 Mg ha−1 in lowland plots to around 260 Mg ha−1 at the highest altitudes. The contribution to above-ground biomass of large-tree species (dbh ≥ 70 cm) decreased with altitude, while the contribution of smaller trees was constant. Contribution of the Fabaceae subfamily Caesalpinioideae decreased with altitude, while those of Clusiaceae, Phyllanthaceae and Burseraceae increased. While potential maximum tree height significantly decreased, wood specific gravity displayed no trend along the gradient. Finally, the decrease in above-ground biomass along the short altitudinal gradient can be at least partially explained by a shift in species composition, with large-tree species being filtered out at the highest altitudes. These results suggest that global change could lead to significant shifts in the properties of montane forests over time.

Termites are dominant invertebrates in tropical soils (Wood & Sands 1978) and are important mediators of decomposition in terrestrial ecosystems (Abe & Matsumoto 1979, Lawton et al. 1996, Lee & Wood 1971, Matsumoto & Abe 1979, Wood & Sands 1978, Yamada et al. 2005). Furthermore, these processes, such as carbon mineralization and nitrogen fixation, are dependent on the species assemblage structure of the termite community (Lawton et al. 1996, Yamada et al. 2005, 2006). Feeding habits of termites reflect their metabolic processes. The three major isopteran groups – wood-feeders, fungus-growers (fungus-growing wood/litter feeders), soil-feeders – appear to play very different roles in the decomposition process (Tayasu et al. 1997, Wood 1976, Wood & Sands 1978, Yamada et al. 2005). Consequently, the relative abundance of each feeding group provides useful information on the function of the termite assemblage in an ecosystem.

Cyclones have been suggested to play a major role in the evolutionary history of the flora and fauna of Madagascar (Wright 1999). In spite of the proposed significance of cyclonic activity, very little is known about the specific effects of cyclones on Malagasy ecosystems (Birkinshaw & Randrianjanahary 2007). Understanding the effects of these severe natural disturbances requires comparing data collected both before and after the event. Because cyclones are stochastic, researching the influence of cyclones on Madagascar's biodiversity is difficult and opportunities to study their impact on forests are rare. Nevertheless, studies of the impact of cyclones on Malagasy biota are imperative because models of global climate patterns predict that large-scale tropical disturbances will increase in frequency and intensity in the future (Metcalfe et al. 2008).

Thousands of plant species throughout tropical and temperate zones secrete extrafloral nectar (EFN) (see www.biosci.unl.edu/emeriti/keeler/extrafloral/worldlistfamilies.htm) to attract ants, whose presence leads to an indirect defence against herbivores (Chamberlain & Holland 2009, Heil 2008, Heil & McKey 2003, Rico-Gray & Oliveira 2007). Although termed ‘extrafloral’ because the nectar is not involved in pollination, EFN can also be secreted within the inflorescences (Bentley 1977, Holland et al. 2010, Martins 2009). Because ants tend to defend reliable food sources against all types of putative competitors, it has been hypothesized that the presence of extrafloral nectaries close to flowers may lead to competition among ants and pollinators, or even to direct ant–pollinator conflicts. Such antagonistic interactions would reduce the access of pollinators to flowers and, thereby, may cause significant ‘ecological costs’ of indirect, ant-mediated defences (Heil 2002).

The directional orientation of pre- and post-reproductive migration was studied in the Brazilian red-bellied toad Melanophryniscus cambaraensis, a species that forms explosive-breeding aggregations at irregular intervals throughout the entire year. Migrating toads were captured by enclosing the breeding site in dual drift fences with inward- and outward-facing funnel traps. Data were collected over 5 mo and totalled 333 captures. The observed directional orientation was significantly different from expected under a uniform distribution for both pre- and post-reproductive migration, regardless of gender. Males and females did not differ significantly from each other in the orientation of entry or exit, and the directional orientation of pre-reproductive migration was not significantly different from post-reproductive migration. It is suggested that the observed directional bias may be due to a dirt road next to the breeding site that could restrict juvenile dispersal to the adjacent forest.

The short-nosed fruit bat, Cynopterus sphinx, begins to visit fruit-bearing trees about 30 min after sunset. Individual bats often hover near or land on fruits or on nearby branches to remove whole or parts of fruits with their mouth. These bats seldom remain in the fruit-bearing trees to feed, but instead carry fruits to feeding roosts, repeating this behaviour several times throughout the night. Analysis of the temporal distribution of feeding behaviour has revealed two peaks of activity, one in the pre-midnight hours when bats fed mostly on ‘steady state’ fruits, and another during the post-midnight hours when bats fed on ‘big-bang’ fruits. Only solitary bats visited and fed on species with steady state fruiting phenologies, whereas groups of bats regularly visited and fed on species with big-bang fruiting phenologies. Thus, plant species which produce large numbers of fruits appear to promote group foraging during the latter hours of the night. It is suggested that the temporal use of available fruits in south India made it possible for C. sphinx to successfully exploit them, and thereby reduced interference competition with conspecifics.

Stressful environments have been suggested to enhance cooperative behaviours in animal communities. Prey animals living in risky environments can also increase long-term benefits by cooperating with neighbours, such as collectively harassing predators. However, empirical studies have rarely tested this prediction in the wild. In this experimental study we explored whether the perceived predation risk influences cooperative mobbing behaviour in tropical forest birds in French Guiana. The predation risk was increased by 5-d-long presentation of visual and acoustic stimuli of pygmy-owls in 24 locations. In order to examine whether mobbing response can vary in relation to the abundance of local predators, we used the Amazonian pygmy-owl (Glaucidium hardyi) as a common predator and the ferruginous pygmy-owl (Glaucidium brasilianum) as a rare predator in the study area. Our results showed that repeated predator-presentations increased mobbing response over time for the rarer owl species, while this effect was not significant for the common owl species. No effect of repeated presentations of either pygmy-owl species was found on the latency of mobbing. Moreover, mobbing latency was shorter and mobbing response was stronger for the common predator species, the Amazonian pygmy-owl. This study provides experimental evidence that birds exhibit stronger mobbing responses when the predator is locally abundant, while repeated encounters can be perceived as more dangerous when the predator is rare.

We investigated the microhabitat preferences and relative abundances of 13 species of woodpecker in Sungai Lalang Forest Reserve, West Malaysia. The availability of suitable microhabitat corresponded strongly with woodpecker abundance, and snags were the most highly preferred foraging substrate across species and study sites. Large amounts of necromass, including snags, were present in 5-y-old logged and unlogged forest, but dead wood was in low abundance in 10-y-old logged forest. The absence or scarcity of large, snag-foraging woodpeckers from older logged stands suggests that this resource may remain in low abundance for a considerable time.

Guiera senegalensis tolerates repeated cutting and pruning to which it is increasingly subjected at the onset of each cropping period, and one to three times during the annual cropping period (June–September). It responds by profusely branching at the shrub base. The topographic and geomorphic influences, and the effect of clearing on the relationships between shrub density, mean individual above-ground biomass and leaf water status were analysed for seven fallow sites. They were sampled 75 km east of Niamey in Niger. Surprisingly, shrub density and mean individual above-ground biomass were highest in the sites that had been recently in fallow and intensively cultivated prior to crop abandonment. Stand above-ground biomass was also positively related to mean predawn and daily minimum leaf water potentials. Consequently, in the studied G. senegalensis stands, above-ground biomass appeared to be controlled by water availability – rainfall, runoff, infiltration – rather than by cropping intensity. Anisohydric stomatal regulation, resulting in large safety margins from critical transpiration, was inferred from the diurnal amplitude of leaf water potential during the dry season. The plant physiological resistance to water stress combined with its population adjustment in density and growth contributes to the sustainable dominance of G. senegalensis.

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.

The demographic history of a flower-cohort of the tropical tree Dicymbe altsonii (Caesalpiniaceae) was studied by collecting litter from flowers, fruits and seeds, and by monitoring seedling survival. Flower production was estimated at 137 to 172 m−2 in a plot of 1 ha. Four percent of the flowers yielded a pod, which contained an average of 2.0 seeds. Post-dispersal mortality over 3 mo was 39% of the initial number of dispersed seeds. Most flowers and fruits were aborted. Insect and vertebrate predation in the tree and on the ground was very low. Reproductive litter production of this species was estimated to be equal to leaf litter production. The amount of phosphorus lost in litter from fruits and flowers was much larger than in leaf litter. This implies that the impact of the biennial flowering events on the nutrient dynamics of the trees and of the ecosystem may be large. It is argued that the reproductive cycle and the pre-dispersal demography of Dicymbe seem to be determined by a scarcity of nutrient resources, and possibly by pollinator limitation.

We studied the removal of seeds of three species of large-seeded tree (Astrocaryum standleyanum, Attalea butyracea and Dipteryx oleifera) from three different heights within six study plots in a lowland forest in central Panama. Fresh fruits with intact seeds fitted with industrial sewing bobbins were placed within semi-permeable exclosures. Removed seeds were tracked to deposition sites, and seed fate was determined. Removals were likely perpetrated by two small rodents, the strictly terrestrial Proechimys semispinosus and the scansorial Sciurus granatensis, because they were the most abundant small rodents in the study site during the study period and were of sufficient size to remove large seeds. Rodent abundance and fruit availability were estimated by conducting censuses. Nine microhabitat variables were measured at each deposition site to determine if these two rodents were preferentially depositing seeds in sites with certain characteristics or were randomly depositing seeds. During the study, rodents handled 98 seeds, 85 of which were not predated upon and could potentially germinate. Removal rates were not influenced by rodent abundance or fruit availability. Seeds were most frequently moved <3 m and deposited with the fruit eaten and the seed intact. However, some seeds did experience relatively long-distance dispersal (>10 m). Rodents preferentially deposited seeds in locations with large logs (>10 cm diameter), dense herbaceous cover, and an intact canopy. The number of large logs was different from random locations. Despite not being able to determine long-term fate (greater than c. 1 y), we show that these small rodents are not primarily seed predators and may in fact be important mutualists by dispersing seeds relatively long distances to favourable germination sites.

We investigated the presumption that wind-wave exposure is a major regulator of vegetation distribution within lakes. Along a 675-km stretch of shore in northern Lake Victoria (Uganda), the pattern of vegetation distribution in relation to shoreline features, and the variation of shoreline swamp area along a gradient of wave exposure were examined. The ability of wave exposure, when combined with bay morphometric characteristics, to predict the lakeward limit of vegetation distribution was assessed. Data were collected through a shoreline survey and from maps. Maximum effective fetch, computed from topographic maps, was used as a surrogate for wave exposure. Our results reinforce and amplify the notion that wave exposure is an important regulator of the within-lake distribution of vegetation. We found shoreline plants to either occupy stretches of shore shielded by coastal islands or hidden by convolutions of the lake margin. The area of shoreline swamps declined exponentially with increasing wave exposure. Of the coastal characteristics examined, bay area had the strongest influence on the lakeward expansion of vegetation. Wave exposure acting together with bay area, accounted for 64.4% of the variance in the limit of lakeward vegetation advancement.

Precipitation and temperature are known to have important effects on forest productivity, but these effects may be strongly mediated through their influence on soil and leaf nutrients. We measured indicators of forest productivity and soil and leaf nutrients across independent gradients of precipitation and elevation/temperature in lower montane Hawaiian forests dominated by a single overstorey species, Acacia koa, situated on 1500–3000-y-old soils that were mixtures of volcanic ash and basalt. Stand basal area was highest at the wettest site, 2000 mm mean annual precipitation (MAP), and leaf N and P were lowest at the driest site, 1000 mm MAP. Soil N availability and leaf N concentration declined across an 850-m elevation gradient, but this was not correlated with stand basal area or soil organic matter content. Across all stands, basal area was negatively correlated with the exchangeable soil P fraction. As well, the soil C:N ratio was negatively correlated with both soil P availability and the size of the primary mineral P fraction. Soil P availability and weathering appear to be important determinants of soil organic matter quantity and quality. Overall, precipitation is the major driving force for forest productivity, but P weathering and availability play important roles in limiting productivity in wetter sites and in controlling soil organic matter dynamics in these N-fixing forests.

The spatial and temporal variation in litter disturbance by a medium-sized bird, the chowchilla (Orthonyx spaldingii Ramsay, Orthonychidae) was documented, and its potential impacts on tree seed germination and early seedling survival in an Australian tropical rain forest experimentally investigated. Chowchilla disturbances occurred on ridges, slopes and drainages in all four seasons surveyed. In some areas litter was completely turned over as frequently as every 5 wk. Tethered seeds exposed to disturbance were moved farther and experienced significantly greater variation in litter cover than those protected from disturbance. When seeds of two canopy trees were placed in litter environments simulating those created by chowchillas, the seeds of one species showed significant effects of litter treatment on germination while those of the other showed no significant effects. Seedling cohorts of four tree species were followed for 6 wk soon after germination and all showed higher survival in vertebrate exclosures. The two most abundant species suffered 68% and 35% mortality in six wks, with the majority of that unambiguously due to chowchillas. It is argued that litter-disturbing birds increase litter heterogeneity and significantly impact early seedling mortality. These effects could be important in maintaining evenness and diversity of the seedling community.

Spider monkeys (Ateles geoffroyi) detect sucrose at a threshold lower than any primate yet tested and prefer sucrose to glucose or fructose in laboratory tests. This preferential selection of sucrose led to the hypothesis that such acute discrimination is related to a diet of sucrose-rich fruits. Furthermore, it has been suggested that fruit sugars may be related to distinct guilds of vertebrate seed-dispersers. The objectives of this study were: (1) to test if spider monkeys select sucrose-rich fruits both within and among plant species and (2) to test the hypothesis that sugar concentration is related to bird, bat or monkey seed-dispersal syndromes. Data were collected from one troop of spider monkeys in south-western Costa Rica. Interspecific comparison of ingested fruits shows that spider monkeys consumed species with significantly higher concentrations of glucose and fructose than sucrose. Similarly, at the intraspecific level, food-fruits had significantly more fructose and glucose than non-food fruits, but no difference was found for sucrose. The three different sugar types were not correlated with the importance of the species in the diet based on the amount of time they spent consuming each species. Although sucrose concentrations were significantly higher in primate-dispersed species compared with those dispersed by other vertebrates, soluble carbohydrates in primate-dispersed fruits were principally composed of glucose and fructose. Neither fructose nor glucose concentrations showed significant differences across the three categories of seed dispersal.

Large areas of the Himalayas have become severely deforested although little has been published about the extent of this problem in the closed Kingdom of Bhutan. A preliminary survey was undertaken during 1983. Without detailed information or accurate maps, LANDSAT 2 imagery was used to prepare a sampling stratification and to plot the distribution of defined vegetation types after sampling and analysis. Eleven forest noda are described in relation to their habitats, and area and timber volume estimates given. Deforestation pressures are discussed.