We investigated the seed dispersal of Aglaia spectabilis, a large-seeded tree species in a moist evergreen forest of Khao Yai National Park in Thailand. Although one-to-one relationships between frugivores and plants are very unlikely, large-seeded plants having to rely on few large frugivores and therefore on limited disperser assemblages, might be vulnerable to extinction. We assessed both the frugivore assemblages foraging on arillate seeds of Aglaia spectabilis and dispersing them and the seed predator assemblages, thereby covering dispersal as well as the post-dispersal aspects such as seed predation. Our results showed that frugivores dispersing seeds were a rather limited set of four hornbill and one pigeon species, whereas two squirrel species were not dispersers, but dropped the seeds on the ground. Three mammal species were identified as seed predators on the forest floor. Heavy seed predation by mammals together with high seed removal rates, short visiting times and regurgitation of intact seeds by mainly hornbills lead us to the conclusion that hornbills show high effectiveness in dispersal of this tree species.

In Iropical seasonal forests, mass seedling death may incidentally occur early in the rainy season following untimely germination provoked by an isolated heavy rainfall. We hypothesized that, in a soil with little moisture retention capacity, irregular rainfall patterns would result in large fluctuations of water supply and, in the early wet season, drought episodes could cause seedling death. This hypothesis was tested in a seasonal tropical forest in Mexico where seedling density is low and the soil consists of almost pure sand with a low water retention capacity. Various patterns of simulated rainfall were applied in the forest to seeds and seedlings of three common tree species. Overall very little difference in germination and seedling survival was observed between the various rainfall treatments. The results showed that rainfall patterns and the soil texture may interact in a much more complex way than was initially hypothesized, and that water availability to seeds and seedlings is not necessarily predictable. The absence of seedlings of the three tree species might be better explained by high seed predation and low light level in the understorey.

The optimal defence hypothesis predicts that plant parts characterized by a high value and/or a high risk of being attacked should exhibit the highest level of defence. We tested this hypothesis with Macaranga bancana ant-plants, which are protected efficiently by resident, mutualistic ants from herbivores, parasites and encroaching vegetation. Because cost-effective defence of the host by ants increases ant fitness, selection should act on ant behaviour to produce patterns of distribution of defence as predicted for direct chemical defence traits. Termites and pieces of tape were equally distributed over the uppermost ten leaves and over the leaf-bearing part of the stems (with termites mimicking a transient herbivore, while tape mimics a long-term stress caused by a climber or plant parasite). This arrangement allowed a separation of putative coevolutionary adaptations in the ants' behaviour from other potential sources of spatial patterns in ant defence, such as differences in herbivore pressure, in the vulnerability of different herbivores, or in direct plant defences. Ant activity dropped rapidly at termite baits, but remained high at tapes for at least 5 h, thereby demonstrating adaptive differential responses to the differences between the two stressors. Most importantly, ants preferentially defended young leaves and shoot parts. The temporal and spatial patterns of ant attention to exogenous stressors thus were clearly adaptive, varying with likely costs and benefits of defence as formulated in the optimal defence theory.

Gaps created by the death of one or more contiguous trees are common in mangrove forests but are poorly understood. In Kosrae, Federated States of Micronesia, where mangrove wood is harvested for local use, most natural gaps were < 50 m2, whereas most logging gaps were > 100 m2. Interior zones, where access is facilitated by roads, were the most heavily exploited. Although the forests contained 11 species, two species were primarily responsible for gap formation. Natural gaps were caused mainly by broken stems and large branches of Sonneratia alba trees, whereas logging gaps were created primarily by harvesting Rhizophora apiculata trees. Most natural gaps were formed by the fall of more than one tree or branch. Seedling densities were higher in logging gaps than in natural gaps and higher in gaps than under intact canopy. Bruguiera gymnorrhiza was the most common seedling species in gaps and under intact canopy. Relative rates of growth in height were faster in gaps than under intact canopy for R. apiculata and B. gymnorrhiza seedlings. Current harvesting practices on the island do not seem to be altering species richness, although R. apiculata may become less common as gaps are increasingly captured by B. gymnorrhiza.

The reproductive ecology of piassava palm (Attalea funifera Mart.) was investigated for 19 months in the Atlantic forests of eastern Brazil. Its breeding biology is characterized by the production of functionally female, male and bisexual inflorescences. Staminate sterility is positively correlated with number of pistillate flowers. Staminate and pistillate flowers are receptive at anthesis. Bagging tests for apomixis were negative. Although geitonogamy can occasionally occur, outcrossing predominates. Pollen is relatively dry, but wind pollination is not a significant factor in cross pollination. Although inflorescences are visited by large numbers of insects, pollination is effected mainly by small sap beetles (Mystrops sp.) and weevils (Phyllotrox tatianae), which feed and breed in fertile staminate flowers. Pistillate flowers, which offer no reward to pollinators, appear to attract insect visitors by olfactory and visual imitation of staminate flowers, that is, via Bakerian mimicry. Flower production, fruit maturation, leaf production and leaf abscission occur continuously throughout the year. Flowering exhibits a distinct peak during the warmest months (Dec–Apr). Given its ubiquity throughout the region, A. funifera may well serve as a flowering and fruiting keystone species.

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

Seed predation by native and alien rodents can limit plant recruitment and ultimately affect forest dynamics and composition (Campbell & Atkinson 2002, Côté et al. 2003, Hulme 1998, Sánchez-Cordero & Martínez-Gallardo 1998). Even partial consumption of seeds by predators may affect plant community structure, though its importance is poorly understood (Steele et al. 1993, Vallejo-Marín et al. 2006). Despite consumption of relatively large portions of seeds by herbivores, seeds can retain their ability to germinate if the embryo remains intact (Dalling & Harms 1999, Janzen 1972, Mack 1998). Germination of damaged seeds may be accelerated or prolonged (Karban & Lowenberg 1992, Koptur 1998, Vallejo-Marín et al. 2006). Damage by seed pests also facilitates ageing stress; which manifests as decreased seedling vigour, decreased seed viability, lower germination percentages and slower germination rates (Priestley 1986).

Litterfall was measured monthly in ten 1 m2 traps in each of two 0.25 ha plots in the rain forest of Southern Bakundu Forest Reserve, Cameroon for 18 months from 1 July 1982 to 31 December 1983. Particular emphasis was placed on measuring species contributions and in relating litterfall to climatic factors; the litterfall data were also used in estimating leaf production. Annual litterfall ranged between 12.9 and 14.1 t ha−1 and was partitioned to leaves (61–66%), branches (23–38%), fruits and flowers (8–12%) and ephiphytes (0.8%). Emergents and top canopy species like Desbordesia glaucescens (evergreen) and Ceiba pentandra (deciduous) contributed more litter than the numerically dominant lower storey species like Cola lepidota and Diospyros spp. Litter fell throughout the year but was greatest during the dry season (November to March); litterfall was thus strongly negatively correlated with environmental moisture variables and could be predicted from its linear regression on time of year, throughfall and relative humidity. By correcting the leaf fall data for leaf weight losses due to grazing and re-translocation, leaf production rates of 10.2 to 11.2 t ha−1 yr−1 were estimated for the forest.

The species composition of vascular epiphytes and phorophytes (trees and lianas) was studied in ten 0.1-ha forest plots distributed over three landscape units (floodplains, swamps and well-drained uplands) in Colombian Amazonia. The aim was to analyse how host-preferences contributed to the patterns in epiphyte assemblages among the landscape units. In the plots 82 species (3310 plants) were holo-epiphytes, 11 species were primary hemi-epiphytes (179 plants) and 61 were secondary hemi-epiphytes (2337 plants). A total of 411 species of tree and liana were recorded as phorophytes. Detrended Correspondence Analysis and Mantel tests showed that the species composition of holo-epiphytes and secondary hemi-epiphytes differed among the landscape units. For both groups the effect of landscape unit on species composition strongly decreased after controlling for the phorophyte composition in the plots. The phorophyte composition significantly explained epiphyte composition and this effect was not removed after accounting for the effect of landscape unit. At the level of individual species, randomization tests yielded only few significant epiphyte–phorophyte associations. For 84% of the epiphyte species the average indicator of patchiness was below 1.5 demonstrating that most epiphyte individuals occurred scattered over different phorophytes. This probably hampered the analyses of host preferences for individual epiphyte species.

An altitudinal survey of correspondences between fruiting phenologies of fleshy-fruited tree species and seasonal dynamics of frugivorous birds on Mt. Kinabalu in Borneo was carried out for 50 weeks across four vegetation types: a hill forest (800 m asl), a lower montane forest (1700 m), an upper montane forest (2000-3000 m) and a subalpine forest (3000-3500 m). In the hill forest, a large fruiting peak following the general flowering phenomenon was observed during October-November in 1996 and a fruitless period was observed during February-April in 1997. During the fruitless period, the number of resident frugivorous birds decreased. A bimodal fruiting pattern was observed in the lower montane forest. A large number of frugivorous temperate migrants were observed when the fruiting peak occurred. The number of resident frugivorous birds increased and several lowland bird species were observed, when the number of resident birds decreased in the hill forest. In the upper montane forest and the subalpine forest, more continuous and irregular fruiting patterns without outstanding peaks were observed and the number of resident frugivorous birds was more stable throughout the year. These suggested (1) there was a strong relationship between fruiting seasonality and seasonal dynamics of temperate migrants in the lower montane forest; (2) seasonal altitudinal movements of lowland bird species to montane vegetation might occur during the fruitless period in the lowland forest; and (3) the continuous fruiting pattern in the higher vegetation zones might be related to the scarcity of available frugivorous birds. The hypothesis that the influx of temperate migrants into the montane vegetation of Mt. Kinabalu is affected by density and habits of resident frugivorous birds is supported. Montane vegetation in Borneo plays an important role as temporal refugia for temperate and altitudinal migrants by supplying fruit resources.

The wet evergreen forest of Nelliampathy in the Western Ghats of Kerala in India is a mixed forest with a high species diversity and basal cover. In this relatively undisturbed ecosystem, canopy gaps are largely formed through single tree fall, but gaps through branch fall, crown fall, standing dead trees or multiple tree fall also occur. Canopy gap formation is more (over 82% of the total gaps created) during the monsoon season. The mean number of gaps formed in this forest is 1.13 ha−1 y−1 and the turnover rate is 83 years. The majority of the gaps created (over 70%) are of smaller size (≥ 100 m2). In this forest, while some top canopy tree species (those capable of exceeding 25 m in height at maturity) such as Palaquium ellipticum and Mesua nagassarium are well represented in seedling, sapling and mature tree stages, others like Aglaia exstipulata and Mastixia arborea are observed only as saplings and/or mature trees with no seedling populations. The possible reasons for these two types of regeneration behaviour by top canopy tree species in the context of canopy gap size and seasonality in gap formation are discussed.

All plant species face a fundamental reproductive trade-off: for a given investment in seed mass, they can produce either many small seeds or few large seeds. Whereas small seeds favour the germination of numerous seedlings, large seeds favour the survival of seedlings in the face of common stresses such as herbivory, drought or shade (Leishman et al. 2000). One mechanism explaining the better survival of large-seeded species is the seedling size effect (SSE) (Westoby et al. 1996): because seeds with large reserves result in bigger seedlings, seedlings from large-seeded species would have better access to light and/or to reliable water supply than seedlings from small-seeded species.

We analysed the selection of tree species consumed by an isolated troop of Mexican howler monkeys (Alouatta palliata mexicana) released in a translocation programme on Agaltepec Island, in Catemaco Lake, Veracruz, Mexico. During November 1989–December 1996, howlers used 36 of the 63 tree species present on the island as food. Selection ratios indicated that six Ficus species (particularly F. pertusa) were among the seven most important food species. Data on time spent feeding showed that the six Ficus species were among the eight most important food species for the monkeys. Howlers spent 64.2% of their feeding time on Ficus products with F. pertusa being consumed significantly more often than foods from other Ficus species. However, monkeys fed on only one third of the 81 adult Ficus trees on the island. No significant differences were found in various food constituents (water, ash, fibre, protein, carbohydrates, lipids) of the six Ficus and two other abundant species in the habitat, whether across species, plant parts (young leaves, mature leaves, fruits), or between seasons (wet, dry). Monkeys consumed Ficus fruits rather the leaves. Fruits showed a much higher energy content per g dry weight than leaves. We also estimated the average daily biomass of leaves and fruits of Ficus spp. consumed by howlers and their energetic contribution to the daily diet of these monkeys. We suggest that some of these tendencies to frugivory reflect the abundance of Ficus trees within the home ranges of the howlers; when few fig trees are present, folivory is the dominant tendency, whereas when many fig trees are present, frugivory is dominant.

While leaf-cutter ants are thought to collect mainly vegetative plant material, they have also been observed collecting seeds or fruit parts on the forest floor (Alvarez-Buylla & Martínez-Ramos 1990, Kaspari 1996). For example, leaf-cutter ants have been observed carrying considerable numbers of Brosimum alicastrum Sw. and Cecropia spp. seeds into their nests (Wirth 1996) and Leal & Oliveira (1998; pers. comm.) found them foraging on the fruits and seeds of 19 different species of Brazilian cerrado vegetation, including six Miconia species. Under some circumstances, seed removal and relocation by leaf cutter ants might even be sufficient to affect local recruitment patterns of trees. For example, in Costa Rica, Atta cephalotes can remove all fallen fig fruit from beneath a Ficus hondurensis crown in a single night (Roberts & Heithaus 1986), while in Venezuela, seedling recruitment of the savanna tree Tapirira velutinifolia was positively associated with the seed harvesting and seed cleaning activities of the ant Atta laevigata (Farji Brenner & Silva 1996).

In rain forests the fate of seeds defecated by mammals is often affected by dung beetles, but these effects can vary with mammal species. In a Colombian forest, differences in Scarabaeinae assemblages attracted to spider monkey (Ateles hybridus) and howler monkey (Alouatta seniculus) defecations were assessed. In total, 791 beetles of 35 species were captured. Mean number of individuals was similar for both dung types; mean number of species was higher for Alouatta traps. The effects of dung type (Alouatta vs. Ateles) and defecation pattern (clumped vs. scattered) on the fate of 220 Rollinia edulis (Annonaceae) seeds were determined. Burial by beetles occurred for 61% of the seeds (mean depth 2.6 cm). Seeds in Alouatta dung and in clumped defecations had higher burial rates. Horizontal movement (mean 11 cm) occurred for 80% of the seeds; no significant effects of experimental factors were detected. Survival was higher for buried vs. surface seeds. In a separate experiment, no differences were detected between dung types in the proportion of seeds buried by beetles. Changes in dung texture might have been responsible for the contrasting results. When assessing the effectiveness of an endozoochorous plant–mammal interaction, secondary dispersal by dung beetles should be addressed too.

In the semi-deciduous forests of Santa Rosa National Park in the Pacific coastal lowlands of northwestern Costa Rica, the large and fast-growing tree Spondias mombin(Anacardiaceae) experiences greater than 95% post-dispersal seed predation by a bruchid beetle (Amblycerus spondiae) on its nuts that have been dispersed to any part of pristine or secondary successional forest. Nuts dispersed (by white-tailed deer) to abandoned pastures immediately adjacent to the forest suffer less than 20% post-dispersal seed predation but seedlings are killed by frequent grass fires. S. mombin displays significant recruitment of saplings and young trees only on forest edges free of fire for long intervals. The very high percent seed predation in the forest and the failure of many nuts to ever be dispersed away from the parent tree is attributed directly and indirectly to the absence of a herbivorous (frugivorous) megafauna that would have been part of the habitat of S. mombin through most of its evolutionary history. These large animals would have consumed large numbers of S. mombin fruits and thereby dispersed the nuts in such a manner as to have both led to more escape from bruchids and an overall reduction in the bruchid population density. By their defecation patterns, these mammals would also have defecated more nuts in sites of high quality for S. mombin sapling survival than is the case at present. In contemporary habitats, S. mombin is culturally deprived in that it can no longer interact with the habitats, animals and densities of animals whose selective pressures were a major force in the evolution of the tree's traits.

Seed dispersal is the first stage of colonization, and potentially affects recruitment. This process deserves more attention in tropical montane cloud forests (TMCF), since secondary succession is common owing to episodic disturbances. We studied annual seed rain in 10 nearby forest stands, ≈7 to ≈100 y following shifting agriculture, and one primary forest stand in southern Mexico to test the hypothesis that seed rain is limited at the scale of neighbouring fragments and that such limitation differs among species with different dispersal modes and successional origin. Annual seed rain was heterogeneous among forest fragments probably due to the prevalence of local seed dispersal, differences in stand age and the proportion of zoochory, and may help explain the patchy distribution of species observed in TMCF. Seed rain abundance and species diversity per unit trap area increased with the age of the stand. Biotically dispersed seeds increased towards older stands relative to abiotically dispersed seeds. Late-successional seeds were rarer in early successional stands than pioneer seeds in late-successional stands, suggesting that long-distance dispersal is generally more common for pioneer plants. Seed dispersal appears to constrain forest regeneration and to influence fragment species composition as a function of the distance from the source forests.

Bromeliads are common as epiphytes in warm neotropical forests (Benzing 1990). Species native to relatively wet forests impound water in a central cup and/or in seperate leaf axils. These tanks receive enough leaf litter and rainwater to support aquatic life (Maguire 1971). In these complex microcosms many groups of freshwater organisms ranging from algae, fungi, bacteria and protozoa through insects to frogs are represented and constitute considerable animal populations (Frank 1983, Laessle 1961, Maguire 1971, Picado 1913, Richardson 1999). Nutrients originating from the decomposition of litter and animal waste are absorbed by specialized trichomes on the bases of the leaves which form the tanks (Benzing 1980, 1990).

Estimation of tree growth is generally based on repeated diameter measurements. A buttress at the height of measurement will lead to overestimates of tree diameter. Because buttresses grow up the trunk through time, it has become common practice to increase the height of measurement, to ensure that measurements remain above the buttress. However, tapering of the trunk means that increasing measurement height will bias estimates of diameter downward by up to 10% per m of height. This bias could affect inference concerning species differences and climate effects on tree demography and on biomass accumulation. Here we introduce a hierarchical state space method that allows formal integration of data on diameter taken at different heights and can include individual variation, temporal effects or other covariates. We illustrate our approach using species from Barro Colorado Island, Panama, and La Selva, Costa Rica. Results include trends that are consistent with some of those previously reported for climate responses and changes over time, but differ in relative magnitude. By including the full data-set and accounting for bias and variation among individuals and over time, our approach allows for quantification of climate responses and the uncertainty associated with measurements and the underlying growth process.