Natural seed deposition patterns and their effects on post-dispersal seed fate are critical in tropical tree recruitment. Previous research showed that the key dispersal agent of the neotropical tree, Virola calophylla, is the spider monkey (Ateles paniscus). Spider monkeys generate a heterogeneous seed deposition pattern because they scatter-disperse seeds diurnally, whereas they clump-disperse seeds at their sleeping sites. The recruitment consequences of this pattern were investigated using manipulative experiments and observations. Scatter-hoarding by spiny rats (Proechimys spp.) caused little rearrangement of the initial seed deposition pattern because they moved seeds only short distances. Seed survival to the seedling stage depended negatively on conspecific seed density and positively on the distance from the nearest adult V. calophylla female. These effects were likely mediated by two important seed predators, spiny rats and beetles (Scolytidae). Furthermore, spider monkeys' seed deposition patterns influenced seed survival. Scatter-dispersed and experimentally dispersed seeds had the highest survival. Conversely, clump-dispersed seeds at sleeping sites, which are far from V. calophylla females, and non-dispersed seeds had equally low survival, suggesting that conspecific density- and distance-dependence acted independently and did not explain all variation in seed survival. Instead, other characteristics of the seed deposition pattern, such as the multi-specific assemblage of seeds at sleeping sites, also affected post-dispersal seed fates.

Resumen: La conexión entre el patrón natural de dispersión de semillas con el destino después de la dispersión es clave para el reclutamiento de árboles tropicales. Mediante experimentos y observaciones se investigó esta conexión utilizando el árbol neotropical Virola calophylla (Myristicaceae). Ateles paniscus (maquisapa), el principal dispersor de sus semillas, genera un patrón de deposición heterogéneo. Durante el día las semillas son depositadas de manera esparcida mientras que en los dormitorios las semillas son depositadas de manera agregada. En este estudio se encontró que los roedores espinosos (Proechimys spp.) almacenaron semillas individuales debajo de la hojarasca, sin embargo estos no alteraron el patrón de dispersión ya que las semillas fueron transportadas distancias cortas y la tasa de predación fue alta. Se encontró que la tasa de sobrevivencia hasta la etapa de plántula tuve una relación negativa con la densidad de las semillas y una relación positiva con la distancia al árbol hembra de V. calophylla mas cercano. Estos efectos sucedieron por medio de roedores espinosos y coleópteros (Scolytidae), predadores importantes de las semillas de V. callophylla. Adicionalemente, el patrón de deposición de los maquisapas influenció la sobrevivencia de las semillas. Tanto las semillas dispersadas por los maquisapas como las dispersadas experimentalmente tuvieron la tasa de sobrevivencia más alta. Por el contrario, tanto las semillas depositadas en los dormitorios, usualmente lejos de hembras de V. calophylla, como las semillas que cayeron debajo del árbol hembra tuvieron bajos niveles de sobrevivencia. Estos reultados sugieren que tanto la densidad como la distancia tuvieron efectos independientes y no explicaron toda la variación observada en la sobrevivencia de semillas. Por el contrario, otras características de la deposición de semillas tales como la riqueza de especies de la comunidad de semillas en los dormitorios también afectaron el destino de las semillas después de dispersadas.

Fruit traits that selectively deter vertebrate seed predators without affecting high-quality seed dispersers are said to exhibit directed deterrence. Directed deterrence has been criticized as being unlikely in natural systems, but has rarely been explicitly tested. We evaluated the potential for directed deterrence to explain the double-layered viscous fruit morphology and fruiting phenology of Terminalia impediens, a common canopy tree endemic to New Guinea. The large fleshy fruits of this tree are consumed and dispersed by cassowaries (Casuarius spp.) and are consumed and killed by palm cockatoos (Probosciger aterrimus). Fruit flesh in this tree species appears to function as a deterrent to seed predation by palm cockatoos; the fruits of T. impediens fall to the ground before ripening, and are avoided by palm cockatoos until after the flesh has rotted off the hard nut. We found that palm cockatoos are able to prey upon seeds from fruits without flesh on the forest floor more efficiently than they can consume seeds from unripe fruit still on the trees. Further, through foraging preference tests, we found that palm cockatoos largely ignore seeds within ripe fruit on the ground, but readily eat the seeds when the fruit flesh has been removed. Cassowaries consume the fruit whole, when ripe, and defecate seeds in piles away from parent trees, where seed predation rates are lower. These results challenge the prevailing view that fleshy fruits evolved in tight synchrony with high-quality seed dispersers and add support to the non-exclusive hypothesis that aspects of fruit fleshiness may also have evolved as a response to seed predation.

A trapping study of five mammal species in wet sclerophyll forest adjacent to rain forest in the Australian Wet Tropics was used to examine the seasonal diversity, abundance and dung-specificity of dung beetles associated with mammal dung. A total of 542 dung beetles from 11 species within three genera was recovered from beneath the traps of 1104 mammal captures. The diversity of beetles associated with the dung of the northern bettong (Bettongia tropica), a mycophagous marsupial, differed significantly from the diversity predicted by a null model. Numbers of beetles varied significantly with type of dung, indicating preference by beetles. Beetle numbers were related positively to a 1-mo lag in monthly mean minimum temperature and less strongly to maximum temperature and rainfall. Significantly more beetles per mammal capture were detected in the wet season than in the dry season. Dung beetles showed a strong preference for either the Eucalyptus woodland (six species) or the adjacent Allocasuarina forest (four species), with only one species occurring in both habitat types. Beetle species from the Eucalyptus woodland were typically only detected in the late wet and early dry seasons, while species in the wetter Allocasuarina forest were generally collected during the late dry and early wet seasons. A significant ‘checkerboard’ species effect was detected in both time and space in both habitat types, suggesting that competition for dung was strong.

Few studies have contrasted faunal communities between flooded and unflooded tropical forests, and such attempts have largely been restricted to a few taxonomic groups. We present the first comparison of the composition and structure of an entire assemblage of mid-sized to large-bodied mammals in adjacent unflooded (terra firme) and flooded (várzea) forests of central-western Amazonia. We extend this comparison to 13 other terra firme and várzea forest sites in order to examine the fundamental dichotomy between mammal communities in these Amazonian environments. We found a consistently impoverished fauna in várzea environments both in terms of primates and other non-volant mammals, although primate density and biomass was substantially higher in várzea than in terra firme. The average Bray–Curtis mammal community dissimilarity between terra firme and várzea forests was 74%, whereas mean dissimilarity within várzea and terra firme samples was 40% and 39%, respectively. The results seem to be largely a function of high habitat heterogeneity and floristic diversity in terra firme and the physical connectivity and proximity of várzeas to adjacent terra firme forests. We suggest that inundated forests should be set aside as a crucial complement to Amazonian reserves dominated by terra firme forests in future biodiversity conservation planning.

Litter production from above-ground (leaves, twigs, fruits, flowers) and below-ground (roots) plant organs is an important component of the cycling of carbon and nutrients in forests. Tropical montane forests possess comparatively large quantities of fine-root biomass, suggesting that litter production by dying fine roots may represent a major component of total litter production. In a comparative study in three tropical montane forests of southern Ecuador at 1890, 2380 and 3060 m elevation, we measured leaf-fall by litter trapping and fine-root litter production by sequential soil coring and fine-root biomass and necromass analysis for about 1 y with the objectives (1) to quantify annual above- and below-ground litter production, and (2) to investigate elevational differences in litter production. Leaf litter mass decreased to less than a third (862 to 263 g m−2 y−1) with increasing elevation (1890 m to 3060 m), whereas fine-root litter production increased by a factor of about four (506 to 2084 g m−2 y−1). Thus, the ratio of leaf to fine-root litter shifted by an order of magnitude in favour of fine-root litter production between 1890 to 3060 m. Fine-root litter production was not synchronized with leaf litterfall and was seasonal only at 3060 m with mortality peaks in the drier and the wetter periods. We conclude that dying fine roots represent a very important fraction of total litterfall in tropical montane forests that can exceed the quantity of leaf litter. At 3060 m, the largest part of the organic material on top of the soil must originate from dying fine roots but not from fallen leaves.

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

The natural seed shadow created by gibbons (Hylobates mulleri×agilis) in Central Kalimantan, Indonesia, was monitored over 11 mo to discern the role of gibbons and post-dispersal events in the spatial pattern of seed germination. Variability in the content and distribution of 183 scats was used to determine which, if any, scat characteristics influenced seed fate. Nine scat characters were evaluated: (1) seed number; (2) number of seed species per scat; (3) scat weight; (4) seed load; (5) rainfall; (6) scat density; (7) distance to nearest fruiting tree; (8) ripe fig abundance; (9) non-fig fruit abundance. More than 99% of monitored seeds were killed, removed, or had germinated during the monitoring period. Vertebrates killed or removed most seeds (86%) and the probability of them moving seeds was highly dependent on non-fig fruit abundance at the time of deposition; factors (2), (6) and (7) also influenced seed removal/predation by vertebrates, depending on whether seeds were deposited in peak or non-peak times of consumption. Insect predation (2% of seeds) occurred mainly in scats that were deposited in months of high ripe fig abundance, while the actual chance of a seed germinating (11% of seeds) was influenced by non-fig fruit abundance at time of deposition and number of species in the original scat. The gibbon-generated seed shadow was profoundly altered by post-dispersal events and variation in the characteristics of the shadow had little lasting impact on the probability of seeds germinating.

The extent, sequence, synchrony and correlates of diel displacements by animals can provide powerful insights into the ecological and social factors that shape an organism's day-to-day activities, but detailed data on spatial ecology are available for very few tropical taxa. Radiotelemetric monitoring of 25 slatey-grey snakes (Stegonotus cucullatus) on a floodplain in the Australian wet-dry tropics for periods of 40 to 355 d (mean=195 d, 136 locations per snake) provided extensive information on habitat use, movement patterns and home range size of these large slender-bodied colubrids. All radio-tracked animals were nocturnal, sheltering by day in soil cracks and beneath tree roots and debris. Snakes did not appear to move between 61% of successive locations and timing of movements was not synchronized among snakes. Most displacements were small (<50m), with males moving further and more often than did females. However, nesting females made occasional long-distance movements, travelling 100–400m to forested areas to oviposit but then returning to their usual home ranges. Snakes of both sexes moved further and more often during the wet-season than the dry-season. Snakes typically moved on a few successive nights then remained sedentary for the next few days, apparently reflecting cessation of activity as soon as a meal was obtained. Home ranges were small (2.9–7.4 ha) and most snakes remained in the same area throughout the year, providing a strong contrast in this respect to the large and seasonally dynamic home ranges of sympatric acrochordid and pythonid snakes.

The population dynamics of the exotic earthworm Hyperiodrilus africanus was investigated in a secondary forest of the Natural Reserve of Lamto (Ivory Coast) over a period of 19 mo. The objectives were to assess seasonal abundance patterns and to determine the adaptive strategies of this species. Each month, 10 soil samples of 100×100×40 cm and 20 monolith samples of 25×25×30 cm were randomly excavated in a plot of 50×95 m and earthworms were extracted by both hand-sorting and wash-sieving methods. The results show significant inter-annual and seasonal fluctuations in population size. Three factors are likely to control population dynamics: (1) rainfall, (2) soil water content and (3) seasonality. The dry season appears to be the most important environmental factor that regulates population abundance when predation, density-dependent regulation and competition phenomena are ignored. Hyperiodrilus africanus exhibited an r strategy, suggesting a high ability to recover populations affected by drought.

Anthropogenic disturbance in Amazonian forests has increased dramatically since the early 1980s and forest disturbance is expected to continue in the early twenty-first century. Logging and conversion to pasture for cattle are two of the largest causes of forest disturbance and destruction. This study examined the distribution and diversity of dung beetles (Coleoptera: Scarabaeidae) in intact forest and under three disturbance regimes (selective logging, clear-cutting and pasture) in a forest tract in southern Pará state, Brazil. Dung beetles were collected using faeces-baited pitfall traps, then identified, measured and weighed. Principal Components Analyses and the Sørensen's Index indicated that the intact and selectively logged areas were similar in terms of species composition but that the pasture areas and clear-cut areas had substantially different groups of species. Beetle size and diversity (as measured by species richness, Shannon index and Simpson's index) were lower in clear-cuts and pasture than in intact forest. The selectively logged forest was no less diverse than intact forest, and beetles were the same size or larger than those in intact forest. Total beetle biomass, however, was highest in the pasture due to the abundance of small-bodied beetles in this habitat. While the fact that selective logging has a relatively minor impact on the dung beetle community is heartening, the projected increase in the amount of highly disturbed landscape in Amazonia is expected to have a severe impact on dung beetle biodiversity in the region.

Herbivory is important in tropical woody plants, but the few data available suggest that rates of herbivory are mostly low in epiphytes. We quantified herbivory at the community level in five bromeliad, three orchid and five fern species of a Mexican humid montane forest. Leaf area loss was <1.5% in bromeliads and orchids, but much higher (7–20%) in ferns. Damage was positively correlated with leaf nitrogen content but not with leaf life span. In contrast to low leaf damage, many bromeliads were infested by curculionid larvae feeding on the meristematic tissue at the ramet base, and we estimate that this accounts for 18 and 31% of ramet and shoot death of large individuals of Tillandsia punctulata and T. deppeana, respectively. Herbivory in flowers, capsules or inflorescence stalks reduced fecundity by c. 14–18% in three of the five bromeliads and by 90% in the orchid Lycaste aromatica, but had little effect on the other species. These data show that even if the leaf area consumed is indeed low in epiphytic orchids and bromeliads, the less conspicuous damage done to reproductive organs and meristematic tissue can have a strong effect on fecundity and survival.

We evaluated the effects of topography on the distribution of understorey herbs, shrubs and small trees of the pantropical genus Psychotria (Rubiaceae) in a 10000-ha rain-forest reserve in central Amazonia. As plots were long and thin, and followed altitudinal isoclines, we were able to avoid the trade off between plot size and precision of measurement of topographical variables. The minimum distance between plots (1 km) was sufficient to avoid spatial autocorrelation in topographical variables. However, indices of plot similarity based on species composition were spatially autocorrelated to distances of at least 4 km. Although Multivariate Analysis of Covariance (MANCOVA) indicated significant effects of altitude, slope, and watershed on species composition within plots, topographical variables were generally poor surrogates for species distributions. Differences between eastern and western watersheds within the reserve were not due to distance effects, and most species occurred in both watersheds, indicating that differences in species assemblages between watersheds are determined by ecological factors. Habitat specialization and local density were not clearly associated with rarity. At scales of 1–10 km, both distance and habitat affect the distribution of understorey shrubs of the genus Psychotria, but much of the variation in species abundances remains unexplained.

We tested the response of seedlings of Dicorynia guianensis, a major timber tree species of French Guiana, to mycorrhizal symbiosis and water limitation in a semi-controlled experiment under natural light conditions. Under well-watered conditions, mycorrhizal colonization resulted in an increase of net photosynthesis, growth and phosphorus uptake. When submitted to water stress, no growth reduction of mycorrhizal seedlings was observed. Mycorrhizal seedlings were more sensitive to drought than non-mycorrhizal ones in terms of carbon assimilation, but not with regard to stomatal closure. In contrast to previous studies on temperate tree seedlings, this result precludes a mycorrhizal effect on the hydraulic properties of this species. Furthermore, our results suggest that below a specific threshold of soil moisture, carbon assimilation of D. guianensis seedlings was decreased by the mycorrhizal symbiosis. This is probably related to the competition between the plant and its host fungus for carbon allocation under low light intensity, even though it did not seem to have a significant effect on mortality in our experiment.

The oligarchy hypothesis proposes that large areas of Amazonian plant communities are dominated by limited sets of species. We tested this hypothesis by (1) quantifying dominance of the 10 most common species, genera and families in each region; and (2) assessing the consistency of relative abundance ranks between areas and across scales in dominance patterns for trees and lianas in two distant Amazonian regions (∼1900 km), the Yasuní and Madidi National Parks in Ecuador and Bolivia, respectively. The analyses were based on sixty-nine 0.1-ha plots in which all woody plants with a diameter at breast height (dbh) ≥2.5 cm were inventoried (19 775 individuals and 1729 species in total). The plots were located at two Yasuní and five Madidi sites, with an average of 10 plots per site. Overall, oligarchic dominance was pronounced at all the spatial scales investigated, although decreasing with increasing scale. Cross-scale relative abundance ranks were more consistent in Yasuní than in Madidi, while no such difference was apparent within single sites. Quantitative dominance and consistency of relative abundance ranks increased with taxonomic rank, being stronger at the family level than at genus and species levels. Species-level dominance was somewhat stronger within the 10 most common families in either region, than in other families. Dominance was similarly strong for canopy (dbh ≥10 cm) and understorey trees (dbh <10 cm), and less pronounced among lianas. In conclusion, our results provide strong evidence that western Amazonian forests can be dominated by limited oligarchies of species, genera and families over large expanses.

We compared seedlings of sandy-soil specialist species (Dryobalanops aromatica and Scaphium borneense) and clay-rich-soil specialist congeners (D. lanceolata and S. longipetiolatum) in a tropical rain forest in Lambir Hills National Park, Malaysia, to determine whether variations in belowground seedling architecture and allometry were related to edaphic specialization. A convergent trait that was phylogenetically independent across the two genera was the presence of a deeper tap-root at any height and any root biomass in sandy-soil specialists than in clay-rich-soil specialists. This trait was fixed independently of the edaphic conditions in which the trees actually grew. Finer-textured soils generally have better water-holding capacity; we concluded that seasonal water limitation would be more severe in sandy soils than in clay-rich soils, and that water limitation would provoke convergence in seedling root depth among species with the same edaphic preferences. All significant differences found in interspecific comparison within Dryobalanops were consistent with the water-availability hypothesis; the sandy-soil specialist had larger root biomass at any total biomass and had smaller leaf biomass at any root biomass than the clay-rich-soil specialist. However, for Scaphium this was not the case, suggesting that factors other than water-limitation may also underlie seedling allometric relationships.

Temporal variation in activity of dung and carrion beetles in tropical forest is considered as a mechanism of ecological segregation between potentially competing species. We describe the diel flight activity of Scarabaeidae collected with baited pitfall traps at Les Nouragues field station in French Guiana. A total of 2663 individuals of 63 species was recorded, from the subfamilies Coprinae, Scarabaeinae and Aphodinae. Temporal guilds of diurnal, nocturnal and crepuscular species were identified. Diurnal species were about twice as numerous and abundant as either nocturnal or crepuscular species. Two main activity patterns characterize the diurnal species while nocturnal and crepuscular species show overlapping activity. The association of activity rhythm with the other niche variables, food selection, functional group, body size and relative abundance, was analysed using multiple correspondence analysis. Small diurnal coprophagous species were opposed to large crepuscular necrophagous species. Species packing is suggested but further analysis showed that the variables were independent of one another. The temporal differentiation of species combined with separation along multiple niche dimensions and resource gradients may facilitate the coexistence of species assumed to be strongly affected by interspecific competition.

The distribution of the forest tree Pisonia grandis (Nyctaginaceae) coincides with seabird colonies on small tropical islands. Its seeds are enclosed in a calyx exuding extremely sticky resin which adheres strongly to feathers. Birds are obviously seed-dispersal vectors, but the multi-seeded infructescences frequently entangle birds, often fatally. On Cousin Island, Seychelles, I investigated the production, germination, survival, and tolerance to seawater of Pisonia seeds, and the occurrence of entanglement with birds. Fresh seeds had high germination success (62–87% in experimental trays), but seedling survival in Cousin's forests was low (0.1% of 6020 seeds survived as seedlings after 2–8 mo). Some seeds tolerated 30 min daily immersions in seawater (8–15% germination after 14–28 d treatment), but not continuous immersion in seawater (reduced germination after 5 d and none after 12 d). Inter-island dispersal is likely via living unencumbered seabirds carrying a few seeds, but not on floating carcasses. Seeds attached to carcasses did not have improved germination or survival. Intra-island propagation is almost entirely vegetative, with negligible local seed dispersal. Pisonia plants therefore do not benefit from fatal entanglements. The extreme stickiness of the seeds evidently evolved to resist removal by seabirds and so facilitate long-distance dispersal. The mortality of some potential vectors is an unfortunate consequence, but has little impact on the large populations of tree- and ground-nesting seabirds which nest in or under these trees.

We aimed at (1) determining how community-wide disruptions affect visitation by frugivores at trees and (2) estimating the impact of visitation shifts on seed fate following fruit consumption, especially seed removal. We compared the seed fate of a frugivore-dispersed tree species (Tetragastris altissima, Burseraceae) in four forested islands with that for a mainland continuous forest at Saint-Eugène, French Guiana. Tetragastris trees attracted opportunistic frugivore species available in the area, the most productive trees attracting more consumer species. Only primates, which are more susceptible to forest disturbances than birds and have low abilities to cross a non-forested matrix, were more frequent at Tetragastris on the mainland than on islands. Only opportunistic frugivorous primate species acting as low-efficiency seed dispersers were recorded. As a result, seed removal was equally low among habitats (nearly 26%), high percentages of seeds dropping below tree crowns. The scarcity of large-bodied specialist frugivorous primates throughout the landscape probably explained this low removal. Our results underline how difficult it is to generalize the cascading effects of disruptions in a frugivore community on tree seed fate, these effects likely varying according to the tree species and animal community involved.

The composition, structure and reproductive phenology of a shrew community were investigated for 1 y at two neighbouring sites in an undisturbed African forest of south-western Gabon. We captured 717 shrews, belonging to four genera and 10 species. The data were analysed to answer three main questions: (1) to what extent does the shrew abundance vary seasonally? (2) is there a shift in species dominance over time? and (3) does the intensity of breeding activity vary seasonally? The number of species captured varied seasonally and tended to be least during the period of minimal trap success. Trap success for the four most abundant species (Sylvisorex johnstoni, Crocidura batesi, Paracrocidura schoutedeni and Sylvisorex ollula) varied seasonally with a minimum around the long dry season. Sylvisorex johnstoni remained the dominant species throughout the year. Seasonal variation in trap success of shrews might be related, at least partly, to their reproductive characteristics. Litter size, based on embryo counts, ranged from 1–4 among the species. Breeding occurred throughout the year, but its intensity was lower during the long dry season corresponding with the period of higher ecological constraints for shrews.

We observed a period of famine in the lowland tropical rain forest of Sabah, Malaysia from August 1999 to September 2000. All six Malayan sun bears (Helarctos malayanus) that were captured and radio-collared were in poor physical condition, and two were later found dead. The physical condition of bearded pigs (Sus barbatus) that were captured, observed or photographed by camera traps also revealed that the pigs were in various stages of emaciation and starvation. We surmise that the famine resulted from prolonged scarcity of fruit during an intermast interval in the study area. These phenomena of emaciated animals and fruit scarcity have also been reported from other areas of Borneo. Lowland tropical rain-forest trees of Borneo display supra-annual synchronized general fruiting. We believe that the starvation we observed and the generally low density of large animals in Borneo forests is a consequence of a history of prolonged food scarcity during non-general-fruiting years, but may be accentuated by anthropogenic factors such as forest fragmentation, selective logging, and reduced density of fig trees in logged forests.