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

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

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

Investigations of bats in naturally fragmented ecosystems may help refine assumptions about bat responses to fragmentation of their habitats by human activity. Bat species assemblages were studied for a 3.5-y period in a naturally fragmented landscape in the north-west Yucatan Peninsula, Mexico. Bats were systematically sampled using mist nets in a total of 16 forest islands of four categories (four sites each): large (>20 ha), small (<5 ha), far and near (sites located >10 km or <1 km away from the nearest forest island, respectively). We captured a total of 1134 bats representing 17 species. Bat diversity and species richness were similar among categories of forest island. Fruit-eating bats (78–93% of captures) were significantly more abundant in large and in small than in forest islands in the far or near categories. Differences in density of Manilkara zapota trees in the forest islands might underlie the observed variations in the abundance of frugivorous bats. Distances traversed by bats (0.65–38 km) between forest islands (typically 100–300 m away), facilitates the mobility of bats across the landscape. However, the moderately rich bat species assemblage detected, suggests that other species may not be able to persist in such naturally fragmented ecosystems.

Termite foraging was monitored with cellulose baits in both the wet and dry season in the semi-arid Okavango Delta region of northern Botswana. Seven wood-feeding species were found. Fungus-growing termites dominated the assemblage in all plots, and four species (Macrotermes michaelseni, Odontotermes sp. A, Allodontermes sp. and Microtermes sp.) were found in most. Foraging by smaller-bodied Allodontermes sp. and Microtermes sp. was largely confined to the wet season. Foraging by M. michaelseni and Odontotermes sp. A was more constant, but showed a general peak in the early dry season (May and June), likely due to nutrient and energy demands associated with alate production. Despite extensive overlap in distributions of these species, co-occurrences on baits were significantly less frequent than expected by chance. In addition, incidence in a plot of Allodontermes sp. and Microtermes sp. was negatively correlated in the wet season, as was that of M. michaelseni and Odontotermes sp. A in the dry season. Differences in body size, life history, and nest structure produce temporal and spatial heterogeneity in the foraging and distribution patterns of termites, and therefore suggest that consideration of community composition can improve prediction of the influence of termite assemblages on decomposition.

Fire history was reconstructed from fire-scarred individuals of the endemic pine (Pinus occidentalis) along climatic gradients in the Cordillera Central, Dominican Republic. We analysed variation in fire frequency by climate, elevation and aspect (windward and leeward of the central massif). A high correspondence between known fires and fire-scar chronologies indicates that the primary rings of this species are annual. Evidence was found for 41 fire years since 1727 A.D.; 28 were landscape-scale fires, nine of which were exceptionally large and linked to El Niño-triggered droughts. Mean fire return interval (FRI; the mean of individual samples) and mean fire interval (MFI; the composite mean of a group of samples) were used to estimate the upper and lower range in fire frequency. Mean FRI of the entire study area was 31.5 y (±24.9 y SD) and MFI for landscape-scale fires was 5.6 y (±4.1 y SD). The fire regime varied significantly with elevation and aspect. Mean FRI was 42.1 y (±27.6 y SD) and MFI was 9.8 y (±16.7 y SD) on moister windward zones, and mean FRI was 16.7 y (±7.8 y SD) and MFI 4.2 y (±1.9 y SD) in drier leeward zones. On windward slopes, high-elevation mean FRI (26.4 y) was significantly shorter than at middle (44.5 y) and low elevations (58.4 y). On leeward slopes, mean FRI did not vary significantly with elevation. The strong windward elevational patterning of the fire regime is driven by the trade wind inversion which traps moist air below 2000–2300 m. Such elevational patterns may be characteristic of montane fire regimes throughout the tropical trade wind belt.

In tropical West Africa, distribution patterns of forest islands in savannas are influenced by fires which occur regularly in the grass stratum. Along continuous forest–savanna transects in the Comoé National Park, the change in the amount and composition of non-woody phytomass was investigated from savanna to forest interior. This was correlated with the cover of vegetation strata above, soil depth, and the occurrence of seasonal surface fires. Phytomass mainly consisted of leaf litter in the forests (about 400 g m−2 at the end of the rainy season, and about 600 g m−2 at the end of the dry season) and of grasses in the savanna (about 900 g m−2). Low grass biomass appeared to be primarily the result of suppression by competing woody species and not of shallow soil. The occurrence of early dry-season fires seemed to be determined mainly by the amount of grass biomass as fuel because fires occurred in almost all savanna plots while forest sites remained unaffected. However, late dry-season fires will encounter higher amounts of leaf litter raising fire probability in forests. Due to the importance of the amount of combustible phytomass, fire probability and intensity might increase with annual precipitation in both savanna and forest.

A recently developed technique in soil ecology is the use of the bait lamina method, for assessing the feeding activity of soil animals in situ. Here the bait lamina method (slightly adapted to tropical conditions) was used for the comparison of four closely situated sites (a primary rain forest, a secondary rain forest and two mixed-species tree plantations) in the Brazilian Amazon (project SHIFT ENV-52). The total feeding activity (portion of empty apertures in a set of laminae) and the vertical distribution of the feeding activity were evaluated for differences between the sites. The feeding activities in the primary and secondary forest were at the same level and significantly lower than in the two plantations. Feeding activity in subplots where surface litter has been experimentally removed was significantly lower than in the controls with the litter layer intact, at all four sites. The abundance of soil macrofauna or Enchytraeidae was not correlated with the results of the bait lamina tests, while the abundance of mesofauna (probably mainly Oribatida) was consistent with the pattern of feeding activity. The feeding activities as determined with bait laminae did not correlate with the decomposition activities determined with litterbags. Due to the easy applicability in combination with its feasibility for statistical evaluation and its consistent responses to site differences in experimental treatments we consider the bait lamina method to be a promising approach for the biological assessment of tropical soils.

In a local biodiversity inventory the locally rare species are of particular importance. The main problem of sample-based inventories is that many species are so rare that they will not be observed. The observed frequencies of species in the sample provide an estimate of the species proportion in the population. This may be used to estimate the number of species which exist in the population, but which were not observed in the sample (shadow species). This non-parametric approach provides an unbiased estimate of the relative frequency distribution of the species in the population, which differs very significantly from the sample distribution, particularly for the rare species. The approach leads to a new and ecologically meaningful estimator of the Rényi–Hill generalized species diversity measure, which includes species abundance, the Shannon–Weaver and Simpson's diversity measures, amongst others. The use of the estimator is illustrated on data from a biodiversity inventory of trees on a 3-ha forest sample plot in Sumatra.

In a subtropical montane forest of north-western Argentina (27°S, 1000 m elevation), we analysed the effect of crown illumination, trunk diameter, foliar phenology and tree species identity as determinants of liana–host tree associations, as well as the spatial pattern of liana abundance in a 6-ha permanent plot. We recorded 2346 liana individuals ≥ 2 cm and 2320 trees ≥ 10 cm dbh. Sixty-five per cent of the trees hosted at least one liana stem. Large and well-lit trees were more likely to support lianas and supported more liana abundance than small and shaded trees. Yet, when trees were standardized by their size (liana basal area/tree basal area ratio), lianas were more abundant in smaller and less-exposed trees. Foliar phenology and tree species identity showed no association with the frequency of liana colonization and their abundance. Overall, tree features played a minor or even neutral role in structuring the liana community within this forest. Instead, lianas showed a positive autocorrelation at spatial scales up to 40 m. This suggests that lianas might be mostly structured by light-and dispersal-related factors such as those involving canopy access or canopy disturbances, with a negligible effect of host species identity and foliar phenology.

Arboreal earthworms are scarce in tropical rain forests, being confined to tree trunks or epiphytes (Fragoso & Rojas-Fernandez 1996). Their above-ground presence might be attributed to (1) temporary responses to flooding (Adis & Righi 1989), (2) permanent responses to acidity, flooding and anoxia of very wet forest soils (Lee 1983), (3) drought (Fragoso & Rojas-Fernandez 1996), (4) accidental events, e.g. mudslides (Picado 1911), or (5) anti-predation responses, e.g. escape from army ants (Gotwald 1995).

In Hawaii, where there are no native reptiles or amphibians, 27 species of reptiles and amphibians have established (Kraus 2003); however, few have been studied to determine their ecological impacts. For example, little is known about the impacts of the Puerto Rican frog, Eleutherodactylus coqui Thomas, that recently invaded (late 1980s) (Kraus et al. 1999), and has established on all four main Hawaiian Islands (Kraus & Campbell 2002). However, there are likely to be consequences because E. coqui can attain high densities (20 570 frogs ha−1 on average in Puerto Rico) and consume large quantities of invertebrates (114 000 prey items ha−1 per night on average in Puerto Rico) (Stewart & Woolbright 1996).

A prominent hypothesis to account for the maintenance of the woody species diversity in tropical forests is niche differentiation with respect to resources (Ashton 1969, Connell 1978). According to the hypothesis, species can coexist when each species is specialized for a specific set of growth conditions. Spatial and temporal variations in the forest understorey light conditions can be an important niche gradient. If species are adapted to a certain light condition for optimizing growth and share different optimal light conditions with each other, they can coexist by reducing direct competition; i.e. the regeneration niche differentiation sensu Grubb (1977). Species difference in rate of exclusion of trees in suboptimal light conditions due to mortality also contributes to species coexistence. Many scientists have emphasized the importance of the spatial and temporal variations in understorey light conditions on species coexistence in tropical forests (Clark & Clark 1992, Kohyama & Hotta 1990, Poorter & Arets 2003).

Seed dispersal, predation, desiccation and seedling survival are strong bottlenecks that impede tropical forest recovery on abandoned agricultural lands (reviewed in Holl 2002). The ability to resprout after disturbances overcomes these barriers, as those individuals bypass the seed stage and have more vigorous shoots than seedlings (Bond & Midgley 2001, Kammesheidt 1999, Kennard et al. 2002). Resprouting is a particularly important recovery mechanism in tropical dry forests (reviewed in Vieira & Scariot 2006). There are a number of reasons why resprouting may be more important in dry forests than in rain forests, including slower decay rates of trunk bases (Ewel 1980), or adaptation of plants to drought (Bond & Midgley 2001, Sampaio et al. 1993).