One component of the high organismal diversity of tropical lowland rain forests is the existence of series of closely related, sympatric species. For example, the six distinct tree species of the monophyletic Polyalthia hypoleuca complex regularly grow sympatrically in various combinations throughout the rain forests of Malesia. Theoretical and empirical evidence has been presented indicating that the members of such series either (1) are well differentiated with respect to at least one major niche component; or (2) may lack differentiated niches. In this study, certain sympatric members of the complex are shown to have clearly diverged in autecological characteristics that affect their distribution including: (1) P. glauca, P. hypoleuca, and P. sumatrana differ in growth characteristics, height at maturity, seedling germination requirements, and are found on soils with differing degrees of hydration; (2) P. discolor grows to a different height and on different substrate types than does P. multinervis; and (3) P. glauca and P. hypoleuca seedlings differ in transpiration characteristics and response to flooding and drought.

Fruit production by an understorey tree, Miconia centrodesma, was monitored in treefall gaps and under intact canopy in a Costa Rican lowland rain forest. Trees in gaps displayed much less seasonality in fruit production than trees of intact forest sites. For example, ripe fruits were common on gap trees for a six month period (January-June) when few or no trees under intact canopy were in fruit. The frequent and aseasonal fruiting of gap trees demonstrates that they are not constrained by phenological cueing mechanisms; the influence of such cues is overridden by habitat. Trees in gaps also produced larger crops, had more extended fruiting episodes, and fruited more frequently than shaded conspecifics. This level of intraspecific variation in fruiting behaviour suggests that treefall gaps play an important role in determining the reproductive success of M. centrodesma. A substantial proportion of an individual's lifetime seed output may be produced during the brief period it occupies a gap. In addition, the large and continuous supply of fruits produced in gaps by M. centrodesma and other understorey plants, may mean that gaps function as ‘keystone habitats’ by providing resident frugivores with fruit during periods of general fruit scarcity.

Bat communities in the understorey of primary lowland dipterocarp forest in peninsular Malaysia and Sabah were sampled with mist nets and harp traps to estimate their trophic structure. Overall, 4 of 26 species (15%) at one site, and 6 of 33 species (18%) at the other site were frugivores, while the remainder were insectivores. In terms of individuals, 7–12% of all captures were frugivores. However, the true proportion of frugivores at both sites was probably closer to 1%, because the sampling procedures were strongly biased towards frugivores. In contrast, previously published studies indicate that frugivores comprise 34–48% of species, and up to 80% of individuals in bat communities in the understorey of Neotropical forest. These results support the hypothesis, developed from studies of bird communities, that the under-storey of Malaysian dipterocarp forest supports relatively few obligate frugivores, at least in non-masting years. However, further data are required on bats in the canopy, and on the foraging ranges of bats to compare the absolute densities of bats in Malaysian and Neotropical forests.

Continuous litterfall measurements were made from 1977 to 1982, at two sites with contrasting topography in a mature tropical deciduous forest in Chamela, Jalisco, on the Pacific Coast of Mexico (19° 30′ N, 105° 03′ W). The climate is strongly seasonal with the annual rainfall (x = 748 mm) concentrated in six months (June to November) and a mean annual temperature of 24.9°C. Results of the five-year study show that at the Valley Site (slope <5°) the mean annual litterfall was 6.58 ±0.15 (SE) Mg ha−1 y−1 composed of 73.3% leaves, 17.1% woody material, 5.6% reproductive remains and 4.0% finely fragmented debris. At the Hill Site (slope 20°–40°) mean annual litterfall was 3.95 ± 0.16 Mg ha−1 y−1, consisting of 68.8% leaves, 17.0% woody material, 9.4% reproductive remains and 4.7% fragmented debris. At the Valley Site the year-to-year variation in total litterfall was not significant. In contrast, at the Hill Site it fluctuated markedly from year to year. Litter production exhibited a pronounced seasonally: at the Hill Site total litterfall peaked near the onset of the dry season; at the Valley Site it occurred two months later, apparently as a result of differences in soil moisture availability between the study sites.

Fruit production by Acacia albida (Leguminosae: Mimosoideae) trees in Mana Pools National Park, Zimbabwe, was monitored over eight years. Timing of ripe fruit-fall varied between years, as did fruit production: production of ripe fruits by the same tree varied from 5.4 kg in 1983 to 290.1 kg in 1988. Baboons reduced fruit production by feeding on unripe fruits and the mass eaten each year was negatively correlated with rainfall. Potential fruit production (i.e. production in the absence of baboons) was high when the late wet season was wet or cool and when fruit production in the previous year was low. Late wet season rainfall and temperature probably determined the degree of defoliation by caterpillars: in 1983 and 1987, when the late wet season was hot and dry, the trees were almost completely defoliated. During the late dry season, A. albida fruits were an important component of the diets of waterbuck, eland, elephant, buffalo and kudu; they were seldom eaten by hippopotamus and were ignored by zebra and warthog.

A possible mutualistic dispersal system between a large-seeded tree of French Guiana, Vouacapoua americana (Caesalpiniaceae), and caviomorph rodents, Myoprocta exilis and Dasyprocta leporina, is described. Mast fruiting of Vouacapoua at the beginning of the wet season coincides with scatter-hoarding seed dispersal. During the wet season, almost 100% of marked seeds on three sites were removed: nearly 70% were buried and the rest were eaten by mammals. Unburied seeds were attacked by insects and/or lost their ability to germinate. Rodents preferred ungerminated seeds, and had no interest in germinated seeds. Seeds were buried individually near natural objects such as palms, branches, logs, lianas, roots and trees. After predation by rodents, seedling distribution did not differ from seed distribution. Most seeds were transported less than 5 m from the feeding plots but some were carried as far as 22.4 m. Between 40 and 85% of dispersed seeds were retrieved during the following month by rodents and eaten. The disinterest of caviomorph rodents in germinated seeds, because of rapid exhaustion of endosperm reserves, prevents feeding from hoarded Vouacapoua during the long dry season when resources are scarce. Seedlings emerging from forgotten or abandoned cached seeds appear to increase the recruitment of Vouacapoua americana.

There was fruiting of the dipterocarps of Pantai Aceh Forest Reserve, Penang, Peninsular Malaysia in September 1986. The opportunity was taken to investigate the establishment and seedling survival of Shorea curtisii, Shorea multiflora and Shorea pauciflora over the subsequent year. The germination and seedling survival of Shorea curtisii was compared between canopy gaps and forest understorey sites.

Under the shaded conditions none of the species grew beyond the two leaf stage over their first year. Shorea multiflora seedlings suffered a 72% mortality, significantly lower than that of Shorea pauciflora (89%) and Shorea curtisii (93%). The major cause of mortality appeared to be drought, though Shorea curtisii was also prone to predation by small mammals.

In a gap, Shorea curtisii seeds probably germinated less well but seedling survival (28% versus 7%) and growth was better than canopy-shaded conspecifics. Seedlings in gaps escaped small mammal predation.

In a study carried out to find out if inselbergs enrich their surroundings with nutrients via drainage, amounts of total nitrogen, nitrate-nitrogen and potassium in rainfall, drainage from bare rock patches and vegetation mats on an inselberg in south-western Nigeria were measured over one year. 43.3 kg ha−1 total nitrogen, 4.8 kg ha−1 nitrate-nitrogen and 10.7 kg ha−1 potassium were recorded in rainfall for the year of study. The amount of total nitrogen in drainage from bare rock was 79% of that in rainfall whilst that in drainage from vegetation mats was 29% of the rainfall amount. The respective values for nitrate-nitrogen were 57% and 13%; for potassium they were 90% and 38%.

It was assumed that the loss of nutrients as water drains through vegetation mats and over bare patches was due to absorption by plants and soil in the mats and lichens in the bare patches. It was therefore concluded that there was no net enrichment of rainwater with nutrrients as it flows over inselberg slopes. There is, however, a funelling of water along with contained nutrients from the inselberg to the surrounding areas. This funnelling is additional to the nutrients and rainfall incident on these surrounding areas and may account for the vegetation around inselbergs being more lush than vegetation in the same area but further away from the inselbergs.

A simple modelling approach was used to assess potential nutrient outflow from inselbergs. The model shows that discharge of nutrients from the edges of inselbergs increases linearly with inselberg diameter. The model further shows that if nutrient funnelling only affects an area near to the edge of the inselberg then nutrient addition is several times higher than would be expected from rainfall deposition alone.