This study compares leaf anatomy, chlorophyll content and photosynthetic induction rates for seedlings of five dipterocarp species growing both by a path and in the understorey of a Bornean heath forest. Hemispherical photographs were used to estimate the light level. Although three of the five species showed significantly higher photosynthetic capacity in high light conditions, there were no significant within-species differences in induction rates. Average induction times to reach 50% (T50%) and 90% (T90%) of maximum photosynthetic rate (Amax) were about 1.5 and 9 min for Shorea pachyphylla. In contrast, these were 18 and 37 min respectively for Dipterocarpus borneensis, and 12 and 25 min for Shorea multiflora. Intermediate values were recorded for Hopea pentanervia and Cotylelobium burckii. There was an overall weak and negative correlation of induction rate with stomatal density. Three species showed more rapid induction loss in their leaves from the path edge vs. the understorey. The results suggest that photosynthetic acclimation can influence some aspects of a leaf's dynamic response to sunflecks, such as Amax and induction loss, while not affecting overall induction rates. This study also shows significant differences among diptero carp species in photosynthetic capacity, induction responses and leaf structure, and in acclimation on these traits.

Patterns of population fluctuation, reproductive activity and age structure were studied in populations of the marsupial Micoureus demerarae occupying two small (7.0 and 8.8 ha) fragments of Atlantic Coastal Forest in southeastern Brazil, from 1995 to 1998. Males, but not females, were observed to move between populations. Estimated sizes of the populations in each fragment were very small, usually below 20 individuals. Breeding usually occurred from September to April. Population peaks came mostly by the end of this season, the delay reflecting the time required for the young to become trappable. In August 1997, the area was hit by a fire severely affecting the smaller fragment. Populations were synchronous before the fire, although they became asynchronous after it, possibly in the short term only. Small population sizes, synchrony and presumable male-biased migration are all likely to make the set of populations more vulnerable to extinction than expected for a metapopulation.

The structure, composition and reproductive phenology of a bat assemblage were investigated in the tropical region of Los Tuxtlas, Mexico. A 90-km2 landscape, originally occupied by rain forest, consisted of forest fragments and natural corridors of vegetation surrounded by pasturelands. Artificial strips of vegetation also were present as live fences. Bats were sampled with mist nets set at ground level in 52 forest fragments, three corridors, nine shaded plantations, six unshaded plantations and three live fences. We sampled each site twice, each time for a 5-h period for two consecutive nights. Bats were captured and released and the species identity and reproductive condition of adult females were recorded. Annual fruiting phenology and fruit production was measured with fruit traps in a forest site in three 500 × 20-m transects. We captured 4799 bats of 39 species. At forest sites we recorded 97% of the species and captured 44% of the bats. In corridors we captured 76% of the species and 16% of the total individuals. In the plantations we captured 71% of the species and 32% of the individuals. In the live fences we captured 32% of the species and 8% of the individuals. Three species, Pteronotus parnelli, Carollia brevicauda and Glossophaga soricina, accounted for 52% of all bat captures. Fruit-eating species and fruit-eating insectivores accounted for 65% of captures. Fleshy fruits were available year-round, but a seasonal pattern was evident. Presence of lactating females seemed to be associated, in general, with rainfall and fruiting seasonality, but individual species displayed different patterns ranging from aseasonal polyoestry to seasonal bimodal polyoestry, seasonal polyoestry and seasonal monoestry. Despite extensive fragmentation of the original rain forest, a species-rich bat assemblage still exists in the landscape studied. Short distances among remaining forest fragments and man-made habitats seem to facilitate persistence and reproductive connectivity among members of this bat assemblage.

Because seasonality in tropical environments is driven by variation in rainfall, phytophagous tropical organisms are expected to exhibit mechanisms of escape in space and time that allow them to synchronize their breeding efforts with suitably wet periods of the year. This hypothesis was addressed by studying the breeding phenology of the nymphalid butterfly Hypolimnas bolina (L.) in the Australian wet-dry tropics. This species favours small, herbaceous larval foodplants that either die off annually or exhibit marked declines in leaf quality during the dry season. As expected, reproductive activity in H. bolina was broadly correlated with both rainfall and humidity, with individuals spending part of the dry season (early April to late August) sheltering in overwintering sites in a state of reproductive diapause. The timing of the overwintering period was similar between the 2 years, which suggests that individuals respond to seasonally predictable cues such as photoperiod. At least in 1998, the exit of butterflies from overwintering sites was relatively sudden and coincided with the first spring rainfall event. These findings suggest that H. bolina copes with seasonal adversity in the tropics by means of a regularly timed diapause.

Little is known about how climatic variability affects fragmented forests and their abrupt edges. We contrasted effects of the 1997 El Niño drought between fragmented and continuous forests in central Amazonia, using long-term data on tree mortality. For 23 permanent 1-ha plots, annualized mortality rates of trees ≥ 10 cm diameter at breast height (dbh) were compared among a ‘baseline’ interval of 5-17 y before the drought, a 12-16-month interval during the drought, and a 12-13-month interval after the drought, using repeated-measures ANOVA. We also examined the size distributions of dead trees for each interval. During the drought, average annual tree mortality rose significantly in both forest edges (from 2.44% to 2.93%) and interiors (from 1.13% to 1.91%), and the magnitude of this increase did not differ significantly between edges and interiors. After the drought, tree mortality declined in all plots, but most dramatically on edges. Mortality rates were more variable over time on edges than interiors, and there was no evidence of time lags in mortality. In forest interiors, the size distributions of trees that died did not differ significantly among the three intervals. On edges, however, relatively fewer small (10-15 cm dbh) and more medium-sized (20-30 cm dbh) trees died in the post-drought interval, compared to other intervals. Moreover, forest edges lost a significantly higher proportion of large (≥ 60 cm dbh) trees than did forest interiors. These results suggest that droughts have relatively complex effects on fragmented Amazonian forests. Drought effects in our forest fragments probably were reduced by prior floristic and structural changes near edges and by adjoining regrowth forest that partially buffered edge vegetation from desiccating conditions.

Lianas (woody vines) contribute substantially to the diversity of woody plants in Yasuní National Park, Eastern Ecuador. In total 606 individuals, belonging to 138 species, were found in two 20-m × 100-m plots. The liana diversity was higher than in any comparable study, but the density was relatively low. Sapindaceae and Leguminosae were the most species-rich families, whereas Leguminosae and Celastraceae were the most abundant families. The number of liana individuals as well as the number of liana species was partially explained by forest structure, but 92% of the variation in number of liana species depended on the number of liana individuals. Areas with high density of small trees had high liana density, and areas with a high number of tree saplings had a relatively high diversity of climbing lianas. The probability of trees being colonized by lianas increased with tree diameter. The presence of one liana on a tree increased its risk of being colonized by additional lianas.

Multiple species of primate disperse seeds and differentially contribute to the seed rain in tropical forests. The goal of this study was to examine seed dispersal by a primate community of five monkey and two ape species in the Dja Reserve, Cameroon. The density of primates in the reserve was calculated to be 77 individuals km-2. Analysis of 5789 faecal clumps demonstrated that 40% of monkey and 74% of ape faecal clumps possessed whole seeds. Six of the seven focal species acted as seed dispersers; faecal clumps passed by the black-and-white colobus (Colobus guereza) did not contain any whole seeds during the study. Seed passage trials on four captive monkey species showed monkeys to have an average seed passage time of 22 hours and defecation rate of five times per day. From the above results, the primate community was estimated to defecate 1129 seeds km-2 d-1. Seeds passed by the primate community came from 125 species of trees, lianas and shrubs, equivalent to at least 34% of the known tree flora. Rarefaction curves indicated that additional collection effort would identify more seed species passed by primates. Germination studies demonstrated that primate-passed seeds are viable. The number of seeds and plant species dispersed suggests that the primate community plays an important role in the maintenance of forest structure.

The influence of a rainfall gradient on the distribution and species richness of some groups of wood-inhabiting basidiomycetes was explored in Costa Rican tropical forests. The relationships between these fungi and wood size and decay stage were also studied. Basidiocarps of all poroid and some corticoid fungi were recorded in three plots of 30 logs in each of dry, moist, and wet forests. The logs were surveyed three times during one year, covering all seasons. The species richness gradient was inversely related to the rainfall gradient, with most species in the dry forest (51), least in the wet forest (37), and intermediate in the moist forest (44). A total of 102 species were identified. Only six species occurred at all three sites. Two of the four most common species were new to science. The composition of wood-inhabiting fungal species in the dry forest varied from both the moist and the wet forest, while species composition in the two latter forest types was difficult to distinguish. Both frequent and rare species utilized the different decay stages as expected from availability of substrate. Perennials and rare species tended to occur on large logs in the dry forest, while all species tended to occur on large logs in the moist forest, but not in the wet forest.

The role of white-tailed rats (Uromys caudimaculatus) as dispersers of seeds of the Australian tropical rain forest tree Beilschmiedia bancroftii, (Lauraceae) was investigated by following the fates of seeds and seedlings over 2 y. Fruits of this tree are too large to be consumed by any avian frugivore except the southern cassowary (Casuarius casuarius), and the only other native mammal capable of dispersing the seeds is the musky rat kangaroo (Hypsiprimnodon moschatus). However, neither of these species has been documented to disperse the seeds of this tree. During a mast year, white-tailed rats cached seeds an average of 13 m from parent trees in a variety of microsites. Although none of the 61 cached seeds followed in this study survived to germination, comparison of seed, cache and seedling distributions suggested that most seedlings arose from rat-cached seeds. White-tailed rats cached seeds in both mast and non-mast years, but the time seeds remained on the forest floor and in caches was significantly shorter in non-mast years, suggesting that synchronous seed production increases the probability that some caches survive to germination. Because white-tailed rats are the most common and widespread native mammal capable of dispersing large-seeds, this study suggests that they may play an important role in the seed and seedling dynamics of large-seeded tree species in Australian tropical rain forests.

Maximum assimilation rate under saturating light level, leaf nitrogen and chlorophyll content and specific leaf mass were measured in forest plants grown under a range of canopy openness. Seedlings from three tree species co-occurring in damar agroforest (Sumatra) were examined: Shorea javanica, Lansium domesticum and Cinnamomum porrectum. A shrub species, Piper hispidum, growing in a different location was also investigated. All species showed pronounced differences in maximum photosynthetic potential when grown under different canopy openness. All tree seedlings showed an increase in maximum assimilation rate (Amax) with canopy openness (CO) until a certain threshold was reached. This saturation threshold varied between species. A steady increase in the maximum assimilation rate over the entire range of canopy openness explored was found only for Piper. Correlation between leaf nitrogen content and Amax was usually highest when expressed on a per unit area basis. However the overall correlation was poor whether expressed per unit mass or per unit area when all species were pooled together questioning the universality of the relationship between both quantities. Potential photosynthetic nitrogen use efficiency, defined as the amount of CO2 uptake per unit leaf nitrogen under saturating light level, was highest in Cinnamomum, supposedly the most light-demanding species, and lowest in Lansium, the understorey specialist.

Although tropical forest birds are known to prey upon small lizards and frogs, no study has documented the attributes of vertebrate-eating birds or whether birds prey opportunistically on the different elements of the herpetofauna within tropical communities. This study is based on a 14-mo investigation on avian diet, supplemented with a 3-y census of frogs and a 1-y census of lizards in a humid forest of central Panama. From 91 bird species, 1086 regurgitates were collected, in which were found 75 lizards and 53 frogs. Over 50% of the common, primarily insectivorous bird species preyed upon lizards or frogs, with a mean frequency of 0.26 prey/sample. These birds (22 species, nine families) foraged on various substrates from different strata of the forest, fed on invertebrates averaging from 3.3 to 17.2 mm in length, weighed from 11 to 195 g, and had bill lengths that varied from 12.2 to 49.8 mm. Based on a logistic regression analysis, intensity of foraging at army-ant swarms was the variable that best explained the likelihood that a bird species preyed upon lizards, leading to a classification that was 91% correct. In contrast, bill length and body length classified correctly 88% of the frog-eating birds, which showed a fairly constant 1:7 bill length/body length ratio (as opposed to a mean but highly variable 1:10 ratio in other species). A multiple regression analysis showed that seasonal variation in intensity of lizard predation was positively related to arthropod abundance except during the breeding season when lizard intake decreased, presumably because nesting birds did not follow ant swarms. Intensity of frog predation correlated with frog abundance over time, the latter being inversely related to arthropod availability. Ninety-seven per cent of all lizards and frogs identified in the diet samples (n = 105) were from two genera, Anolis and Eleutherodactylus, respectively. Prey size distribution in the regurgitates suggested an optimal prey size of 33.5 mm snout-vent length (SVL) for lizards and 14.5 mm SVL for frogs. Birds preyed opportunistically on the different Anolis species, but almost exclusively upon juvenile individuals. Abundances of the different Eleutherodactylus species correlated with their predation rates, but these frogs represented only 10% of all the frogs observed during the censuses. The two most common local anurans, Colostethus flotator and Bufo typhonius, were not taken by any bird species.

With 86 species, Iwokrama Forest in central Guyana has the highest reported bat biodiversity for a protected area in the world. Using standardized capture data for 73 of these 86 species, we document community structure of bats in terms of species diversity, relative abundance, gross biomass, feeding guilds, vertical stratification and a trophic-size niche matrix. Based on faunal surveys in 1997, with similar amounts of effort in the forest canopy and at ground level, the greater fruit-eating bat (Artibeus lituratus) was by far the most ecologically dominant species in terms of frequency of capture and biomass. In total, frugivores comprised 70% of the species diversity and 78% of the biomass. The most common species of bat were fully partitioned in a resource niche matrix of size and trophic guild when vertical stratification was included as a variable. We conclude that resource partitioning and species packing differentially affect relative size in tropical bats, and are better summarized and analysed in three dimensions.

Large mammals often play important roles in determining the structure and composition of plant communities. This study focused on the extent to which wild pigs (Sus scrofa) influence the dynamics of tree seedlings and saplings in a lowland rain forest at Pasoh Forest Reserve in West Malaysia. Native wild pigs are common in the study area and may significantly influence growth and survivorship of woody plants in the understorey through several activities namely, nest building, soil rooting and seed predation. To test experimentally the impact of pigs on the plant community, eight 49-m2 exclosures were constructed. After 2 y, the number of recruits inside exclosures was three times greater than in unfenced control plots. Stem density was highly correlated with species richness, which also increased significantly inside exclosures. Height growth of plants was greater in the exclosures by 52.5% for trees between 1 and 7 m tall. Trees less than 1 m tall, however, exhibited no differences in growth. Mortality of plants also did not differ between treatments. The observed differences between exclosure and control plots can be attributed to soil-rooting and seed predation, suggesting that these two behaviours of wild pigs are important to plant dynamics in the understorey.

Thirty-six of the 70 species of bats known from Belize were recorded from the area around Lamanai, Orange Walk County: two in roosts and 34 in about 680 mist net hours that produced 560 captures. Day roosts used by 35 of the species were located using radio-tracking (Sturnira lilium, Platyrrhinus helleri, Centurio senex and Bauerus dubiaquercus) or general searching for roosts (Rhynchonycteris naso, Saccopteryx bilineata, Saccopteryx leptura, Dicli durus albus, Mimon bennettii, Micronycteris schmidtorum, Carollia brevicauda, Carollia perspicillata and Eptesicus furinalis). Data on the day roosts of 23 other species were determined from the literature. Most species reported from Lamanai (19) roosted in hollows, while others used foliage (6), tents (3), sheltered sites (2), crevices (2), open sites (1), and a few species used more than one type of day roost (hollows and crevices (1); hollows and foliage (1); hollows, foliage and tents (1)). The fauna consisted of 13 aerial foragers, 9 gleaners, 11 fruit/leaf eaters, one trawler, one flower-visitor and one blood-feeder. In day roost use and foraging behaviour, the Lamanai fauna did not differ significantly from that of Paracou, French Guiana, but both these locations differed from the bat fauna of Kruger National Park, South Africa, in foraging behaviour.

The influence of local precipitation and temperature on long-term growth dynamics in two species of seasonally dry tropical forest trees were investigated. Growth records were extracted from tree rings in Guanacaste province, Costa Rica. These chronologies provide a long-term (c. 85-y) record of tree growth for two species with contrasting phenologies. Annual growth, in both species, was dependent on annual and/or monthly variation in local precipitation but less so on temperature. For each species, however, patterns of growth reflected unique degrees of sensitivity to monthly rainfall and rainfall during previous years. It is hypothesized that such differences were due to the rooting depth of these species. A review of the literature also indicated similar diverse cambial growth responses by tropical trees to variation in annual and monthly climate. Lastly, it was shown that variation in longer term fluctuations in the Pacific and Atlantic oceans, as measured by the El Niño Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO), significantly influenced local precipitation in Guanacaste only during the wettest portion of the wet season. Such temporal sensitivity may have differentially influenced the longer-term growth of some tropical tree species but not others. Together, these results support the hypothesis that tropical tree species respond individualistically to variation in local and regional climate and that some tropical assemblages may in fact be structured by species-specific differences in soil water-use.

Above- and below-ground morphology of seedlings (up to 98 cm in height) were compared by allometric analyses in tropical heath forest and peat-swamp forest in Central Kalimantan. Thirteen abundant species were selected, including two species found in both forests. In above-ground morphology, heath forest seedlings invested more in leaf mass, while peat-swamp forest seedlings invested more in stem mass, stem height, crown area and leaf area. In below-ground morphology, heath forest seedlings invested more in root mass and depth, while peat-swamp forest seedlings invested more in lateral development of the root system. Both specific leaf area and area per leaf of heath forest seedlings were lower than those of peat-swamp forest seedlings. This differentiation in seedling morphology between forest types was evident as a plastic response in the two shared species. Heath forest seedlings on coarse-textured bleached sand with low water retention suffer occasional drought whereas peat-swamp forest seedlings on waterlogged peat rarely experience drought. We concluded that seasonal water limitation brought about the convergence in seedling morphology within heath forest because average understorey irradiances and soil nutrient concentration were assumed to be similarly low in both forests.

In an area of savanna-forest (S-F) mosaic of Cameroon, at Kandara near Bertoua, an enclosed savanna bordered by young semi-deciduous forests was selected for detailed studies of vegetation and soil carbon isotope compositions with a view to estimating the rate of forest advance into savannas. Forest floristic composition and structure were analysed in small plots along two S-F transects and within two large stands. Tree species counts and basal area (BA) measurements gave convergent results defining (1) an edge forest with low BA values that forms an irregular strip parallel to the S-F border, (2) a large colonization zone zone composed of pioneer species (Albizia species, with individuals of very large diameter) and (3) a mature forest composed of abundant Rinorea individuals and large individuals of Triplochiton scleroxylon and Piptadeniastrum africanum. Carbon stable isotopes were deter mined from organic matter of soil profiles sampled at various depths in savanna, colonization-zone and mature forest. In the deep soil horizons (40-50 cm) of the colonization-zone profiles, δ13C values similar to those of the present savanna reveal the past existence of a large-tree savanna. In subsurface horizons (15-20 cm), δ13C values intermediate between those of savanna and mature forest prove the encroachment of the forest ecosystem on savanna. Using 14C measurements, the mean residence time (MRT) of soil organic matter of these last horizons was determined with precision owing to the atmospheric 14C pulse from nuclear bomb tests prior to 1964. By assuming an exponential age distribution of organic compounds and by taking account of MRT and remaining carbon from the savanna, the coloniza tion zone was found to be 60-80 y old. The age of the colonization zone being the same near the present savanna and near the mature forest, it seems that the forest advance was probably not a linear process but would result from the coalescence of Albizia thickets born in savanna.

We studied the resource allocation process of a large-seeded species, Dryobalanops lanceolata, during germination and early stages of seedling growth in Sarawak, East Malaysia. The seeds contained high contents of starch (74.3% of the total 1.57 g mean dry weight of the cotyledon) and lipid (15.0%). All of these reserves were exhausted by the time the first two pairs of leaves had developed (about 40 d after planting), but relatively little had been reserved in leaf or root by that time. This suggests that the large amount of seed reserve of D. lanceolata is necessary just to form a certain size of stem and the necessary number of leaves to set the plant up for photosynthesis. After seed reserves were exhausted, shoot elongation and new leaf production stopped, and most photosynthate was allocated to the expansion of the root system and to storage in the root as starch. The storage reserves in the root are thought to be used for the next growing stage, not to act as insurance for sprouting in case of shoot damage.

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 suitability of several methods for estimating light conditions in the understorey of tropical forests, and of different sampling schedules was evaluated. Light conditions at 16 understorey sites in a Panamanian lowland forest were continuously measured for 9 mo with quantum sensors and photodiodes. Light conditions at the sites were also assessed indirectly with hemispherical fisheye photographs, plant canopy analysis, 38-mm photographs, 24-mm photographs and a spherical densiometer. Estimates from all indirect methods, except the spherical densiometer, were highly correlated with the direct measurements. Short-term direct light measurements for a day or a week also correlated with long-term light conditions. The indirect measures differed by up to c. 70% from the direct measures relative to single site measurements. Hence, the indirect methods are inadequate where single site light conditions have to be assessed accurately. However, because light conditions encountered in the understorey varied up to 13-fold, the indirect methods were found to be well suited to rank understorey light conditions among a large number of sites. The results from frequent and infrequent sampling schedules differed only slightly, suggesting that taking indirect measures at the beginning and the end of a study offers a reasonable compromise between accuracy and sampling effort.