A monospecific stand of the alien shrub Mimosa pigra (Mimosaceae) was examined weekly for 14 months from March 1984. A total of 44 phytophagous insect species were found on M. pigra. The five most abundant of these made up 74% of the total community. This insect community in general showed a distinct seasonal cycle of abundance with maximum numbers during the wet season. However, a few species had a completely different pattern.

Two species, Mictis profana (Hemiptera: Coreidae) and Platymopsis humeralis (Coleoptera: Cerambycidae), were observed to cause substantial damage to M. pigra. When compared with the fauna of M. pigra from its native region, Central America, that of the Northern Territory is low in leaf and flower-feeding insects. It is suggested that these types of insects be sought as future biocontrol agents to complement those native insects causing damage and those biocontrol agents already released.

Contemporary defaunation of fragmented forests potentially alters patterns of seed predation and dispersal. Alternatively, the remaining fauna may compensate for missing animals, resulting in equivalent rates of seed dispersal and predation. In the Los Tuxtlas region of southern Mexico, populations of large terrestrial fruit-eating mammals are diminished or absent from many forest remnants. This study reports fruit removal and seed predation patterns of Poulsenia armata (Moraceae), in forest fragments and a continuous forest (LTBS). Contrary to expectation, we found no differences in seed predation (mean ± SD) between LTBS (7.2 ± 1.8 seeds per station) and forest fragments (5.6 ± 1.1). However more fruits were removed in the LTBS (11.4 ± 0.9 fruits per station) than in forest fragments (8.1 ± 0.8). Animal activity, recorded by camera traps, differed between animal guild with fewer seed dispersers in forest fragments (mean = 0.43 ± 0.02 photos wk−1) than in the LTBS (mean = 0.68 ± 0.05). Fruits and seeds attracted many species of mammal (n = 12) in both habitats, indicating substantial redundancy. Remnant forest patches in the Los Tuxtlas landscape retain great ecological value, both as refuges for mammals and habitats for trees, such as P. armata.

Montane tropical and subtropical rain forests are complex ecosystems, characterized by marked rainfall and temperature gradients with altitude, which in turn control the vegetation altitudinal zones (Hueck 1978). Montane forests are often referred to as cloud forests in recognition of the important influence of a dense and frequent cloud cover that conditions forest structure and functioning (Bautista-Cruz & del Castillo 2005, Holder 2004).

In tropical plant communities with diverse species, many congeners are found to coexist. Do environment or biotic interactions structure the coexistence of congeners in tropical forest communities? In this paper, we aimed to disentangle the effect of environment (first-order effects) and species interactions (second-order effects) on the spatial distributions of tree species. We used a classification scheme and torus-translation to test the first-order interaction of 48 species from 17 genera in a fully mapped 20-ha dipterocarp tropical seasonal rain-forest plot in Xishuangbanna, south-west China. Then we used heterogeneous Poisson null models to reveal significant uni- and bivariate second-order interactions. The results demonstrated that (1) 34 of the 48 studied species showed a significant relation with at least one topographic variable. This confirmed that topographical heterogeneity is important for distribution of these congeners. Spatial segregation (36.6%) and partial overlap (34.8%) were the most common bivariate association types in Xishuangbanna plot, which indicated first-order effects (environment) were strong. (2) For small-scale associations, 51% saplings (1 to ≤ 5 cm) (68.8% for large trees with dbh > 5 cm) of the species showed non-significant associations. For large-scale associations, 61.6% saplings (81.2% for large trees) of the species showed non-significant associations. Lack of significant species interactions provides evidence for the unified neutral theory. In conclusion, both environment and biotic interactions structure congeneric species' coexistence in tropical seasonal rain forest in this region.

Several monodominant rain-forest trees in New Caledonia have population size structures suggesting establishment following large-scale disturbance, with eventual replacement by shade-tolerant species predicted in the absence of future disturbance. Links of dominance and population dynamics to leaf-level photosynthesis were investigated in seedlings of 20 tree species from these forests, grown in experimental sun and shade conditions. In particular, we tested whether episodically regenerating (ER) species, including monodominants, have higher assimilation rates at high irradiances and lower tolerance of shade than continuously regenerating species (CR). ER species had higher maximum net assimilation rates (Amax-area) in sun plants (9.6 ± 0.4 μmol m−2 s−1) than CR species (6.2 ± 0.3 μmol m−2 s−1) and high plasticity, typical of shade-intolerant species, but monodominant species did not differ from other ER species. CR species had leaf-level traits consistent with shade tolerance, including lower dark respiration rates (Rd-area = 0.47 ± 0.03μmol m−2 s−1; Rd-mass = 7 ± 1 nmol g−1 s−1) than ER species (Rd-area = 0.63 ± 0.06 μmol m−2 s−1; Rd-mass = 11 ± 2 nmol g−1 s−1) in shade plants. Hence leaf-level assimilation traits were largely consistent with regeneration patterns, but do not explain why some shade-intolerant species can achieve monodominance.

In 2000, we established a 24-ha plot in Peninsular Thailand to investigate how forest composition, structure and dynamics vary with spatial heterogeneity in resource availability. Detailed soil and topographic surveys were used to describe four edaphic habitats in the plot. Disturbance history was inferred from historical records and floristic analysis. The plot included >119 000 trees ≥1 cm dbh in 578 species, and was recensused in 2010. Species distributions, floristic turnover, stand structure, demographic rates and biomass dynamics were strongly influenced by heterogeneity in soils, topography and disturbance history. Over 75% of species were aggregated on specific edaphic habitats leading to strong compositional turnover across the plot. Soil chemistry more strongly affected species turnover than topography. Forest with high biomass and slow dynamics occurred on well-drained, low fertility ridges. The distribution and size structure of pioneer species reflected habitat-specific differences in disturbance history. Overall, above-ground biomass (AGB) increased by 0.64 Mg ha−1 y−1, from 385 to 392 Mg ha−1, an increase that was entirely attributable to recovery after natural disturbance. Forest composition and stand structure, by reflecting local disturbance history, provide insights into the likely drivers of AGB change in forests. Predicting future changes in tropical forests requires improved understanding of how soils and disturbance regulate forest dynamics.

Mangrove species have developed nutrient conservation mechanisms to adapt to oligotrophic intertidal environments. However, nutrient enrichment occurs worldwide, particularly in estuarine and coastal regions. Mangrove species may change their adaptive strategies if nutrient availability increases substantially. To understand how nutrient resorption (a major nutrient conservation strategy) responds to nutrient enrichment, a common mangrove species in China, Aegiceras corniculatum (black mangrove), was selected, and saplings were cultivated in nutrient-enriched soils. After one year, neither N nor P resorption efficiency showed significant variations with nutrient availability and there was no difference between N and P resorption efficiency. Overall, nutrient resorption efficiency of A. corniculatum remained at ∼40%, lower than the global average levels of evergreen plants (∼50%), indicating incomplete resorption of nutrients. Incomplete resorption was also evidenced by the nutrient concentrations, resorption proficiency and N: P ratio of plant leaves. Collectively, these results indicate that black mangrove can maintain constant nutrient resorption efficiency under eutrophic conditions.

Megaherbivores play a central role in the evolution and functioning of ecosystems. In tropical forests elephant species are some of the few remaining megaherbivores. Through elephant foraging, nutrients that would be locked in leaves and stems, taking months or years to decay, are quickly liberated for use. In 10 experimental sites in Kibale National Park, Uganda, we set up 10 pairs of plots (4 × 4 m), each pair involved one treatment, elephant dung addition, and one control. After 1 y, we quantified growth (height and leaf number) and survival of young light-demanding (12) and shade-tolerant (19) plant species (439 stems in total). In general, the addition of elephant dung did not increase seedling growth, and it only increased the number of leaves in shade-tolerant plants with a large initial number of leaves. Researchers have speculated that the loss of elephants would shift the composition of African forests to slow-growing tree species. However, this is not supported by our finding that shows some slow-growing shade-tolerant plants grew more new leaves with additional nutrient input from elephant dung, a condition that would occur if elephant numbers increase.

Pollen and seed dispersal are key ecological processes, directly impacting the spatial distribution, abundance and genetic structure of plant populations; yet, pollen- and seed-dispersal distances are poorly known. We used molecular markers to identify the parental origin (n = 152 adult trees) of 177 Spondias radlkoferi (Anacardiaceae) seeds deposited by the spider monkey (Ateles geoffroyi) in latrines located beneath 17 sleeping-trees in two continuous forest sites (CF) and two forest fragments (FF) in the Lacandona rain forest, Mexico. We estimated mean parent-offspring (PO) distances per latrine and, for those seeds (54% of seeds) with more than one candidate parent (i.e. the potential maternal and parental parents), we also estimated parent-parent (PP) distances per latrine, and tested if PO and PP distances differed between forest types. Global PO and PP distances per latrine averaged 682 m (range = 83–1741 m) and 610 m (range = 74–2339 m), respectively, and did not differ significantly between CF and FF. This suggests that pollen dispersal is extensive in both forest types and that long seed dispersal distances (>100 m) are common, thus supporting the hypothesis that the spider monkey is an effective seed disperser of S. radlkoferi in continuous and fragmented forests.

We used long-term population data for the ruddy-capped nightingale thrush (Catharus frantzii Cabanis), to examine the influence of forest conditions on annual productivity, survival and growth rate (λ) in a montane forest reserve of Chiapas, southern Mexico, from 1995 to 2003. Productivity was higher in primary, mature forest than in secondary, young forest. More adults were captured in primary forest (n = 132) than in secondary forest (n = 64). Adult survival (φ = 0.79) and encounter rate (ρ = 0.36) did not vary across habitats. Males and females had similar survival between primary and secondary forests (φ = 0.80 vs. 0.83, and 0.77 vs. 0.79, respectively). Juvenile survival (φ = 0.67) was only 12% lower than for adults. Overall, the population of C. frantzii appeared to be declining at 3% y−1 (λ = 0.97, SE = 0.09, 95% CI = 0.88–1.03). Productivity and survival correlated positively with λ across years within habitats, although survival was the primary, significant demographic parameter determining λ. Although habitat alteration may have reduced the carrying capacity and productivity in secondary forest, there was no apparent negative effect on population persistence in this habitat. Thus, secondary forests represent habitats that may facilitate the long-term persistence of C. frantzii populations.

Spatial association patterns reflect underlying mechanisms of coexistence, community structure of plant species in tropical forests. We hypothesized that if spatial associations between two species shift toward segregation patterns during the course of growth, deterministic mechanisms, such as interspecific competition and habitat differentiation, would prevail, whereas if no directed change in spatial associations between two species is observed and, consequently, the initial association pattern is retained through growth, the two species would experience weak interspecific competition and show no habitat differentiation. To assess the underlying mechanisms operating between confamilial species, we analysed spatial associations among 11 dipterocarp species in terms of three growth stages distinguished on the basis of dbh in the Pasoh 50-ha plot in Peninsular Malaysia. We analysed the spatial associations of all possible combinations among identical stages (165 pairs) and among different stages (330 pairs) for each pair of 11 species, except between identical species. Our previous study revealed that the 11 species could be characterized into two classes: seven fast-growing species exhibited high growth and mortality rates, spatial aggregation on a small scale, and positive habitat associations, while four slow-growing species exhibited low growth and mortality rates, spatial aggregation on a large scale, and no habitat associations except one. Spatial segregation was observed between fast-growing species (32 pairs, 17%) and between species of different classes (35 pairs, 14%), but not between slow-growing species. Throughout the growth stages, positive associations with other species were maintained for slow-growing species versus fast-growing species. In contrast, changes in initial associations toward segregation were observed more in fast-growing species. These results indicated that interspecific competition or habitat differentiation dominated for fast-growing species, while non-directed random processes dominated for slow-growing species.

Behavioural sex-role reversal occurs when males and females exchange their standard roles in territorial defence or parental care. One circumstance under which sex-role reversal may occur is when males are a limiting resource, so that females have to compete for access to mates. Here we report on male rarity and male and female behaviour of species within the damselfly genus Nesobasis, endemic to Fiji. Earlier reports suggested that, in some members of this genus, males were seldom observed and that females of these species were consequentially territorial, a phenomenon described as ‘sex-role reversal’. Quantitative estimation of the ratio of adult males to females at 15 localities in 13 Nesobasis species (1489 individuals) indicated that males were extremely rare in some species, yet common in others. This interspecific variability in male rarity cannot be explained by elevation or habitat. Formal observations of three species with abundant males revealed that males of these species were highly territorial: they physically challenged intruders while remaining within a confined area. By contrast, in three species where males were consistently rare or absent, females were not territorial: instead, they moved widely and were primarily engaged in oviposition. While we do not know the underlying reason for the unusual rarity of males at oviposition sites in some species, it is clear that this rarity has not provided sufficient selection pressure to generate genuine sex-role reversal.

The unavoidable impact of roads on arboreal fauna in protected areas has received little attention. We investigated this impact on two gibbon species in Khao Yai National Park, Thailand: two groups had home ranges traversed by roads (roadside groups) and another two lived nearby roads (interior groups). Roads partially delineated the edges of home ranges of roadside groups, and gibbons crossed them only at a few locations. Gibbons’ space use decreased near roads for roadside groups and showed road reluctance as their crossing rates were smaller than those produced by a null movement model. Generalised linear models (GLMs) indicated that a long canopy gap reduced gibbons’ crossing probability, whereas forest cover had a positive effect. A large part of the road network had a low probability of being crossed by gibbons according to GLMs, especially at areas around park headquarters. Roads were still relatively permeable to gibbon movement with a mean 35% crossing probability. The relatively short and narrow road network in the park constitutes a positive assessment of the standards of how roads should be built in protected areas. Nonetheless, this assessment might be the consequence of the park being set in a mountainous region with difficulties of road development.

Balanites maughamii appears to be an obligate elephant-dispersed species. Its fruits are strongly scented and produce a large range of volatiles, particularly aliphatic acids such as hexanoic and isovaleric acid. The seed coat can resist a compression force of >1.5 kN. Seeds removed from the seed coat, and those from compressed seeds or from elephant dung, have better germination than seeds enclosed by undamaged seed-coats, which largely failed to germinate over a 2-mo period. Mastication by elephants may be necessary to split the seed coat to allow germination and the germinant to emerge from the seed coat. We identify four traits of elephant-dispersed fruits; they are dull-coloured, presented on the ground, strongly scented and have exceptionally strong seed coats.

Primates are important seed dispersers in tropical forests, but they are being lost due to forest fragmentation. We compared post-dispersal seed fate and seedling density for the tree Dialium guianense, in forest fragments in which its main seed disperser, the mantled howler monkey (Alouatta palliata) is present, and in fragments in which it is absent. We also carried out a germination experiment to assess gut-passage effect. Seeds extracted from fruits had very low germination (2%) compared with defecated seeds (70%). Seeds in monkey faeces had a lower probability of being attacked by predators, but a higher probability of being attacked by fungus, when compared with seeds inside fruits. Seed fate was similar in fragments with vs. without monkeys, and in sites under parent trees vs. under monkey sleeping sites. Seedling density was highest under sleeping sites in fragments with monkeys, followed by sites under parent trees in fragments with monkeys, and it was lowest in uninhabited fragments, regardless of deposition site. Our study adds to an increasing line of evidence suggesting that loss of frugivores can have strong consequences for plant recruitment.

The permanence and stability of 20 territories of the dikdik Rhynchotragus kirki, were studied at Arusha National Park Tanzania. Response criteria included the structure, size and vegetation attributes of territories, density of dikdik, and spatial distances between neighbouring territories. Fourteen of the territories studied were spatially fixed and stable while six were unstable. Two of the unstable territories were completely abandoned. Mean territory size was 0.11 and 0.13 ha during the rainy and dry seasons, respectively. 14.2% of circular territories and 42.9% of elliptical and kidney-shaped territories were stable. The figure of 55 dikdik km−2 sighted during morning censuses was lower than that for evening censuses by 13.5%. Spatial distance between territories ranged from 4.5 m to 100 m, an indication that population density might be a function of the size of suitable habitat. Although shrub canopy cover within stable territories decreased by 44.6% between 1982 and 1987, and some territories were realigned with changes in rainfall pattern, pair-bond was maintained by dikdik in 70% of the territories studied.

A new method for investigating the age structure of the patch mosaic of a tropical forest by utilizing radiocarbon dating techniques on fallen trees is proposed. Aboveground nuclear explosions in the early 1960s, before the nuclear test ban treaty, created a spike in the 14C concentration content of the atmosphere. The amount of radiocarbon in the outer layers of wood collected from trunks of trees that had died in known years (1970–1989) on Barro Colorado Island (BCI) and Gigante Peninsula (Panama) was analysed to test the hypothesis that radiocarbon concentration was predictive of year of tree death. The date of tree death was negatively related to the level of 14C, following a trend similar to published data on tree rings from German and Amazonian trees. Combining our data with these data in a statistical analysis revealed a significant predictive effect of radiocarbon on year. Analysis of covariance showed that there was no significant difference among the slopes of the three groups of data, but there was significant heterogeneity among the intercepts. The differences suggest a need for site-specific calibration and refinement of field protocols. The technique shows promise and suggestions are made to improve its usefulness for future studies.

Biological invasions can have negative consequences for resident biota, particularly when disease-causing organisms are involved. Austropuccinia psidii, or guava rust, has rapidly spread through the tropics affecting both native and non-native Myrtaceae. In Puerto Rico, the rust has become common on Syzygium jambos, an invasive tree native to South-East Asia. What are the drivers of infection, and do refugia exist across a heterogeneous landscape? We address these questions using species distribution modelling and beta regressions. The realized and potential distribution of Syzygium jambos is extensive. The model produced an AUC of 0.88, with land-use categories and precipitation accounting for 61.1% of the variation. Predictability of S. jambos is highest in disturbed habitats, especially in mountainous regions with high precipitation. All 101 trees surveyed and measured across Puerto Rico showed signs of infection to varying extents. Infection severity was consistently associated with annual mean temperature in all top beta regression models, but was also commonly associated with tree size and precipitation variables. We found no safe sites for S. jambos. Many trees were extremely unhealthy and some were dead, suggesting that S. jambos may soon become extinct on the island or reduced to persistent stump sprouts. Native vegetation may benefit from the local demise of S. jambos. While the rust has not jumped to native Myrtaceae, vigilance is required, as host-shifts have occurred in other tropical regions.