Plant communities and ecosystem processes in seres at multiple altitudes in the tropical montane forest zone of northern Borneo were studied to understand the patterns and mechanisms of the secondary succession after shifting cultivation. A total of 25 stands (and additional three stands) were sampled with stand ages ranging from 2 to 55 y after slash and burn at altitudes between 900 and 1400 m asl. Plant species composition, above-ground biomass (AGB), chemical properties of soils, litter and foliar samples were investigated in each stand. A TWINSPAN analysis classified five plant communities primarily as a sere but with two altitudinal communities in the later successional phase. AGB accumulated steadily at the rate of 2.42 Mg ha−1 y−1 during the succession for the first 55 y due to the ontogenetic development of plants as well as plant community shifts. At the onset of secondary succession, pool of soil NO3-N and soil total P was high probably because burning caused flushes of minerals originating from the burnt plant materials. Pool of soil NO3-N and soil total P decreased with increasing stand age during the succession. Leaf-litter N:P ratios of dominant species significantly increased with increasing stand age suggesting disproportionately greater P deficiency than N deficiency in the later successional phase. It is suggested that tree species shifted to those of greater P-use efficiency during succession in response to decreasing soil P availability. We conclude that the interaction of altitude with the reduction of soil N and P availability was related to the altitudinal split of plant communities in the later phase, while pioneer communities were wide-ranging across altitudes reflecting richer soil nutrients.

Some species-rich secondary forests in New Caledonia have a monodominant canopy. Here we investigate growth and biomass allocation traits that might explain single-species’ dominance of these post-disturbance stands, and their later decline in the absence of large-scale disturbance. Seedlings of 20 rain-forest trees were grown in two light treatments in a nursery house. In the sun treatment, monodominants grew faster (56.7 ± 1.4 mg g−1 wk−1) than subordinates (40.2 ± 2.6 mg g−1 wk−1). However, some episodically regenerating (ER) subordinates had high growth rates similar to those of monodominants. In the shade treatment, monodominants and subordinates had similar growth rates (33.7 ± 2.6 and 34.0 ± 1.9 mg g−1 wk−1 respectively). Notably, monodominants in both sun and shade treatments had lower root mass fraction (0.29 ± 0.02 and 0.27 ± 0.02 g g−1 respectively) than subordinates (0.39 ± 0.02 and 0.37 ± 0.02 g g−1). Fast growth in sunny conditions is probably imperative for these relatively shade-intolerant ER monodominants. In field conditions, high shoot mass fraction combined with efficient root performance may facilitate faster growth in monodominants competing with other ER species in sunlit sites. Slower growth in shade may contribute to loss of dominance over time in undisturbed forests.

Environmental productivity is important in determining defensive or tolerance traits of plants, with nutrient-rich savannas showing tolerance and nutrient-poor showing defence traits. Animals are affected differently by such traits due to differences in size, and other characters. We studied differences in browsing as a response to plant traits by elephant, giraffe and impala in Mikumi, a nutrient-poor savanna, and Serengeti, a nutrient-rich savanna, both in Tanzania, for a total of 4 mo; 2 mo at each site. Browsing time on a plant, species and height browsed were recorded. Spinesence reduced biting rate by elephant in Serengeti to 3.8 bites min−1, compared with 4.7 without spines, but had no effect on impala or giraffe. Leaf size affected biting rate by giraffe, decreasing with size in Serengeti from 19.8 bites min−1 to 17.4 bites min−1, increasing in Mikumi, from 17.7 to 19.5 bites min−1, but did not differ in elephant and impala. Biting rate by elephant in Serengeti decreased with browsing height from 0.6 m to 4.2 m and by impala in Mikumi decreased from 0.25 m to 1.5 m, while that of giraffe in Mikumi increased with browsing height, peaking at 4.2 m. The effect was comparable for elephant and impala.

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.

Forest fragmentation, habitat loss and isolation may have a strong effect on biodiversity in tropical forests. This can include modification of the genetic diversity and structure of plant populations. In this study, we assessed the genetic diversity and structure of the tree Manilkara zapota in 15 naturally formed fragments of semi-evergreen tropical forest, as well as in an adjacent continuous forest for comparison. Forest fragments were scattered within a matrix of wetlands and were highly variable in terms of size and degree of isolation. The naturally fragmented populations of M. zapota had slightly less allelic diversity (Ar: 3.4) than those of the continuous forest (Ar: 3.6), when corrected for sample size. However, populations in the fragments and continuous forest had very similar heterozygosity levels (HE: 0.59 in both cases). Low levels of genetic differentiation were observed among populations (FST: 0.026) and genetic structure was not consistent with isolation by distance, indicating high levels of gene flow. Genetic diversity was not explained by fragment size or degree of isolation. The relatively high genetic diversity and low inter-population genetic differentiation observed in M. zapota may be the result of long-distance pollen and seed dispersal, as well as the high proximity among patches.

During their ontogeny many organisms exhibit size and/or stage-specific variability in a variety of features related to morphology and ecology, leading to a shift in the ecological niche between size- or stage groups. We analysed such ecological shifts between four larval stage groups in each of two syntopic species of frogs (a total of 5870 individuals) in two West African savanna ponds in Côte d'Ivoire. We hypothesized and confirmed differences between stage groups in ecological variables related to microhabitat and feeding niche. Stage groups differed up to 1‰ in δ15N and 1.5‰ in δ13C isotopic signatures, up to 10 cm in selected water depth, up to 6 m in distance to the pond's edge, and in the coverage of submerged vegetation (range = 10–50%). However, the hypothesis that tadpoles with generalized mouthparts (Kassina spp.) exhibit more pronounced ontogenetic shifts in food-web position than a specialized filter-feeding species (Phrynomantis microps), and that differences between larval stages are more pronounced in a heterogeneous habitat (offering more choices of habitat and food niches) than in a homogeneous habitat (offering less choices) was only partly confirmed. This study underlines that potential niche shift during different ontogenetic stages is an important factor to be considered in ecological studies.

Patterns in above-ground biomass of tropical forests over short altitudinal gradients are poorly known. The aim of this study was to investigate the variation of above-ground biomass with altitude in old-growth forests and determine the importance of changes in floristic composition as a cause of this variation. We used a dataset from 15 1-ha permanent plots established from lowland (200 m asl) to submontane forests (900 m asl) in the Ngovayang Massif, south-western Cameroon. We analysed variation over altitude in two specific functional traits, the potential maximum tree height and the wood density. Forest above-ground biomass decreased from 500–600 Mg ha−1 in lowland plots to around 260 Mg ha−1 at the highest altitudes. The contribution to above-ground biomass of large-tree species (dbh ≥ 70 cm) decreased with altitude, while the contribution of smaller trees was constant. Contribution of the Fabaceae subfamily Caesalpinioideae decreased with altitude, while those of Clusiaceae, Phyllanthaceae and Burseraceae increased. While potential maximum tree height significantly decreased, wood specific gravity displayed no trend along the gradient. Finally, the decrease in above-ground biomass along the short altitudinal gradient can be at least partially explained by a shift in species composition, with large-tree species being filtered out at the highest altitudes. These results suggest that global change could lead to significant shifts in the properties of montane forests over time.

Anthropogenic disturbance often results in the proliferation of native species of particular groups that leads to biotic homogenization. Leaf-cutting ants are an example of such winner organisms in tropical rain forests, but their response to disturbance in dry forests is poorly known. We investigated Atta colony density in areas of tropical dry forest in Brazil with different distance to roads and vegetation cover. Atta colonies were surveyed in 59 belt transects of 300 × 20 m, covering a total area of 35.4 ha. We found 224 Atta colonies, 131 of which were active and belonged to Atta opaciceps (87 colonies, 2.45 ha−1), A. sexdens (35 colonies, 0.98 ha−1) and A. laevigata (9 colonies, 0.25 ha−1). The density of active colonies sharply decreased from 15 ± 2.92 ha−1 in the 50-m zone along roads to only 2.55 ± 1.65 ha−1 at distances up to 300 m. The reverse pattern was observed for inactive colonies. Active Atta colonies preferentially occur in areas with low vegetation cover, while inactive colonies prefer areas with high vegetation cover. We demonstrate for the first time that anthropogenic disturbances promote the proliferation of leaf-cutting ants in dry forest in Brazil, which may affect plant regeneration via herbivory and ecosystem engineering as demonstrated for rain forests.

The tropical dry deciduous forest (TDF) of the semi-arid region of Bajio in Mexico is dominated by successional communities, in which Lysiloma microphyllum is irregularly distributed, however the environmental factors influencing its establishment have been poorly studied. We conducted field experiments to isolate the impact of three factors on the early life-history stages of this tree. Over a 2-y period, we monitored the effects of (1) predation, (2) understorey light and (3) aspect on germination, seed-to-seedling transition (establishment) and seedling survival, and we found that open space negatively affected germination (14.9 ± 1.5% vs 96 ± 1.5% in shade; mean ± SE), while shade increased seedling establishment and survival (36.9 ± 8.2% vs 4.7 ± 3.8% in open sites). Predation decreased survival and was strongest in open conditions (0 vs 62.7 ± 9.4% in shaded exclosures). In contrast, aspect had little influence on germination and survival. The results suggest that shaded microsites positively affect the early life stages of L. microphyllum, a key process in TDF recovery.

Primary seed dispersal of many rain-forest seeds occurs through defecation by mammals. Dung beetles are attracted to the defecations and through their dung-processing behaviour these insects change the initial pattern of seed deposition. Final seed deposition patterns, i.e. where and how seeds are deposited after dung beetle activity has taken place, may strongly depend on seed size. In this study we addressed the following question: Do different sizes of seeds have different deposition patterns following dung beetle processing? We conducted a field experiment in lowland Amazonian rain forest in Brazil using 200-g dung-piles containing seed mimics of three sizes: 3.5, 8.6 and 15.5 mm long. Seed deposition condition after dung beetle activity was dependent on seed size. Small seeds were more often buried in beetle tunnels, while medium and large seeds more often remained on the soil surface, either clean or still covered by dung. A low proportion of seeds of all sizes remained on the soil surface covered by loose soil excavated by dung beetles. We speculate that the latter deposition pattern, though not very frequent, might be highly favourable for both seed survival and seedling establishment.

From the saprotrophs that decay plant material to the pathogens and mutualists that shape plant demography at local and regional scales, fungi are major drivers of tropical forest dynamics. Although endophytic fungi are abundant and diverse in many biomes, they reach their greatest diversity in tropical forests, where they can influence plant physiology, performance and survival. The number of quantitative studies regarding endophytes has increased dramatically in the past two decades, but general rules have not yet emerged regarding the biogeography, host affiliations, local or regional distributions, or phylogenetic diversity of endophytes in most tropical settings. Here, endophytic fungal communities associated with 18 species of eupolypod fern were compared among forest reserves in Panama, Costa Rica and Mexico. Molecular sequence data for >2000 isolates were used to determine the relationships of host taxonomy, forest (site), and environmental dissimilarity to endophyte community composition. Communities in related ferns differed significantly among forests, reflecting the interplay of geographic distance and environmental dissimilarity. Although the same phyla and classes of fungi were prevalent at each site, they differed in relative abundance. All sites were dominated by the same order (Xylariales), but sites differed in the phylogenetic clustering vs. evenness of their endophyte communities. By addressing the relationship of endophyte communities to host taxonomy, geographic distance and environmental factors, this study complements previous work on angiosperms and contributes to a growing perspective on the factors shaping communities of ecologically important fungi in tropical forests.

In southern African savannas, geoxylic suffrutices or ‘underground trees’ attain only a hundredth to a tenth the height of normal trees, but other traits have received little attention. Geoxylic suffrutices and congeneric trees were compared for minimum and maximum values of seven morphological traits. Thirty-six geoxyle-tree pairs co-occurring in Katanga (Democratic Republic of the Congo) were compared, based on data from standard floras. The tree/geoxyle ratio ranged from 0.92 to 1.67 and was greater than 1 in 12 of 14 trait comparisons. However, the difference was significant in only five comparisons. Reproductive traits generally did not differ. The maximal value of leaf traits (lamina length, lamina width, petiole length) was 33–67% greater in trees. The morphological traits of geoxyles are not much altered compared with their tree counterparts, especially for reproductive traits. For vegetative traits, geoxyles express a restricted part of the phenetic space of trees, being unable to attain trait values as high as those of their tree congeners. However, unlike bonsais or alpine dwarfs, the leaves of geoxyles are not much smaller compared with normal trees.

Scatter-hoarding by rodents is expected to benefit palm recruitment by allowing cached seeds to escape predation and to colonize new areas, but evidence that seedlings emerge from cached seeds is scarce. We aimed to assess to what extent seedling establishment of two palm species (Astrocaryum aculeatissimum and Attalea humilis) is favoured by seed caching by rodents in a large Atlantic Forest remnant. We mapped the location of conspecific seedlings within circular plots of 15-m radius around five adult individuals of each palm species, checking if seedlings established from dispersed (>2 m from parent palms) or non-dispersed seeds (0–2 m from parent palms), and from buried or unburied seeds. We found a total of 42 A. aculeatissimum seedlings and 16 A. humilis seedlings. Nearly all (98%) seedlings established from seeds dispersed away from parents (mainly located 10–15 m from parents), and 83% and 75% of seedlings of A. aculeatissimum and A. humilis, respectively, established from seeds buried in the soil. Results show that both palm species depend almost entirely on caching of seeds by rodents to establish seedlings. Our study suggests that checking for endocarps associated with established seedlings can accurately estimate the process behind seedling establishment, improving our understanding about the net outcome of seed caching for large-seeded palms.

Bush encroachment has serious consequences on ecosystem functioning through alteration of species composition and ecosystem productivity. However, little is known regarding the spatial patterning of invading shrubs in semi-arid savannas. Cartesian coordinates of two invading woody species (Vachellia karroo and V. nilotica), were recorded in a 20 × 20-m plot on a grassland at Matopos research station, south-west Zimbabwe. We recorded a total of 308 plants including both saplings and shrubs from the two study plant species. Second-order spatial statistics was applied in order to understand the spatial pattern of encroaching plants. We predicted that the encroaching plants would be spatially aggregated because of facilitation that occurs in harsh environmental conditions. Consistent with our predictions, the two species were aggregated, with no evidence of inter- and intra specific species competition. This study demonstrates that encroaching trees in semi-arid savanna generally do not show self organization during early growth stages.

To address how seasonality affects the richness and abundance of tropical insects, we compared the canopy and understorey communities of fruit-feeding butterflies in a seasonal Atlantic forest in south-eastern Brazil. Butterflies were sampled over 1 y using a standardized design with baited traps. A total of 2047 individuals in 69 species were recorded (1415 in the canopy, 632 in the understorey). Clear differences were found between canopy and understorey, with significantly higher butterfly abundances in the canopy. We observed two marked peaks of abundance and richness in both strata; one at the transition from dry to the wet seasons, and the other at the transition from wet to dry seasons. We found lower species turnover throughout the year in the canopy. We interpret this as evidence that temperature is more important than rainfall in explaining the yearly variation of abundance in vertical strata. The higher temperatures found in the canopy may allow butterflies to maintain activity in this stratum all year round, whereas the understorey is subject to colder temperatures, thus presenting a higher species turnover. These results improve our understanding of diversity gradients between evergreen and seasonal tropical forests, allowing insights into how climate and beta diversity gradients interact.

We studied lianas in a subtropical wet forest in Puerto Rico to understand how hurricane impacts and past human land-uses interact to affect liana dynamics over a 14-year period. We compared a high-intensity land-use area, where the forest that had been cleared, and used for subsistence agriculture before being abandoned in 1934 then regrew to a low-intensity land-use area, in which there had been only some selective experimental logging by the USDA Forest Service in the 1940s. Prior to our study, both areas were strongly affected by Hurricane Hugo in 1989, and again damaged to a lesser degree by Hurricane Georges in 1998, increasing canopy openness and subsequently increasing tree stem densities. Between 2001 and 2015, changes in the light environment and the recovery of forest structure resulted in roughly a 50% reduction in tree stem densities in the high-intensity land-use area, as recruited saplings naturally thinned. In this area, liana abundance increased by 103%, liana biomass tripled, and occupancy of trees by lianas grew by nearly 50%. In the low-intensity land-use area, juvenile stem densities were stable, and resultantly liana abundance only increased by 33%, liana biomass rose 39%, and the occupancy of trees was constant. Liana flower and fruit production increased over the 14-year interval, and these increases were much greater in the high-intensity land-use quadrats. Results of this study do show how rapid forest tree successional dynamics coincide with liana increases, but the confounding of hurricane effects of disturbance at our site, prevent us from asserting that the increases in liana density and biomass can be attributed to the same causes as those in forests elsewhere in the Neotropics.

Crypsis and aposematism are common antipredator strategies that can each be coupled with behaviours that maximize predator deterrence or avoidance. Cryptic animals employ camouflage to conceal themselves within their environment and generally rely on immobility to avoid detection by predators. Alternatively, aposematic animals tend to rely on an association between conspicuous colouration and secondary defence to deter potential predators, and tend to exhibit slow movements in response to predators. The goal of the present study was to determine how cryptic Craugastor sp. and aposematic Oophaga pumilio respond to simulated human and bird model predators. Oophaga pumilio responded more often with movement to both the human (17/22) and bird (9/25) predators than Craugastor sp. (human: 2/21; bird: 0/21). The increased movement resulted in a greater average flight initiation distance, latency to move, and distance fled in O. pumilio. These findings suggest that cryptic Craugastor sp. rely on immobility to avoid detection, whereas aposematic O. pumilio utilize movement, possibly as a mechanism to increase the visibility of their warning signals to potential predators. Furthermore, O. pumilio exhibited greater movement in response to humans, suggesting that they actively avoid trampling by large threats, rather than considering them predators.

Riparian forests (RF) provide shelter, feeding resources and commuting areas and are fundamental for local fauna during long drought periods in tropical dry forests. Nevertheless, information regarding vertebrate ecology in tropical RF is scarce. The studies of bats in riparian habitats have been mostly focused on insectivorous assemblages in non-tropical regions. We contrasted the occurrence of frugivorous bats between RF and upland dry forest (UDF) in a Neotropical dry forest region and evaluated how vegetation structure modulates frugivorous bat presence and abundance. We sampled bat ensembles and vegetation structure in three UDF and three RF sites in Jalisco, Mexico. Bat ensembles and populations were analysed with generalized linear models, including as independent factors: (1) habitat and (2) vegetation attributes. In 72 nights we captured 840 bats belonging to seven species. No effect of habitat type or vegetation structure on species richness was found, but habitat type did affect bat species composition and abundance. Moreover, vegetation structural traits affected frugivorous bat abundance. Frugivore abundance was higher in RF than in UDF probably because RF provides greater resources and more roosting sites. Riparian forests also present more canopy cover and accessible flight spaces. Our results support the importance of RF for frugivorous bats in terms of abundance and composition. Additionally, the lack of differences in species richness between UDF and RF highlights the importance of both habitats for maintaining frugivorous bats, as well as the related ecosystem processes and services in tropical dry forest landscapes.

Seed-consuming rodents are increasingly recognized for their roles in the maintenance of tree species diversity, by acting on crucial post seed-dispersal processes. Yet, studies examining the extent to which rodents may act as secondary seed dispersers and/or predators in Madagascar's forests are limited. Thread-marking seed experiments were run to address this, using the seeds of two native large-seeded, frugivore-dispersed tree species (Abrahamia thouvenotii and Cryptocarya crassifolia), in disturbed and less-disturbed habitats in the rain forests of Ranomafana National Park, during the dry season. Data show that post-dispersal handling of seeds by rodents (predation and removal) was significantly lower in disturbed than in less-disturbed habitats (1.31–3.78 times lower; n = 2200). Also, seeds were more likely to be predated or left on the forest ground after removal than being larder- or scatter-hoarded: 27–78% of the removed seeds were found on the ground, <12% found in burrows and there was no evidence of scatter-hoarding (n = 132). Based on pictures from camera traps, the native rodent species, Nesomys rufus, was potentially responsible for seed predation and/or removal in the less-disturbed habitat; but no indication of the rodent species active in the disturbed habitat was obtained. The lack of scatter-hoarding suggests a limited role of rodents in secondary seed dispersal in this system. These findings form a preliminary account of the potential roles of rodents in post seed-dispersal processes in Madagascar's forests, but this warrants further study.

Maintenance of biodiversity in tropical agrarian landscapes is challenging in the face of anthropomorphic simplification of habitats. As part of an experiment testing influences of planting treatment on tree recruitment in southern Mexico, counts of bird species were made over 10 years in twenty-four 30 × 30-m fenced plots in over-grazed pasture. Plots were planted with native tree species or left as unplanted controls in 2006. Annual censuses of birds in the plots from 2007–2016 indicated statistically significant increases in the number of fruit-eating species and individuals as vegetation matured, but increases in non-frugivorous species and individuals over the decade were not significant. Among four species of planted animal-dispersed trees that bore fruit during this time, Cecropia obtusifolia consistently produced substantial crops after 2009. In 2015, all 53 planted or passively recruited female trees of mature size of this species bore fruit. The summed body masses of fruit-eating birds in each of 24 plots were significantly correlated with rank order of available fruit per plot. Differential use of habitat patches in an agrarian landscape suggested substantial value to frugivores, but less to non-frugivorous birds than expected.