Following the 2003 invasion of the armoured scale Aulacaspis yasumatsui to Guam, changes to population traits of the dominant Cycas micronesica were determined. Belt transects with a width of 4 m and an average length of 120 m were established in October 2004 to document plant mortality until January 2011. Stem height, basal diameter and leaf number were also measured for each plant and used to determine density, demography and allometric relationships. Allometric traits and a left-skewed demographic structure of the pre-invasion C. micronesica habitat documented a thriving population with high recruitment potential. Aulacaspis yasumatsui dispersed into the study site 4 mo after the initial census. All seedlings were killed within 9 mo and all juvenile plants were killed within 40 ± 10 mo. Mortality reached 92% by 6 y after chronic scale infestations. Allometry and demography of the 2011 survivors described a collapsing C. micronesica population of stressed and reproductively challenged trees with no recruitment. This classic example of the enemy release hypothesis has resulted in a homogeneous decline in plant density from 2007–2011. The trend predicts extirpation of C. micronesica from west Guam habitats by 2019.

A climate model, based on effects of water availability and temperature, was recently proposed to explain global variation in bat species richness along altitudinal gradients. Yet such studies are sparse in the tropics and near-absent in Africa. Here we present results from an altitudinal study of bat diversity from Mount Mulanje, Malawi. Using ground nets, canopy nets and harp traps, we sampled eight sites across three habitat zones from 630 m to 2010 m asl. We assessed the influence of climatic, geographic and biotic variables on measures of estimated species richness, Fisher's α, and an unbiased index of compositional turnover. We recorded 723 individuals and 30 species along the gradient, revealing a ‘low plateau’ pattern in estimated species richness, peaking at 1220 m, which is congruent with the global climate model. Measures of local habitat structure significantly explained a large degree of variation in species richness and compositional turnover between sites. Fisher's α was further significantly correlated to mean annual relative humidity, suggesting a background climatic influence.

In this study we investigated the importance of two species of fruit bat (Rousettus leschenaulti and Cynopterus sphinx) as seed dispersers for a species of fruit tree (Syzygium oblatum) found in the Xishuangbanna Tropical Botanical Garden in South-West China. We found that although R. leschenaulti and C. sphinx were the two primary seed dispersers of S. oblatum over half of the fruit produced by the tree (65%) fell to the ground. Out of the fruit collected, R. leschenaulti and C. sphinx were able to disperse seeds up to 73 m from the parent tree with the highest density of feeding roosts occurring at 21.3 m (SE = 5.2 m). We found no signs that either species of bat used the parent tree as a feeding roost, instead choosing specific trees that were at lower densities compared with other trees in the forest that were not used. When comparing the viability of seeds in three different habitats (under parent tree, in forest gap, under feeding roost) survival analysis revealed that seedling survival was significantly higher in the forest gap (91.7% ± 4.41%) than under the parent tree (78.3% ± 1.67%), but was not significantly different to seedling survival underneath feeding roosts (86.7 ± 1.67%). Further work also showed that the seeds did not have to be removed from the fruit or ingested by the bat in order to germinate. We conclude that although S. oblatum is not dependent on R. leschenaulti and C. sphinx for successful germination of its seeds, these two species of bat are important seed dispersers and can move seeds to areas where there is a greater chance of germination success and survival.

This study examined whether high nutrient concentrations associated with leaf-cutting ant nests influence plant growth and plant water relations in Amazon rain forests. Three nests of Atta cephalotes were selected along with 31 Amaioua guianensis and Protium sp. trees that were grouped into trees near and distant (>10 m) from nests. A 15N leaf-labelling experiment confirmed that trees located near nests accessed nutrients from nests. Trees near nests exhibited higher relative growth rates (based on stem diameter increases) on average compared with trees further away; however this was significant for A. guianensis (near nest 0.224 y−1 and far from nest 0.036 y−1) but not so for Protium sp. (0.146 y−1 and 0.114 y−1 respectively). Water relations were similarly species-specific; for A. guianensis, near-nest individuals showed significantly higher sap flow rates (16 vs. 5 cm h−1), higher predawn/midday water potentials (−0.66 vs. −0.98 MPa) and lower foliar δ13C than trees further away indicating greater water uptake in proximity to the nests while the Protium sp. showed no significant difference except for carbon isotopes. This study thus shows that plant response to high nutrient concentrations in an oligotrophic ecosystem varies with species. Lower seedling abundance and species richness on nests as compared with further away suggests that while adult plants access subterranean nutrient pools, the nest surfaces themselves do not encourage plant establishment and growth.

A number of studies have pointed out that abiotic factors and recolonization dynamics appear to be more important than biotic interactions in structuring river–fish assemblages. In this paper, we studied the fish assemblages in 27 floodplain lakes, with perennial connection to the river, in the middle section of the Magdalena River (Colombia), to examine spatial pattern in freshwater fish diversity in relation to some environmental parameters. Our objective was to examine relationships between floodplain-lake fish communities and environmental variables associated with lake morphology, water chemistry and river–floodplain connectivity in a large river–floodplain ecosystem. During the study, a total of 18 237 fish were caught from 50 species (regional richness; 17 were migrants and 33 residents). In the present study, the most diverse order was Characiformes with 20 species, followed by Siluriformes, with 19 species. Characidae and Loricaridae were the richest families. The range of species richness (local richness) varied between five and 39 species. Similarity of local assemblages (using the presence–absence data) depends on the distance between lakes. A positive relationship was observed between the Ln of the total abundance of each species and the number of lakes where they were found. Out of all the environmental parameters taken in the lakes, only the size (Log Area) and relative perimeter length are significantly related to local assemblage species richness. It has not been possible to demonstrate that the connectivity (distance) from lakes to the main river can be considered a predictor of the local richness.

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.

Research has increasingly established that mesoherbivores influence the regeneration of woody plants. However the relationship between mesoherbivore density and degree of impact, and the spatial component of this impact, has not been well established. Using a novel sampling design, we assessed in iMfolozi Park, South Africa, the impact of impala (Aepyceros melampus) across the full complement of woody species within the home range, evaluating its spatial component and relationship to impala density. We used four GPS collars, in separate breeding herds, and a GIS to detect zones of different density of impala in the landscape, thus defining a fine-grain browsing gradient. We assessed impact on woody recruits (≤ 0.5 m height) across this gradient by means of 1600 random 1 × 1-m quadrats. Densities of woody seedlings, and mean percentage of remaining canopy, were significantly less in areas of high impala density versus low-density areas. There was a significant correlation between increasing impala density and decreasing density of favoured woody recruits. We propose a hypothesis of impala-induced patch dynamics. It seems likely that the ubiquitous impala may create and sustain a shifting mosaic of patches, and thus function as a key determinant of landscape heterogeneity.

Many tropical tree species have buttresses at the standard breast height (1.3 m above ground) of diameter measurement, with a presumable role in improving nutrient acquisition or tree anchorage in the ground (Newbery et al. 2009, Richter 1984). Measuring the diameter using standard dendrometrical tools such as callipers or graduated tapes, which require that the cross-section of the trunk has a convex shape, is then impossible (Nogueira et al. 2006). The recommended method in this case is to measure the diameter above the buttress (DAB), thus possibly leading to biased estimates of the basal area (West 2009), of tree above-ground biomass (Dean & Roxburgh 2006, Dean et al. 2003) and of tree growth (Metcalf et al. 2009). As an alternative, one can measure the basal area at breast height of buttressed trees, using a method that can deal with the irregular non-convex shape of the cross-section of the stem such as the Picus calliper, photogrammetry or 3D laser scanning (Badia et al. 2003, Dean 2003, Newbery et al. 2009).

The distribution of mangrove forests is limited to the coastal zones of tropical and subtropical regions, and their total area is far smaller than that of upland forests (Spalding et al. 2010). Mangrove forests often show unique patterns of biomass allocation and carbon dynamics because they are periodically submerged by tides (Komiyama et al. 2008). Therefore, the contribution of mangrove forests to the global carbon fixation process should be carefully evaluated even though their distribution area is limited.

Mangroves generally grow in nutrient-poor environments and maintain high levels of productivity through unique adaptations for nutrient conservation (Reef et al. 2010). One such adaptation in mangroves is highly efficient resorption of limiting nutrients from senescing leaves prior to abscission (Feller et al. 2003). Thus processes that lead to loss of foliage prior to senescence and nutrient resorption (e.g. storms and herbivory) can be detrimental to tree growth and productivity (Bryant et al. 1983, May & Killingbeck 1992). Furthermore, decomposition of fallen leaves by soil microbial communities (Alongi 1994, Holguin et al. 2001) and crabs (Nagelkerken et al. 2008) is another important process contributing to the recycling of nutrients that are in short supply. Therefore, processes that lead to a substantial reduction in litterfall can have a strong negative effect on nutrient cycling and forest productivity. Mangroves have long been recognized as an important source of organic carbon (both particulate and dissolved) for the surrounding tropical coastal ecosystems (Bouillon et al. 2008, Kristensen et al. 2008). Thus, processes affecting litterfall in mangroves can affect the surrounding marine food webs.

Lantana camara L. (Verbenaceae) is a shrub of Neotropical origin that has spread to at least 60 countries (Day et al. 2003), and its ability to rapidly occupy disturbed habitat has led to it being named one of the ten worst weeds on the planet (Cronk & Fuller 1995, Sharma et al. 2005). A number of traits may have contributed to its success as an invasive species. For example, L. camara increases the available soil nitrogen in otherwise nitrogen-poor ecosystems (Sharma & Raghubanshi 2009), it is extremely resilient to disturbance (Gentle & Guggin 1997a, Hiremath & Sundram 2005), it is allelopathic to native plants (Achhireddy & Singh 1984, Gentle & Duggin 1997b) and its fruits are dispersed by a variety of birds (Mandon-Dalger et al. 2004, Swarbrick et al. 1998). A potentially unappreciated aspect of L. camara biology that may also contribute to its invasiveness relates to pollination ecology.

Habitat fragmentation may affect essential ecosystem processes, such as pollination, causing negative effects on plants and pollinators (Aizen & Feinsinger 1994, Jennersten 1988, Lennartsson 2002, Liow et al. 2001, Murcia 1996). Effects of fragmentation on plant–pollinator interaction were evaluated in several studies (Aguirre & Dirzo 2008, Dauber et al. 2010, Dick 2001, Donaldson et al. 2002, Dunley et al. 2009, Fuchs et al. 2003, Ghazoul & McLeish 2001, Lopes & Buzato 2007). The Brazilian savanna, called cerrado, has been fragmented due in large part to extensive agricultural activity (Carvalho et al. 2009). Studies with the main objective of evaluating the influence of fragment size on ecosystem processes and on plant reproductive output has not been determined in cerrado. The plants of this type of vegetation seem to produce generally low number of fruits per flower (Gribel & Hay 1993, Munin et al. 2008, Ortiz et al. 2003). This may be due to the low soil fertility (Franco 2002, Haridasan 2000). But the recent fragmentation of this biome may reduce even more their plant reproductive success because it can increase the effect of pollination limitation and inbreeding caused by the habitat isolation and degradation.

Palms are important components of tropical forest plant communities, due both to their abundance (Henderson et al. 2000) and to the network of interactions with their pollinators and dispersers (Henderson 2002, Zona & Henderson 1989). Forest fragmentation alters the biotic and abiotic conditions of habitats (Ewers & Didham 2006, Fahrig 2003) and it has been observed that Attalea palms increase their densities in disturbed sites (Aguiar & Tabarelli 2009, Andreazzi et al. 2012, Lorenzi et al. 2004). Increased light availability (Salm 2005, Souza & Martins 2004), changes in seed dispersal and predation patterns (Andreazzi et al. 2012, Pimentel & Tabarelli 2004, Wright et al. 2000), and ability to recover after disturbance (Souza & Martins 2004) are among the main mechanisms that have been proposed to explain enhanced palm densities. However, how altered conditions following disturbances influence the dynamics of flower and fruit production is still little understood.

The impact of hurricanes on tropical forests has been well documented in recent decades, with hurricane disturbance hypothesized to be a leading contributor to maintenance of the high diversity of trees in lowland tropical rain forests (Frangi & Lugo 1991, Vandermeer et al. 2000). Hurricanes have a heterogeneous impact both on landscapes and tree species (Liu & Fearn 2000, Walker et al. 1996). Damage to trees can take many forms, from leaf loss to stem snapping to uprooting, and is variable across the landscape due to topography, wind speed, direction and tree density (Walker 1995).