Spatial analysis can be used to relate the patterns of tree species to their regeneration syndromes – pioneer to late-successional – and is a first step in refining hypotheses about the species traits and biotic and abiotic factors that give rise to forest community dynamics. This study examines the spatial pattern of the most abundant trees in three 0.45-ha plots in species-poor lowland rain forests on oceanic islands in Tonga, Western Polynesia, that experience frequent natural disturbance and have a 3000-y history of shifting cultivation. We contrast secondary vs. remnant late-successional forest, with particular attention paid to the spatial dispersion and clustering of tree species, and the presence of spatial dependence in the density of seedlings and saplings. Shade-tolerant species were not strongly clustered at any scale. They did not appear to be dispersal limited, in late successional forest, and only some showed patterns consistent with density-dependent mortality (more clumped when small). Shade-tolerant species were more clumped in secondary forest, and may be dispersal-limited there because vertebrate dispersers prefer primary forest. Shade-intolerant species were clumped in gaps in late-successional forest, but some were also clumped in secondary forest, indicating that they too may be dispersal limited during secondary succession. We also compared the species composition of seedlings and saplings in the centre of plots with trees in the surrounding area and inferred that active dispersal (by vertebrate frugivores) contributed as much as 50% to site species richness.

Studies in western Amazonian forests have found that similarities in soil cation concentration and texture explain floristic similarities between sites, when these are measured using trees, pteridophytes or Melastomataceae. However, it is not known to what extent the three plant groups react to the same soil characteristics, because tree studies have almost always been conducted in different areas than studies on the understorey plant groups. We made inventories in 23 sites representing non-inundated rain forests on clayey to loamy soil in three regions of western Amazonia. Significant Mantel correlations between the floristic patterns of trees and pteridophytes were found in all three regions when floristic differences were measured with species presence–absence data. When species abundance data were used, and when the floristic patterns of trees and Melastomataceae were compared, significant correlations were found in one or two regions. Mantel correlations between plant groups were highest in the two regions where the observed variation in soil characteristics was largest. In all regions, the same soil variables emerged with significant Mantel correlations with trees, pteridophytes and Melastomataceae. Soil calcium and magnesium were most frequently retained in the models of multiple regression on distance matrices. On average, soil differences explained 50% of the variation in floristic differences (range = 14–84%), and geographical distances explained 16% (range = 0–64%). Our results demonstrate that beta diversities of the three plant groups are highly correlated, and that much of this congruence is explained by similar reactions to soil variation. These results support the idea that pteridophytes, and to a lesser degree Melastomataceae, can be used as indicators of general floristic and edaphic patterns in Amazonian rain forests. Since understorey plants are much quicker to inventory than trees, this would make it possible to recognize and map floristic patterns over huge areas of lowland Amazonia within a reasonable time.

One possible mechanism underlying species losses in the tropics is an increase in predation due to habitat degradation. Relative levels of predation at three heights (ground, 1–1.5 m, > 5 m for nests and > 3 m for caterpillars) were compared across a gradient of disturbance in the Subic Bay Watershed Forest Reserve, Philippines over a 2-mo period. Four 750-m transects were established in each habitat type (closed-canopy forest, open-canopy forest, rural areas) where artificial nests and caterpillar models were placed within 10-m-radius plots and checked after a 5-d exposure period. Nests in open-canopy forest were least predated (16.7%), with predation in rural areas (58.3%) being higher than in closed-canopy forest (32.8%). Predation on nests at 1–1.5 m was significantly lower than ground nests. General linear mixed model analysis suggested that effects of habitat type on nest predation differed among heights. Attacks on caterpillars increased with disturbance (46.1–59.4%), but height was not found to have a significant effect on predation. Markings on plasticine models, camera traps and live traps were used to establish possible predators. Shifts in predator dominance among the habitats were observed. Vegetation cover, tree density and small mammal abundance were not correlated with mean predation in the transects.

Parasites are ubiquitous in wild animals, with host-specific life histories considered as major determinants of prevalence and parasite assemblage patterns. It is predicted that habitat differences in logged rain forests influence population performances of small mammals and consequently may change the infection patterns of local animal populations with regard to endo- and ectoparasites. We investigated patterns of helminth species assemblages (Nematoda, Platyhelminthes) in two rat species (Leopoldamys sabanus, Niviventer cremoriventer) and two tree shrew species (Tupaia tana, T. longipes) in three logged and three unlogged rain forests in Borneo by examining 337 faecal samples with non-invasive faecal egg count (FEC). Nematode eggs prevailed in 95% of all samples with up to five (mean 1.9 ± 1.1) morphotypes. Whereas members of Strongylida were most prevalent in L. sabanus, T. tana and T. longipes, Spirurida dominated in N. cremoriventer that revealed at the same time the lowest average nematode prevalence and FEC. Cestode eggs were only found in L. sabanus and T. tana. Composition and abundance patterns of the parasitic helminth assemblages were influenced by logging. As hypothesized, species richness of nematode morphotypes and mean number of infections per host of T. longipes were larger in logged than in unlogged forest. In contrast, L. sabanus was more heavily infected with cestodes in unlogged than in logged forest and also revealed larger egg counts for strongylids and spirurids in unlogged forest. Our results suggest that forest degradation and altered environmental conditions influence helminth diversity and infection patterns of small mammals with contrasting trends among host species. The inconsistent logging-induced changes in helminth assemblages from different hosts indicate that specific sets of habitat-host-parasite interactions are uniquely influenced by the effects of logging. Consequently, predictions on changes of parasite diversity and prevalence with regard to habitat disturbance need to be based on the individual life histories of the hosts (and the parasites).

The proliferation of climbers can have deleterious effects on tree regeneration, especially in forest canopy gaps where climbers increase in abundance. In response to the colonization by climbers, the supporting tree can suffer a reduction in growth and its allometric relationships may be modified. We evaluated the effects of three species of climber on the performance of the pioneer tree Ceiba pentandra in a moist semi-deciduous tropical forest in Ghana. In each of three gaps, four plots were set up, each with eight Ceiba seedlings paired with a single plant of one of three climber species, planted within 5–10 cm of the tree seedling, plus a control (no climber). The climber species were: Centrosema pubescens, a nitrogen-fixing woody climber; Combretum racemosum, a woody climber and Dioscorea praehensilis, an herbaceous climber. After 12 mo, Centrosema and Combretum had about four to five times more biomass than Ceiba seedlings. There was no effect of climber competition on Ceiba biomass growth, and no relationship between climber biomass and Ceiba growth rate. Individual climber species, however, had other effects: Combretum caused a significant reduction in the height and diameter growth of Ceiba, whilst competition with Centrosema was associated with significant reduction in the crown area and increase in internode length in Ceiba. The results indicate that even very different climber species appear to cause negative effects on trees during regeneration.

Twelve native woody species were studied to investigate the influences of soil fertility and root morphology on colonization by arbuscular mycorrhizal (AM) fungi during seedling establishment and growth. Seedlings were grown in soils of low and high natural fertility, uninoculated or inoculated with AM fungi, under greenhouse conditions. The mycorrhizal root colonization and plant responsiveness were higher among early successional species than late successional ones. Among early successional species, in both soils, mycorrhizal colonization provided significant increase in total dry mass, growth rates of shoot and root, root length, density of root tissues, root surface area and P concentration and content in the shoot. Early successional species grown with AM fungi displayed significant decreases in carbon allocation to roots, specific root length and the length and incidence of root hairs. Mycorrhizal colonization did not affect the root morphology of the late successional species in either soil. The growth of these woody species was influenced by differences in soil fertility. There was positive correlation between the degree of plant responses to AM inoculation with the percentage of root colonized by AM fungi. In both soils, plant responsiveness and mycorrhizal root colonization correlated positively to root-hair incidence and root-hair length and correlated negatively to fine-root diameter. The results suggest that during the establishment of seedlings, the large responses to the inoculation and colonization of roots by AM fungi are related to both the successional status and root morphological plasticity of the host plant, regardless of soil fertility.

Flood depth has been frequently used to explain the distribution of plant species in seasonally flooded grasslands, but its relation with vegetation production has remained ambiguous. The relationship between flooding and above-ground biomass at the end of the flooding season and during the dry season was studied to assess the impact of reflooding on the Logone floodplain, Cameroon. Above-ground biomass of a combination of all species and of the individual perennial grasses Oryza longistaminata and Echinochloa pyramidalis showed a positive linear relationship with maximum flood depth up to 1 m. The gradient of these relationships became steeper and their fit better during the 2 y following the installation of the flooding, showing the response lag to floodplain rehabilitation. Flood duration only explained the above-ground biomass of the combination of all species and not of the individual species. Above-ground biomass data from other floodplains in the three main African geographic regions showed a similar relationship with maximum flood depth less than 1 m. Dry-season regrowth, important because of its high nutrient quality during forage scarcity, was not directly related to maximum flood depth, possibly because of its dependency on the period of burning and soil moisture. Presented data indicate that a rise of water level of 1 cm corresponds to an increase in above-ground biomass of c. 150 kg DM ha−1.

Understanding the causes of savanna–forest dynamics is vital as small but widespread changes in the extent of tropical forests can have major impacts on global climate, biodiversity and human well-being. Comparison of aerial photographs for 50 rain-forest patches in Kakadu National Park had previously revealed a landscape-wide monotonic expansion of rain-forest boundaries between 1964 and 2004. Here floristic, structural, environmental and disturbance attributes of the changes were investigated by sampling 588 plots across 30 rain-forest patches. Areas that had changed from savanna to rain forest were associated with a significantly higher abundance of rain-forest trees and less grasses, relative to stable savanna areas. Ordination analyses showed that overall floristic composition was not significantly different between newly established rain forest and longer established rain forest. Generalized linear models also indicated that contemporary levels of disturbance (fire and feral animal impact) and environmental variables (slope and soil texture) were poor predictors of historical vegetation change. We concluded that (1) the rain-forest boundaries are highly dynamic at the decadal scale; (2) rain-forest expansion is consistent with having been driven by global environmental change phenomena such as increases in rainfall and atmospheric CO2; and (3) expansion will continue if current climatic trends and management conditions persist.

This study investigates whether increases in elephant populations may influence the structure of African savannas, and consequently may affect other herbivores through changes in habitats. Two contrasting periods in terms of elephant population densities were compared in Hwange National Park, Zimbabwe: the early 1980s and the late 1990s. Elephant population density and other ungulate population densities were estimated for a c. 400-km2 area from road counts. Vegetation structure at the landscape scale was assessed using aerial photographs for the same area. All browsers and grazers declined between the early 1980s and the late 1990s, whereas elephants experienced a 16-fold increase. At the landscape scale, vegetation structure changed little with no evidence of an opening of the habitats. These results do not support any kind of medium-term facilitation between elephants and other herbivores. They rather suggest a negative effect of elephants on other herbivore species when elephants are present at high densities. This study rules out a scenario where the decrease of the different herbivore populations was caused by large changes in vegetation structure due to elephant activity.

We studied the response of vegetation and vertebrate assemblages to fire and grazing, and their interacting effects, in Eucalyptus woodland in north-eastern Australia. In this vegetation type, many pastures remain free of cattle grazing due to the occurrence of a native shrub poisonous to livestock. Vegetation (floristic data and 22 habitat variables) and vertebrate fauna (birds, mammals, reptiles) were sampled in 29 standardized 50 × 50-m quadrats in the 2001 wet season, representing four treatments: sites burnt recently (within 2 y) and grazed by cattle (4–8 ha per livestock unit); sites unburnt (last burnt >2 y ago) and grazed; sites burnt recently and ungrazed; and unburnt and ungrazed sites. Fire and grazing had a significant influence on vegetation: both grazing and fire reduced ground cover (fire in grazed sites 51–23%, fire in ungrazed sites 68–39%) and increased the cover of forbs (8% in burnt and grazed sites, 3% if ungrazed) and tussock grasses (20% in grazed and unburnt sites and 5% when ungrazed). Grazing caused a shift in floristic composition from the perennial hummock grass Trioda pungens to tussock grasses (e.g. Aristida spp., Enneapogon spp.), forbs (e.g. Phyllanthus spp.) and shrubs (e.g. Acacia spp.). Of the vertebrate groups, birds responded more to fire effects (9 species), reptiles to grazing effects (6 species) and mammals to the interaction (2 species). Species reacted to increases in bare ground (e.g. crested pigeon Ocyphaps lophotes, hooded robin Melanodryas cucullatus, Ctenophorus nuchalis) and to the dominant ground cover (e.g. Ctenotus pantherinus) or change in vegetation architecture (e.g. singing honeyeater Lichenostomus virescens, variegated fairy-wren Malurus lamberti). The clearest example of an interacting effect was the cycle of complementary dominance between the rodents Pseudomys delicatulus and P. desertor, the latter's post-fire recovery becoming more muted in sites where cattle grazed (modelled time for population recovery twice as long as in ungrazed sites).

The tree Lysiloma microphyllum (Fabaceae) dominates in the seasonally tropical dry forests of central Mexico. In this study foliar N and P concentrations (on leaf mass basis), foliar N and P resorption efficiency and proficiency, as well as the decomposition of senescent leaves of L. microphyllum were studied in primary and in regenerating, secondary seasonally tropical dry forests. Our study included an area of early successional forest (10 y old), with phosphorus-poor soils and comparatively abundant nitrogen, an area of late-successional forest (∼60 y old), in which soil P and N were comparatively abundant, and an area of primary forest, in which soil P was comparatively abundant and N was less abundant than in the secondary counterparts. N and P concentrations in mature leaves varied across forests, reflecting soil nutrient availability. Nitrogen concentration in senescent leaves did not change among sites, which led to very different patterns of N resorption. In contrast, P concentration in senescent leaves was lower in the early than in late-successional and primary forests, which resulted in similar patterns of resorption. Leaf decomposition increased from 70% mass loss in the first year in the early successional to ∼80% in the same period in late-successional and primary forests. The element loss during decomposition change across forests in the following order: for N, early successional = late-successional > primary forest, and for P, primary forest > late-successional > early successional forest. Overall, the pattern of variation in leaf chemistry and nutrient release on the forest floor among sites is consistent with soil nutrient availability along this sequence, while decomposition rate may be related with the P concentration in senescent leaves.

Tropical montane rain forest is widely considered to be a highly threatened hotspot of global diversity (Brummitt & Nic Lughadha 2003), and one of the least understood humid tropical forest ecosystems in terms of nutrient cycling (Bruijnzeel & Proctor 1995). There is, therefore, an urgent need to improve our understanding of nutrient cycling processes in this ecosystem, including the absorption of nutrients (mainly N and P) from senescing leaves, which may be a key component of adaptive mechanisms that conserve limiting nutrients (Killingbeck 1996). Nutrients which are not resorbed, however, will be circulated through litterfall in the longer term (Aerts 1996). The degree of nutrient resorption affects litter quality, which consequently affects decomposition rates and soil nutrient availability (Aerts & Chapin 2000). The importance of resorption in nutrient conservation has led to general hypotheses that species adapted to nutrient-poor environments have high resorption efficiencies (Richardson et al. 2005), and that low leaf nutrient concentrations are associated with high resorption efficiencies within species (Aerts 1996, Kobe et al. 2005). Nutrient resorption has also been shown not to differ greatly between growth forms (e.g. shrubs, grasses, forbs and trees) (Aerts 1996). However, its relative importance among plant functional groups is still highly controversial (Richardson et al. 2005).

Bates' theory of mimicry (Bates 1862) postulates that vertebrate predators avoid attacks on chemically defended butterflies, and a profitable species, usually referred to as the mimic, can obtain protection by resembling one or more unpalatable models. The evolution of Batesian mimicry requires that predators meet, taste and learn to avoid the models before meeting the mimics. For this reason, some authors have adopted the assumption that mimic population sizes must be smaller than the models' populations (Fisher 1930, Huheey 1980, Lindström et al. 1997).

Frugivorous bats are important seed dispersers for many plant species (Cox et al. 1991, Fleming & Heithaus 1981, Hodgkison et al. 2003a, McConkey & Drake 2006, Nyhagen et al. 2005, Utzurrum 1995). They regularly consume figs in the wild (Fujita & Tuttle 1991, Kalko et al. 1996, Shilton et al. 1999). Various species of pteropodid bats have been reported foraging on the fruits of more than 30 fig species in tropical and subtropical Asia, Africa and Australia (Bhat 1994, Fujita & Tuttle 1991, Marshall & McWilliam 1982, Thomas 1984). Food transit times in frugivorous bats are relatively rapid; generally less than 30 min (Laska 1990, Tedman & Hall 1985). Several studies have demonstrated that seed germination was either enhanced or unaffected after passage through the digestive tract of bats (Figueiredo & Perin 1995, Fleming & Heithaus 1981, Lieberman & Lieberman 1986).