Although large herbivore habitat use has been extensively studied, more information is still required on the use of heterogeneous vegetation types. Over 3 y we carried out monthly road transects in the Zambezi National Park (ZNP), Zimbabwe, to determine the impala density in each of five vegetation types. In addition we determined grass and browse chemical composition to test if at the time the impala switches from grass to browse, grass nutritive quality had declined below that of browse. Furthermore, grass height was measured in the five vegetation types. The impala used mixed, acacia and terminalia vegetation types, which constituted 37% of the protected area and avoided grassland and the predominant Zambezi teak (60% of ZNP) vegetation types. At the time of the diet switch by the impala from grass to browse, woody plant leaf nutritive quality was higher than grass in terms of nitrogen, calcium and acid detergent fibre content. The three vegetation types used by the impala had short to medium grass height. We concluded that when the impala switched from grass to browse the grass nutritive quality was lower than that of the browse.

Spatial distribution of resources is known to govern animal distribution and behaviour. However, few empirical studies have formally evaluated this relationship. Unlike previous studies in which a patch or gap of floral resources is defined a priori by the observer at a subjective perception scale, we used the Spatial Analysis by Distance IndicEs (SADIE) to assess the location, length and spatial co-occurrence of patches and gaps of Palicourea padifolia inflorescences and hummingbird activity (feeding, perching, vocalizing, flying past and agonistic behaviour) in a tropical montane cloud forest of central Veracruz, Mexico. Along a 1010-m transect, both resource and hummingbird activity had a distribution approximately 200% more aggregated than expected by chance, at a scale of tens to hundreds of metres in length. In addition, aggregation patterns of resource and overall and agonistic hummingbird activity were found to be positively associated in 2009 but negatively in 2010. Campylopterus curvipennis and Amazilia cyanocephala were the most frequent species involved in vocal and agonistic activity. The difference observed between the two years may be due to changes in the composition and dominance of hummingbird species with different foraging strategies. In both years, hummingbird overall activity was positively correlated to size of resource patches.

The frequency of selection of functional groups and plant species by free-ranging cattle foraging in a diverse environment and its changes during the dry and the following prehumid seasons were investigated using direct observations and bite counting. The study was conducted at two sites in the Bolivian–Tucuman montane forests in southern Bolivia, by including datasets of a total of 16 animals. Across both study sites and the entire observation period (May to October/November), the cattle were found to select a broad spectrum of plant species from different functional groups. However, just a limited number of species made up a considerable contribution to overall plant selection. The functional group of the graminoids was selected most frequently, but their contribution to plant selection decreased significantly from 63.5% of total bites in May to 15.9% in September/October, in accordance with a decrease in availability. Selection of woody plants (shrubs and tree parts, the latter mainly in the form of leaf litter and fruits) increased with time, reaching its peak at the beginning of the prehumid season, while the herbs showed a curvilinear pattern of selection which was highest in August. Plant species belonging to the functional groups of ferns, climbers and epiphytes were also selected by the cattle, but generally at low relative proportions. Plant selection might be influenced by temporal differences in nutritional quality and availability of the preferred plant species and functional groups. Sampling behaviour seems to be the most likely reason for the inclusion of a broad range of plant species with overall low contribution to plant selection.

A range of species eating the same fruit suggests that niche overlap can occur, along with potential competition among them. To test if the overlap in the coterie of fruit-eating birds is larger than would be expected by chance, we performed a comparison with coteries generated from the use of null models. The study was carried out in an area of savanna woodland of 127 ha in Uberlândia city, Brazil. Four individuals of five zoochorous plant species were selected and 60 h of focal observation was performed on each species. We recorded species of birds that consumed fruits and the quantity of fruit removed. We used an index of Proportional Similarity (PS) between each pair of plant species, using the relative proportion of fruit taken by each bird species of each plant. The mean value of observed PS was compared with the mean PS generated from randomizations. Thirty-six bird species were recorded eating fruits in the selected plant species. The mean overlap observed (PS = 0.183) was significantly higher (P = 0.032) than the mean overlap generated by the null models (PS = 0.123). This pattern suggests that competition is not an important factor in the formation of the coteries and there is sharing of resources. The abundance of fruits offered, especially in the rainy season, and the relatively low number of frugivorous species may be factors explaining the low influence of interactions and therefore the overlap between coteries.

Co-evolutionary processes have moulded interactions between hummingbirds (Trochilidae) and ornithophilous flowers. Generally, long corollas exclude short-billed trochilids, whereas short corollas allow access for both long- and short-billed species. At La Mucuy, Sierra Nevada National Park, Mérida, Venezuela, we studied interactions between Aphelandra runcinata (Acanthaceae) and its avian pollinators. Of 13 trochilid species reported from this site, only two, Coeligena torquata and C. eos, have bills long enough to allow legitimate access to the nectar of A. runcinata flowers. However, we observed that hummingbirds with much shorter bills were also able to extract nectar and pollinate the flowers. This is due to a reversible compression mechanism in A. runcinata, caused by the pressure exerted by the bird in flight and the physical opposition of the inflorescence. The compression mechanism observed in A. runcinata flowers is a morphological characteristic that provides mutualistic advantages for both the plant and its avian visitors. The spectrum of potential pollinators is increased by giving access to nectar even to species with short or medium-long bills. Moreover, nectar-robbing, a foraging strategy that does not result in pollen transfer common among short-billed trochilids, seems to be reduced.

We assessed the differences and similarities in diel activities among five phytophagous bat species at two habitats over two seasons within the Sierra del Rosario Biosphere Reserve in Cuba. We characterized temporal patterns of activity and overlap of temporal activity for frugivore and nectarivore bat species (Artibeus jamaicensis, Monophyllus redmani, Phyllonycteris poeyi, Phyllops falcatus and Brachyphylla nana) that occur in tropical evergreen forest sites with distinct altitude and vegetation structure during wet and dry seasons. Capture frequencies using mist-nets of 1180 capture events were the empirical basis for analyses. For each species we compared activity patterns between habitats, between seasons, between males and females, as well as between reproductive and non-reproductive females. We also assessed temporal overlap among each possible pair of species at each habitat and used Monte Carlo simulations to evaluate assemblage-wide temporal niche overlap using a new algorithm, termed Rosario, designed specifically for temporal data. The two habitats had the same species composition and bat diel rhythms tended to be consistent across habitats, seasons and sexes for most bat species. In general bat species pairwise temporal niche overlap was high, and the ensemble-wide temporal overlap was consistently high across habitats and seasons indicating a common constraint for bat activities. Activity peaks of most bat species coincided at 4–5 h after sunset, this being in sharp contrast to other Neotropical bat assemblages at continental sites where activity peaks usually overlap within the first 2 h after sunset. This strong disparity in timing of activity peaks between continental and insular bat assemblages can provide the framework for the generation of hypotheses that explain the potential role of time as a mediator of ecological interactions in bat assemblages.

Nocturnal activity is generally presumed, but rarely evaluated in studies of tropical small mammals. When evaluated, activity is frequently presented as a fixed pattern, but actually it is the influence of biotic and abiotic factors on individuals. We investigated effects of age, sex, minimum temperature, reproductive and climatic seasons on activity of Didelphis aurita (Didelphimorphia, Didelphidae) in an Atlantic Forest area in south-eastern Brazil from June 2009 to December 2010. We captured 37 individuals, 51 times (28 females and 23 males). Activity of D. aurita was mostly nocturnal, but some individuals were active during the day (12%, N = 6). Nocturnal activity was bimodal, more prevalent in adults than juveniles, and different from most neotropical marsupials. Contrary to expectations, individuals of D. aurita were more active at colder temperatures, which indicates that low temperatures do not limit foraging behaviour.

Canopy gaps create a temporary spatial heterogeneity, often allowing pioneer species to establish and grow in mature forests. In this study, we asked whether the above model holds for tropical dry forests in the Florida Keys. Six hundred and forty-eight canopy gaps in an extensive Key Largo forest were identified with a LiDAR digital canopy model. The structure and composition of juvenile trees were examined in 45 selected gaps in three stands of known age, and weighted averaging calibration and regression were applied to the data to determine the successional age optimum for each tree species, and the inferred age for each gap based on its sapling composition. Less than 1% of the forest area was recorded as canopy gaps in the LiDAR model. The inferred stand ages were about 70 y greater in canopy gaps in young forest than in the surrounding, unimpacted forest. This suggested that gap formation advanced succession rather than reversing or resetting it. The apparent lack of recruitment by early-successional species may be due to the small size of canopy gaps in this forest, and the minimal contrast between gap and understorey environments; light and water conditions in the small gaps may favour late-successional rather than pioneer species. Establishment of pioneer species may not take place without intense, large-scale disturbances such as fires and hurricanes that remove the entire canopy and consume or erode soils.

Two core questions in plant community ecology are to what extent the distributions of species are structured by local environmental conditions, and whether taxa differ in this regard. We compared the distributions of trees, Melastomataceae and ferns on soil and topographic gradients in a Costa Rican lowland rain forest (trees and ferns 983 plots, Melastomataceae 277 plots). To test whether these plant groups differed in the prevalence or type of habitat specialization, we calculated species’ environmental optima and tolerances on each gradient. Habitat specialization was defined as a significantly biased optimum, or a narrow tolerance, relative to values obtained under spatially restricted randomizations of species occurrences. Within plant groups, we also asked whether the dispersion of species optima differed from random expectation on each gradient. Fern optima were over-dispersed on multiple gradients, implying considerable interspecific habitat partitioning, and tree optima were over-dispersed in relation to topographic position. Habitat specialization was more prevalent in the two predominantly understorey groups than in trees (75% of Melastomataceae species, 81–87% of ferns, 57–58% of trees). Species optima of Melastomataceae and ferns also tended towards lower landscape positions than did those of trees, perhaps reflecting a higher proportion of drought-sensitive species in these two groups.

We examine the density- and distance-dependent seedling survival of Philenoptera sutherlandii, a common pod-bearing and dehiscent legume (Fabaceae) in Ongoye Forest, South Africa. Short-range ballistic dispersal causes seed to fall beneath the parent tree, where density- or distance-dependent mortality effects are expected to be concentrated. One hundred and eighty marked seedlings were monitored in a 0.5-ha plot containing 30 adults. Our survival data do not support the escape hypothesis. Predation levels declined with increasing seedling density (positive density-dependent survival), but seedling survival after 15 mo was not distance-dependent. Nevertheless, a unimodal (hump-shaped) recruitment curve, typically associated with decreasing seedling density and increasing seedling survival with distance, was observed. In the context of ballistic dispersal, this recruitment curve may indicate a hump-shaped dispersal kernel with predator satiation at high seedling densities near a parent tree. This recruitment curve likely arises because generalized insect seedling predators while attracted to the adult trees also tend to forage farther away. Short dispersal distances, in turn generate the high densities needed to satiate seed and seedling predators. Predator satiation results in long-term survival rates in P. sutherlandii similar to more widely dispersed and less common tree species.

Relatively little is known of the relationships between many lepidopteran species and their larval food plants in tropical rain forests, compared with temperate ecosystems. Species are often known only from the adult form, and the larvae and aspects of ecology, host plant, etc. are unknown (Williams 1971). Many species in the moth genus Achaea sometimes occur at high enough population densities to be defoliators, and several species are associated especially with forest trees: some are agricultural pests on groundnuts and castor oil plant (Ricinus communis) (Pinhey 1975, M. Shaw, pers. comm.). Achaea catocaloides occurs from West Africa through Uganda to East Africa (Seitz 1925) and has been recorded in interactions with ants in Cameroon (Dejean et al. 1991).

The movement of African ungulates between habitats is determined by diverse factors including forage composition, availability and quality, water availability, topography, the catenary level and the effect of fire on vegetation. We assessed how grass flushes, following dry-season fires, and availability of water influenced seasonal movements of hartebeest, impala, warthog, white rhino, wildebeest and zebra in Ithala Game Reserve, a fenced reserve in South Africa. Over a 6-d period each month for 4 y, road transects covering a representative sample of the reserve's different vegetation types, and 23% of the reserve's total area, were carried out. We recorded the species, number, sex and age class of herbivores, obtaining 8742 records (total herbivores sighted = 47055), and obtained positional data on sightings over the last 2 y of the study. Using a GIS-based approach, we determined that ruminant, but not non-ruminants, were significantly attracted to dry-season grass flushes, and that presence or absence of such flushes significantly affected their mean distance to water and hence seasonal movements on the catena.

Little information is available to test the various theories which have been proposed to explain the evolution of cauliflory. This study provides such data from observations in Trinidad of the numbers of potential pollinators visiting trunk and canopy flowers and on the size of canopy and trunk flowers and fruits. Subsidiary observations were made on the partitioning of resources between the sexes within flowers. Significantly more potential insect pollinators were trapped around the trunk flowers of two cauliflorous species than were caught around their canopy flowers. Trunk flowers were found to be larger than canopy flowers in four of the seven cauliflorous species studied, but they were smaller in one species. The higher probability of fruit set on trunks than in the canopy may have selected for cauliflory and subsequently increased trunk flower size in insect-pollinated understorey tropical trees. There was a tendency for flowers on the trunk not only to be larger but also to allocate relatively more dry weight to female parts and result in larger fruit than those in the canopy. These observations are consistent with Wallace's theory of the evolution of cauliflory, which argues that the condition arose in the dark understorey of the tropical forest, as a result of selection for trunk flowers which are more apparent to pollinators than are canopy flowers. However, other explanations for the evolution of cauliflory are not precluded as they are not mutually exclusive.

Population energy budgets of four sympatric isopods, Burmoniscus ocellatus, Burmoniscus sp. (Philosciidae), Formosillo raffaelei and Orodillo maculatus (Armadillidac), were calculated at two sites in a Hong Kong mixed forest. Mean population standing stock of the four species ranged from 1.25 to 13.61 kj m-2. Mean total isopod biomass at the two sites was 0.85 and 1.85g m-2. Annual production of the four species varied from 4.24 to 30.43 kj m-2 with 5.2–26.4% (energy content) allocated to reproduction. Annual production of the four species combined at the two sites was 23.22 and 50.15kJ m-2. ratios varied from 2.24 to 4.27. Annual population consumption on mixed litter by the four isopod species ranged from 28.4 to 183.0 kj m-2. Total annual consumption by all species at the two sites was 233.7 and 360.2 kj m-2 (1.96 and 2.53% of annual litter fall). Isopod respiratory rales were proportional to body weight, with an exponent ranging from 0.68–0.78 at 23°C. The annual population metabolism of the four species varied from 14.62 to 86.11 kj m-2. Total annual isopod metabolism at the two sites was 116.33 and 185.95 kj m-2. These results are discussed with reference to the role of isopods in litter breakdown and energy flow in the Hong Kong forest.

We investigated whether changes in nutrient availability affected N, P, S and polyphenol concentrations in different leaf-development stages of three brevideciduous and three evergreen dominant woody species in a nutrient-limited savanna woodland in Central Brazil. Treatments included eight years of annual fertilization with 100 kg ha−1 of N, P, N plus P and control, each replicated in four randomized 15 × 15-m plots. All species increased S concentrations (minimum 28%) in young and mature leaves in fertilized plots. Dalbergia miscolobium decreased total phenol concentrations with P (−34.3%, −23.7%) and NP fertilization (−28.2%, −17.1%). Blepharocalyx salicifolius increased total phenol (27.6%, 18.8%) and tannin (46.3%; 43.5%) in P fertilized and increased total phenol (33.9%) and tannin (27.8%, 43.5%) in NP fertilized plots. Total phenol concentration decreased with leaf age in Ouratea hexasperma, Styrax ferrugineus and Blepharocalyx salicifolius, which also decreased tannin concentration with leaf age. For all treatments, brevideciduous species had higher N, P, total phenols and tannin concentrations and lower S concentration than evergreens. These differences between phenological groups suggest that tropical ecosystems responses to environmental changes are more complex than anticipated by global vegetation models, with consequences for predictions in ecosystem functions and resilience.

Wood density and wood chemical traits are strong predictors of tree performance, carbon stock, and wood decomposition, which play important roles in ecosystem processes and carbon and nutrient cycling in forests. However, it remains unknown how root wood traits are related to stem wood traits. We examined the relationships of wood density and wood chemical traits (lignin and nitrogen concentrations, carbon-to-nitrogen ratio) between the stems and coarse roots of 90 individuals representing 53 tropical tree species in Malaysian Borneo. We developed regression equations of each wood trait using the standardized major axis method. Each root wood trait was highly correlated with the corresponding stem wood trait, and most regression equations fitted well (R2 > 0.5). The lignin concentration of roots was significantly greater than that of stems. We conclude that root wood traits can be estimated from the corresponding stem wood traits in South-East Asian tropical trees. Further analysis of coarse root decomposability will provide more accurate estimates of carbon and nutrient fluxes in tropical forest ecosystems.

As part of the programme Écosystèmes et Paléoécosystémes des Forêts Intertropicales (ECOFIT,France),we are engaged in multisite comparative studies of how forests regenerate across ecotones such as those between forests and savannas (Vincens et al. 2000).One such ecotone comprises the forest succession from bare soil that occurs naturally on beach successions along meandering rivers. To gauge the development of foliar layers during succession and quantify changes of efficiency of the vegetation in capturing the available solar energy, we are measuring the Leaf Area Index (LAI) of transects within forests and across their edges.

Interest in the colour of fruits eaten by vertebrates has a long history (Ridley 1930, Turcek 1963, van der Pijl 1972). Within a given geographical area, colours of bird-consumed fruits compared with mammal-consumed fruits are fairly consistent (Janson 1983, Wheelwright & Janson 1985, Willson & Whelan 1990), but comparisons among different regions reveal selective pressures of different animal groups (Lord 2002, Willson et al. 1989). One consistent pattern among regions is that fruits with a two-colour display typically are eaten by birds (Wheelwright & Janson 1985, Willson & Thompson 1982, Willson & Whelan 1990). Thus, it is thought that such bicoloured displays are specifically adapted to attract birds and plants with these displays presumably benefit from seed dispersal by birds (Janson 1983, Willson & Whelan 1990).

Protection-based ant–plant mutualisms may vary in strength due to differences in ant rewards, abundance of protective ants and herbivory pressure. We investigated geographical and temporal variation in host plant traits and herbivory pressure at five sites spanning the distribution range of the myrmecophyte Humboldtia brunonis (Fabaceae) in the Indian Western Ghats. Southern sites had, on average, 2.4 times greater abundance of domatia-bearing individuals, 1.6 times greater extrafloral nectary numbers per leaf, 1.2 times larger extrafloral nectary sizes, 2.2 times greater extrafloral nectar (EFN) volumes and a two-fold increase in total amino acid and total sugar concentrations in EFN compared with northern sites. A strong protection-based mutualism with ants occurred at only one southern site where herbivory was highest, suggesting that investments in attracting ants correlate with anti-herbivore benefits gained from the presence of protective ants. Our results confirm a temporally stable north–south gradient in myrmecophytic traits in this ant-plant as several of these traits were re-sampled after a 5-y interval. However, the chemical composition of EFN varied at both spatial and short-term temporal scales suggesting that only repeated measurements of rewards such as EFN can reveal the real spectrum of trait variation in an ant–plant mutualistic system.

Physical dormancy (PY) is typically induced by seed coat impermeability that develops once the moisture content of seeds drops below a species-specific threshold. Considering this, we utilized Albizia julibrissin (Fabaceae) to ask (i) whether seeds that mature on the outer branches of trees (directly exposed to sunlight) are more likely to be impermeable than seeds matured under canopy cover; (ii) whether this difference might be explained by the maternal environment in which the seeds mature; and (iii) which conditions impose secondary dormancy following dispersal? Temperature was tracked in both shaded and sun-exposed seed pods throughout the growing season using data-loggers. Temperatures remained lower in pods under canopy cover than those exposed to direct sunlight. Consequently, the moisture content of seeds collected from sun-exposed branches were significantly lower than seeds matured under canopy cover, thereby producing a higher percentage of impermeable seeds. A dispersal-mimicking experiment revealed that seeds matured in sun-exposed branches and subsequently dispersed to an open site for 4 months were more likely to develop impermeability (i.e. secondary dormancy). The opposite was found to be true for seeds matured in shaded branches and subsequently dispersed to a canopy-covered site. We conclude that the microclimate of both the maternal environment in which seeds mature, and the site to which they disperse, determines the development of primary and secondary dormancy, respectively.