We studied the relationship between flower size and nectar properties of hummingbird-visited flowers in the Brazilian Atlantic Forest. We analysed the nectar volume and concentration as a function of corolla length and the average bill size of visitors for 150 plant species, using the phylogenetic generalized least squares (PGLS) to control for phylogenetic signals in the data. We found that nectar volume is positively correlated with corolla length due to phylogenetic allometry. We also demonstrated that larger flowers provide better rewards for long-billed hummingbirds. Regardless of the causal mechanisms, our results support the hypothesis that morphological floral traits that drive partitioning among hummingbirds correspond to the quantity of resources produced by the flowers in the Atlantic Forest. We demonstrate that the relationship between nectar properties and flower size is affected by phylogenetic constraints and thus future studies assessing the interaction between floral traits need to control for phylogenetic signals in the data.

The wet tropical forests in Madagascar have endemic dung beetles that have radiated for tens of millions of years using a limited range of resources produced by the species-poor mammalian fauna. Beetles were trapped in two wet-forest localities over 4 years (6407 trap nights, 18,869 individuals). More limited data for six other local communities were used to check the generality of the results. Local communities are relatively species poor (around 30 species) in comparison with wet-forest-inhabiting dung beetle communities elsewhere in the tropics (typically 50 or more species). The species belong to only two tribes, Canthonini and Helictopleurina (Oniticellini), which have evolved, exceptionally for dung beetle tribes, completely nocturnal versus diurnal diel activities, respectively. Patterns in the elevational occurrence, body size and resource use suggest that interspecific competition restricts the numbers of locally coexisting species exploiting the limited range of resources that are available. On the other hand, regional turnover in the species composition is exceptionally high due to a large number of species with small geographical ranges, yielding a very large total fauna of dung beetles in Madagascar (>250 species). Apart from exceptionally low local (alpha) diversity and high beta diversity, the Malagasy dung beetle communities are ecologically distinctive from comparable communities in other tropical regions in having high numerical dominance of the most abundant species, small average body size and low degree of resource specialization.

The abundance and distribution of reptiles and amphibians inhabiting tropical monsoonal wetlands in Kakadu National Park, northern Australia, were monitored between late 1979 and 1982. Seasonal trends in species richness, and the influence of various environmental attributes (including those caused by feral ungulates) on species distribution patterns were also examined.

These wetlands support a high proportion of the amphibian species known from the Park, but are of less importance to reptiles. Within the wetlands, the structurally more complex forested ‘margins’ support many more species than the treeless floodplains. Amphibian species distributions seem to be influenced primarily by elevation, through its effects on soil moisture and flooding levels, while reptile distribution patterns reflect a more complex set of environmental factors, with structural attributes (e.g. vegetation height structure and cover, refuge abundance, leaf litter cover and depth, extent of flooding) being of prime importance.

Feral buffalo and pigs, through their grazing, trampling and wallowing, may considerably influence such structural attributes and change the duration and extent of water lie, and thus indirectly affect species distribution patterns. Current buffalo culling programmes provide an opportunity to monitor vegetation and faunal changes, and quantify feral animal impact post facto.

High-nutrient patches are important for regulating the structure and physiognomy of dystrophic habitats. Leaf-cutting ants create these rich patches in many neotropical habitats. Burning, however, could diminish or even annul the effects of ant nests on soil properties. To test this hypothesis, we compared the nutrient concentrations at various depths in soil samples near three nests of the leaf-cutting ant Atta laevigata and three non-nest soils, located in 10-ha plots subjected to burning or with fire-protection within a Brazilian cerrado. Root density in ant-nest soil was greater than in non-nest soil in both unburned and burned plots. Besides, the concentration of Ca, Mg, K and P increased 2–50-fold in ant nests from the unburned area compared to non-nest soils. In contrast, nutrient concentrations and pH in burned ant nests were similar to or lower than non-nest soils, but the nests maintained higher values of organic matter and cation exchange capacity. The positive effect of leaf-cutting ant nests as high-nutrient patches may be strongly reduced in habitats with frequent burning. In this case, the negative effects of leaf-cutter herbivory on a plant community could surpass the benefits of local nutrient enrichment by their nests.

Resumo: Sauveiros modificam as propriedades físicas e químicas do solo, alterando a estrutura e fisionomia local. Entretanto, queimadas podem reduzir os efeitos dos formigueiros nesses ambientes como, por exemplo, pela diminuição do forrageamento das formigas e, conseqüentemente, pela baixa incorporação de material orgânico ao solo. Este estudo testou o efeito do fogo sobre a concentração de nutrientes no solo de colônias de Atta laevigata em área de cerrado. A densidade de raízes foi maior nas colônias do que áreas controle, independentemente da presença do fogo. Na ausência de queimadas, as concentrações de nutrientes foram até 50 vezes superiores nos sauveiros. Contudo, queimadas reduzem a concentração de nutrientes e pH nas colônias. Possivelmente, essa baixa concentração seja atribuída à maior demanda pela vegetação remanescente, em resposta à perturbação provocada pelo fogo. Nesse caso, os efeitos negativos da herbivoria podem superar os benefícios causados por meio da disponibilização de nutrientes pelos sauveiros.

Dominant woody species can determine the structure and composition of a plant community by affecting environmental conditions experienced by other species. We explored how dominant tree species affect the tree species richness, diversity, evenness and vertical structural heterogeneity of non-dominant species in wet and dry miombo woodlands of Tanzania. We sampled 146 plots from eight districts with miombo woodlands, covering a wide range of topographic and climatic conditions. We recorded 217 woody plant species belonging to 48 families and 122 genera. Regression analysis showed significant negative linear associations between tree species richness, relative species profile index of the non-dominant and the relative abundance of the dominant tree species (Brachystegia spiciformis and Brachystegia microphylla in wet, and Brachystegia spiciformis and Julbernardia globiflora in dry miombo woodlands). Shannon diversity and evenness had strong non-linear negative relationships with relative abundance of dominant tree species. A large number of small individual stems from dominant and non-dominant tree species suggesting good regeneration conditions, and intensive competition affecting survival. We suggest that dominant miombo tree species are suppressing the non-dominant miombo tree species, especially in areas with high recruitments, perhaps because of their important adaptive features (extensive root systems and ectomycorrhizal associations), which enhance their ability to access limited nutrients.

Results of a 3-y study on the populations of three evergreen woody species (Byrsonima crassifolia, Palicourea rigida and Bowdichia virgilioides), from a regularly burnt savanna, in Venezuela, are reported. Tree density, size structure, fruit-seed production per tree of different size classes and soil seed bank were estimated. Viable seed production was one order of magnitude higher in B. crassifolia, which was also the only species with a permanent soil seed bank. Seeds of B. virgilioides germinated readily after dispersal, whilst seeds of P. rigida showed an innate dormancy synchronously released after a year. Both of the latter species seemed to maximize the first growth season by germinating at the beginning of the favourable season. In B. crassifolia, germination proceeds with an early small burst of germination, possibly followed by a second peak at the beginning of the next rainy season and little or no germination thereafter. The results showed that despite the high fire frequency, the studied species produce a substantial number of viable propagules, and have the capacity to germinate in field conditions (readiness depending on the species). Sexual reproduction is expected, therefore, to play an important role, as suggested by their reproductive investment, in long-term population maintenance.

The effects of habitat fragmentation on seed dispersal can strongly influence the evolutionary potential of tropical forest plant communities. Few studies have combined traditional methods and molecular tools for the analysis of dispersal in fragmented landscapes. Here seed dispersal distances were documented for the tree Dipteryx panamensis in continuous forest and two forest fragments in Costa Rica, Central America. Distance matrices were calculated between adult trees (n = 283) and the locations of seeds (n = 3016) encountered along 100 × 4-m transects (n = 77). There was no significant difference in the density of seeds dispersed > 25 m from the nearest adult (n = 253) among sites. There was a strong correlation between the locations of dispersed seeds and the locations of overstorey palms favoured as bat feeding roosts in continuous forest and both fragments. Exact dispersal distances were determined for a subset of seeds (n = 14) from which maternal endocarp DNA could be extracted and matched to maternal trees using microsatellite analysis. Dispersal within fragments and from pasture trees into adjacent fragments was documented, at a maximum distance of 853 m. Results show no evidence of a fragmentation effect on D. panamensis seed dispersal in this landscape and strongly suggest bat-mediated dispersal at all sites.

We studied the impact of dung deposition by the red howler monkey (Alouatta seniculus), and subsequent burial by dung beetles and other biotic and abiotic processes, on the distribution of small seeds in the soil seed bank (Nouragues Reserve, French Guiana). Seeds were collected from 54 soil samples taken under three sleeping sites and adjoining control sites, at three positions according to a fixed grid and at three different depths (0–2, 2–4 and 4–6 cm). Despite large differences between the three sites, defecation areas (latrines) were found to contain more seeds and higher seed diversity than control areas. Seed density decreased with depth in the top 6 cm in two sites but not in the third. Shannon diversity decreased with depth in both defecation and control areas. Differences in the distribution of seeds of different species were found according to size and growth habits (pioneer vs non-pioneer species). The viability of seeds, ascertained from toughness and integrity of the seed coat, varied according to depth, site and defecation. Seed viability was on average higher in defecation areas compared with control areas.

Invasive weeds like Lantana camara have a range of effects on animals such as elephant. These plants are not edible by the Asian elephant (Elephas maximus). They also compete for space with elephant food plants and take over large areas of elephant habitat. We tested whether the addition of L. camara to a model consisting of measured environmental variables improved predictions of habitat use by elephant in Mudumalai Tiger Reserve, India. Elephant dung density was used to assess elephant habitat use from 62 line transects 1-km in length. Results indicated that habitat and impact of human settlements significantly influenced elephant habitat use at a landscape scale. However, we found no evidence for the hypothesis that the addition of L. camara significantly predicted elephant habitat use at the landscape level. We then tested the association of L. camara on elephant habitat use in the dry deciduous forest (DDF) where there was a significant interaction between DDF and L. camara. In the DDF, L. camara significantly predicted elephant habitat use. We conclude that while no significant effects of L. camara were seen at the level of an entire reserve, at a finer scale and in specific habitats negative effects of this invasive plant on elephant habitat use were observed.

Sexes and also within sex phenotypes, frequently differ in morphological traits associated with efficiency and performance in foraging and mating behaviours. In butterflies and other flying animals, phenotypic differences in wing size and traits associated with flight are involved in flight performance and individual fitness, but explorations of links among two or more traits and intrasexual differences are scarce. Foraging patterns were studied in a population of Heliconius charitonia butterflies having three phenotypes (females and two male phenotypes) which differ in their wing morphology and reproductive behaviour. As in previous studies, intersexual differences in foraging patterns were found; more interestingly, intrasexual differences were found between alternative male mating strategies. Using morphological and behavioural data, as well as data from previous flight analyses in Heliconius butterflies, we show that intrasexual differences may be explained by the energetic demands of each phenotype. Energetic expenditure is partially related to phenotypic variability in flight morphology and efficiency, and at least in both male phenotypes, differences may also be related to the energetic demands of alternative mating strategies.

Although many studies have now demonstrated that both richness and abundance of gall-inducing insect species are directly and indirectly (via the host plant) influenced by soil quality, the empirical evaluation of it in the field remains anecdotal at best. The effects of soil fertility on richness and abundance of gall-inducing insects associated with a widespread savanna species, Eremanthus glomerulatus, were evaluated under experimental field conditions in Brasilia, central Brazil. The effect of soil fertility on gall-inducing insects species richness was evaluated using three treatments: (1) plots fertilized with nitrogen; (2) plots fertilized with phosphorus; and (3) control plots: soils without fertilization. Species richness of gall-inducing insects (six species of Cecidomyiidae) did not differ among the treatments. Leaves with galls had higher nitrogen concentrations (mean = 15.0 ± 0.5 mg g−1), compared with leaves without galls (mean = 9.0 ± 0.7 mg g−1) on plants that occurred in soils with addition of nitrogen. Similarly, leaves with galls had higher foliar phosphorus concentration (mean = 1.0 ± 0.04 mg g−1) than leaves without galls (mean = 0.6 ± 0.05 mg g−1) in plots with addition of phosphorus. In galled leaves, a negative relationship between gall density and nitrogen concentration was found for one gall-inducing insect species, while three species showed a positive relationship between gall density and leaf nitrogen concentration. A negative relationship between gall density and concentration of leaf phosphorus was observed for four of the six gall-inducing insect species studied. No relationship was found between gall density and leaf nitrogen and phosphorus concentration in ungalled leaves. We argue that foliar nitrogen and phosphorus concentration respond to gall density in galled leaves and therefore, gall-inducing insect species are capable of manipulating their host plant, modifying the foliar nutrients of E. glomerulatus in sclerophyllous savanna.

Nodulation of Pterocarpus officinalis appears to be widely distributed in the swamp forest of Guadeloupe even under conditions of permanent waterlogging. The large majority of the nodules were found above the water table and as such were located on large aerial buttresses or on root hairs which develop mainly in emerged soil. Further, large trees modify their environment by accumulating litter between the buttresses to the point of ensuring sufficient topographic elevation to keep a volume of soil regularly emerged. Consequently the nodules were concentrated in a small circle (5 m in diameter) around the oldest trees. A few nodules (5%) survived under the water table, provided that healthy root hairs were present, and this kept the rate of nodulation constant over a vertical gradient (0.9 nodule g−1 root DW). The C2H4-evolution rate of P. officinalis, 2.6–5.9 μmol h−1 g−1, appeared to be quite low compared to that of the potted Gliricidia sepium cuttings (19.4 μmol h−1 g−1), but was considerably higher than that of the woody liana Dalbergia monetaria (1.0 μmol h−1 g−1) from the same swamp forest site as P. officinalis. It was concluded that P. officinalis is a N2-fixing tree species under the waterlogged conditions of tropical swamp forests, and was hypothesised that the symbiotic nitrogen fixation on P. officinalis buttresses and root hairs could be considered as an additional adaptation to flooded soil and a contribution to its success in the tropical swamp forests of the Caribbean region.

Animals often select for habitats that increase their chance of survival by balancing the need to acquire food, reproduce and avoid predation. Perennial blooms of golden jellyfish (Mastigias papua etpisoni) are present in Jellyfish Lake, Palau, a popular tourist destination. Based on the species’ economic importance and unusual behavioural complexity, increased understanding of jellyfish habitat selection is necessary. We used a novel approach, a REMUS autonomous underwater vehicle, to quantify jellyfish distribution, abundance and habitat, and compared these findings to traditional methods. Midday acoustic surveys showed jellyfish distribution was patchy and the population resided mainly on the eastern side of the lake, as it is known that jellyfish migrate eastward towards the sun. Highest vertical densities of jellyfish were at 6–7 m, potentially to mitigate UV damage or photoinhibition of their photosymbionts, suggesting a coupling exists between their vertical distribution and water properties. Abundance estimates of jellyfish were ~2.75 and ~7.1 million (~2 million excluding bell diameters <1 cm) from acoustic and net samples, suggesting the methodology employed underestimated the population's smaller size fraction and non-synoptic surveys could impact estimates due to unresolved patchiness. Our approach could investigate population dynamics, behaviour or habitat associations on fine scales.

Above- and below-ground morphology of seedlings (up to 98 cm in height) were compared by allometric analyses in tropical heath forest and peat-swamp forest in Central Kalimantan. Thirteen abundant species were selected, including two species found in both forests. In above-ground morphology, heath forest seedlings invested more in leaf mass, while peat-swamp forest seedlings invested more in stem mass, stem height, crown area and leaf area. In below-ground morphology, heath forest seedlings invested more in root mass and depth, while peat-swamp forest seedlings invested more in lateral development of the root system. Both specific leaf area and area per leaf of heath forest seedlings were lower than those of peat-swamp forest seedlings. This differentiation in seedling morphology between forest types was evident as a plastic response in the two shared species. Heath forest seedlings on coarse-textured bleached sand with low water retention suffer occasional drought whereas peat-swamp forest seedlings on waterlogged peat rarely experience drought. We concluded that seasonal water limitation brought about the convergence in seedling morphology within heath forest because average understorey irradiances and soil nutrient concentration were assumed to be similarly low in both forests.

Seed dispersal by frugivorous animals has the potential to affect both the demography and the patterns of gene flow of plant populations. In many tropical and subtropical forests a large number of seeds are efficiently dispersed by ‘non-restricted frugivores’ (NRFs, animals for which fruits do not represent the main bulk of their diet), a group commonly underestimated as seed dispersers. Here, we synthesize data from three different neotropical forests (Argentina, Panama and Costa Rica), evaluating several aspects of seed dispersal by two species of Cebus monkeys. Capuchin monkeys are NRFs broadly distributed throughout Central and South America that are potentially long-distance seed dispersers. In this study we evaluated the influence of the foraging behaviour of Cebus apella and C. capucinus on the patterns of seed dispersal. Even though the distribution of fruit types significantly differed among forests, no evidence of diet selection was found, indicating that the fruits consumed by monkeys represent a random sample of the pool available at each site. Neither seed treatment, nor the evenness with which fruit species were consumed, differed among forests. In contrast, the feeding time per fruiting tree (10–45 min), the diversity of fruits consumed (H = 2–3.3), and seed dispersal distances (100–400 m), differed among the three forests. Thus, capuchin monkeys consume a high diversity of fruits in transit producing a scattered dissemination of seeds in all study forests. This study highlights the ecological and evolutionary significance of seed shadows generated by NRFs, without neglecting the possibility that differences in the distribution of fruit patches, species richness and a range of environmental attributes among the studied forests, exert a strong influence on the outcome of the interaction between NRFs and plants.

Much of the unique native vegetation of Mauritius has been destroyed. Coastal ebony (Diospyros egrettarum I.B.K. Richardson) forest forms an extreme type of Mauritian lowland forest which no longer exists on mainland Mauritius and only survives on one offshore islet, Ile aux Aigrettes. Undisturbed D. egrettarum forest is resistant to invasion by exotic plants, which have now invaded most relict patches of native lowland vegetation in Mauritius. Human disturbance however, has allowed many exotics (particularly Flacourtia indica (Burm. fil.) Merrill) to invade and form new vegetation types. Much of the disturbance was caused by illegal woodcutting up to 1985, prompted by an acute fuelwood shortage in Mauritius. On the basis of 132 4 X 4 m quadrats, we recognize 10 types of natural, semi-natural and exotic vegeta-tion. The conservation of the remaining natural ebony woodland vegetation requires the total cessation of woodcutting and the eradication of Tabebuia pallida (Lindl.) Miers (potentially the most damaging exotic species).