Drip-tips are a common phenomenon in tropical rain forests, often believed to facilitate drainage of water from the leaf surface and, in that way, reduce epiphyll growth. Some authors suggest a function in reducing splash soil erosion, leaching of substances from the leaf, and light reflectance, while other studies did not find any such correlations. We used an experimental approach to test for the effect of drip-tips on the development of epiphyllous lichen communities. Artificial leaves with and without pronounced drip-tips were exposed in a tropical lowland rain forest at La Selva Biological Station (Costa Rica) for a period of 38 mo, and the physical behaviour of rainwater was tested. On leaves with drip-tips, the water ran off in small, frequent drops 8–30 mm3 in size. On leaves without drip-tips, the water accumulated in the apex region and dripped off periodically in large drops 50–150 mm3 in size. Nevertheless, there was no significant difference in the development of epiphyllous lichen communities on leaves with and without drip-tips, in terms of area covered, species richness and composition. However, leaves without drip-tips had more debris accumulated in the apex region and, at the same time, fewer lichen species present in this region. Thus, while drip-tips do have an influence on how water is channelled off the leaf surface, they do not impair the development of epiphyllous lichen communities, except for the apex region where the presence of drip-tips does in fact enhance, not reduce, the establishment of lichens, by preventing the accumulation of debris. We conclude that, while drip-tips may have an ecological function, this function is unrelated to the development of epiphyllous lichen communities.

Recent observations from the tropics indicate seasonal peaks in breeding and vocal activity of some bird species. However, information about seasonality in vocal activity at the community level is still lacking in the tropics. We examined seasonal variation in the diurnal vocal activity of lowland rain forest birds on Mount Cameroon, using weekly automatic sound recording throughout the whole year and related it to rainfall and temperature. We show that the bird community in lowland rain forest vocalized year-round, but species richness as well as the vocal activity of the community varied greatly during the year. This variation coincided with the seasonality of rainfall. The highest number of species (31.5 on average) sang at the beginning of the driest period, followed by a gradual decrease in singing with increasing rainfall (minimum 14.5 species). This indicates that intensive rainfall indirectly limits the vocal activity of the tropical rain-forest bird community. Temporal turnover of vocalizing species as well as within-day variation in vocal activity was highest during the transition period between dry and rainy seasons. We suggest that this could reflect differing timing in the breeding activity of particular feeding guilds to follow seasonal peaks of their diets.

Measurements were conducted within a fence-exclosure between February 2008 and July 2009 to investigate the influence of soil moisture on ecosystem CO2 fluxes in a Themeda triandra-dominated grassland of a humid Kenyan savanna. Rainout shelters were constructed to reduce ambient rainfall by 0%, 10% and 20% respectively to attain variable soil water content (SWC) during plant growth. SWC within the top 30 cm layer, above-ground biomass, soil and plant nitrogen (N) concentrations were assessed monthly alongside CO2 fluxes. Net ecosystem CO2 exchange (NEE) and ecosystem respiration (Reco) were measured with closed chambers while carbon (C) partitioning during the wet and dry seasons were assessed through pulse 13C labelling. There were significant seasonal and between plot differences in SWC, above-ground biomass, canopy light utilization efficiency (α), CO2 fluxes and C allocation pattern resulting from differences in SWC. The ecosystem was a net C sink during the wet and C neutral during the dry seasons. The study showed strong seasonal fluctuations in ecosystem CO2 fluxes and underscores the significant role of the savanna grasslands in regional C balance due to its expansive nature. The savanna grassland is however vulnerable to low soil moisture, with significant reduction in CO2 uptake during drought.

In the Ciénaga Grande de Santa Marta, a brackish lagoon system on the Caribbean coast of Colombia, about 60% of the mangrove forests died from hypersalinization. The die-back was first encountered in 1964 and mass mortality started in the late 1960s. Although efforts are being made to reestablish the destroyed areas, regeneration is slow, which may be partly due to Junonia evarete caterpillars defoliating Avicennia germinans seedlings. The interaction between insects and seedlings was studied. Both J. evarete butterflies and caterpillars were abundant during the main rainy season, the time of highest fruit production in A. germinans. During the dry season the herbivore disappeared. The caterpillars fed exclusively on A. germinans propagules, seedlings, and pneumatophores. They preferred young seedlings to older plants and did not feed on trees. At some sites, 100% of the A. germinans seedlings died due to the caterpillar attack. Seedlings at open, disturbed sites were attacked more than seedlings protected by small roofs and trenches or those under a closed canopy. Only seedlings protected by insect nets or seedlings germinating at the beginning of the dry season had good chances of survival. The results suggest that in the highly disturbed areas of the Ciénaga Grande regeneration of A. germinans is strongly inhibited by the feeding behaviour of J. evarete caterpillars.

Five species of rodent (Rattus rattus wroughtoni, Mus platythrix, Funambulus tristriatus, Cremnomys blanfordi and Golunda ellioti) were live-trapped over a period of eight months in three different habitat types (moist evergreen forest, moist deciduous forest and teak plantation) in Anaimalais Wildlife Sanctuary, Tamil Nadu, India. Small mammal densities ranged between 16.3 individuals ha−1 and 20.7 ha−1 for the natural forest sites and were 10.4 ha−1 in the teak plantation. Moist deciduous forest had the highest species richness and diversity scores. Although the teak plantation site had the same mammal species richness as the moist evergreen forest, numbers of individuals and overall small mammal biomass in the plantation was far lower than on the natural forest sites. Compared to moist deciduous forest, species richness and diversity were significantly lower on the teak plantation. R. r. wroughtoni and M. platythrix were the two most common species captured on all three sites. R. r. wroughtoni was the most common small mammal species captured, reaching densities of 14.5 ha−1 in moist evergreen forest. G. ellioti was the least common species, present only in moist deciduous forest. Demographic patterns and microhabitat selection were examined for R. r. wroughtoni, M. platythrix, and F. tristriatus. Only M. platythrix appeared to show any distinct seasonality in reproduction, with an increase in capture of breeding individuals towards the end of the wet season. Discriminant analysis did not reveal any distinct microhabitat preferences for any of the species. However, R. r. wroughtoni showed a significant association with bamboo, and F. tristriatus was associated with areas of higher canopy height and density in moist deciduous forest.

Patterns of trap response in the Central American spiny rat (Proechimys semispinosus), a frugivorous forest rodent, were examined in relation to age, sex, density and resource abundance. Populations on four small islands (designated numbers 4, 8, 14, and 52) in Gatun Lake (central Panama) were sampled by live-trapping for four nights every month for four years. Trappability was calculated as the proportion of all individuals known to be alive that were actually captured. Mean body mass at first capture was within the range of subadult body masses and differed among islands but not between sexes. Trappabilities summed over the entire study were generally low and differed among islands and age classes (juveniles, subadults and adults) and between sexes. In general, adults were more trappable than juveniles and subadults, and females (particularly adults) were more trappable than males. Trappability and the number of captures per individual varied seasonally and were generally greatest during December and January. Monthly estimates of these two variables were examined for autocorrelation, and the order of the autoregressive error model was determined separately for each island population. The arcsine of trappability and the number of captures per individual were regressed on log10 densities of spiny rats and of fruiting trees and lianas after controlling for autocorrelation. Both trappability indices were negatively related to the density of fruiting trees and lianas on islands 8 and 14, indicating that spiny rats may be seasonally food-stressed. The number of captures per individual was related positively to the density of spiny rats on island 52 and negatively on island 8. Results indicate that spiny rat populations must be sampled with greater intensity and duration than temperate forest rodents.

Philornis is a neotropical, monophyletic genus of Muscidae (Diptera) (Couri et al. 2007) that includes many bird parasites (Skidmore 1985). The interaction system of Philornis and birds is very peculiar: fly adults are free-living and only larvae interact with birds (Couri 1985, 1999; Dodge 1963). Larval trophic habits are known for 22 of the 49 species (de Carvalho et al. 2005) and are divided into three groups: coprophagous (P. aitkeni and P. rufoscutellaris), free-living haematophagous (P. falsificus) and subcutaneous (18 spp.). Philornis downsi is unusual because the first and the early second instars display a subcutaneous phase, whereas the late second and third phases show a nest-dwelling haematophagous phase (Fessl et al. 2006).

The objective of this study was to investigate the effects of tree cover and season on soil N dynamics and microbial biomass in a semi-arid southern African savanna in Zimbabwe. We used a randomized complete block design with five blocks of 100 × 100 m, demarcated in a 10-ha pocket of Colophospermum mopane-dominated woodland protected from grazing and fire. In each block, we randomly selected three mopane trees with large canopies (8.3 m crown diameter) and another three with small canopies (2.7 m crown diameter). We determined soil organic carbon and nutrient concentrations, litterfall N and C inputs, microbial biomass and N transformations beneath large and small mopane trees as well as in the intercanopy areas. Soil organic carbon, microbial biomass, N, P and K were more than twice those beneath large trees than in the intercanopy areas. Rainy-season net mineral N accumulation rate in the surface soil (0–10 cm) ranged from 3.71 μg g−1 mo−1 in the intercanopy areas to 8.80 μg g−1 mo−1 beneath large trees; correspondingly, net nitrate accumulation rate ranged from 1.33 to 3.60 μg g−1 mo−1. Dry-season net mineral N and net nitrate accumulation rates were similar across sampling sites and did not exceed 2 and 0.4 μg g−1 mo−1, respectively. Litterfall N inputs were positively and significantly correlated with soil N availability, microbial biomass N and N transformations. At all sampling sites, microbial biomass and mineral N pools in the dry season were maximum when soil moisture (∼5%) and N transformations were minimum. In contrast, when soil moisture (9–13%) and N transformations were maximum in the rainy season, microbial biomass and mineral N pools were minimum. It is concluded that the improved soil conditions beneath isolated trees in semi-arid savannas may enhance herbaceous biomass yield especially of canopy shade-tolerant species.

This study compares leaf anatomy, chlorophyll content and photosynthetic induction rates for seedlings of five dipterocarp species growing both by a path and in the understorey of a Bornean heath forest. Hemispherical photographs were used to estimate the light level. Although three of the five species showed significantly higher photosynthetic capacity in high light conditions, there were no significant within-species differences in induction rates. Average induction times to reach 50% (T50%) and 90% (T90%) of maximum photosynthetic rate (Amax) were about 1.5 and 9 min for Shorea pachyphylla. In contrast, these were 18 and 37 min respectively for Dipterocarpus borneensis, and 12 and 25 min for Shorea multiflora. Intermediate values were recorded for Hopea pentanervia and Cotylelobium burckii. There was an overall weak and negative correlation of induction rate with stomatal density. Three species showed more rapid induction loss in their leaves from the path edge vs. the understorey. The results suggest that photosynthetic acclimation can influence some aspects of a leaf's dynamic response to sunflecks, such as Amax and induction loss, while not affecting overall induction rates. This study also shows significant differences among diptero carp species in photosynthetic capacity, induction responses and leaf structure, and in acclimation on these traits.

Island biotas often have lower species diversity and less intense competition has been hypothesized as a result. This should result in lower habitat specificity compared with mainland habitats due to larger realized niches. We investigate microhabitat associations of canopy trees with regard to differences in topography on an oceanic island (Viti Levu, Fiji) using twenty 10 × 60-m plots. We find high tree-species diversity (112 species with dbh ≥ 10 cm in a total of 1.08 ha) and high endemism (c. 60%), compared with other islands in Western Polynesia. Our sample plots aggregate into three distinct groups that are mostly defined by micro-topography: (1) ridges and steep slopes (well-drained sites), (2) moderate slopes and ridge flats (moderate drainage), and (3) flats (poor drainage). Associations with microhabitat are found for more than 50% of the 41 most common species but only one species is apparently restricted to a single habitat. These findings are similar to other rain forests and demonstrate considerable niche differentiation among island rain-forest tree species.

Understanding the habitat preferences of native and non-native species may offer valuable insights into the mechanisms favouring invasion of disturbed habitats. This study investigated the determinants of trap-site detection probability of three native (Maxomys surifer, Maxomys whiteheadi and Leopoldamys sabanus) and one invasive (Rattus rattus) species of terrestrial murid (Muridae) in logged and unlogged forests of northern Borneo. We established four and two trapping grids in repeatedly logged and unlogged forest, respectively, for a total of 500 sampled trap sites. From these, we obtained 504 detections of the four species over 3420 trap nights. For each species, probability of detection was modelled as a function of both the structural components and disturbance level of the forest patch measured around each trap site. Each of the four species showed contrasting microhabitat preferences: M. surifer favoured increased canopy closure and intermediate ground and understorey vegetation cover; M. whiteheadi preferred increased ground vegetation cover and canopy height; L. sabanus favoured sites with larger amounts of coarse woody debris and less leaf litter; and R. rattus was associated with increased ground vegetation cover. Within logged forest, detection probabilities of the three native species did not vary significantly with level of patch disturbance, whereas that of the invasive R. rattus increased markedly in more degraded sites. This latter finding will have increasingly important implications when considering the rapid degradation of forests in the region, and the resulting expansion of suitable habitat for this competitive species.

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 a range of systems, studies on mistletoe distribution on the host plant have documented a number of factors that affect their occurrence and spread (Aukema & Martinez del Rio 2002a, Bowie & Ward 2004, Overton 1996, Reid et al. 1995). These patterns can be determined by host specificity, environmental conditions, host plant characteristics (Martinez del Rio et al. 1995) and the movement patterns of dispersal agents (Aukema & Martinez del Rio 2002a, 2002b). In mistletoe plants, host choice can be considerably influenced by the advantages of interacting with relatively abundant hosts (Norton & Carpenter 1998, Norton & De Lange 1999). Besides the relative abundance of host species, characteristics such as branch size, age and height can have a strong effect on mistletoe attachment resulting in size-related mistletoe infection patterns (Overton 1994). Generally positive relationships between mistletoe infection and host size have been demonstrated worldwide (Donohue 1995, Martinez del Rio et al. 1996, Norton et al. 1997, Reid & Stafford Smith 2000) and they have been interpreted in terms of the preferences by dispersing birds to perch and feed in taller trees (Aukema & Martinez del Rio 2002a) and trees accumulating infections as they age (Overton 1994). Aukema & Martinez del Rio (2002a) reported more frequent perching in taller-than-average trees by the phainopepla (Phainopepla nitens), which is the principal disperser of the desert mistletoe Phoradendron californicum. Thus, visits by mistletoe-seed-dispersing birds, and therefore mistletoe seeds received, tend to increase with tree height (Aukema & Martinez del Rio 2002a). Using a simple metapopulation model, Overton (1994) predicted the frequency of parasitized trees to increase with host age. Therefore, assuming that size is a good proxy for age, large trees are likely to be more infected than smaller trees. Reid & Stafford Smith (2000), using experimentally disinfected trees, found that larger trees were disproportionately re-infected with mistletoes. This size–intensity relationship may be used to describe mistletoe infection patterns. However, several previous studies have shown size–intensity relationships to be weak (Aukema & Martinez del Rio 2002a, Donohue 1995, Overton 1994, Reid & Stafford Smith 2000). This indicates that other factors may be important in determining mistletoe infection intensity, including that already parasitized hosts of a specific height are more likely to receive seeds than non-parasitized hosts of the same height or dispersers are likely to be attracted to trees for reasons other than size (Aukema & Martinez del Rio 2002a).

Phenology is a key ecosystem process that reflects climate–vegetation functioning, and is an indicator of global environmental changes. Recently, it has been suggested that land-use change and timber extraction promote differences in forest phenology. We use remote-sensing data to describe regional leaf phenological patterns in combination with field data from 131 plots in old-growth and disturbed forests distributed over subtropical forests of Argentina (54–65°W). We assessed how climate is related to phenological patterns, and analysed how changes in forest structural characteristics such as stock of above-ground biomass relate to the observed phenological signals across the gradient. We found that the first three axes of a principal component analysis explained 85% of the variation in phenological metrics across subtropical forests, ordering plots mainly along indicators of seasonality and productivity. At the regional scale, the relative importance of forest biomass in explaining variation in phenological patterns was about 15%. Climate showed the highest relative importance, with temperature and rainfall explaining Enhanced Vegetation Index metrics related to seasonality and productivity patterns (27% and 47%, respectively). Within forest types, climate explains the major fraction of variation in phenological patterns, suggesting that forest function may be particularly sensitive to climate change. We found that forest biomass contributed to explaining a proportion of leaf phenological variation within three of the five forest types studied, and this may be related to changes in species composition, probably as a result of forest use.

Seedlings in tropical forests are ultimately the source of canopy trees, thus factors controlling their composition and growth potentially influence the composition of the forest. Seedlings are primarily limited by above-ground competition with trees, but below-ground competition is potentially also important. Over 4 y we experimentally reduced below-ground competition by trenching to 50 cm and reduced drought stress by irrigating in the dry seasons (6 cm every 2 d) in the understorey of a semi-evergreen rain forest in Panama. There were four irrigated plots and four unirrigated, in each plot there were eight subplots (four trenched, four untrenched); 32 seedlings (two per subplot) of each of four tree species were equally allocated to the four treaments; the four species were: Aspidosperma cruenta; Gustavia superba; Simarouba amara and Tachigali versicolor. Over all species together, trenching increased seedling height by 41% and leaf area by 140% over 4 y. The cause was likely to be increased nutrient supply, because the amounts of N, K and Ca were higher in trenched plants, though concentrations were not higher. Irrigation had no significant effect on growth. Irrigation, but not trenching, reduced seedling mortality. We conclude that below-ground competition was a major limitation for seedling growth for at least some common species (Gustavia and Tachigali in this experiment). More experiments are necessary to determine whether below-ground competition is also important in other tropical rain forests on fairly fertile soils.

South-East Asian tropical rain forests experience sporadic, but profuse, seed production after general flowering, leading to the synchronous emergence of various seedlings and subsequent seedling dynamics, which play a crucial role in determining species distribution and coexistence. We examined the relative importance of both biotic (initial height, conspecific seedling density) and abiotic (canopy openness, per cent sand, soil water content) drivers using survival data for 1842 seedlings of 12 dipterocarp species for 1.5 y following mast fruiting in an old-growth Bornean tropical rain forest. More than 30% of all dipterocarp seedlings survived 1.5 y after mast fruiting. When all species were analysed together, we found that initial seedling height, canopy openness and conspecific seedling density affected dipterocarp seedling survival. Negative density dependence indicated that predators were not satiated, but dipterocarp seedlings rather suffered from host-specific natural enemies or intraspecific competition. Species-level analyses of seven dipterocarp species showed large variation in response to biotic and abiotic factors. These results suggest that interspecific differences in the relative importance of biotic and abiotic effects on seedling survival might contribute to species coexistence.

Landscape-scale studies of community traits such as species richness and community composition are sorely needed to explore the impact of large-scale disturbance events such as ENSO (El Niño Southern Oscillation)-induced burning and habitat isolation on rain-forest communities. Here we assess butterflies in continuous forest, in unburned isolates surrounded by burned forest and in burned forest, in addition to areas sampled before the most recent (1997/98) large-scale burn event in Borneo. Overall levels of species richness were significantly higher pre-ENSO and in continuous forest than in unburned isolates and burned forest. There was, however, some variation among butterfly families in these patterns, with no significant differences among habitats (continuous forest, isolates and burned forest) for the Hesperiidae and significant differences for the other butterfly families. Patterns of community composition showed that similarity was greater between distant continuous forest and isolates than between either of these and burned forest. Since the unburned isolates were surrounded by the burned forest this indicates that the habitat (burned or unburned) overrides geographical differences. Dominant species that contributed substantially to differences among habitats were often completely absent from either burned or unburned forest. The combined patterns of species richness and community structure suggest that burning affects forest ecosystems by a replacement of dominant species while habitat isolation may affect areas by leading to the local extinction of rare species.

The production and predictability of nectar resources in a population of Stachytarpheta glabra (Verbenaceae) and their use by insects and hummingbirds on ironstone outcrops in south-east Brazil were investigated. The phenology, density, nectar production, reproductive biology and floral visitors were studied, as well as territory size and daily nectar consumption by its main pollinator, Colibri serrirostris. The plant is abundant in the area, aggregated, and has a long flowering period, with very variable daily flower output. Although it can self-fertilize, it requires a pollen vector. Insect visitors totalled 21 species of bees and lepidopterans, including both pollinators and nectar robbers. Individuals of C. serrirostris defend their territories against other hummingbirds and large insects. Nectar production per hummingbird territory (mean size c. 462 m2) was estimated as 68.6–104 mL d−1 in dense areas at the flowering peak, an amount well above the estimated daily consumption of 13 mL by territory holders. Still, defence of large areas seems necessary to reduce nectar theft and cope with spatial resource unpredictability. Phenological characteristics, high density, and the fact that plants are perennial make S. glabra an attractive resource for nectar-feeders in general, and the main long-lasting nectar source for hummingbirds in the area.

The direct removal of adult trees by logging affects tree recruitment in tropical rain forests. However, secondary effects of logging, such as loss of vertebrate seed dispersers may also affect tree recruitment. We studied the recruitment and spatial distribution of five tree species namely Balanites wilsoniana, Celtis zenkeri, Chrysophyllum albidum, Cordia millenii and Ricinodendron heudelotii in Kibale, Budongo and Mabira Forests in Uganda. These forests have been subjected to varying degrees of disturbance leading to changes in their vertebrate seed dispersers. Vertebrate frugivores of the five tree species were identified. Three 1-ha plots were established around adult trees of the same five species in each forest and the distance from the juveniles to the nearest adult conspecific was measured to generate a recruitment curve. Frugivore visitation rates were high in the less disturbed Budongo and Kibale (2.2 and 1.6 individuals h−1 respectively) compared with the highly disturbed Mabira (0.9 individuals h−1). In the frugivore-impoverished forest, 70–90% of juveniles established beneath adult conspecifics, whereas in the less-disturbed forests juveniles were established up to 80 m from adult conspecifics. Shade-tolerant species capable of recruiting beneath adult conspecifics appeared to maintain their populations without dispersal. Consequently, disturbances leading to significant loss of vertebrates may alter tree recruitment and spatial distribution with consequences for long-term population viability of shade-intolerant tropical trees.