In rain forests the fate of seeds defecated by mammals is often affected by dung beetles, but these effects can vary with mammal species. In a Colombian forest, differences in Scarabaeinae assemblages attracted to spider monkey (Ateles hybridus) and howler monkey (Alouatta seniculus) defecations were assessed. In total, 791 beetles of 35 species were captured. Mean number of individuals was similar for both dung types; mean number of species was higher for Alouatta traps. The effects of dung type (Alouatta vs. Ateles) and defecation pattern (clumped vs. scattered) on the fate of 220 Rollinia edulis (Annonaceae) seeds were determined. Burial by beetles occurred for 61% of the seeds (mean depth 2.6 cm). Seeds in Alouatta dung and in clumped defecations had higher burial rates. Horizontal movement (mean 11 cm) occurred for 80% of the seeds; no significant effects of experimental factors were detected. Survival was higher for buried vs. surface seeds. In a separate experiment, no differences were detected between dung types in the proportion of seeds buried by beetles. Changes in dung texture might have been responsible for the contrasting results. When assessing the effectiveness of an endozoochorous plant–mammal interaction, secondary dispersal by dung beetles should be addressed too.

Nepenthes madagascariensis is a carnivorous plant which captures its prey in pitcher-like leaves. It is endemic to Madagascar where it occurs along the eastern coast. Altogether 94.3% of its prey animals belong to three taxa: Formicidae (80.2%), Diptera (9.7%) and Coleoptera (4.4%). The prey compositions of the dimorphic lower and upper pitcher types differ significantly, especially in the markedly higher proportion of ants in lower pitchers and the higher number of flying insects in upper pitchers. A comparison concerning the trap frequency of taxa with literature data from Asian Nepenthes species showed that the upper pitchers of N. madagascariensis contained much higher proportions of Coleoptera, Diptera and Lepidoptera; these differences may partly be due to seasonal reasons. No significant correlation could be established between the numbers of prey items with pitcher size. This paper is the first characterization of the prey composition of the little known N. madagascariensis.

Nectarivorous flower mites can reduce the volume of nectar available to pollinators. The effects of the flower mite Proctolaelaps sp. on nectar availability in flowers of a melittophilous bromeliad Neoregelia johannis (Bromeliaceae) was evaluated in a coastal rain forest in south-eastern Brazil. In a randomized block experiment utilizing 18 flower pairs, one per bromeliad ramet, pollinators (Bombus morio) and mites were excluded, and then nectar volume, sugar concentration and sugar mass were quantified over the anthesis period. Mites significantly reduced nectar volume early in the morning (6h00–8h00), but not later (10h00–12h00). Mites decreased total volume of nectar available up to 22%. Sugar concentration in nectar was higher earlier in the morning, and decreased between 10h00–12h00. The pronounced consumption of nectar by mites during the period of higher sugar concentration reduced the total amount of sugar available to pollinators by 31%. This is the first study showing that flower mites decrease nectar rewards in a melittophilous plant. Because nectar volume by itself incompletely describes nectar production rates and the effects of nectar removal by flower mites on the availability of sugar, our study highlights the inclusion of sugar content in future studies assessing the effects of thieves on nectar production rates.

As a proven food resource generalist, Meyer's parrot (Poicephalus meyeri) was expected to track the availability of all significant food resources in its diet over time. Here we recorded all feeding activity during 366 standardized road transects for correlation with an index of relative food resource abundance over 18 mo. As expected, Meyer's parrot made food resource decisions according to relative abundance at landscape level. Feeding activity on food resources available throughout the year (e.g. ripe Kigelia africana fruit) or not visible from the air (e.g. unripe Diospyros lycoides fruit), however, did not correlate significantly with fluctuations in their relative resource abundance. In addition, over 70% of all feeding bouts were in the high canopy and over 70% of all food items consumed formed bi-coloured displays. The influence of estimated protein and energy acquisition rates from different food resources was insignificant. Therefore, important selection criteria for utilization by Meyer's parrot include relative abundance and visibility from the air (i.e. food resources with the highest probability of encounter when dispersing from a central roost). Sensitivity to fluctuations in resource abundance at landscape level demonstrates the relative importance of maximizing net gain per unit foraging time by minimizing foraging flight distance.

Large seasonal variation in the rate of change in girth of tropical rain-forest tree species has been described, but its origin is still under debate. We tested whether this variation might be related to variation in atmospheric relative humidity through its influence on bark water content and thickness. Variation in trunk circumference of 182 adult trees was measured about twice a month in an undisturbed tropical rain forest over 18 mo using dendrometers. Furthermore, a laboratory experiment was conducted to test the direct influence of relative air humidity on bark water content and thickness. In the field, most trees displayed highly positive rates of change in girth at the onset of the wet season, while a quarter of the trees displayed negative changes during long dry seasons, whatever their total annual growth. This variation was correlated with environmental conditions, particularly with atmospheric relative humidity. Trees with high bark water content and thickness displayed a stronger decrease in girth during the dry season. In the chamber experiment, desiccation induced a decrease in the diameter of the trunk sections in tandem with a decrease in bark water content. As a result, seasonal variation in the rate of change in girth of tropical rain-forest trees reflects variation in trunk biophysical properties, through the influence of relative humidity on bark properties, but not directly variation in secondary growth.

The concept of ecosystem engineering has catalysed novel approaches and models for non-trophic species interactions and ecosystem functions. Ecosystem engineers physically modify abiotic and biotic environments, thereby creating new habitats that can be colonized by a new suite of species. In the Peruvian Amazonas, we tested whether peccaries (Tayassuidae) function as ecosystem engineers by creating and maintaining wallows. Such wallows could be critical aquatic habitats and breeding sites for anuran species during dry seasons. We compared hydroperiods of 21 peccary wallows and 13 naturally formed ponds across three dry seasons and found that wallows had a consistently higher mean water surface area than ponds. We also examined the pH, dissolved oxygen and temperature, and found no significant differences in these parameters between water bodies. Wallows had a significantly higher density of tadpoles, metamorphs and adult anurans, as well as higher β-diversity and species richness than ponds. This study not only provides the first systematic evidence of the ecosystem engineering processes of peccaries, but also reveals the positive consequences of such for anuran species.

The directional orientation of pre- and post-reproductive migration was studied in the Brazilian red-bellied toad Melanophryniscus cambaraensis, a species that forms explosive-breeding aggregations at irregular intervals throughout the entire year. Migrating toads were captured by enclosing the breeding site in dual drift fences with inward- and outward-facing funnel traps. Data were collected over 5 mo and totalled 333 captures. The observed directional orientation was significantly different from expected under a uniform distribution for both pre- and post-reproductive migration, regardless of gender. Males and females did not differ significantly from each other in the orientation of entry or exit, and the directional orientation of pre-reproductive migration was not significantly different from post-reproductive migration. It is suggested that the observed directional bias may be due to a dirt road next to the breeding site that could restrict juvenile dispersal to the adjacent forest.

Because anuran species are highly dependent on environmental variables, we hypothesized that anuran species richness and the number of reproductive modes from different Brazilian localities vary according to climatic and altitudinal variables. Published data were compiled from 36 Brazilian localities and climatic and altitudinal data were extracted from an available database. A partial redundancy analysis (pRDA) showed that 23.5% of the data set's variation was explained by climatic and altitudinal data, while the remaining 76.5% remained unexplained. This analysis suggests that other factors not analysed herein may also be important for predicting anuran species richness and the number of reproductive modes in Brazil. Altitude and total annual rainfall were positively correlated with anuran species richness and the number of reproductive modes, and total annual rainfall was strongly associated with these two biotic variables in the triplot of pRDA. The positive association of total annual rainfall and the negative association of the concentration of annual rainfall were already expected based on physiological and reproductive requirements of anurans. On the other hand, temperature was not associated with richness or the number of reproductive modes.

Dioecious plants often exhibit male-biased sex ratios and sexual differences in life history traits such as plant size, growth rate and frequency of flowering, which arise from the different costs of reproduction for male and female plants. In tropical dioecious species sexual differences in reproductive costs have been demonstrated for several subcanopy species, but few canopy dioecious trees have been studied. We recorded the sexual expression of c. 2600 trees of Cecropia schreberiana and Dacryodes excelsa, two canopy dioecious species, during several censuses over 2 y in a 16-ha plot located in ‘subtropical wet forest’ in the Luquillo Mountains, Puerto Rico. There were similar numbers of male and female trees of C. schreberiana but D. excelsa had a female-biased population. Cecropia schreberiana showed no differences in male and female diameter distributions or growth rates, suggesting that reproductive maturation and longevity are similar for both sexes. This lack of differences in size and growth rate in C. schreberiana may result from mechanisms to compensate for the higher cost of reproduction in females, no resource limitation related to its pioneer life-history, or similar male and female reproductive costs. In contrast, D. excelsa males were larger than females, probably because males grow slightly faster than females. This sexual difference in D. excelsa may reflect a higher cost of reproduction in females than in males. Spatial segregation of males and females into different habitats is not common in tropical forest and neither C. schreberiana nor D. excelsa males and females exhibited significant spatial segregation. The contrasting results for these two canopy species reflect their different life history strategies in this hurricane-affected forest.

We tested the hypothesis that species of a diverse leaf-litter ant community are separated by the temperature preferences of their broods along a thermal gradient. Therefore, temperature preferences of brood-tending workers from 41 ant species co-occurring in four types (alluvial, limestone, kerangas and dipterocarp forest) of primary rain forest in Sarawak, Malaysia were measured in an experimental set-up. Preferred temperatures of species ranged from 16.0 °C to 31.7 °C, with the median at 25.8 °C. The ten commonest species (n ≥ 4) showed significantly different temperature preferences. In particular, species of the genus Pheidole differed clearly in their preferences over a broad range of temperatures. Temperature preferences varied significantly among ant assemblages from different forest types and nest sites. Experimentally obtained temperature preferences of species correlated significantly with vegetation density in the plots inhabited by the respective species, but not with plot canopy cover. When we tested the temperature preferences of all ant species with null models for niche overlap, we found a significant niche separation only among the tested species from the kerangas. Our results suggest that nest temperature is an important ecological factor for leaf-litter ants in rain forests on Borneo, but other factors may override its influence during community assembly.

Pteridium caudatum is a fern that frequently invades burnt areas in the Yucatán Peninsula and other neotropical sites. While post-fire regeneration of this fern apparently occurs mainly by vegetative means, little is known about the role of its spores in post-fire regeneration and in colonization of newly invaded fields. Central to these questions is whether bracken fern spores maintain their viability after fires. Here we experimentally evaluate the effect of fire-induced temperatures on Pteridium caudatum spore germination. We used 1200-cm3 blocks containing a constant fuel load of 47.4 g of litter, in which we placed spores at three different depths. The blocks were then ignited, and temperatures at each depth were monitored at 1-min intervals for 2 h. One day after the experimental fires, spores were dug out and cultured at 25 °C and 12-h light/dark cycles. Soil temperatures decreased significantly in relation to depth during fires. Spores on the surface were severely affected by fire, while those buried at 1 and 3 cm showed 77% germination. Germination in unburned controls was 86%. Our results suggest that during fires, Pteridium caudatum spores buried a few centimetres below the surface have a high percentage of viability, which could explain the rapid establishment of this species in burnt fields.

The ecological importance of trees lasts much longer than their life spans. Standing dead trees (snags) and fallen trunks and branches are an important component of above-ground carbon stocks and nutrient reserves, provide habitat for wildlife, and interact with disturbance regimes (e.g. by serving as fuel for fires) (Clark et al. 2002, Harmon et al. 1986, Pyle et al. 2008). Despite these diverse functions, woody debris stocks remain poorly quantified in tropical forests in general (Brown 1997), and in tropical dry forests in particular (Harmon et al. 1995). More empirical studies of the patterns of woody debris and processes that control its dynamics are needed to understand its role in global biogeochemical cycles and for ecosystem simulation models, many of which do not represent coarse woody debris (CWD) as a separate pool (Cornwell et al. 2009).