We used aquatic macro-invertebrates as a model to investigate the relationship between the regional species richness (RSR) and local species richness (LSR) in Peninsular Malaysia. A total of 38 streams (local scale) in seven catchments (regional scale), were sampled for aquatic macro-invertebrates. Eleven environmental variables (i.e. pH, DO, velocity, temperature, width, depth, TSS, BOD, COD, ammonia and canopy cover) were measured to assess their importance for local species richness. The average species richness was 34.9 species per region and the average abundance was 1380 individual per region. The highest number of species was 41, while the lowest species richness was 31. We applied local-regional richness regression models to explore the nature of the RSR–LSR relationship and then used variation partitioning to determine the relative importance of RSR and environmental conditions on LSR. We found a linear RSR–LSR relationship, which indicates unsaturated communities for macro-invertebrates in Malaysian streams and absence of local control with strong effects of regional processes. Variation in LSR explained by RSR was 43%, while the variation fraction in LSR explained by environmental conditions was low (2%) and not significant. We conclude that the variation in LSR is mainly controlled by the regional diversity pool (i.e. RSR) for aquatic macro-invertebrates in Peninsular Malaysia. However, weak effects of environmental conditions may reflect relatively low variability in the habitat among investigated streams. Further studies at larger scales, and involving different regions in this area, will be useful to draw comprehensive conclusions about determinants of local species diversity for stream invertebrates.

Nitrogen (N) availability is a major control on fine-root growth and distribution with depth in forest soils. We investigated fine-root dynamics in response to N addition in a montane rain forest with N-limited above-ground production. Control and N-fertilized (125 kg urea-N ha−1 y−1) treatments were laid out in a paired-plot design with four replicates (each 40 × 40 m). During 1.5 y of treatment, fine root-biomass, necromass and production were assessed by sequential coring at three soil depths (organic layer, 0–10 cm and 10–20 cm mineral soil), whereas fine-root redistribution with depth was assessed by ingrowth cores. Total fine-root biomass, necromass and production in the controls were 458 ± 21 g m−2, 101 ± 9 g m−2 and 324 ± 33 g m−2 y−1, respectively. No significant difference at any depth was detected under N fertilization. Fine-root biomass in the organic layer decreased over time under N addition. At 10–20 cm in the mineral soil, fine-root biomass in ingrowth cores increased significantly after 1.5 y of N fertilization compared with the control. The increased available N may have induced the change in fine-root distribution to explore the deeper mineral soil for other nutrients which may cause additional limitation to above-ground production once N limitation is alleviated.

Avian hosts may either resist the negative effects of nestling ectoparasites by minimizing the number of parasites, or tolerate parasitism by increasing their fecundity via the reproductive compensation hypothesis. Little is known about the interactions between ectoparasites and their avian hosts in the tropics. We (1) examined nestling development rates, and tested whether (2) parasitism by a subcutaneous ectoparasitic botfly (Philornis sp.) had negative effects on the condition of nestlings, and (3) these negative effects were minimized in larger broods in a tropical cavity-nesting bird, the planalto woodcreeper (Dendrocolaptes platyrostris), in primary and secondary Atlantic forests in the northern province of Misiones, Argentina. Nestling mass and ectoparasite load per nestling reached maxima when nestlings (n = 50) were between 10 and 14 d old. General linear mixed models predicted that mass at fledging declined with increasing nestling parasite load, suggesting that botflies had a negative influence on fledging condition. Parasite load per nestling declined with increasing brood size indicating that woodcreepers that increase their reproductive output minimize the negative effects of parasitism. Overall we found evidence to support the tolerance via reproductive compensation hypothesis. Future tests of the reproductive compensation hypothesis may help determine the underlying mechanism of the observed negative correlation between parasite load of nestlings and brood size.

Soil and adjacent leaf-litter environments support a diverse decomposer fauna. This has led to what is known as ‘the enigma of the soil fauna’, or the question of how it is possible for such large numbers of species to coexist without obvious biotic mechanisms, such as competitive exclusion, limiting coexistence (Anderson 1975). Dietary specialization or effective partitioning of food resources could be a mechanism to avoid niche overlap among sympatric soil/litter species (Chahartaghi et al. 2005, Jennings & Barkham 1975). However, unravelling the complexities of trophic relationships can be difficult, especially in soil/leaf-litter habitats where both consumers and prey are small, diverse and often unidentifiable (Scheu & Falca 2000). As such, the trophic relationships among species in these habitats typically remain unresolved.

We surveyed the community composition of trees that host the mistletoe Agelanthus natalitius (Loranthaceae) at two sites (Highover and Mtontwane) in South Africa. We recorded a total of 1464 trees (Acacia karroo and A. caffra) hosting 1202 mistletoes in the 64 surveyed plots (20 × 50 m). There were almost four times as many A. karroo as A. caffra at Highover and three times as many A. karroo as A. caffra at Mtontwane. There was no significant difference in prevalence (percentage of infected trees) at Highover (A. karroo = 22% and A. caffra = 26%), but a significantly greater percentage of A. caffra trees were parasitized at Mtontwane (A. karroo = 25% and A. caffra = 34%). Intensity of infection (number of mistletoe infections per tree) was higher for A. karroo (0.73 ± 0.04 and 1.03 ± 0.64) than for A. caffra (0.66 ± 0.01 and 0.89 ± 0.035) at Highover and Mtontwane, respectively. Prevalence and intensity of infection showed a significant positive relationship with tree size for both host species at both sites. We tested the genotype-by-environment interaction effects in this mistletoe by conducting reciprocal transplant experiments (64 individual trees each received 20 seeds). Initial germination was not site-, substrate- or host-sensitive. However, a general pattern was found that hypocotyls of the germinated seeds grew longer when seeds were placed on the same host species as the parent plant within their own source locality. Consistent with this observation, mistletoes placed on their source host species generally had higher survival than those transferred to non-source host species after 6 mo. Overall, mistletoe seeds from parent plants on A. karroo and mistletoe seeds placed on A. karroo had the highest survival. This could be the result of an adaptation of the mistletoe to the most frequently encountered host species.

Hemiepiphytes comprise two major categories, those that begin their life cycle as epiphytes and later establish soil contact through long descendent roots (primary hemiepiphytes), and those that germinate in the soil and climb up using adherent roots, eventually becoming epiphytes after losing soil contact (secondary hemiepiphytes) (Putz & Holbrook 1986). In several features root-climbing lianas are similar to secondary hemiepiphytes, including adhesion by adventitious roots, ability to colonize host-trees of different sizes (Putz 1984), and colonization generally restricted to a single phorophyte, differing mainly in the retention of soil contact through strong stems.

Abundance and physiology of three understorey tree fern species were compared in a Mexican cloud forest. We hypothesized that the distribution of species would be associated with canopy openness and leaf physiological characteristics. In gullies (1–2% full sun), Alsophila firma was abundant, Cyathea divergens was distributed in moderately open places (4–9%), and Lophosoria quadripinnata preferred more open canopy (9–30%). Although 11 leaf traits of five plants of each species growing under closed and open canopies over 1 y did not differ within species, there were significant interspecific differences. Alsophila firma had comparatively low maximum electron transport rate ETRmax (26.8 ± 1.81 μmol m−2 s−1) and ETR light saturation point (ETRLSP: 261 ± 36.1 μmol m−2 s−1), high specific leaf area (SLA), thin leaves and decreased quantum yield during a leaf desiccation experiment. Cyathea divergens had relatively high maximum quantum yield (0.84 ± 0.004), ETRmax (37.3 ± 1.8 μmol m−2 s−1) and ETRLSP (409 ± 40.0 μmol m−2 s−1). Lophosoria quadripinnata had comparatively thick leaves, low SLA, high predawn water potential, high density (606 ± 25.5 mm−2) and small length (0.026 ± 0.002 mm) stomata. The results support the hypothesis that light sensitivity shapes tree fern distribution in the cloud forest.

Mast-fruiting is the intermittent and synchronous production of large fruits by a population of plants at long intervals (Herrera et al. 1998, Kelly 1994). Several hypotheses have been proposed concerning the adaptive advantages of mast-fruiting (Janzen 1971, 1974; Kelly 1994), and some field observations have provided evidence for these hypotheses (Norton & Kelly 1988, Shibata et al. 1998, Sork 1993). The predator-satiation hypothesis is one well-known explanation for reproductive synchrony in plants and animals (Janzen 1971, 1974; Kelly 1994). This hypothesis claims that mast fruiting at irregular intervals of several years is an effective means of satiating vertebrate fruit predators: low seed production can only support low densities of predators during the periods between mast-fruiting events, but more fruits are produced than predators can consume in masting years (Janzen 1971, Kelly 1994). Thus, it may be said that mast-fruiting is a defence strategy of plants against post-dispersal vertebrate fruit predators.

Maximum assimilation rate under saturating light level, leaf nitrogen and chlorophyll content and specific leaf mass were measured in forest plants grown under a range of canopy openness. Seedlings from three tree species co-occurring in damar agroforest (Sumatra) were examined: Shorea javanica, Lansium domesticum and Cinnamomum porrectum. A shrub species, Piper hispidum, growing in a different location was also investigated. All species showed pronounced differences in maximum photosynthetic potential when grown under different canopy openness. All tree seedlings showed an increase in maximum assimilation rate (Amax) with canopy openness (CO) until a certain threshold was reached. This saturation threshold varied between species. A steady increase in the maximum assimilation rate over the entire range of canopy openness explored was found only for Piper. Correlation between leaf nitrogen content and Amax was usually highest when expressed on a per unit area basis. However the overall correlation was poor whether expressed per unit mass or per unit area when all species were pooled together questioning the universality of the relationship between both quantities. Potential photosynthetic nitrogen use efficiency, defined as the amount of CO2 uptake per unit leaf nitrogen under saturating light level, was highest in Cinnamomum, supposedly the most light-demanding species, and lowest in Lansium, the understorey specialist.

Spatial organization within animal populations is often thought to reflect the outcome of strategies implemented by each individual to enhance its reproductive success and survival (Clutton-Brock 1989). Thus, while females usually focus on the acquisition of food and breeding sites, male dispersion is more often determined by the distribution and availability of females (Clutton-Brock 1989). Due to these factors, intraspecific competition for space could lead to the adoption of a territorial strategy, whenever the benefits of territorial defence are higher than the costs (Brown & Orians 1970). Among small mammals, two main hypotheses have been proposed to explain the occurrence of territoriality in females. Ostfeld (1990) proposed that females should defend food resources, so the distribution and availability of food items should determine the cost–benefit relationship of adopting a territorial strategy. However, Wolff (1993) developed a hypothesis, based on small rodents, that females should defend nest sites in order to avoid infanticide, the so-called pup-defence hypothesis.

Changes in the composition and structure of mid-altitude, semi-deciduous tropical forest in Mpanga Research Forest Reserve, Uganda are described for a 25-year period between 1968 and 1993. Three surveys of a 0.64 ha (80 m × 80 m) permanent plot were carried out in 1968, 1982 and 1993, during which a total of 397 trees with a dbh≥9.5 cm were identified. Forty-nine species were identified in total, representing 19 families. Eight individuals remain unidentified. Dbh measurements were recorded for 359 non-buttressed trees, whilst the equivalent measurement for 38 buttressed trees was the diameter of the trunk immediately above the buttress. Basal area, diversity and density of trees increased within the plot during the survey period by, respectively, 8% (from 39.2 to 42.2 m2 ha−1). 7% (from 44 to 47 species) and 11% (459 to 508 trees ha−1). The main compositional changes were increases in understorey trees and a decline in serai taxa. Growth rates (productivity) and turnover were lower during the period 1982 to 1993 than the period 1968 to 1982. Rates of growth and mortality were generally highest in serai species and lowest in main canopy taxa. Mortality rates were also highest amongst the smallest trees enumerated (dbh <30 cm). Changes in composition and structure over the survey period are believed to reflect forest recovery after low intensity pit-sawing was curtailed from 1951. Forest recovery also may have caused the reduced growth rates and turnover recorded for the most recent survey period, by restricting the opportunities for light-demanding, faster-growing and relatively productive serai taxa, and to have outweighed any effects of externally-driven processes, such as changes in atmospheric conditions.

Fine roots are very important in ecology because of their role in nutrient and water uptake, and as a source of organic matter to the soil. In carbon-cycle models, fine roots are a significant organic matter pool (Potter 1999) with high net primary productivity (Jackson et al. 1997) and turnover (Gill & Jackson 2000). In ecosystem production studies, fine roots are usually divided between biomass and necromass.The sum of both pools is defined as root mass (Klinge & Herrera 1978) or total root biomass (Böhm 1979). In tropical forests the study of fine-root biomass is restricted because of the difficulties in distinguishing live roots. Visual methodologies are not adequate in tropical forests where high diversity is expressed through many root morphologies. On the other hand, definitions of root death are ambiguous and differ between different studies (Comas et al. 2000). Fine-root mass is easier and more accurate to measure than fine-root biomass because subjective selection criteria are avoided. However, in the measurement of below-ground production, the estimation of fine-root biomass is essential (Jackson et al. 1997). The adaptation of objective selection methods (Comas et al. 2000, Joslin & Henderson 1984) to measure live and dead root fractions is urgently needed.

Defoliation, often caused by herbivory, is a common cause of biomass loss for plants that can affect current and future growth and reproduction. There are three models that predict contrasting compensatory growth responses of plants to herbivory and resource availability: (1) Growth rate model, (2) Compensatory continuum hypothesis and (3) Limiting resource model. The predictions of these three models were tested on the tree Brosimum alicastrum and the liana Vitis tiliifolia. Seedlings were subjected to three levels of experimental defoliation (0%, 50% and 90% leaf removal) along a light resource gradient (1%, 9% and 65% of full sun). In both species, defoliation significantly increased leaf production rate and relative growth rate of leaf area, but not of biomass. Net assimilation rate was the strongest driver of biomass growth in both species, but leaf area ratio and specific leaf area were also important in B. alicastrum. Compensatory responses of leaf area growth in B. alicastrum were significantly greater in higher than lower light availability, consistent with the compensatory continuum hypothesis predictions, but in contrast to the growth rate model predictions. The limiting resource model offered an explanation for all possible experimental outcomes by directly considering the effects of environmental differences in resource availability.

For birds, moulting is an energetically costly endeavour (Murphy & King 1991), the timing and location of which may be flexible and governed by local ecological factors (Pyle et al. 2009, Rohwer et al. 2005). Some species or individuals may pause during long-distance migration, or migrate specifically to moult (Greenberg et al. 1974, Pyle et al. 2009, Rohwer et al. 2005, 2008). This strategy may be most common when food abundance reaches a nadir at the end of the breeding period, promoting movement to areas where food is more plentiful and the energetic and nutritive demands of moult may be met more suitably (Rohwer et al. 2005). This pattern is exemplified by insectivorous songbirds breeding in temperate, western North America that pause on southward migration to moult amidst the food flush that occurs following heavy rains in the Mexican monsoon region (Pyle et al. 2009, Rohwer et al. 2005, 2009), or more rarely, migrate upslope after breeding to moult in more moist, productive areas at higher elevation (Butler et al. 2002, Greenberg et al. 1974, Rohwer et al. 2008, Steele & McCormick 1995). Such altitudinal migration may be much more common in the Neotropics where many species engage in seasonal shifts in elevation. Hypotheses proposed to explain this behaviour, however, have focused on links made between migration and a principally frugivorous or nectarivorous diet (Levey & Stiles 1992, Stiles 1985, 1988) and not on moult requirements or phenology. Fruit and nectar availability may vary seasonally over an elevational gradient, and birds may migrate in order to track peak abundances (Levey & Stiles 1992, Loiselle & Blake 1991). Hummingbirds may also track arthropod (particularly spider) abundance, but this possibility remains little explored (Cotton 2007, Stiles 1980).

The effect of the red land crab (Gecarcinus lateralis) on leaf litter biomass and nutrient transformation was investigated in a semi-deciduous tropical forest on coastal dunes using access and exclusion plots observed for six months. Crabs were in burrows during drought, but began foraging immediately after rainfall. Crabs accelerated litter disappearance significantly during the wet season at one site located beneath Brosimum alicastrum, but had no effect beneath a nearby Enterolobium cyclocarpum. The difference is tentatively attributed to small leaflet size in the latter species which crabs were unable to handle and consume. At both sites, litter in exdosures had approximately doubled by the end of the ensuing dry season. At the Brosimum site it is attributed to sporadic crab detritivory occurring after dry seasonal rains. At the Enterolobium site it is attributed to preferential retention of litter in the cxclosures during strong dry season winds. The nutrient content of litter exposed to, or protected from, crabs was not significantly different at either site and differences in litter nutrient pools reflected differences in litter biomass. Accelerated nutrient mineralization due to crab detritivory was concentrated early in the wet season before leaching began from the soils, and it is suggested that this altered seasonal pattern of mineralization may reduce the loss of nutrients from the site in percolating water.

Field observations and laboratory experiments on unweathered and weathered dune sand beneath a tropical deciduous forest in Veracruz, Mexico were used to test the hypothesis that temporary nutrient adsorption by more weathered soil facilitates more effective nutrient recycling through the stimulation of a superficial fine root system. An analysis of soil solution composition in the field indicated that K, P and were being more effectively retained in weathered sand topsoil than in recent sand but, in a leaching experiment, only was more effectively adsorbed by this soil. Fine roots in weathered sand were more concentrated superficially than in recent sand, and a bioassay with seedlings of Cedrela odorata showed more fine root proliferation in this medium than in recent sand. In combination, these data suggest that weathering of sand in this area promotes an increased nitrate adsorption capacity which may stimulate greater root proliferation in topsoils and lead to the entrainment of other nutrients in a more concentrated topsoil-vegetation cycle. If these results can be applied to the larger domain of tropical soils generally, they suggest that nitrate adsorption may play an important role in stimulating effective nutrient recycling by forests occupying weathered soils.