Although levels of parasitism can vary greatly among individual bats of the same species, little is known about the characteristics of hosts that affect such variation. Bats were captured via mist nets from June 1995 to July 1997 from 28 localities throughout Paraguay. Over 17 500 ectoparasites were collected from 2909 bats; however, analyses of ectoparasite abundance were restricted to more abundant taxa of host and ectoparasite. We quantified the abundances of 29 taxa of ectoparasite on 19 species of bat host, as well as total abundance of ectoparasites regardless of taxonomic affiliation for 22 species of bat from Paraguay. The effects of host sex and host body size on these estimates of ectoparasite abundance were evaluated separately for each species of host. Ectoparasites did not respond consistently to host body size: ectoparasite abundance increased with host body size in 12 instances and decreased with host body size in 11 instances. Regardless of the existence or direction of effects of host body size on ectoparasite abundance, female hosts generally harboured more ectoparasites than did male hosts. Differences in host quality associated with the sex of bats, especially those related to behaviour, may be a more important determinant of ectoparasite abundance than are differences in size. Opportunities for host transfer are critical for species persistence of ectoparasites; consequently, ectoparasite populations on host individuals that form social groups or colonies should be larger, less prone to stochastic extinction, and have greater opportunity for speciation.

Gaps created by the death of one or more contiguous trees are common in mangrove forests but are poorly understood. In Kosrae, Federated States of Micronesia, where mangrove wood is harvested for local use, most natural gaps were < 50 m2, whereas most logging gaps were > 100 m2. Interior zones, where access is facilitated by roads, were the most heavily exploited. Although the forests contained 11 species, two species were primarily responsible for gap formation. Natural gaps were caused mainly by broken stems and large branches of Sonneratia alba trees, whereas logging gaps were created primarily by harvesting Rhizophora apiculata trees. Most natural gaps were formed by the fall of more than one tree or branch. Seedling densities were higher in logging gaps than in natural gaps and higher in gaps than under intact canopy. Bruguiera gymnorrhiza was the most common seedling species in gaps and under intact canopy. Relative rates of growth in height were faster in gaps than under intact canopy for R. apiculata and B. gymnorrhiza seedlings. Current harvesting practices on the island do not seem to be altering species richness, although R. apiculata may become less common as gaps are increasingly captured by B. gymnorrhiza.

The species composition of vascular epiphytes and phorophytes (trees and lianas) was studied in ten 0.1-ha forest plots distributed over three landscape units (floodplains, swamps and well-drained uplands) in Colombian Amazonia. The aim was to analyse how host-preferences contributed to the patterns in epiphyte assemblages among the landscape units. In the plots 82 species (3310 plants) were holo-epiphytes, 11 species were primary hemi-epiphytes (179 plants) and 61 were secondary hemi-epiphytes (2337 plants). A total of 411 species of tree and liana were recorded as phorophytes. Detrended Correspondence Analysis and Mantel tests showed that the species composition of holo-epiphytes and secondary hemi-epiphytes differed among the landscape units. For both groups the effect of landscape unit on species composition strongly decreased after controlling for the phorophyte composition in the plots. The phorophyte composition significantly explained epiphyte composition and this effect was not removed after accounting for the effect of landscape unit. At the level of individual species, randomization tests yielded only few significant epiphyte–phorophyte associations. For 84% of the epiphyte species the average indicator of patchiness was below 1.5 demonstrating that most epiphyte individuals occurred scattered over different phorophytes. This probably hampered the analyses of host preferences for individual epiphyte species.

An altitudinal survey of correspondences between fruiting phenologies of fleshy-fruited tree species and seasonal dynamics of frugivorous birds on Mt. Kinabalu in Borneo was carried out for 50 weeks across four vegetation types: a hill forest (800 m asl), a lower montane forest (1700 m), an upper montane forest (2000-3000 m) and a subalpine forest (3000-3500 m). In the hill forest, a large fruiting peak following the general flowering phenomenon was observed during October-November in 1996 and a fruitless period was observed during February-April in 1997. During the fruitless period, the number of resident frugivorous birds decreased. A bimodal fruiting pattern was observed in the lower montane forest. A large number of frugivorous temperate migrants were observed when the fruiting peak occurred. The number of resident frugivorous birds increased and several lowland bird species were observed, when the number of resident birds decreased in the hill forest. In the upper montane forest and the subalpine forest, more continuous and irregular fruiting patterns without outstanding peaks were observed and the number of resident frugivorous birds was more stable throughout the year. These suggested (1) there was a strong relationship between fruiting seasonality and seasonal dynamics of temperate migrants in the lower montane forest; (2) seasonal altitudinal movements of lowland bird species to montane vegetation might occur during the fruitless period in the lowland forest; and (3) the continuous fruiting pattern in the higher vegetation zones might be related to the scarcity of available frugivorous birds. The hypothesis that the influx of temperate migrants into the montane vegetation of Mt. Kinabalu is affected by density and habits of resident frugivorous birds is supported. Montane vegetation in Borneo plays an important role as temporal refugia for temperate and altitudinal migrants by supplying fruit resources.

Litterfall was measured monthly in ten 1 m2 traps in each of two 0.25 ha plots in the rain forest of Southern Bakundu Forest Reserve, Cameroon for 18 months from 1 July 1982 to 31 December 1983. Particular emphasis was placed on measuring species contributions and in relating litterfall to climatic factors; the litterfall data were also used in estimating leaf production. Annual litterfall ranged between 12.9 and 14.1 t ha−1 and was partitioned to leaves (61–66%), branches (23–38%), fruits and flowers (8–12%) and ephiphytes (0.8%). Emergents and top canopy species like Desbordesia glaucescens (evergreen) and Ceiba pentandra (deciduous) contributed more litter than the numerically dominant lower storey species like Cola lepidota and Diospyros spp. Litter fell throughout the year but was greatest during the dry season (November to March); litterfall was thus strongly negatively correlated with environmental moisture variables and could be predicted from its linear regression on time of year, throughfall and relative humidity. By correcting the leaf fall data for leaf weight losses due to grazing and re-translocation, leaf production rates of 10.2 to 11.2 t ha−1 yr−1 were estimated for the forest.

Seed predation by native and alien rodents can limit plant recruitment and ultimately affect forest dynamics and composition (Campbell & Atkinson 2002, Côté et al. 2003, Hulme 1998, Sánchez-Cordero & Martínez-Gallardo 1998). Even partial consumption of seeds by predators may affect plant community structure, though its importance is poorly understood (Steele et al. 1993, Vallejo-Marín et al. 2006). Despite consumption of relatively large portions of seeds by herbivores, seeds can retain their ability to germinate if the embryo remains intact (Dalling & Harms 1999, Janzen 1972, Mack 1998). Germination of damaged seeds may be accelerated or prolonged (Karban & Lowenberg 1992, Koptur 1998, Vallejo-Marín et al. 2006). Damage by seed pests also facilitates ageing stress; which manifests as decreased seedling vigour, decreased seed viability, lower germination percentages and slower germination rates (Priestley 1986).

Studies of predation on propagules of the mangroves Avicennia marina, Bruguiera exaristata, Ceriops tagal and Rhizophora stylosa were made in a forest in northern Australia to test the generality of the dominance-predation model. This model states that an inverse relationship exists between the dominance of a species in the canopy of mangrove forests and the rate of predation on the propagules of that species. Significant differences in predation were found among the four species, and among patches of forest dominated by the different species. Predators attacked more than 50% of the propagules of all species except R. stylosa, so are likely to significantly affect forest structure. The intensity of predation did not, however, vary as the dominance-predation model predicted. Instead, predation on the propagules of a species appeared to depend on the availability of propagules of other, more highly preferred, species.

Sympatric lizards in a transitional forest of Roraima, Brazil, dividing Amazon rain forest from savanna, contained a lizard assemblage of 16 species representing six families. Lizards varied in size, activity (diurnal versus nocturnal), microhabitats used, exposure to various conditions of light availability, prey types, and prey sizes. Overlaps in microhabitat occurrence varied from 0 (no overlap) to 1.0 (total overlap) whereas overlaps in prey types varied from 0.005 to 0.607. Microhabitat overlaps were higher overall than dietary overlaps. Pseudocommunity analyses on microhabitat data indicate that the community is not randomly assembled and that two distinct guilds exist, a leaf-litter guild and an arboreal guild, each with four species. Similar analyses on diet data revealed no apparent guild structure ast the first rank (nearest neighbour). Lizard diets did not differ from a random assortment based on prey type. At lower levels, the assemblage was structured with respect to food. Variation in prey use among lizard species was tied more closely to the effect of lizard body size on prey size (lizards ate different-sized prey items). Although exploitative competition among species may maintain structure within this assemblage it does not necessarily cause the observed differences. Several species are nearly identical ecologically to sister taxa in other environments and within different lizard assemblages suggesting that composition of the local assemblage limits the species that can enter the assemblage. Finally, lack of structure at the lowest (most similar) neighbour ranks may reflect the impact of a transitional habitat on stability of species interactions at the local level.

The insular distribution and abundance of the spiny rat (Proechimys semispinosus) were studied by live-trapping rats on 50 small forested islands in Gatun Lake, Republic of Panama. Rats were found on 29 of these islands. Rat abundance was not correlated with island size or isolation, in contrast to temperate rodents, and may be due to the highly patchy nature of tropical forests and the differing floristic compositions of the study islands. Rat occurrence on islands was related positively to island size and negatively to island isolation. All islands greater than 2.1 ha contained spiny rats, whereas most islands less than 0.9 ha did not contain rats. The relationship between occurrence, size, and isolation are illustrated by a three-dimensional response surface. Results suggest that colonization and extinction regularly occur on these islands and that (1) larger islands with year-round fruit production, regardless of isolation, will have persistent populations of rats, (2) small isolated islands will never or only very rarely have rats owing to a lack of a year-round food source and the difficulty of immigration, and (3) small near islands frequently will have rats when fruits arc present. No other species of mouse-or rat-like rodents were captured on the islands. We suggest that P. semispinosus is a better colonist than other sympatric forest species, is more of a habitat generalist, and has a more flexible demographic structure allowing persistence in heterogeneous and changing environments.

Plant responses to herbivory vary depending on herbivory type, yet the comparative effects of defoliation (e.g. by insects) and pruning (e.g. by large mammals) on a single tree species are poorly documented. We investigated this in the Northern Province of South Africa by comparing the regrowth of Colophospermum mopane trees previously defoliated by caterpillars or pruned by elephants, the two main browsers of C. mopane foliage. Shoots were up to 160% and 125% longer after natural (elephant) and simulated pruning and leaves ~25% longer in regrowth after natural pruning (n = 13–15 trees per treatment). Shoot density and chemical defences in leaves (tannin:protein ratio and total polyphenolic concentration) were, however, no different from control trees. Simulated defoliation resulted in statistically insignificant changes to regrowth in terms of leaf and shoot size (both slightly decreased) and shoot density (slightly increased). Natural (caterpillar) defoliation, however, resulted in regrowth with significantly decreased shoot and leaf size (about 50% and 20% of control lengths, respectively), as well as decreased leaf chemical defence. Shoot and leaf length were longer on trees flushing for the first time after pruning and late-season defoliation had a greater negative impact than mid-season defoliation. Despite the differences in regrowth characteristics after pruning and defoliation, mopane plants showed no apparent trade-off in investment between tolerance and resistance after either herbivory type, as neither regrowth nor chemical defence occurred at the expense of the other.

In the semi-deciduous forests of Santa Rosa National Park in the Pacific coastal lowlands of northwestern Costa Rica, the large and fast-growing tree Spondias mombin(Anacardiaceae) experiences greater than 95% post-dispersal seed predation by a bruchid beetle (Amblycerus spondiae) on its nuts that have been dispersed to any part of pristine or secondary successional forest. Nuts dispersed (by white-tailed deer) to abandoned pastures immediately adjacent to the forest suffer less than 20% post-dispersal seed predation but seedlings are killed by frequent grass fires. S. mombin displays significant recruitment of saplings and young trees only on forest edges free of fire for long intervals. The very high percent seed predation in the forest and the failure of many nuts to ever be dispersed away from the parent tree is attributed directly and indirectly to the absence of a herbivorous (frugivorous) megafauna that would have been part of the habitat of S. mombin through most of its evolutionary history. These large animals would have consumed large numbers of S. mombin fruits and thereby dispersed the nuts in such a manner as to have both led to more escape from bruchids and an overall reduction in the bruchid population density. By their defecation patterns, these mammals would also have defecated more nuts in sites of high quality for S. mombin sapling survival than is the case at present. In contemporary habitats, S. mombin is culturally deprived in that it can no longer interact with the habitats, animals and densities of animals whose selective pressures were a major force in the evolution of the tree's traits.

Habitat alteration can have far-reaching consequences for natural communities and can alter existing species interactions in profound ways. Working in a tropical dry forest ecosystem in the Guanacaste Province of Costa Rica, we measured seed removals and seed dispersal distances for Acacia collinsii and papaya seeds to determine if habitat disturbance affects ant community composition and the associated interactions between ants and seeds. Two hundred and forty experimental seed depots were observed in four sites that differed in land-use history and disturbance severity: secondary forest, forest edge, Acacia collinsii edge, and open-pasture. Both seed removals and average dispersal distances achieved by ants differed among habitats. Habitat disturbance did not negatively affect seed removals by ants in our study; seed removals were highest in the most disturbed habitat, the open pasture (38.3% of seeds removed within 2 h). Ant community composition and the relative abundance of key seed dispersers also differed among habitats. In all sites combined, ten species of ant were observed dispersing seeds, with two species, Pheidole fallax and Ectatomma ruidum, in combination being responsible for 92% of all observed seed removals. The abundance of P. fallax and E. ruidum differed among habitats, with E. ruidum being the most abundant ant species collected in the open-pasture habitat and P. fallax being the most abundant in the edge habitats. Pheidole fallax ants dispersed seeds significantly further (mean ± SD = 2.11 ± 1.35 m, maximum = 5.2 m) than did E. ruidum (mean ± SD = 0.7 ± 0.81 m, maximum = 3.85 m), a difference we attribute to recruitment behaviour and not body size. Habitat disturbance thus alters the ant community and the relative abundance of key seed-dispersing ant species, with cascading effects on seed removals and seed dispersal distances.

Habitat selection can be detected at different scales. For small mammals, habitat studies normally evaluate micro- or meso-habitat selection, but rarely are multiple scales analysed simultaneously. These studies use quantitative data of structural characteristics around the trap stations to evaluate selection. We test an alternative method to evaluate habitat selection in three didelphid marsupials (Didelphis aurita, Philander frenatus and Metachirus nudicaudatus), using a spool-and-line device, and measure habitat selection at two spatial scales. Habitat was characterized by seven habitat variables measured at ten points of direction change along the path traversed by each individual, and at 25 trap stations distributed in a 1-ha area. Micro-habitat selection was estimated at each point by comparing habitat measures between the direction selected against other directions. Meso-habitat selection was estimated by comparing habitat measurements on the whole path of an individual against habitat measures on the 25 trap stations. Patterns of selection for each species could only be detected at the meso-habitat scale, although a few individuals in each species were selective at the micro-habitat scale. Studies of habitat selection need to address the scale of study quantitatively, if possible comparing two or more scales to determine the scale of selection.

A population of the giant leather fern Acrostichum danaeifolium was observed during an 18-mo period at La Mancha (19°36′00″N, 96°22′40″W), Veracruz, Mexico. The study site was 230 m from a brackish-water lagoon, in the understorey of the mangroves, which are dominated by Avicennia germinans (Avicenniaceae). Acrostichum danaeifolium showed a clumped distribution pattern, and one third of the population became fertile during this time. Plants had a mean number of 9.4 ± 0.45 sterile leaves, which developed continuously at a rate of 14.6 ± 0.44 leaves y-1. The mean life span of sterile leaves was 7.7 mo. Although soil water was always available, phenological patterns of fertility, leaf production and leaf growth were strongly correlated with the seasonal climate. Individual leaf growth and leaf size increased significantly during the rainy season. Fertile leaves emerged exclusively from April to August and had a mean life span of 4.1 mo. Spore release was restricted to the wet season, when conditions for germination were favourable. Environmental triggers of fertility are discussed and phenological patterns are compared with ferns and angiosperms from other habitats.

Mistnets were set at ground level and 11–30 m above ground in lowland rainforest at Kuala Lompat in peninsular Malaysia, and Sepilok in Sabah, to compare the abundance of fruit bats in the subcanopy and at ground level. Capture rates in the subcanopy were up to 100 times greater than at ground level, averaging 3–7 bats per net-night. Species diversity was higher in the subcanopy than forest understorey. Two species that were frequently captured in the subcanopy, Megaerops wetmorei and Dyacopterus spadiceus, were previously thought to be rare. The abundance of Old World fruit bats in the subcanopy indicates that their roles in pollination and seed dispersal of Malaysian forest trees may be greater than previously recognized. Further research on foraging ranges, food selection and roosting habits is required to determine the overall importance of fruit bats in forest regeneration through seed dispersal, and the adequacy of existing reserves for their conservation.

Large rivers have played a prominent role in biogeographic theory for their potential to act as barriers for the dispersal of terrestrial organisms,and therefore be involved in the generation of species diversity (Brown & Lomolino 1998). In this paper, we document the potential role of macrophyte rafts as a mechanism by which Amazonian rivers could act as dispersal agents rather than barriers, transferring organisms across banks and possibly across very large distances. These vectors could therefore act against speciation and towards homogenization of the local biota.

We identified and quantified regional and local environmental factors and spatial variation associated with tree-species composition across a 2000-m altitudinal gradient of Andean forest in north-western Argentina. A network of 47 1-ha plots was established along the altitudinal gradient within an area of about 25 000 km2; all trees ≥ 10 cm dbh were identified and measured. Constrained ordinations and variance-partitioning analyses were performed to investigate the determinants of tree-species distribution at the regional scale, across and within forest types (i.e. dry and cloud forests). We marked and measured a total of 22 240 trees belonging to 160 species. Significant environmental factors and spatial location combined accounted for 35% of total variation explained. A high proportion of variation was explained by climatic factors that were spatially structured; after removing the spatial effect, climate explained more variation in species composition across the complete gradient than did local factors. Relative importance of regional and local factors varied with geographic extent. Local factors explained more variation in tree-species composition at the within-forest scale than at the scale of the complete gradient. Our findings support the conceptual model of multi-scale controls on vegetation distribution, where local community composition and abundance result from processes at both regional and local scales.

The introduction of bamboo to montane rain forests of the Luquillo Mountains, Puerto Rico in the 1930s and 1940s has led to present-day bamboo monocultures in numerous riparian areas. When a non-native species invades a riparian ecosystem, in-stream detritivores can be affected. Bamboo dynamics expected to influence stream communities in the Luquillo Experimental Forest (LEF) were examined. Based on current distributions, bamboo has spread downstream at a rate of 8 m y−1. Mean growth rate of bamboo culms was 15.3 cm d−1. Leaf fall from bamboo stands exceeded that of native mixed-species forest by c. 30% over a 10-mo study. Bamboo leaves (k = −0.021), and leaves from another abundant riparian exotic, Syzygium jambos (Myrtaceae) (k = −0.018), decayed at relatively slow rates when submerged in streams in fine-mesh bags which excluded macro-invertebrate leaf processors. In a second study, with leaf processors present, bamboo decay rates remained unchanged (k = −0.021), while decay rates of S. jambos increased (k = −0.037). Elemental losses from bamboo leaves in streams were rapid, further suggesting a change in riparian zone / stream dynamics following bamboo invasion. As non-indigenous bamboos spread along Puerto Rico streams, they are likely to alter aquatic communities dependent on leaf input.

Fire is the most prevalent form of disturbance in the cerrado savannas of south-central Brazil, commonly occurring at 2-to 3-y intervals (Coutinho 1990). Frequent fires are known to increase tree mortality (Sato & Miranda 1996), but it is unclear how they affect the growth of the surviving trees. Damage to the crown from scorching is likely to have a direct negative effect on plant growth, however the reduction in tree density due to repeated burning could indirectly stimulate growth because of release from competition. Understanding the relative strength of these contrasting direct and indirect effects of fire on tree growth is important for predicting human impacts on the cerrado vegetation.

With 86 species, Iwokrama Forest in central Guyana has the highest reported bat biodiversity for a protected area in the world. Using standardized capture data for 73 of these 86 species, we document community structure of bats in terms of species diversity, relative abundance, gross biomass, feeding guilds, vertical stratification and a trophic-size niche matrix. Based on faunal surveys in 1997, with similar amounts of effort in the forest canopy and at ground level, the greater fruit-eating bat (Artibeus lituratus) was by far the most ecologically dominant species in terms of frequency of capture and biomass. In total, frugivores comprised 70% of the species diversity and 78% of the biomass. The most common species of bat were fully partitioned in a resource niche matrix of size and trophic guild when vertical stratification was included as a variable. We conclude that resource partitioning and species packing differentially affect relative size in tropical bats, and are better summarized and analysed in three dimensions.