Bates' theory of mimicry (Bates 1862) postulates that vertebrate predators avoid attacks on chemically defended butterflies, and a profitable species, usually referred to as the mimic, can obtain protection by resembling one or more unpalatable models. The evolution of Batesian mimicry requires that predators meet, taste and learn to avoid the models before meeting the mimics. For this reason, some authors have adopted the assumption that mimic population sizes must be smaller than the models' populations (Fisher 1930, Huheey 1980, Lindström et al. 1997).

Plant facilitation can improve the diversity of plant communities in several ecosystems, especially in stressful environments. The establishment of tree species on rocky outcrops can be limited by several biotic and abiotic factors. The richness and abundance of forest trees species on rocky outcrops surrounded by a large forest remnant in south Brazil were correlated with the cover of Bromelia balansae, a spiny stoloniferous species commonly occurring at forest–grassland transitions. Sixty plots were established on three flat rocky outcrops (20 in each). In each plot the coverage of bromeliads was estimated into three classes (0%, 1–50% and 51–100%) and all seedlings (individuals 10–30 cm in height) were counted and identified. ANOVAs with randomization tests were performed to establish the effect of different bromeliad cover classes on the richness and abundance of seedlings. The cover of bromeliads was positively related to the richness and abundance of young pioneer tree species. Evidence suggests that B. balansae can act as a nurse plant for tree seedlings, but manipulative experiments are needed to confirm this.

The adult Auchenorrhyncha community within the understorey of a montane tropical forest in Vietnam is described A total of 1132 specimens representing 223 morphospecies and 16 families was found in a 4300-sweep sample None of the species exceeded the 5% dominance level More than half the species are represented by single individuals within the 309 ms of vegetation Spatial community pattern is mosaic like at a scale of hundreds of metres as the similarity of 100 sweep samples does not depend on their spatial distance Areas 1 5–3 km distant from one another differ markedly in their Auchenorrhyncha communities These between-site differences exceed the intra-site community heterogeneity Population density of Auchenorrhyncha species is not correlated with their body size The Auchenorrhyncha community within a forest markedly differs from the community of an adjacent ruderal area A transitional zone between these habitats is intermediate in Auchenorrhyncha species composition

A population of Garra ceylonensis in a rocky, hill stream was studied by monthly sampling over a period of two years. The monthly population density, which varied from 1.28 to 4.16 m-2 with a mean of 2.37 m-2, was negatively correlated with the water speed. Asymptotic length (L∞) and the growth constant (K) were found to be 180.5 mm total length and 0.62. Maximum size observed was 174 mm, which is attained in about five years, but 99% of the population had a life expectancy of less than 3.4 years. The overall male to female ratio of the population was 0.58. The sex ratio was 1.0 in smaller size classes but decreased steadily with increasing size. There was a major spawning season following the main rainy period in contrast to the trend of most tropical freshwater fish species, which show enhanced breeding during the rainy season. The mean length and age at sexual maturity in females appear to be 109 mm and eighteen months. Fecundity varied between 740 and 4390. Average longevity and natural mortality were 4.8 years and 1.86. The mean biomass, average annual production and turnover ratio of the population were about 23.7 gm-2 wet weight, 41.2gm-2 and 1.7, respectively.

Mosses are one of the most important and dominant plant communities, especially in the temperate biome, and play a significant role in ecosystem function and dynamics. They influence the water, energy and element cycle due to their unique ecology and physiology. The present study was undertaken in three different temperate forest sites in the Garhwal Himalayas, viz., Triyuginarayan (Kedarnath Wildlife Sanctuary (KWLS)), Chakrata, and Kanasar forest range. The study was focused on understanding the influence of mosses on soil physical properties and nutrient availability. Different physico-chemical properties were analysed under two different substrata, that is, with and without moss cover in two different seasons, viz., monsoon and winter. We observed mosses to influence and alter the physical properties and nutrient status of soil in both seasons. All soil physical and chemical properties, except magnesium, showed significant difference within the substrates, among all the sites and across the two seasons. Besides the soil characteristics underneath the moss vegetation, the study also highlights the diversity of mosses found in the area. Mosses appear to create high nutrient microsites via a high rate of organic matter accumulation and retain nutrients for longer periods thus, maintaining ecosystem stability.

Environmental complexity and spatial heterogeneity are important factors influencing the structure of ant species assemblages. This paper documents the effect of different vegetation and environmental factors on ant community structure and functional group composition in different habitat patches. Ants were sampled at 16 sites distributed across five habitat types in the Kuldiha Wildlife Sanctuary. Sampling was performed 10 times over a 2-y period using pitfall traps. A total of 100 species belonging to 41 genera were collected during the study. Ant species richness was best explained by a combination of percentage grass cover, percentage litter cover and number of saplings whereas percentage litter cover and soil nitrogen concentration significantly explained the variation in ant species abundance. Dominant Dolichoderinae were present only at forest edge and were found to be associated positively with percentage bare ground cover and negatively with percentage litter cover. Generalized Myrmicinae, subordinate Camponotini and tropical climate specialists were prevalent in shaded forest habitats whereas opportunists were more common in two types of open habitat. Our study underpins the influence of vegetational complexity, litter and soil chemical properties on the structure and composition of ant species assemblages and various functional groups across forested habitats in this little-studied region.

We examined changes in a community of seedlings/saplings 10–150 cm tall associated with the presence of a widely invasive plant, Lantana camara and environmental covariates along 67 randomly located transects, in Mudumalai, India. We compared plant species assemblage and grass cover in L. camara-invaded and uninvaded plots in three habitats. Multivariate analyses revealed a significant association of all environmental covariates with plant species assemblage. Pairwise tests indicated that L. camara was significantly associated with changes in plant species assemblage and grass cover within the moist and dry deciduous forest, but not in the thorn forest. The relationship between L. camara and that of elephant browse plants varied with species. A linear regression analysis indicated that L. camara invasion was the only significant predictor of grass occupancy. Our results indicate that in addition to other factors, L. camara was associated with altering plant species assemblage, some elephant browse plants and grass cover in the moist and dry deciduous forest. It appears that L. camara can have a major effect on diversity within this reserve, but whether this effect is by L. camara driving the change or being associated with other habitat change requires further experimental evidence.

Fruit-eating birds play an important role in the seed dispersal of many tropical plants (e.g. Herrera 1984), and the foraging behaviour of avian frugivores may affect their seed-dispersal capabilities (Loiselle & Blake 1999,Schupp 1993, Traveset 1994). For instance,shorter visits tend to produce less clumped seed distributions (Graham et al. 1995). Also,avian frugivores often feed on the fruits of several plant species over short periods of time (Herrera 1984, 1988a; Levey et al. 1994) in some non-random pattern (Herrera 1998). This potentially produces a predictable spatial pattern of the dispersed seeds (White & Stiles 1990). Forest destruction leads to fragmentation and degradation of the remaining habitats, which may influence patterns of adult tree distribution if the production, predation, dispersal, and/or regeneration of tree seeds is affected (Harrington et al. 1997). If dispersal of avian frugivores is disrupted by habitat fragmentation, plant species might face reduced regeneration, or even local extinction if they depend on a single, locally extinct disperser (Kellman et al. 1996). Increased predation of seeds and regenerating plants in the edges and gaps may also directly reduce regeneration rates (Corlett & Turner 1997, Harrington et al. 1997, Schupp 1988).

Calcium is an important nutrient for birds, especially for eggshell production and the mineralization of the skeleton of developing young. In temperate regions insects and seeds that form the bulk of the diet of breeding passerines do not contain sufficient calcium to meet the needs of breeding females and young; these birds obtain their calcium by eating snails, woodlice and millipedes. Little is known about the way tropical frugivorous passerines meet their calcium needs. The calcium contents of fruits of 34 species eaten by birds during the breeding season in mature floodplain forest in south-eastern Peru were determined. The suitability of these fruits as calcium sources for hypothetical 10-g and 25-g birds and for 26 species of frugivore that breed at the study site was evaluated based on bird body weight and on the rictal width of the bill, which influences feeding. Fruits of five species in the study area appear to be suitable sources of calcium for birds ≤25 g, although those of Ficus killipii (Moraceae) are likely optimal. The latter contain a lot of calcium (2.48% dry weight of pulp or c. 4.15 mg per pulp per fruit) and are small enough (mean diam. = 9 mm) for most birds to swallow whole, and trees produce large crops. Snails, woodlice and millipedes are common in the area and also contain sufficient calcium to meet birds’ needs. In addition, birds could likely meet their calcium needs through geophagy at natural mineral licks.

Epiphytic orchids are very diverse in montane forests, but fragmentation modifies this diversity. Twenty fragments were quantified to evaluate the effects of fragmentation on the alpha and beta diversities of epiphytic orchids in a montane forest located in southern Mexico. The following factors were evaluated: area, core area, shape, edge density, Euclidean nearest-neighbour distance fragment and contrast index. In each fragment, two transects of 2 × 50 m were drawn, and the trees with a diameter at breast height ≥ 20 cm were recorded. In each tree, the orchid species present were identified and quantified. Twenty-three species of epiphytic orchid in 234 phorophytes corresponding to 20 species were recorded. The epiphytic orchid richness per tree and species turnover was different between the phorophytes. The edge density and the contrast index had significant effects on the alpha diversity, while the isolation of the fragments significantly affected the beta diversity. The edge density positively affected the alpha diversity of the epiphytic orchids, likely through microclimatic changes caused by fragmentation. Drought-tolerant species were common on the edges of the fragments, and shade-tolerant species established on the core area of the fragments. This pattern most likely depends on the ecological range of the taxa, which is crucial to their development and persistence in fragmented habitats.

Ants are important agents of seed dispersal and they can play a fundamental role in the establishment and survival of plants (Beattie 1985). Leaf-cutting or fungus-growing ants (Myrmicinae: Attini) are dominant elements of the ant fauna throughout the neotropics. They collect different types of vegetative and reproductive plant material that serve as substrate for underground fungus gardens,which are the only food source for their larvae (Stradling 1991).

Despite the aseasonality of temperature and day length of many tropical regions, especially when compared with temperate latitudes, most tropical animals show fairly pronounced seasonal shifts in foraging, movement patterns and reproduction (Flecker & Feifarek 1994, Saul 1975, Wolda & Fisk 1981). Understanding reproductive seasonality in tropical avian communities involves distinguishing among complex interactions between weather, resource abundance, hormones, behaviour and other life-history traits (Wikelski et al. 2003). While there is a great deal of evidence that many tropical bird species breed seasonally (Hau 2001, Marchant 1959, Miller 1963, Snow & Snow 1964), we still understand little of the causes which drive observed patterns (Wikelski et al. 2003). Most studies which address the seasonality of reproduction in tropical birds have focused on locations with fairly extreme temporal changes in rainfall (Cruz & Andrews 1989, Lack 1950, Marchant 1959, Poulin et al. 1992, Voous 1950), and comparatively few have looked at relatively aseasonal low-latitude locations (Miller 1963, Moreau 1950). Similarly, though a few studies have pointed out slight variation in the within-species initiation of breeding based on microhabitat (Wikelski et al. 2003), we know very little about how micro-habitat choice for nesting may affect (or be affected by) breeding seasonality. In this study I describe the nesting cycle of the spotted barbtail (Premnoplex brunnescens), from the Ecuadorian Andes to better understand how reproduction may be seasonal when climatic cues are subtle or absent.

Many studies conclude that light is the most important resource that determines plant performance of tree saplings in tropical rain forests, and implicitly suggest that soil resources are less important. To provide a quantitative test for soil versus light effects on sapling performance, we studied how saplings of the shade-tolerant tree species Brosimum alicastrum responded to contrasting levels of light availability and soil fertility in a Mexican tropical rain forest. Therefore saplings were selected from ten low-light exposure (crown position index <1.5) and ten high-light exposure (crown position index ≥2.5) sites either on productive alluvial soils, or on poor sandy soils on adjacent hills. Annual growth responses were scored for 58 saplings. The soil–light interaction had a strong positive effect on branching rate and leaf area production, rather than light or soil alone. Height growth only increased at higher light availability. Herbivore damage was higher on the more productive soil and, to a lesser extent, at higher light availability. Our results suggest that saplings (1) responded differently to soil and light availability, (2) expanded in overall size when both soil and light limitations are released, but only increased in height with increasing light intensity (3) and faced a trade-off between expansion and defence along both soil and light gradients. This study emphasizes the role of soil resources, in interaction with light availability, on the plastic responses in saplings living in a tropical forest understorey.

Major tropical rivers have been suggested to be important dispersal barriers that increase the beta diversity of animal communities in lowland rain forests. We tested this hypothesis using assemblages of frogs in the floodplains of the Sepik River, a major river system in Papua New Guinea. We surveyed frogs at five sites within a continuous 150 × 500-km area of lowland rain forest bisected by the Sepik, using standardized visual and auditory survey techniques. We documented 769 frogs from 44 species. The similarity in species composition decreased with logarithm of geographical distance between the sites, which ranged from 82 to 465 km. The similarity decay did not depend on whether or not the compared sites were separated by the Sepik River or whether the species were aquatic or terrestrial breeders. Likewise, a DCA ordination of frog assemblages did not show separation of sites by the river as a significant factor explaining their composition. Our results suggest that even major rivers, such as the Sepik, may not act as dispersal barriers. Rivers may not limit the distribution of frogs and therefore have a limited effect on determining frog species abundance and assemblage structure in rain forests.

The reproductive success of plants depends to a very large degree on the quantity and quality of seed dispersal. If dispersal is by animals (zoochory), characteristics of fruits such as colour, size, shape and nutritional content have been shown to influence the likelihood of visitation by frugivores or the rate of fruit removal (e.g. Fuentes 1994, Howe 1983, Murray et al. 1993). While these characteristics function in the attraction of dispersers, plants may also evolve characters that manipulate the behaviour or the physiology of dispersers after the consumption of fruits and the ingestion of seeds. An example of such post-consumption manipulation of dispersers' behaviour by plants is provided by mistletoes. The viscous mistletoe seeds stimulate the disperser (usually birds) to either rub the cloaca (when seeds are passed through the gastro-intestinal tract) or the bill (when seeds are regurgitated) on a branch (e.g. Reid 1991). It has also been proposed that fruits might manipulate the disperser's physiology by including laxatives that determine the optimal passage time through the disperser's gut (Murray et al. 1994), although this view has recently been challenged (Witmer 1996).

The establishment and growth of a young tree requires a microsite that falls within a range of specific environmental conditions. Microsites will to some degree be modified by such neighbouring plants as are already established, a circumstance that will in turn lead to either a positive or negative spatial association among the individuals. Such patterns of spatial interactions are amenable to statistical inference. Positive associations may result when one species ameliorates overall hostile conditions, such as the shade and moisture provided the seedlings of long-leaf pine by the canopy of the saw palmetto (Allen 1956). Indeed, positive associations appear widespread in arid and cold habitats (reviewed in Tirado & Pugnaire 2003). However, on the forest floor of the humid tropics, negative associations are presumably more likely (Montgomery 2004). Harms et al. (2004) recently found a correlation between high density of small palms and a low density of tree saplings across four Neotropical sites, while Wang & Augspurger (2004) demonstrated that dwarf palms and cyclanths reduce seedling recruitment on the forest floor in Costa Rica.

Our aim was to disentangle the effects of different heat sources and the non-thermal properties of the substrate in the microhabitat choices of two lizard species living in savanna habitats of central-western Brazil: the teiid Ameivula aff. ocellifera (N = 43) and the tropidurid Tropidurus oreadicus (N = 23). To this end, a mixed structural resource selection function (mixed-SRSF) approach was used, modelling the probability of finding a lizard on a certain microhabitat based on environmental variables of used and simultaneously available places. First, we controlled for the effects of solar radiation, convection and the physical thermal properties of the substrate on substrate temperature. Then we assessed the effects of solar radiation, convection, conduction and the non-thermal properties of the substrate in the probability of use of a certain microhabitat. Results confirmed that substrate temperature was mediated by: air convection > solar radiation > physical thermal properties of the substrates. Moreover, the mixed-SRSF revealed that direct solar radiation and the non-thermal properties of the substrates were the only drivers of microhabitat selection for both species, with approximately the same strength. Our novel approach allowed splitting of the effect of different mechanisms in the microhabitat selection of lizards, which makes it a powerful tool for assessing the conformation of the interactions between different environmental variables mediating animal behaviour.

The spatial organization of epiphytes has come under increasing attention. This kind of information is necessary for the general understanding of their ecology and for the design of sustainable harvesting methods. In this study, the small-scale (local) distribution of epiphytic bromeliads was studied using correlograms and permutational regression on distance matrices. Fieldwork was carried out in a young secondary forest stand in the central cordillera of Colombia at 3150 m asl. A complete census of the bromeliads in this plot was made, using a lattice with 400 quadrats. Six species of bromeliad were found (1008 individuals). All of these except one showed an aggregated spatial pattern. This pattern was independent of the position of the trees in the sampled plot. The distribution of the bromeliads was determined by the availability of substrate (branch surface area per quadrat), the proximity of conspecifics and the geomorphology of the terrain. The structure of the forest surrounding an epiphyte had an influence on the position of the epiphyte in the tree (height measured as distance from the canopy). The use of two-dimensional, lattice-based sampling strategies is discussed as a possible method for comprehensive surveys of epiphyte populations in natural forests.

Descriptions of the fine scale distribution of organisms have frequently been used to investigate various ecological phenomena. Unfortunately, the most widely used spatial analysis techniques are based on single index statistics, which convey only minimal information about the biological processes underlying the studied distributions. Such statistics cannot detect changes in pattern over different scales, and cannot identify some types of distribution. Additionally, both the use of such statistics on the distribution of individuals which have a non-negligible size, and the frequent failure to use an edge correction for points close to the boundaries of a sampled area, have led to the over-reporting of ‘spaced out’ (‘regular’) distributions. Using two spatial distributions recently analysed with a single index statistic (termite mounds, and earthmounds created by termites), I illustrate the benefits gained from using the spatial functions K(t), G(y) and F(x) to analyse both ‘point events’ and events which have a non-negligible size. These functions are considerably more informative about the nature of a spatial pattern and offer wide scope for the fitting of spatial models to biological distributions.