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.

In many plants, the defence systems against herbivores are induced, and may be involved in recruiting the natural enemies of herbivores. We used methyl jasmonate, a well-known inducer of plant defence responses, to manipulate the chemistry of Ficus hahliana along a tropical altitudinal gradient in order to test its ability to attract the enemies of herbivores. We examined whether chemical signals from MeJA-treated trees (simulating leaf damage by herbivores) attracted insect enemies in the complex settings of a tropical forest; and how this ability changes with altitude, where the communities of predators differ naturally. We conducted the research at four study sites (200, 700, 1700 and 2700 m asl) of Mt Wilhelm in Papua New Guinea. Using dummy plasticine caterpillars to assess predation on herbivorous insect, we showed that, on average, inducing plant defences with jasmonic acid in this tropical forest increases predation twofold (i.e. caterpillars exposed on MeJA-sprayed trees were attacked twice as often as caterpillars exposed on control trees). The predation rate on control trees decreased with increasing altitude from 20.2% d−1 at 200 m asl to 4.7% d−1 at 2700 m asl. Predation on MeJA-treated trees peaked at 700 m (52.3% d−1) and decreased to 20.8% d−1 at 2700 m asl. Arthropod predators (i.e. ants and wasps) caused relatively more attacks in the lowlands (200–700 m asl), while birds became the dominant predators above 1700 m asl. The predation pressure from birds and arthropods corresponded with their relative abundances, but not with their species richness. Our study found a connection between chemically induced defence in plants and their attractivity to predators of herbivorous insect in the tropics.

The maintenance of biodiversity in tropical forests is thought to be dependent on fine-scale mechanisms of niche partitioning that allow species to coexist. This study examined whether three species of short-tailed fruit bat that co-occur at a lowland tropical forest site in Costa Rica (Carollia castanea, C. perspicillata, C. sowelli) avoid inter- and intraspecific competition through dietary specialization on species in the genus Piper. First, dietary composition was examined using faecal samples (N = 210), which yielded three main findings: (1) bat species and sexes vary in overall reliance on fruits of Piper, with a higher percentage of seeds of Piper detected in the diets of C. castanea (98.2%) and females (91.5%); (2) adults and juveniles partition species of Piper by habitat, with a lower percentage of mid- to late-successional species of Piper detected in adults (20.8%); and (3) overall, there is a strong dietary overlap among and within the three species of Carollia. Second, controlled choice experiments were conducted with individual bats (N = 123) to examine preferences for different species of Piper. These results indicated few differences in Piper preference based on bat species, sex, age class or reproductive status, suggesting preference is not the primary mechanism shaping the observed differences in dietary composition. Overall, the dietary composition and preference similarities suggest there is strong competition both among and within the three species of Carollia for food resources.

To better understand the role of seed banks in ecological succession of dry forests, we compared similarities between vegetation and seed banks and assessed the relative contributions of seed dispersal and persistence in chronosequences in the Brazilian semi-arid region. To sample the standing vegetation and the seed bank, we collected data in three sites with three successional ages in each one (5 y, 25 y and 45 y). A total of 180 soil samples (three sites × three successional ages × 10 plots × two components) were collected. The composition of the seed bank was assessed by the seedling emergence method. Of 166 species identified in the standing vegetation, only 50 (30.1%) were also present in the seed bank, resulting in low similarity (Jaccard index = 0.02–0.21) and reflecting the rarity of woody species and the dominance of annuals (71% of richness). The relative importance of seed persistence and seed dispersal to seed banks composition were balanced in most cases (difference was not rejected in four out six comparisons). Those results suggest that seed banks in tropical dry forests are largely the result of high dispersal rates and the persistence of allochthonous annual species that contribute to decoupling seed bank and vegetation composition.

Cascading effects of high trophic levels onto lower trophic levels have been documented in many ecosystems. Some studies also show evidence of extended trophic cascades, in which guilds dependent on lower trophic levels, but uninvolved in the trophic cascade themselves, are affected by the trophic cascade due to their dependence on lower trophic levels. Top-down effects of large mammals on plants could lead to a variety of extended trophic cascades on the many guilds dependent on plants, such as pollinators. In this study, floral-visitor and floral abundances and assemblages were quantified within a series of 1-ha manipulations of large-mammalian herbivore density in an African savanna. Top-down effects of large mammals on the composition of flowers available for floral visitors are first shown, using regressions of herbivore activity on metrics of floral and floral-visitor assemblages. An extended trophic cascade is also shown: the floral assemblage further altered the assemblage of floral visitors, according to a variety of approaches, including a structural equation modelling approach (model with an extended trophic cascade was supported over a model without, AICc weight = 0.984). Our study provides support for extended trophic cascades affecting floral visitors, suggesting that trophic cascades can have impacts throughout entire communities.

Studies integrating variation in species composition among sites are useful in understanding the impacts of land-use changes on the spatial distribution of biodiversity. However, the failure to recognize the distinction between beta diversity components, dissimilarity due to species replacement (i.e. turnover) and dissimilarity due to species loss from site to site (i.e. nestedness), can lead to inappropriate use of some indices. Here, we evaluated how the spatial distribution of anuran beta diversity components, turnover and nestedness, is associated with local and landscape descriptors in a tropical agricultural landscape with a recent history of agriculture expansion in south-eastern Brazil. Overall, 27 anuran species were found in the region with average ± SD species richness in each pool of 9.5 ± 3.5 species, ranging from 4 to 15 species. We observed that species turnover was the major component for anuran dissimilarity among pools, indicating that anuran species occurring in species-poor pools are not subsets of anuran species occurring in species-rich pools. Local variables and geographic distance were not important descriptors explaining the variation of anuran beta diversity. In contrast, the distance of the pools to the nearest forest fragment explained 16% of the variance in total beta diversity, 5% of the nestedness component and 2% of spatial turnover. Our results show that pools distributed across farmland landscapes are harbouring different anuran species composition, and together, these pools are contributing to the regional diversity of anurans in this region which is considered one of the most deforested and fragmented within Brazil.