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Atlantic Forest (AF) is a threatened megadiverse biome distributed from north to south along the ocean of South America and is considered a hotspot of biodiversity. Currently, over 3000 ant taxa are known to occur in AF ecosystems, and many more are expected but may never be acknowledged. The patterns and processes structuring AF ant communities are not well known, urging such studies. Temperature is a fundamental environmental condition that modulates ant species occurrences at different local and regional scales. Global warming may deeply impact species occurrence, dynamics and interactions, and efforts to amplify our understanding of AF biodiversity are urgent. Ants are widely distributed in the dunes, and many species are sensitive to local changes in temperature as some species are considered thermophilic. In open areas such as dunes, the temperature varies considerably over 24 h, with great changes mainly between day and night. In this study, we sought to answer whether the foredune ant community of the Restinga, one of the habitats of the AF, is structured by temperature from day and night. For this, we tested the following hypotheses: (i) temperature influences ant diversity; (ii) in warmer periods, there is a decrease in richness, with an increase in abundance; and (iii) ant species composition varies throughout the day and, consequently, at different temperatures. We arbitrarily drew a parallel transect to the ocean composed of 15 pitfall trap units spaced every 30 m. Traps were changed in five sampling periods: T1 (9:10-13:10 h), T2 (13:40-18:40 h), T3 (19:00-23:00 h), T4 (23:00-03:00 h) and T5 (03:00-07:00 h). In each period, we recorded the ambient temperature and relative humidity. We recovered 11 ant species on the foredunes. Our results showed that the richness and abundance of ants in the daytime period was higher than in the night-time period, suggesting that temperature positively affected these two parameters of the studied community. The species composition also changed over the sampling periods. Considering that our aim was to describe the species diversity across 24 h of sampling, this 'quick-shot' of the ant community allowed us to determine that temperature and humidity shape their occurrence and activity. These results indicate that there is an interplay between these factors that are correlated and play an important role in structuring ant communities in Restinga foredunes. [ABSTRACT FROM AUTHOR]

Land‐use changes and habitat fragmentation can alter biodiversity and associated ecosystem functions.We investigated whether cropland expansion in south‐east Amazonia decreases ecosystem functions performed by ants and dung beetles by altering their communities.We sampled both groups in two forest types, in south‐eastern Amazonia: undisturbed riparian forests and riparian forests surrounded by croplands. We sampled ants and dung beetles with epigaeic pitfall traps, and experimentally assessed seed removal and predation by ants, and faeces and seed removal by dung beetles.Although ant and dung beetle abundance and richness did not differ across riparian forests, species composition of both groups did. Ants found seeds faster in undisturbed riparian forests, but the proportion of seed removal did not differ between forests. The abundance of predatory ants and the predation of termites by ants did not differ between forests.Seed and dung removal by dung beetles did not differ across riparian forests. Despite the observed differences in dung beetle composition, we did not find the effects on ecosystem functions probably due a functional redundancy of species.The quality of ecosystem functions provided by ants is lower in riparian forests surrounded by croplands, while changes in dung beetle diversity did not impact their ecosystem functions, with potential effects on the natural recovery of these disturbed riparian forests. [ABSTRACT FROM AUTHOR]

The cerrado savanna of Brazil embraces an area of approximately 2 million km2, in which vegetation physiognomies may vary from open grassland to forest with a discontinuous herbaceous layer. Here we describe the main ecological factors accounting for the prevalence of ants on cerrado foliage, and present a general characterization of the arboreal ant fauna of this savanna. The high incidence of ants on cerrado foliage results mostly from the wide occurrence of predictable liquid food sources in the form of extrafloral nectaries (EFNs) and insect honeydew, which act as efficient promoters of ant activity on vegetation. In addition, stem galleries and cavities constructed by boring beetles and insect galls create a nesting space frequently used by arboreal ants. Specific studies involving ants, herbivores and plants are reported to demonstrate the impact that foliage-dwelling ants can have on phytophagous insects, herbivory levels, and ultimately on host plants. These studies show that: (i) ants visit EFNs and likely benefit from this resource; (ii) EFN-gathering ants can benefit particular plant species by reducing herbivory and increasing plant fitness; (iii) presence of EFNs does not affect ant species richness within a given tree; (iv) there is not a particular ant species composition typical of plants with EFNs; (v) although plants with EFNs are visited by more ant individuals than non-nectariferous plants, this visitation pattern does not translate into lower numbers of herbivores on the nectariferous plant community. We suggest some promising research avenues to elucidate how community-level parameters can be tied to the ecology of ant-plant associations in cerrado. [ABSTRACT FROM AUTHOR]

In this paper we tested the assumption that smaller and more isolated remnants receive fewer ant colonizers and lose more species. We also tested hypotheses to explain such a pattern. We sampled ants in Brazil for 3 years in 18 forest remnants and in 10 grasslands between them. We tested the influence of remnant area and isolation on colonization rate, as well as the effect of remnant area on extinction rate. We tested the correlation between remnant area and isolation to verify the landscape design. Colonization rate was not affected by remnant area or isolation. Extinction rate, however, was smaller in larger remnants. Remnant area and isolation were negatively correlated. We tested two hypotheses related to the decrease in ant species extinction rate with increased remnant area: (i) small remnants support smaller and more extinction-prone populations; and (ii) small remnants are more often invaded by generalist species, which suffer higher extinction inside remnants. The density of ant populations significantly increased with area. Generalist species presented a lower colonization rate in larger remnants, contrary to the pattern observed in forest species. Generalist species suffered more extinction than expected inside remnants. The lack of response of colonization rate to remnant area can be explained by the differential colonization by generalist and forest species. The decrease of ant population density in smaller remnants could be related to loss of habitat quality or quantity. The higher colonization by generalist ant species in the smaller remnants could be related to landscape design, because smaller remnants are more similar to the matrix than larger ones. Our results have important implications for conservation strategies because small remnants seem to be more affected by secondary effects of fragmentation, losing more forest species and being invaded more often by generalist species. Studies that compare only species richness between remnants cannot detect such patterns in species composition. [ABSTRACT FROM AUTHOR]

Entomopathogenic fungi are important natural enemies of insects. However, there is little information on the insect‐suppressive potential of these fungi and possible effects of farming management on this. Meanwhile, changes in natural landscapes due to agricultural intensification have caused considerable biodiversity loss and consequent decay of ecosystem services. However, the adoption of practices such as agroforestry in agroecosystems can foster abiotic and biotic conditions that conserve biodiversity, consequently restoring the provision of ecosystems services. Here, we assessed the effect of management systems (agroforestry or full‐sun) on the pest‐suppressive potential of entomopathogenic fungi in Brazilian coffee plantations. We used the insect bait method coupled with survival analyses to assess the speed of kill by entomopathogenic fungi and their presence in soil samples from both farming systems. We found that insects exposed to agroforestry soils died more quickly than insects exposed to full‐sun soils. Of the fungi isolated from the bait insects, Metarhizium was found most frequently, followed by Beauveria. Meanwhile, Fusarium was frequently isolated as primary or secondary infections. We propose that the differential survival of insects is indicative of a greater suppressive potential by entomopathogenic fungi in agroforestry, and that this could be promoted by the diversified landscape, microclimatic stability, and reduced soil disturbance in agroforestry systems. Furthermore, our results provide a useful demonstration of the potential use of the insect bait method to investigate pest‐suppressive potential through bait insect mortality, and we term this the "bait survival technique." [ABSTRACT FROM AUTHOR]

Resource-ratio theory predicts that consumers should achieve optimal ratios of complementary nutrients. Accordingly, different trophic groups are expected to vary in their N-limitation depending on the extent to which they feed primarily on carbohydrate (CHO) or protein. Among arboreal ants, N-limitation ranges from high (for trophobiont tenders), intermediate (leaf foragers) and low (predators). We report results from a manipulative field experiment in a Brazilian savanna that tests the differential attractiveness of nitrogen and CHO to arboreal ants, as well as experimentally examines changes in broader ant foraging patterns in response to protein and CHO supplementation. Every tree within 32 20 × 20 m plots were supplemented with either protein, CHO; protein + CHO or a water control (n = 8 in each case) for a 7-day period in each of the wet and dry seasons. As predicted, different trophic groups responded differentially to supplementation treatment according to the extent of their N-limitation. The richness and abundance of the most N-limited group (trophobiont tenders) was highest at protein supplements, whereas less N-limited trophic groups showed highest species richness (leaf foragers) or abundance (predators) at CHO supplements. Protein supplementation markedly increased the general foraging abundance of trophobiont tenders, but decreased the abundance of leaf foragers. We attribute the latter to increased competition from behaviorally dominant trophobiont tenders. Our study provides experimental evidence that nutrient availability is a major factor influencing arboreal ant communities, both directly through the provision of different resources, and indirectly through increased competitive pressure. [ABSTRACT FROM AUTHOR]

Several impacts arising from anthropogenic activities hinder ecosystem properties, but the effects of habitat area size on ecosystem functioning remain little known. We aimed to evaluate the effects of area size, and the associated abundance and species richness of collembola, oribatid mites and other arthropods on litter decomposition, phosphorus and nitrogen release within tropical forests. We designed a natural mesocosm experiment with plots varying in area size (0.16 - 3.24 m2), with both a control and a faunal limitation treatment (naphthalene addition). After 240 days we found lower litter decomposition and higher phosphorus release (both about 30%) in litterbags from the faunal limitation treatment. However, variations on these ecosystem properties were not related to area size, arthropod richness or abundance in this treatment, likely because of the loss of key species. Conversely, plots without faunal limitation showed a positive linear effect of area size on decomposition, and interactive effects among area size and collembolan richness, abundance and other arthropod richness. The larger the area, the smaller the positive role of collembola and other arthropod richness on decomposition, while the opposite pattern occurred for collembolan abundance. The indirect effects of arthropods on decomposition have a more significant role within smaller areas, which have a restricted microbial community with a lower array of fungal enzymes and foraging strategies available. As far as we know, this is the first evidence that the role of arthropods in decomposition may be mediated by area size, but only when arthropod biodiversity has not been reduced. We highlight the need for further assessments of these relationships in larger scales, while also measuring microbial communities, as the impact of biodiversity loss on ecosystem functioning may be even greater when coupled with habitat loss. [ABSTRACT FROM AUTHOR]

Local biodiversity can be expected to be similar worldwide if environmental conditions are similar. Here, we hypothesize that tropical ant communities with different types of regional species pools but at similar habitat types in Brazil and Indonesia show similar diversity patterns at multiple spatial scales, when comparing (1) the relative contribution of alpha and beta diversity to gamma diversity; (2) the number of distinct communities (community differentiation); and (3) the drivers of β-diversity (species replacement or species loss/gain) at each spatial scale. In both countries, rainforests and savannas (biome scale) were represented by three landscapes (landscape scale), each with four transects (site scale) and each transect with 10 pitfall traps (local scale). At the local scale, α-diversity was higher and β-diversity lower than expected from null models. Hence, we observed a high coexistence of species across biomes. The replacement of species seemed the most important factor for β-diversity among sites and among landscapes across biomes. Species sorting, landscape-moderated species distribution and neutral drift are potential mechanisms for the high β-diversity among sites within landscapes. At the biome scale, different evolutionary histories produced great differences in ant community composition, so the replacement of species is, at this scale, the most important driver of beta diversity. According to these key findings, we conclude that distinct regional ant species pools from similar tropical habitat types are similarly constrained across several spatial scales, regardless of the continent considered. [ABSTRACT FROM AUTHOR]

In this paper we aim to show that proportional sampling can detect species–area relationships (SARs) more effectively than uniform sampling. We tested the contribution of alpha and beta diversity in ant communities as explanations for the SAR. Tropical forest remnants in Viçosa, Minas Gerais, Brazil (20 °45′ S, 42 °50′ W). We sampled 17 forest remnants with proportional sampling. To disentangle sampling effects from other mechanisms, species richness was fitted in a model with remnant size, number of samples (sampling effects) and an interaction term. A SAR was observed independent of the number of samples, discarding sampling effects. Alpha diversity was not influenced by remnant size, and beta diversity increased with remnant size; evidence to the fact that habitat diversity within remnants could be the dominant cause of the SAR. Such a relationship between beta diversity and remnant area may have also arisen due to the combined effects of territoriality and aggregation of ant species. The proposed model, together with proportional sampling, allowed the distinction between sampling effects and other mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: Based on recent papers studying the effect of leaf-cutting ants on soils, we hypothesized that Atta robusta nests modify chemical properties in oligotrophic Restinga soils. We tested if the nests (i) increase mineral nutrients, organic matter, cationic exchangeable capacity, pH, and (ii) decrease aluminum saturation. Such soil variables were determined at three depths from both active A. robusta nests and control sites. Only K concentration was greater in nests but the other parameters were not significantly modified. The exception was aluminum saturation which was significantly lower in sampled nests. Low clay content is suggested as main explanation which nullifies the effects of nests. Furthermore, complexation of aluminum with organic acids from decomposition may explain its reduced saturation. [Copyright &y& Elsevier]