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Ants, an ecologically successful and numerically dominant group of animals, play key ecological roles as soil engineers, predators, nutrient recyclers, and regulators of plant growth and reproduction in most terrestrial ecosystems. Further, ants are widely used as bioindicators of the ecological impact of land use. We gathered information of ant species in the Atlantic Forest of South America. The ATLANTIC ANTS data set-which is part of the ATLANTIC SERIES data papers-is a compilation of ant records from collections (18,713 records), unpublished data (29,651 records), and published sources (106,910 records; 1059 references), including papers, theses, dissertations, and book chapters published from 1886 to 2020. In total, the data set contains 153,818 ant records from 7,636 study locations in the Atlantic Forest, representing 10 subfamilies, 99 genera, 1,114 ant species identified with updated taxonomic certainty, and 2,235 morphospecies codes. Our data set reflects the heterogeneity in ant records, which include ants sampled at the beginning of the taxonomic history of myrmecology (the nineteenth and twentieth centuries) and more recent ant surveys designed to address specific questions in ecology and biology. The data set can be used by researchers to develop strategies to deal with different macroecological and regional-wide questions, focusing on assemblages, species occurrences and distribution patterns. Furthermore, the data can be used to assess the consequences of changes in land use in the Atlantic Forest on different ecological processes. No copyright restrictions apply to the use of this data set, but we request that authors cite this data paper when using these data in publications or teaching events.

Changes in land-use and climate increase the flammability of forests across southeast Amazonia, potentially driving abrupt fire-mediated transitions to derived savannas – grass-dominated degraded forests with scattered trees. However, the extent to which the forest fauna undergoes a parallel process remains poorly understood. Here we test the hypothesis that the process of fire-driven forest shifts towards derived savannas has congruent cascading effects on ant communities by causing declines in forest specialists and an influx of open-habitat taxa. In 2013 we collected ants using subterranean, epigaeic and arboreal pitfall traps in three adjacent 50-ha plots: an unburnt control and two treatment plots that were burnt either triennially or annually from 2004 to 2010. Frequent fire was associated with a marked decline of specialist forest species (almost 50%), and an influx of open-habitat taxa that were absent from the unburnt plot. The effects were particularly pronounced for epigaeic ants: their abundance, biomass, species richness and species composition were impacted by fires, and this was the main stratum occupied by the open-habitat species. Previous studies have shown that a similar conversion is not triggered by single fires, and they therefore require recurrent fires. Our results provide experimental evidence that the process of tropical forest conversion towards derived savannas caused by repeated burning is a broad one that affects not only plants, but involves parallel compositional shifts of animal communities. The prevention of recurrent fires is a priority challenge for avoiding widespread biotic conversion of tropical forests to derived savannas.

The widespread clearing of tropical forests causes lower tree cover, drier microclimate, and higher and drier fuel loads of forest edges, increasing the risk of fire occurrence and its intensity. We used a manipulative field experiment to investigate the influence of fire and fuel loads on ant communities and their interactions with myrmecochorous seeds in the southern Amazon, a region currently undergoing extreme land-use intensification. Experimental fires and fuel addition were applied to 40 × 40-m plots in six replicated blocks, and ants were sampled between 15 and 30 days after fires in four strata: subterranean, litter, epigaeic, and arboreal. Fire had extensive negative effects on ant communities. Highly specialized cryptobiotic and predator species of the litter layer and epigaeic specialist predators were among the most sensitive, but we did not find evidence of overall biotic homogenization following fire. Fire reduced rates of location and transport of myrmecochorous seeds, and therefore the effectiveness of a key ecosystem service provided by ants, which we attribute to lower ant abundance and increased thermal stress. Experimental fuel addition had only minor effects on attributes of fire severity, and limited effects on ant responses to fire. Our findings indicate that enhanced fuel loads will not decrease ant diversity and ecosystem services through increased fire severity, at least in wetter years. However, higher fuel loads can still have a significant effect on ants from Amazonian rainforests because they increase the risk of fire occurrence, which has a detrimental impact on ant communities and a key ecosystem service they provide.

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.

Espécies que habitam a restinga apresentam adaptações para seu desenvolvimento e sobrevivência sob inúmeros fatores ambientais estressantes. A seleção de um habitat particular deve depender destes diversos componentes do ambiente físico, associado às interações biológicas. O presente estudo foi realizado na restinga herbáceo- arbustiva do Morro dos Conventos para determinar a influência da distância do oceano, fatores bióticos e abióticos sobre a comunidade de formigas de solo. Foram instaladas 65 armadilhas de solo em dois transectos arbitrários de 650 metros a partir do oceano em direção ao continente. Um total de 71 espécies de formigas foi amostrado. Os gêneros Pheidole, Solenopsis e Camponotus foram os gêneros mais representativos. Foi encontrada uma relação positiva entre distância do oceano e riqueza de espécies de formigas, bem como entre distância do oceano e riqueza de espécies de plantas. Das hipóteses testadas, apenas as que estavam relacionadas com a vegetação foram aceitas. A riqueza de espécies de formigas esteve relacionada com a riqueza de espécies de plantas e cobertura do solo. A riqueza de espécies de plantas pode ter influenciado o aumento da riqueza de espécies de formigas pelo aumento da variedade de recursos para consumo e nidificação. Além disso, a vegetação pode alterar as condições microclimáticas, com o aumento da umidade e diminuição da temperatura, fatores extremamente importantes em ambientes com alta incidência de radiação solar e altas taxas e evapotranspiração como a restinga. Esses resultados permitem sugerir a importância da vegetação, e os componentes ligados a ela, como fatores locais determinantes da riqueza de espécies de formigas em Restinga. Species inhabiting Brazilian coastal sand dunes (restingas) may feature a number of adaptations in their development and survival in these physical stressful environments. The present study determined the effect of biotic and abiotic factors on the assemblage of grounddwelling ants in a sand dune ecosystem of the Santa Catarina coastal plain in Brazil. Both linear and quadratic models were significant, but the quadratic model fitted the obtained data better. Furthermore, we also found a relationship between plant species richness and distance from the ocean only by using the quadratic model. Ant species richness was correlated with plant species richness, litter and vegetation coverage. Different environmental factors associated with plant species richness may have influenced the ant species richness by increasing the diversity and amount of available resources. The vegetation may also offer protection from higher temperatures by providing shade, a humid microclimate and a source of water, which is a limiting factor in sand dune environments. Our results showed the importance of plant species richness, and soil cover by litter and plants as local characteristics determining ant species richness in sand dunes. Further studies should explore additional habitat components, such as biotic interactions, as determinants of ant species richness.

Several ecological and evolutionary processes can drive changes in diversity at different spatial scales. To determine the scale at which these processes are most influential, we hypothesized that (i) broad-scale differences between ecoregions had greater influence on ant species richness and species turnover than local differences among fragments within ecoregions; and (ii) the degree of dissimilarity in ant species composition is larger between Tropical Dry Forest fragments and the surrounding vegetations than among Tropical Dry Forests located in different ecoregions, indicating that extant Tropical Dry Forests are relicts of a broader distribution of this vegetation. To examine ant diversity patterns, we built a nested hierarchical design on three spatial scales, ranging from fragments (local scale), Tropical Dry Forest + surroundings vegetation (landscape scale) and Brazilian ecoregions (regional scale). We used 450 sampling units (45 sampling units × two fragments × five ecoregions = 450). A null model based on the sample was used to identify variations in the random distribution across spatial scales. Spatial partitioning of ant diversity showed that observed β1 diversity (between fragments) and β2 diversity (among ecoregions) were higher than expected by chance. When the partitioning was analysed separately for each region, the observed β1 diversity (Tropical Dry Forest and surrounding vegetation) was higher than expected by the null hypothesis in all ecoregions of Brazil. Based on species composition and diversity patterns, we stress the importance of creating more protected areas throughout the coverage area of Tropical Dry Forests, favouring a more efficient conservation process.

Environmental indicators can be used to evaluate natural recovery processes. Although several studies have used ant assemblage metrics as environmental indicators, few try to explain the response of these insect assemblages to forest recovery. Thus, we carried out a vertical ant sampling design to verify the sensitivity of ant assemblages from different microhabitats (epigeic, arboreal and hypogeic) to natural forest recovery. We also verified whether changes to the diversity measures (species richness, composition and evenness) of these assemblages could be predictable and explained by changes in the resource quantity and conditions, and structural and resource heterogeneity that also occur along the natural forest recovery gradient. Additionally, we verified the potential of ant species as indicators of forest recovery. We sampled ants in a pasture and seven forest remnants with different recovery times that represent a forest recovery gradient along a chronosequence. Although, the non response of species richness and evenness, species composition changed along the recovery gradient and the dissimilarity between the ant species composition of pasture and forest habitats increased with the age of the forest remnant. This was supported by ant species indicators of pasture and forest areas pointed out by the IndVal test. The variation of ant species composition of the two groups of habitat types (pasture and forest) could be explained by the different responses of open habitat and forest specialist ants to the increase in vegetation cover along the recovery gradient. Therefore, species composition and indicator species by habitat type seems to be the most predictable data for the use of ants in environmental monitoring programs.

Soil compaction, a process that decreases the free space among soil particles and hinders the underground movement of soil organisms, is one of the increasing impacts of mankind on the world’s ecosystems. We investigated the responses of subterranean ants to soil compaction by testing the following predictions: (i) soil from a trail is more compressed, leading to (ii) a decrease in species richness and a selective shift in ant assemblage composition, which is made up by (iii) species with a smaller body size that can apply a greater relative strength to move through soil particles. We carried out this study in and outside of a recreational ecology trail in a forest fragment in Vicosa, MG, Southeastern Brazil. The compaction was higher in the soil from the trail than outside of it. No change was observed in species richness, but soil compaction promoted a shift in ant assemblage composition, with ant size decreasing with an increase in soil compaction. However, ants did not appear to apply a greater strength to soil particles for moving in habitats with a high soil compaction. Overall, organisms at superficial soil layers appeared to be sensitive to even moderate human impacts that promote a filtering of the ant assemblage species composition, with small body size being a required trait.

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.

Remnant isolation following fragmentation is considered to be one of the main drivers of ecological decline in modified landscapes. Thereby, connecting remnants using ecological corridors has been increasingly suggested as being important for conservation. Our objectives were to test isolation effects on extinction, colonization and turnover rates of a litter-dwelling ant assemblage, and to evaluate effectiveness of ecological corridors to mitigate habitat fragmentation consequences. We used a mesocosm manipulative design, with three different isolation treatments: far, near and near connected by a corridor, sampled fortnightly for 60 days. Fragmentation caused an ongoing decrease in ant species richness, probably due to a negative balance between extinction and colonization. Extinction was steady with time, while colonization decreased over the same period. This outcome highlights the key role that colonization plays in the persistence of populations of litter-dwelling ants. Turnover rates increased with time in the treatment with a corridor, but remained steady in the other treatments. We conclude that corridors are important for not only immigration to remnants, but also emigration, acting as a two way traffic route. Thus, it may be an important “leakage” point for threatened species, with implications for their conservation status.

The evaluation of the success of restoration efforts is an essential step for environmental monitoring programs, providing reliable and intricate information on the response of biotic and abiotic elements of ecosystem following the restoration programs adopted. The aim of this study was to evaluate the efficacy of different rehabilitation efforts after gold mining activities using ants as bioindicators. We tested the following hypotheses: (1) the ant species richness and composition vary with the technique of revegetation and (2) the number of epigaeic and hypogaeic ant species increases with resources. We selected four tailing dumps from gold mining, one spontaneously revegetated (“Natural”) and the other three areas with different rehabilitation techniques, namely: Grassy 2005—rehabilitation with grasses in 2005; Grassy 2006—rehabilitation with grasses in 2006, and Shrubby 2004—rehabilitation with grasses, herbaceous, and shrubs in 2004. Ants were sampled using epigaeic and hypogaeic pitfall traps. Species accumulation curves show that the “Natural” area has a higher number of species. We found differences in species composition of epigaeic and hypogaeic ants among the different areas sampled. We conclude that Camponotus fastigatus can be taken as a good indicator of environmental rehabilitation in areas impacted by mining activities. Moreover, Ectatomma edentatum, Dorymyrmex brunneus, Crematogaster evallans, and Solenopsis invicta can also indicate that the rehabilitation process is not yet completed.

High-nutrient patches are important for regulating the structure and physiognomy of dystrophic habitats. Leaf-cutting ants create these rich patches in many neotropical habitats. Burning, however, could diminish or even annul the effects of ant nests on soil properties. To test this hypothesis, we compared the nutrient concentrations at various depths in soil samples near three nests of the leaf-cutting ant Atta laevigata and three non-nest soils, located in 10-ha plots subjected to burning or with fire-protection within a Brazilian cerrado. Root density in ant-nest soil was greater than in non-nest soil in both unburned and burned plots. Besides, the concentration of Ca, Mg, K and P increased 2–50-fold in ant nests from the unburned area compared to non-nest soils. In contrast, nutrient concentrations and pH in burned ant nests were similar to or lower than non-nest soils, but the nests maintained higher values of organic matter and cation exchange capacity. The positive effect of leaf-cutting ant nests as high-nutrient patches may be strongly reduced in habitats with frequent burning. In this case, the negative effects of leaf-cutter herbivory on a plant community could surpass the benefits of local nutrient enrichment by their nests.Resumo: Sauveiros modificam as propriedades físicas e químicas do solo, alterando a estrutura e fisionomia local. Entretanto, queimadas podem reduzir os efeitos dos formigueiros nesses ambientes como, por exemplo, pela diminuição do forrageamento das formigas e, conseqüentemente, pela baixa incorporação de material orgânico ao solo. Este estudo testou o efeito do fogo sobre a concentração de nutrientes no solo de colônias de Atta laevigata em área de cerrado. A densidade de raízes foi maior nas colônias do que áreas controle, independentemente da presença do fogo. Na ausência de queimadas, as concentrações de nutrientes foram até 50 vezes superiores nos sauveiros. Contudo, queimadas reduzem a concentração de nutrientes e pH nas colônias. Possivelmente, essa baixa concentração seja atribuída à maior demanda pela vegetação remanescente, em resposta à perturbação provocada pelo fogo. Nesse caso, os efeitos negativos da herbivoria podem superar os benefícios causados por meio da disponibilização de nutrientes pelos sauveiros.

Summary The dynamics of re-colonisation of disturbed patches may aid in the understanding of spatial variation of species richness. The present study experimentally tested the hypothesis that the variation of litter ant local species richness and composition is caused by the dynamics of re-colonisation after disturbances. We were particularly interested in whether the re-colonisation was by pre-existent species or species new to the patches, and whether the succession of species evidences the existence of dominance-controlled or founder-controlled communities. Litter patches of a forest remnant in Southeast Brazil were disturbed by removing most animals through litter drying, and litter samples were returned to the same sites from where they were removed. Ant species richness and composition were compared before and 2 months after the disturbance. Dissimilarity among disturbed and non-disturbed samples was compared to infer the succession model occurring after disturbance. Ant species richness did not recover after 2 months, and species composition of the disturbed samples showed more new colonisers than pre-existent species. Dissimilarity among samples in the disturbed plots was smaller than in the control plots, indicating a directional, or dominance-controlled, succession. The changes in species composition observed were caused by a decrease of some species, particularly predators, and an increase of species that are possibly opportunistic. Patches of litter are naturally disturbed in time and space, and evidence from the present paper indicates that succession occurring in these patches would lead to different species richness and compositions. Thus the dynamics of re-colonisation contributes to explaining the diversity of litter-dwelling ant communities at larger spatial and temporal scales. In each patch the succession seems to be directional, with opportunist species re-colonising preferentially empty plots. Therefore, these communities may attain a high diversity due to a small-scale patch dynamics model.

Land-cover change and ecosystem degradation may lead to biotic homogenization, yet our under- standing of this phenomenon over large spatial scales and different biotic groups remains weak. We used a multi-taxa dataset from 335 sites and 36 heterogeneous landscapes in the Brazilian Amazon to examine the potential for landscape-scale processes to modulate the cumulative effects of local disturbances. Biotic homogenization was high in production areas but much less in disturbed and regenerating forests, where high levels of among-site and among-landscape b-diversity appeared to attenuate species loss at larger scales. We found consistently high levels of b-diversity among landscapes for all land cover classes, providing support for landscape-scale divergence in species composition. Our findings support concerns that b-diversity has been underestimated as a driver of biodiversity change and underscore the importance of maintaining a distributed network of reserves, including remaining areas of undisturbed primary forest, but also disturbed and regenerating forests, to conserve regional biota.

Aim To t est the Rapoport effect using null models and data sets taken from the literature. We propose an improvement on an existing method, testing the Rapoport effect in elevational and latitudinal distributions when distributions are restricted by sampling. Location Global. Methods First, we hypothesized that real range size distributions are similar to those expected by null assumptions (expected by only imposing boundaries to species distributions). When these distributions were different from those expected under the null assumptions, we tested the hypothesis that these distributions correspond to those expected when a Rapoport effect occurs. We used two simulation methods, random and pseudo-random, which differed only in that the latter one assumes fixed species mid-points, coinciding with real mid-points. Observed correlations between range size and mid-point were compared with the frequency distribution of 1000 simulations, using both simulation methods. We compared the correlation curves generated by 1000 simulations with those of the observed distributions, testing whether correlations indicated a Rapoport effect.

Studies about processes determining biodiversity in Pantanal are urgently needed and the use of invertebrates for this purpose may be an efficient tool. The purpose of this paper is to verify whether ants could be used to predict human impacts on Pantanal, assessing how environmental characteristics of gallery forest influence arboreal ant species richness. Specifically, we tested the hypotheses that: (i) resource availability (estimated by tree density) and (ii) diversity of environmental conditions (estimated by structural heterogeneity) positively influence arboreal ant species richness and composition. Ants were sampled in a gallery forest in the Miranda River. Ant species richness did not respond to tree density, but increased with structural heterogeneity. Species composition was affected both by tree density and structural heterogeneity. The species list produced in the present study showed a high similarity between arboreal ant faunas of Cerrado and Pantanal, which are contiguous biomes. The relationship of ant species richness with heterogeneity, as well as the observed changes of species composition with tree density and heterogeneity may be explained by the presence of a variation of environmental conditions, which create several micro-habitats in the forest. The response of the ant community can reflect human impacts on the forests of the studied region, which are usually modified to create patches for sport fishing and by pathways used in ecotourism.

In this paper, we tested four hypotheses relative to edge and shape effects on ant communities: (i) forest edges have lower species richness than the remnant core; (ii) species richness increases with distance from the edge; (iii) irregularly shaped remnants have lower species richness than more regular remnants; (iv) there is a higher similarity of species composition between edge and core in irregular than in regular remnants. We sampled litter ant communities on the edge and core of ten remnants, in Viçosa, Minas Gerais, Brazil. Species richness was larger at the forest core than at the edges, although did not increase with distance from the edge. Species richness did not vary with shape complexity. The similarity of species composition between edge and core showed a decreasing trend with remnant area, and did not vary with shape complexity. The observed differences of species richness between forest core and edge may be due to higher harshness of edges, caused by environmental changes. The absence of relationship between species richness and distance from the edge might indicate the range of edge effects, which would be smaller than the smallest distance of core sampled. Therefore, edges would affect litter-dwelling ant species richness in a distance smaller than 50 m. The observation of species composition allowed us to notice an effect of fragmentation that would not be noticed if we were considering only species richness. Edge may serve as step to generalist species, which may use it to colonise forest remnants. Furthermore, small remnants are more colonisation-prone by such species, and have a more homogeneous species composition than large remnants.

To study the abundance and occurrence of herbivore insects on plants it is important to consider plant characteristics that may control the insects. In this study the following hypotheses were tested: (i) an increase of plant architecture increases species richness and abundance of gall-inducing insects and (ii) plant architecture increases gall survival and decreases parasitism. Two hundred and forty plants of Baccharis pseudomyriocephala Teodoro (Asteraceae) were sampled, estimating the number of shoots, branches and their biomass. Species richness and abundance of galling insects were estimated per module, and mortality of the galls was assessed. Plant architecture influenced positively species richness, abundance and survival of galls. However, mortality of galling insects by parasitoids was low (13.26%) and was not affected by plant architecture, thus suggesting that other plant characteristics (a bottom-up pressure) might influence gall-inducing insect communities more than parasitism (a top-down pressure). The opposite effect of herbivore insects on plant characteristics must also be considered, and such effects may only be assessed through manipulative experiments.

Many plant species possess structures on their leaves that often harbour predatory or fungivorous mites. These so-called domatia are thought to mediate a mutualistic interaction; the plant gains protection because mites decimate plant pathogenic fungi or herbivores, whereas the mites find shelter in the domatia. We tested this hypothesis using two species of coffee ( Coffea spp.) plants that posses domatia consisting of small cavities at the underside of the leaves, and which often harbour mites. We assessed densities of domatia, of the predatory mite Iphiseiodes zuluagai Denmark and Muma (Acari: Phytoseiidae) and of herbivorous mites Oligonychus ilicis (McGregor) (Acari: Tetranychidae) and Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae) on Coffea arabica L. (Rubiaceae) and Coffea canephora Pierre in the field. Over a period of 50 days, C. arabica harboured on average 7.5 times more predatory mites and 0.4 ‐ 0.66 fewer prey mites than C. canephora . Hence, the higher density of predatory mites on C. arabica could not be explained by higher densities of prey. However, the density of domatia on C. arabica was on average 1.65 times higher than on C. canephora , and within each species, leaves with higher densities of domatia also harboured more predators. This suggests a positive effect of domatia on predatory mites. In the laboratory, survival of adult female predatory mites on leaves of C. arabica with open domatia was indeed significantly higher than on leaves with closed domatia. Hence, predatory mites benefited from the domatia. However, plants with higher densities of domatia did not harbour fewer herbivores. Taken together, our study only provides partial evidence for a mutualistic interaction between coffee plants and predatory mites, mediated by domatia.

The present study aimed to verify (1) whether seasonal increases in neotropical populations of Plutella xylostella are directly provoked by regular influxes of migrants, and (2) whether temporal variation in food availability is the ecological process behind such predictable events. Over 3 years, plants that P. xylostella prefers were cultivated and irrigated in order to provide a continuous and abundant supply of food. Nevertheless, seasonal oscillations in the population of the herbivore still occurred. The hypothesis of seasonal availability of host plants could not explain the population pattern. In April, when the insect was practically extinct from the area, an artificial infestation (immigration) with 10,000 pupae established a precocious population. Therefore, the start of the natural cycles of population growth, during July–August, seems to be due to external factors, rather than an improvement in local conditions for resident individuals. In the beginning of the natural cycles, the increase in the density of adults significantly preceded the increase in immatures. Plutella xylostella does not diapause, and therefore immigration is the proximate cause of the seasonal population increases. Hypotheses about local factors are suggested to explain the decreasing phase of the predictable population cycles.

Several mechanisms may lead to species loss in fragmented habitats, such as edge and shape effects, loss of habitat and heterogeneity. Ants and crickets were sampled in 18 forest remnants in south-eastern Brazil, to test whether a group of small remnants maintains the same insect species richness as similar sized large remnants, at three spatial scales. We tested hypotheses about alpha and gamma diversity to explain the results. Groups of remnants conserve as many species of ants as a single one. Crickets, however, showed a scale-dependent pattern: at small scales there was no significant or important difference between groups of remnants and a single one, while at the larger scale the group of remnants maintained more species. Alpha diversity (local species richness) was similar in a group of remnants and in a single one, at the three spatial scales, both for ants and crickets. Gamma diversity, however, varied both with taxa (ants and crickets) and spatial scale, which may be linked to insect mobility, remnant isolation, and habitat heterogeneity. Biological characteristics of the organisms involved have to be considered when studying fragmentation effects, as well as spatial scale at which it operates. Mobility of the organisms influences fragmentation effects, and consequently conservation strategies.

Ephemeral plants and most tropical crops are available to herbivore insects as irregular and unpredictable patches of resources. Insects that exploit patched habitats usually have well-developed migratory ability, and migration is a fundamental process in the cycle of colonization and extinction of the local populations. We ask here whether Plutella xylostella (Lepidoptera: Yponomeutidae) uses the aging process of the host plant to modulate its migratory activity. The insect was reared in the laboratory on the leaves from the middle estratum (fourth expanded leaves) of cabbage (Brassica oleraceae var. capitata) of various ages, and on leaves from three strata of the mature plant. Females that spent their larval phase in young and tender plants lived for a shorter period of time and laid eggs immediately after metamorphosis. In contrast, mature plants, particularly the new leaves from the superior stratum, favored the development of adult phenotypic traits that occur in migratory forms, such as reduced body size, increased longevity and delayed reproductive activity. We suggest that the lesser nutritional quality and the short temporal persistence of mature plants are selective forces favoring individuals that are better prepared to abandon their habitat soon after emergence. Plutella xylostella may use the predictable ontogenetic changes of the ephemeral host plant to modulate its physiological and behavioral migratory ability.

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.

Aim 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. Location Tropical forest remnants in Vicosa, Minas Gerais, Brazil (20 °45′ S, 42 °50′ W). Methods 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. Results 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. Main conclusions The proposed model, together with proportional sampling, allowed the distinction between sampling effects and other mechanisms.

Processes acting on different spatial and temporal scales may influence local species richness. Ant communities are usually described as interactive and therefore determined by local processes. In this paper we tested two hypotheses linked to the question of why there is local variation in arboreal ant species richness in the Brazilian savanna ('cerrado'). The hypotheses are: (i) there is a positive relationship between ant species richness and tree species richness, used as a surrogate of heterogeneity; and (ii) there is a positive relationship between ant species richness and tree density, used as a surrogate of resource availability. Arboreal ants were sampled in two cerrado sites in Brazil using baited pitfall traps and manual sampling, in quadrats of 20 m � 50 m. Ant species richness in each quadrat was used as the response variable in regression tests, using tree species richness and tree density as explanatory variables. Ant species richness responded positively to tree species richness and density. Sampling site also influenced ant species richness, and the relationship between tree density and tree species richness was also positive and significant. Tree species richness may have influenced ant species richness through three processes: (i) increasing the variety of resources and allowing the existence of a higher number of specialist species; (ii) increasing the amount of resources to generalist species; and (iii) some other unmeasured factor may have influenced both ant and tree species richness. Tree density may also have influenced ant species richness through three processes: (i) increasing the amount of resources and allowing a higher ant species richness; (ii) changing habitat conditions and dominance hierarchies in ant communities; and (iii) increasing the area and causing a species-area pattern. Processes acting on larger scales, such as disturbance, altitude and evolutionary histories, as well as sampling effect may have caused the difference between sites.

In this paper we tested the hypothesis that ant mosaics are generated and maintained by stochastic processes, against the general idea that deterministic processes, such as competition, are the main forces that structure these communities. We analysed 14 published ant mosaics, described for crops and natural forests, transforming their data in presence/absence matrices. These matrices were submitted to species co-occurrence analysis, using software that generates null models. The observed species co-occurrence index was then statistically compared to the null matrices, to test whether there is evidence for biological processes structuring the ant communities. From the 14 mosaics analysed, seven had less and one had more co- occurrence than expected by chance. In six mosaics, species co-occurrence was within the 95% limits of frequency distribution of randomized matrices. Even though the observation of ant spatial distribution, together with association indices between species pairs, have usually been interpreted as a result of negative interactions, our results show that in only 50% of the studied mosaics there is evidence for this explanation. Furthermore, there are alternative hypotheses to explain the result of less co-occurrence than expected by chance, besides the competition hypothesis. Association of ant species with resources and condi- tions may also explain the observed pattern, although these hypotheses are rarely exploited. In conclusion, competition may be an important process when studying assembly rules in ant communities, although it is certainly not the only process involved. The importance of other biological processes and of stochastic events has to be taken into account to explain the species distribution patterns.

Ant communities are generally extremely interactive, and competition between ant species seems to be widespread. This characteristic of ant communities tends to produce a uniform pattern of nest distribution. In this study, we aimed to test the nest distribution pattern, putting forward hypotheses to explain the pattern. Nest mapping was carried out by delimiting ten one-square-meter quadrats, randomly located in a remnant of tropical rainforest in Viçosa, Brazil. In each quadrat, the nests were surveyed in the litter and surface soil up to 3 cm deep. A total of 295 nests from 41 ant species were collected in the ten quadrats. The pattern of nest distribution in the whole forest was aggregated, while the species showed a random distribution. The pattern of nest distribution inside each quadrat was also aggregated. The presence of species, such as Brachymyrmex sp.1 and Hypoponera sp.4 , with high nest densities suggests the occurrence of nest budding. This may be the reason for the aggregated nest distribution. Another explanation for this apparent aggregation is species specialization in a patchily distributed habitat. The results suggest that competition is not an important process in the regulation of soil and litter ants distribution and, consequently, in the regulation of species richness in the studied area.

The species saturation hypothesis in ground-dwelling ant communities was tested, the relationship between local and regional species richness was studied and the possible processes involved in this relationship were evaluated in the present paper. To describe the relationship between local and regional species richness, the ground-dwelling ant fauna of 10 forest remnants was sampled, using 10 1 m 2 quadrats in each remnant. The ants were extracted from the litter by using Winkler sacs. Using regression analyses, an asymptotic pattern between local and regional species richness was detected. This saturated pattern may be related to three processes: (i) high interspecific competition; (ii) habitat species specialization; or (iii) stochastic equilibrium. It is concluded that non-interactive processes, such as stochastic equilibrium and habitat specialization may act as factors regu- lating species richness in this community. The predominance of locally restricted species, in all sampled remnants, seems to indicate the occurrence of a high degree of habitat specialization by the ant species. This result is evi- dence for the hypothesis that community saturation has been generated by non-interactive processes. Although ants are frequently described as highly interactive, it is possible that interspecific competition is not important in the structuring of ground-dwelling ant communities.

A study in a remnant of cerrado vegetation in Sao Paulo State, Brazil, was carried out to investigate the possible role of leaf-cutting ants in the creation of nutrient-rich patches and their consequent influence on plant establishment and growth. The results showed that leaf-cutting ants had neither detectable effect on local nutrient enrichment nor on plant community structure. It is suggested that leaf-cutting ants may affect early successional stages of the vegetation, when colonies are more abundant and disperse into the habitat. Foi feito um estudo em um remanescente de vegetacao de cerrado no Estado de Sao Paulo, com o objetivo de testar o papel das sa£vas na criacao de manchas ricas em nutrientes e sua consequente influencia no estabelecimento e crescimento das plantas. Os resultados mostraram que as sauvas nao tiveram nenhum efeito detectavel no enriquecimento local de nutrientes e nem na estrutura das comunidades vegetais. Sugere-se que as sauvas possam afetar os estadios iniciais da sucessao ve...

We studied the departure rules from flower patches used by bee pollinators of the tropical shrub weed Triumfetta semitriloba Jacq. (Tiliaceae). Flowering plants were distributed in well delimited clumps, in each of two pasture areas (A1 and A2) and one area of forest gap (A3), in Viçosa, southeastern Brazil. Five solitary bee species, Augochlorella michaelis, Augochloropsis cupreola, Pseudocentron paulistana, Ceratinula sp., Melissodes sexcincta, and one social bee, Plebeia droryana, were observed. Three departure rules were examined:(1) "residence time" (time spent per patch); (2) "giving-up time" (time spent in the patch between the last successful resource encounter and departure); (3) "probabilistic rule". Three log-linear models were delineated to analyze the "probabilistic rule" of departure: (1); DP*;TLF*;TPF*;TTP; (2) DP*;TLF*;TPF*;ALF; (3) DP*;TLF*;TPF*;NFV, where DP is departure from the patch; TLF is time spent in the last visited flower; TPF is time spent in penultimate visited flower; TTP is total time spent in the current patch; ALF is activity in the last visited flower; NVF is total number of visited flowers on the current patch. Flowering plants were considered as flower patches. The results showed that the departure from patches of flowers was influenced by intrinsic factors, such as body size, energetic requirements and pollen load size, and by extrinsic factors, such as resource availability and distribution, and density of resource patches. Small bodied bees, with lower energetic requirements and smaller pollen loads (Ceratinula sp. and P. droryana) or bees which occurred in A3, the area with fewer flowers per patch and lower density of flower patches ( Ceratinula sp. and A. michaelis), used a "residence time" departure rule. Species with larger body size or which occurred on areas of higher density of flower patches and with more flowers per patch, A1 and A2 (P. paulistana, M. sexcincta, A. cupreola), used a "probabilistic" role of departure.

In this study, the composition of ant communities was compared in four adjacent phytophysiognomies in Morro dos Conventos Restinga, Brazil. We tested our hypothesis that the ant community composition differs between habitats across a gradient from sea to inland continent. Ant species were sampled with pitfall traps. Overall, 71 ant species were collected. Ant species composition differed between phytophysiognomies. Our results suggest that environments were more similar in the adjacent than in the more distant phytophysiognomies, a pattern similar to the vegetation zonation and gradient sea–inland Restinga. Thirteen species determined more than 50% of the dissimilarity between phytophysiognomies. Solenopsis saevissima was the species that contributed more to ant species composition distinction between phytophysiognomies, followed by Pheidole and Camponotus species. The type of vegetation is one of the main factors affecting the composition of ant communities in Restinga. The role of plants is linked to the availability of resources and conditions and they may determine ant assemblage composition and different interactions occurring in Restinga.

Fire and herbivory are known to modify plant community structure. Many studies have suggested that fire ashes may increase soil nutrients in dystrophic soils. Herbivores may also change plant community structure through direct effects of herbivory and affecting nutrient cycling. Leaf-cutting ants were traditionally viewed as herbivores, although their role may be more complex, because their nests affect both chemical and physical soil properties, thus affecting plants indirectly. We investigated the effects of frequent burning and of leaf-cutting ants on the nutrient status of an herbaceous and a shrub species occurring in the Brazilian Cerrado, a habitat that is characterized by natural burnings. The proximity of ant nests resulted in an increase of nutrients in the leaves of both vegetation strata, whereas burning sometimes resulted in a decrease of nutrients. Our results do not lead to a possible positive effect of fire on plant nutrient content. On the other hand, ant nests may represent an important source of nutrients for plants on the nutrient-depleted Cerrado soils and may accelerate vegetation recovery after burning.