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Wood-boring beetle larvae act as ecosystem engineers by creating stem cavities that are used secondarily as nests by many arboreal ant species. Understanding the heterogeneity and distribution of available cavities and their use by ants is therefore key to understanding arboreal ant community assembly and diversity. Our goals were to quantify the abundance and diversity of beetle-produced cavity resources in a tropical canopy, reveal how ants use these resources, and determine which characteristics of the cavity resource contribute to ant use. We dissected branches from six common tree species in the Brazilian Cerrado savanna, measuring cavity characteristics and identifying the occupants. We sampled 2310 individual cavities, 576 of which were used as nests by 25 arboreal ant species. We found significant differences among tree species in the proportion of stem length bored by beetles, the number of cavities per stem length, average entrance-hole size, and the distribution of cavity volumes. The likelihood that a cavity was occupied was greater for cavities with larger entrance-hole sizes and larger volumes. In particular, there was a strong positive correlation between mean head diameters of ant species and the mean entrance-hole diameter of the cavities occupied by those ant species. Wood-boring beetles contribute to the structuring of the Cerrado ant community by differentially attacking the available tree species. In so doing, the beetles provide a wide range of entrance-hole sizes which ant species partition based on their body size, and large volume cavities that ants appear to prefer.

Fire-suppression is of concern in fire-prone ecosystems because it can result in the loss of endemic species. Suppressing fires also causes a build-up of flammable biomass, increasing the risk of severe fires. Using a Before-After, Control-Impacted design, we assessed the consequences of high-severity fires on Neotropical savanna arboreal ant communities. Over a 9-year period, we sampled the ant fauna of the same trees before and after two severe fires that hit a savanna reserve in Brazil and the trees from an unburned savanna site that served as a temporal control. The ant community associated with the unburned trees was relatively stable, with no significant temporal variation in species richness and only a few species changing in abundance over time. In contrast, we found a strong decline in species richness and marked changes in species composition in the burned trees, with some species becoming more prevalent and many becoming rare or locally extinct. The dissimilarity in species richness and composition was significantly smaller between the two pre-fire surveys than between the pre-and post-fire surveys. Fire-induced changes were much more marked among species with strictly arboreal nesting habits, and therefore more susceptible to the direct effects of fire. The decline of some of the ecologically dominant arboreal ant species may be particularly important, as it opens substantial ecological space for cascading community-wide changes. In particular, severe fires appear to disrupt the typical vertical stratification between the arboreal and ground-dwelling faunas, which might lead to homogenization of the overall ant community.

Territoriality is costly, and the accurate identification of intruders and the decision to perform aggressive responses are key behavioral traits in social animals. We studied aggression among individuals belonging to close and distant nests of the plant-ant Azteca muelleri , which lives in stems of the pioneer tree Cecropia glaziovii . More specifically, we aim to investigate if the DE (dear-enemy effect—less aggression towards neighbors than strangers) or NN (nasty-neighbor effect—less aggression to strangers than neighbors) effects or even none of them apply for this iconic Azteca-Cecropia system. We further checked if ant aggression towards conspecifics is related to cuticular hydrocarbon profiles (CHCs), which provide chemical cues for nestmate recognition. Therefore, we sampled 46 nests of A . muelleri in three Brazilian Atlantic forest fragments and performed behavioral trials within and between sites. Consistently with the DE effect, we found higher aggression levels in ‘between sites’ versus ‘within sites’ treatments as well as a positive effect of spatial distance on ant aggressiveness. We found no effect of the overall dissimilarities on CHC blend on ant aggressiveness, but of one CHC class, the methylated alkanes. Overall, we provide key insights on nest-mate recognition in obligatory ant-plant mutualisms.

An understanding of the spatiotemporal patterns of species distribution is a major goal in community ecology. This understanding is particularly challenging for highly seasonal and diverse habitats, such as transition zones between major biomes, like the Cerrado-Amazon transition (CAT). Within the CAT, there are many kinds of vegetation, including the ecotonal forests, marked by a high seasonality and floristic elements belonging to both surrounding biomes. Here, our primary goal is to examine the temporal variation of ant communities in ecotonal forest fragments of the CAT. More specifically, we assessed whether arboreal ants and ground-dwelling ants responded differently to seasonality. Thus, we sampled ants in the arboreal and ground strata, across the dry and wet season, in six ecotonal forest fragments in the CAT. We found that the seasonal variation was higher for ground-dwelling than arboreal ant communities, and only ground-dwelling ants differed in species richness between dry and wet seasons.Implications for conservationOur results show that ground-dwelling ant communities are more sensitive to seasonal variation than are arboreal ants. These ants often represent the bulk of ant diversity in tropical forests, and the current climate change scenario can be particularly harmful to them. Therefore, future conservation practices need to give special attention to ground-dwelling ants, especially in the CAT, facing increasing anthropogenic pressure.

Ecologically dominant species can shape the assembly of ecological communities via altering competitive outcomes. Moreover, these effects may be amplified under limited niche differentiation. Nevertheless, the influences of ecological dominance and niche differentiation on assembly are rarely considered together. Here, we provide a novel examination of dominance in a diverse arboreal ant community, defining dominance by the prevalent usage of nesting resources and addressing how it influences community assembly. We first used a series of quantitative observational and experimental studies to address the natural nesting ecology, colony incidence on surveyed trees, and level of dominance over newly available nesting resources by our focal species, Cephalotes pusillus. The experimental studies were then used further to examine whether C. pusillus shapes assembly via an influence on cavity usage by co-occurring species. C. pusillus was confirmed as a dominant user of cavity nesting resources, with highly generalized nesting ecology, occupying about 50% of the trees within the focal system, and accounting for more than a third of new cavity occupation in experiments. Our experiments showed further that the presence of C. pusillus was associated with modest effects on species richness, but significant decreases in cavity-occupation levels and significant shifts in the entrance-size usage by co-occurring species. These results indicate that C. pusillus, as a dominant user of nesting resources, shapes assembly at multiple levels. Broadly, our findings highlight that complex interactions between a dominant species and the resource-usage patterns of other species can underlie species assembly in diverse ecological communities.

Interspecific trade-offs in foraging strategies can facilitate species coexistence in diverse communities with overlapping resource use, especially in taxa with complex social-foraging strategies. The discovery-dominance trade-off hypothesis is often invoked to help explain coexistence of ant species that use overlapping food resources, wherein colonies of some species are better at collectively discovering new food, while others have superior social fighting abilities to subsequently assert dominance over a resource. This hypothesis has yet to be tested in diverse arboreal ant communities. We assessed the competitive outcomes of arboreal ants at new food resources and further asked if the number of ants present and their body size influenced the observed outcomes. We did not find support for a discovery-dominance trade-off. Instead, we identified a discovery-defense strategy, where in the first species to collectively forage at a new food resource usually defended it successfully from other species. This suggests that the discovery phase is the most important for determining the outcome of competition over food in arboreal ants. This importance was further supported by the insight that the number of ants present largely determined the access of species to food resources, not individual body size. Broadly, our results suggest that although arboreal ants rely on similar food resources, coexistence may be mediated in part by the prevalence of the discovery-defense strategy: most species have the capacity to be the first to discover newly available food resources within the complex canopy, and discovery is coupled with the ability to defend a new food resource long enough to benefit from it.

Unraveling the spatiotemporal dynamics of communities is critical to understand how biodiversity responds to global changes. However, this task is not trivial, as these dynamics are quite complex, and most studies are limited to few taxa at small local and temporal scales. Tropical mountains are ideal indicators of biodiversity response since these endangered and complex ecosystems include many distinct habitats within small geographical areas, harboring a megadiverse fauna, especially insects. Indeed, while insects are particularly sensitive to environmental and climatic changes, the extent of the impact of climate variability on mountain tropical insect diversity remains poorly understood. Here we present time‐series data from a decade of studying the spatiotemporal dynamics of ants, butterflies and dung beetles. We assessed patterns of species richness change along the elevational gradient for each taxonomic group per sampling year and cumulatively over years. We then quantified community changes over time by measuring the variation in species richness across sampling years (temporal trends in α‐diversity), and the temporal variation in species composition (temporal β‐diversity) evaluating species gains and losses over time. We also evaluated the variation of air temperature and humidity through meteorological stations within the sampling years. We detected a classical pattern of species richness decline with elevation, albeit with a noticeable increase in species richness variation with increasing elevation. The temporal β‐diversity exhibited considerable variability across elevations, taxa, and time. Only dung beetles presented a positive relationship with humidity variation over the years. Critically, both rare and common species drove extirpations and colonizations, and we found no trend of temporal decline of insect species at local and regional scales. Our study shows that insect metacommunity responses to elevation and global changes are rather complex, and stresses the importance of long‐term studies that incorporate multiple sampling periods and different groups of organisms in tropical mountains.

There is often a vertical stratification of the vegetation in tropical forests, where each forest stratum has a unique set of environmental conditions, including marked differences in habitat heterogeneity, physical complexity, and microclimate. Additionally, many tropical forests are highly seasonal, and we need to consider the temporal variation in environmental conditions when assessing the functional aspects of their organisms. Here, we tested the hypothesis that vertical stratification and seasonality shape tropical ants’ functional ecology and that there are differences in the functional trait diversity and composition between arboreal and ground-dwelling ant communities. We collected ants in the arboreal and ground strata in the rainy and dry seasons in six different areas, measuring seven morphological traits to characterize their functional ecology and diversity. Irrespective of the season, we found a distinct functional composition between arboreal and ground-dwelling ants and a higher functional richness on the ground. However, ground ants were more functionally redundant than arboreal ants. The differences in functional richness and redundancy between ant inhabiting strata and season could also be observed in the community-weighted mean traits: arboreal and ground ant traits can be distinguished in Weber’s length, mandible length, eye length, and eye position on the head capsule. The differences in these functional traits are mainly related to the ants’ feeding habits and the complexity of their foraging substrates. Overall, by providing the first systematic comparison of continuous traits between arboreal and ground-dwelling ants, our study opens new investigation paths, indicating important axes of functional diversification of tropical ants.

We evaluated how habitat type influences community temporal dynamics in a heterogeneous tropical mountain landscape. We sampled ants, dung beetles, and fruit-feeding butterflies across two mountaintop habitats: campo rupestre and forest islands in the Southern Espinhaço Range, Brazil. We quantified temporal dynamics by assessing variations in species richness across sampling years and in species composition, focusing on species gains and losses. Species richness did not differ between environments and most species were unique to either campo rupestre or forest islands. We found no consistent pattern of species gains or losses among insect communities or habitat types, with such temporal dynamics being more prevalent for butterflies in the campo rupestre . In the campo rupestre , recent periods were dominated by colonization-driven homogenization following widespread species losses. In forest islands, extirpations prevailed for ants, colonizations for butterflies, and processes were balanced for dung beetles. The campo rupestre showed greater temporal dynamics in species richness and composition, particularly for butterflies and dung beetles, resulting in more frequent species gains. Habitat type shapes the temporal dynamics of insect communities in heterogeneous tropical mountaintop landscapes. Forest islands sustain more temporally stable insect metacommunities, while open environments and more mobile organisms have greater temporal dynamics.

The Earth's most diverse group of organisms is facing an imminent crisis, as recent investigations suggest a remarkable decline in insect diversity. Within this context, altimontane forest islands might emerge as important refuges holding an invaluable diversity of species that would be doomed to disappear. Here, we aimed to examine the impact of fire on the temporal variation of ant, bee, butterfly, dung beetle, and wasp communities in natural and highly threatened altimontane forest islands. We predicted that fire incidence would increase the natural variation in the structure of these insects' communities over time. Furthermore, we predicted that each taxon would respond accordingly to their ability to move between forest islands (i.e., vagility). We sampled these five bioindicator taxa in the rainy seasons of 2014, 2015, 2018, and 2020 within 14 forest islands in southeast Brazil. We assessed the incidence (presence/absence) of fire occurrence on each forest island toward the end of the dry season in each sampling year. We found an influence of fire incidence on the species composition changes over time (temporal β‐diversity) in the less vagile insect groups: ants, and dung beetles. Nevertheless, we found no influence of fire incidence on shifts in species composition of highly vagile insects: bees, butterflies, and wasps. Importantly, species turnover was the primary component of temporal β‐diversity driving the interannual variation of all insect taxa examined in this study. Our results highlight the distinct responses of more‐or‐less vagile insect groups to fire in forested ecosystems and shed light on the drivers of vulnerability and resilience of these groups to this critical anthropogenic pressure. By understanding and elucidating the intricate responses of distinct insect communities to global stressors, we can strengthen our capacity to predict future trends in biodiversity decline and provide valuable insights for conservation efforts and environmental management strategies. Fire incidence influences changes in species composition over time (temporal β‐diversity) in less vagile insect groups (ants and dung beetles). Species turnover is the primary component of temporal β‐diversity driving the interannual variation of all insect taxa examined in this study.