Simulated biomechanical performance of morphologically disparate ant mandibles under bite loading

Insects evolved various modifications to their mouthparts, allowing for a broad exploration of feeding modes. In ants, workers perform non-reproductive tasks like excavation, food processing, and juvenile care, relying heavily on their mandibles. Given the importance of biting for ant workers and the significant mandible morphological diversity across species, it is essential to understand how mandible shape influences its mechanical responses to bite loading. We employed Finite Element Analysis to simulate biting scenarios on mandible volumetric models from 25 ant species classified in different feeding habits. We hypothesize that mandibles of predatory ants, especially trap-jaw ants, would perform better than mandibles of omnivorous species due to their necessity to subdue living prey. We defined simulations to allow only variation in mandible morphology between specimens. Our results demonstrated interspecific differences in mandible mechanical responses to biting loading. However, we found no evident differences in biting performance between the predatory and the remaining ants, and trap-jaw mandibles did not show lower stress levels than other mandibles under bite loading. These results suggest that ant feeding habit is not a robust predictor of mandible biting performance, a possible consequence of mandibles being employed as versatile tools to perform several tasks.

The effects of pollution by multiple metals derived from long-term smelting activities on soil mite communities in arable soils under different land use types in East China

Soil pollution represents a threat to soil biodiversity and to soil and human health. However, many ecotoxicological issues, such as the impact of heavy metal pollution on the soil mite community and its spatial distribution in areas with complex environmental factors, are not fully understood. Here, an investigation was conducted in an arable area (about 11 km²) enclosed by surrounding mountains. The study area was contaminated with potentially toxic metals derived from copper smelting that was functioning for over 10 years. The area comprised four land use types: woodlands, dry fields, paddy fields, and wastelands, and was divided into 141 study sites each with an area of 6.25 ha. The soil metal (Cu, Zn, Pb, and Cd) contents, pH, and organic matter were determined and their distributions were established. Furthermore, soil mite (Acari) community properties (species richness, individual abundance, and Shannon-Wiener diversity index) were determined, and the distributions of total species number and abundance were ascertained. Soil metal pollution strongly reduced soil mite community, but the effects depended on mite groups or species and their sensitivity to different metals as well as land use types. CANOCO analysis revealed that the order Oribatida was more highly correlated with soil metal contents, whereas the other three orders responded to soil metal contents depending on land use types, mite properties, or metals. SADIE method indicated that the coordinate relationship between mite species number and metal concentration was more negative (4-25% of the study sites) than positive (4-12%). The metal pollution levels in the soil were evaluated by single and integrated pollution and ecological risk indices.

The role of morphological traits in predicting the functional ecology of arboreal and ground ants in the Cerrado-Amazon transition

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.

Ecological strategies of (pl)ants: Towards a world-wide worker economic spectrum for ants

Current global challenges call for a rigorously predictive ecology. Our understanding of ecological strategies, imputed through suites of measurable functional traits, comes from decades of work that largely focussed on plants. However, a key question is whether plant ecological strategies resemble those of other organisms.Among animals, ants have long been recognised to possess similarities with plants: as (largely) central place foragers. For example, individual ant workers play similar foraging roles to plant leaves and roots and are similarly expendable. Frameworks that aim to understand plant ecological strategies through key functional traits, such as the 'leaf economics spectrum', offer the potential for significant parallels with ant ecological strategies.Here, we explore these parallels across several proposed ecological strategy dimensions, including an 'economic spectrum', propagule size-number trade-offs, apparency-defence trade-offs, resource acquisition trade-offs and stress-tolerance trade-offs. We also highlight where ecological strategies may differ between plants and ants. Furthermore, we consider how these strategies play out among the different modules of eusocial organisms, where selective forces act on the worker and reproductive castes, as well as the colony.Finally, we suggest future directions for ecological strategy research, including highlighting the availability of data and traits that may be more difficult to measure, but should receive more attention in future to better understand the ecological strategies of ants. The unique biology of eusocial organisms provides an unrivalled opportunity to bridge the gap in our understanding of ecological strategies in plants and animals and we hope that this perspective will ignite further interest. Read the free Plain Language Summary for this article on the Journal blog.

Data of ant community compositions and functional traits responding to land-use change at the local scale

Aim: Off-reserve conservation is a major contributor to China biodiversity conservation efforts, biodiversity conservation being achieved within afforestation and low-intensity agriculture in fragmented landscapes. Functional trait is more strongly related to ecological processes than taxonomic diversity and reflects ecosystem functioning and species responses to environmental changes. In this study, we selected five habitats that differ in degree of disturbance to explore the effects of land use on ant community compositions, traits distributions and functional diversity change. We assessed how habitat disturbance affects the ant community compositions and traits distributions and asked if ant functional diversity respond to disturbance at the local scale? Location: Lüchun County, Yunnan Province, southwest China. Methods: Pitfall traps were used to survey ant communities. Additionally, we measured four ant morphological traits (eyes diameter, distance between eyes, femur length of the hind-leg and Weber's length) to assess the functional traits distributions and functional diversity. Shade plot of ant relative abundance was used to explore species distribution amongst different habitats. Kernel density plot was used to explore ant traits distribution patterns amongst different habitats. Non-metric multi-dimensional scaling ordination, based on ant Weber's length, was used to explore the ant traits compositions amongst different habitats. The fourth corner model was used to evaluate the association between ant traits and environmental variables. The FR_ic, RaoQ and FE_ve indices were selected as three complementary measures of the multivariate functional traits space and functional redundancy of different habitats. Results: We collected 14258 ants, representing 89 species, 40 genera and seven subfamilies. Aphaenogasterschurri and Tetramoriumciliatum were the common species of secondary forest; P.sagei, P.pieli, Cardiocondylawroughtonii, Recurvidrisnuwa, Tapinnomamelanocephalum, Monomoriumpharaonis and M.orientale were the common species in plantations; and Iridomyrmexanceps and Cardiocondylanuda were the common species in managed farms. Ants had medium eye diameters, narrow distances between eyes, medium leg lengths and smaller body sizes in greatly-disturbed habitats; and ants had an increasing eye diameter and narrowing of the space between eyes, while the leg length and Weber's length became shorter in moderately-disturbed habitats. Ant trait composition, based on Weber's length, showed significantly differences amongst five habitats. The fourth corner analysis indicated that ant species traits were significantly correlated with environmental variables. The functional diversity of secondary forest, lac plantation and lac plantation-corn agroforest were higher than those in dryland farm and rice paddy. Functional diversities were significantly negatively correlated with bare ground cover and significantly positively correlated with leaf-litter cover, leaf-litter thickness and plant cover. Main conclusion: Our results indicated that ant traits distribution patterns were affected by land-use changes, followed by anthropogenic disturbance pressures at the local scale. Ant traits compositions in greatly-disturbed habitats also differed from the habitats with less disturbance. It is unfavourable for the survival of the large body-size ants in more open habitats with more anthropogenic disturbance. Compared with secondary forest, dryland farm and rice paddies were less resistant and more vulnerable and lac plantations had approximately functional diversity of ant communities, suggesting that lac plantations might be resistant as secondary forest to species loss.

Alpha and beta phylogenetic diversities jointly reveal ant community assembly mechanisms along a tropical elevational gradient

Despite the long-standing interest in the organization of ant communities across elevational gradients, few studies have incorporated the evolutionary information to understand the historical processes that underlay such patterns. Through the evaluation of phylogenetic α and β-diversity, we analyzed the structure of leaf-litter ant communities along the Cofre de Perote mountain in Mexico and evaluated whether deterministic- (i.e., habitat filtering, interspecific competition) or stochastic-driven processes (i.e., dispersal limitation) were driving the observed patterns. Lowland and some highland sites showed phylogenetic clustering, whereas intermediate elevations and the highest site presented phylogenetic overdispersion. We infer that strong environmental constraints found at the bottom and the top elevations are favoring closely-related species to prevail at those elevations. Conversely, less stressful climatic conditions at intermediate elevations suggest interspecific interactions are more important in these environments. Total phylogenetic dissimilarity was driven by the turnover component, indicating that the turnover of ant species along the mountain is actually shifts of lineages adapted to particular locations resembling their ancestral niche. The greater phylogenetic dissimilarity between communities was related to greater temperature differences probably due to narrow thermal tolerances inherent to several ant lineages that evolved in more stable conditions. Our results suggest that the interplay between environmental filtering, interspecific competition and habitat specialization plays an important role in the assembly of leaf-litter ant communities along elevational gradients.

Asynchrony in Seasonal Patterns of Taxonomic and Functional Diversity in an Aboveground Ant (Hymenoptera: Formicidae) Community (Florida, USA)

Seasonal dynamics of diversity patterns are a key component to understand when assessing ecological communities across temporal scales given that long-term trends in diversity are often a product of the intricate dynamisms that occur at shorter temporal scales. However, seasonal trends in diversity are usually dependent on local-scale conditions, such as habitat types or the demographic characteristics of a given fauna, thus requiring better data coverage from consistent local-scale sampling. Furthermore, the assessment of seasonal dynamics in the context of functional diversity derived from trait-based data is often lacking in many important taxa such as insects. In this study, I quantify and describe the diversity of a Floridian subtropical aboveground ant community from monthly sampling across seasons using both contemporary taxonomic diversity metrics and functional diversity metrics. Results show differences in the timing of peaks across different diversity metrics. Species richness and abundances peak in months leading up to wet seasons while functional richness and divergence peak near the end of the wet season. This asynchrony is likely a result of species-specific differences in natural histories and demographic dynamics. While clear temporal dynamics are observed across diversity metrics, differences between wet or dry seasons were lacking for all metrics except functional richness. Fine-scale sampling data of seasonal trends in insect communities compiled from studies like this will be essential tools for future assessments and predictions of insect biodiversity.

Vertical stratification of insect abundance and species richness in an Amazonian tropical forest

Tropical forests are among the most biodiverse biomes on the planet. Nevertheless, quantifying the abundance and species richness within megadiverse groups is a significant challenge. We designed a study to address this challenge by documenting the variability of the insect fauna across a vertical canopy gradient in a Central Amazonian tropical forest. Insects were sampled over two weeks using 6-m Gressitt-style Malaise traps set at five heights (0 m–32 m–8 m intervals) on a metal tower in a tropical forest north of Manaus, Brazil. The traps contained 37,778 specimens of 18 orders of insects. Using simulation approaches and nonparametric analyses, we interpreted the abundance and richness of insects along this gradient. Diptera, Hymenoptera, and Coleoptera had their greatest abundance at the ground level, whereas Lepidoptera and Hemiptera were more abundant in the upper levels of the canopy. We identified species of 38 of the 56 families of Diptera, finding that 527 out of 856 species (61.6%) were not sampled at the ground level. Mycetophilidae, Tipulidae, and Phoridae were significantly more diverse and/or abundant at the ground level, while Tachinidae, Dolichopodidae, and Lauxaniidae were more diverse or abundant at upper levels. Our study suggests the need for a careful discussion of strategies of tropical forest conservation based on a much more complete understanding of the three-dimensional distribution of its insect diversity.

The contribution of the BIOTA/FAPESP Program to the advancement of the knowledge on terrestrial invertebrates

Abstract The variability of the organisms living in a given area constitute what is referred to as biodiversity, one of nature’s fundamental properties, responsible for the balance and stability of ecosystems. The loss of biodiversity has been of great concern to scientists, especially because of the role played by human activities in this regard, able to lead to irreversible circumstances. The São Paulo Research Foundation (Fundação de Amparo à Pesquisa do Estado de São Paulo, FAPESP) plays a major role in supporting research efforts in the most diverse branches of science. In the late 1990´s, FAPESP launched a major program to promote research on biodiversity, named BIOTA/FAPESP. So far, this program has financed the conduction of 26 projects, involving research activities in most of Brazil, while focusing mainly the State of São Paulo. These projects have generated about 1140 publications in peer-reviewed journals of high standard, providing relevant information, including the original description of 1187 species and 76 genera, the complementary description of 350 species, as well as a number of inventory works, biological studies, etc. The program has also been instrumental in the establishment or adequacy of research facilities and training of new taxonomists. Most extensively studied groups of terrestrial invertebrates include Insecta of the orders Hymenoptera, Lepidoptera and Diptera, and Arachnida of the subclasses Araneae and Acari. Distinct projects have also contributed to the detection of organisms potentially useful as biological control agents and in the determination of maps of major interest for the establishment of public policies. In the future, priority groups for study should include the Annelida and the Nematoda, for the potential both have as beneficial organisms, or for the potential some Nematoda have as organisms harmful to plants and animals.

Digging Deeper into the Ecology of Subterranean Ants: Diversity and Niche Partitioning across Two Continents

Soil fauna is generally understudied compared to above-ground arthropods, and ants are no exception. Here, we compared a primary and a secondary forest each on two continents using four different sampling methods. Winkler sampling, pitfalls, and four types of above- and below-ground baits (dead, crushed insects; melezitose; living termites; living mealworms/grasshoppers) were applied on four plots (4 × 4 grid points) on each site. Although less diverse than Winkler samples and pitfalls, subterranean baits provided a remarkable ant community. Our baiting system provided a large dataset to systematically quantify strata and dietary specialisation in tropical rainforest ants. Compared to above-ground baits, 10–28% of the species at subterranean baits were overall more common (or unique to) below ground, indicating a fauna that was truly specialised to this stratum. Species turnover was particularly high in the primary forests, both concerning above-ground and subterranean baits and between grid points within a site. This suggests that secondary forests are more impoverished, especially concerning their subterranean fauna. Although subterranean ants rarely displayed specific preferences for a bait type, they were in general more specialised than above-ground ants; this was true for entire communities, but also for the same species if they foraged in both strata.

Venom Function of a New Species of Megalomyrmex Forel, 1885 (Hymenoptera: Formicidae)

Alkaloids are important metabolites found across a variety of organisms with diverse ecological functions. Of particular interest are alkaloids found in ants, organisms well known for dominating the ecosystems they dwell in. Within ants, alkaloids are found in venom and function as potent weapons against heterospecific species. However, research is often limited to pest species or species with parasitic lifestyles and thus fails to address the broader ecological function of ant venom alkaloids. Here we describe a new species of free-living Megalomyrmex ant: Megalomyrmex peetersi sp. n. In addition, we identify its singular venom alkaloid (trans-2-butyl-5-heptylpyrrolidine) and elucidate the antibiotic and insecticidal functions of its venom. Our results show that Megalomyrmex peetersi sp. n. venom is an effective antibiotic and insecticide. These results are comparable to venom alkaloids found in other ant species, such as Solenopsis invicta. This research provides great insight into venom alkaloid function, and it is the first study to explore these ideas in the Megalomyrmex system.

Spine and dine: A key defensive trait promotes ecological success in spiny ants

A key focus of ecologists is explaining the origin and maintenance of morphological diversity and its association with ecological success. We investigate potential benefits and costs of a common and varied morphological trait, cuticular spines, for foraging behavior, interspecific competition, and predator-prey interactions in naturally co-occurring spiny ants (Hymenoptera: Formicidae: Polyrhachis) in an experimental setting. We expect that a defensive trait like spines might be associated with more conspicuous foraging, a greater number of workers sent out to forage, and potentially increased competitive ability. Alternatively, consistent with the ecological trade-off hypothesis, we expect that investment in spines for antipredator defense might be negatively correlated with these other ecological traits. We find little evidence for any costs to ecological traits, instead finding that species with longer spines either outperform or do not differ from species with shorter spines for all tested metrics, including resource discovery rate and foraging effort as well as competitive ability and antipredator defense. Spines appear to confer broad antipredator benefits and serve as a form of defense with undetectable costs to key ecological abilities like resource foraging and competitive ability, providing an explanation for both the ecological success of the study genus and the large number of evolutionary origins of this trait across all ants. This study also provides a rare quantitative empirical test of ecological effects related to a morphological trait in ants.

Twigs occupied by Pheidole Westwood, 1839: Is there a difference between species?

Abstract: Pheidole is a genus with wide geographical distribution and diversity, especially in the leaf litter of neotropical forests, where nests are found at the soil-litter interface, in the soil and vegetation, among leaves, seeds, and twigs. Despite the availability of twigs and Pheidole species diversity in the leaf litter, most of this resource is not occupied, which suggests the existence of filters. This study analyzes whether twigs occupied by Pheidole species differ for the outer structure and anatomy of the wood. Twigs were collected from preserved Atlantic Forest fragments in southeastern Brazil. Twigs with Pheidole colonies were measured and the wood anatomy analyzed. We collected 224 twigs with Pheidole colonies, but the analysis was done at 41% due to wood decomposition. Five species were recorded in these twigs, which differ for the outer structure and anatomy of the wood. These results suggest the existence of preference in the occupation of twigs determined by wood structure.

Functional richness shows spatial scale dependency in Pheidole ant assemblages from Neotropical savannas

There is a growing recognition that spatial scale is important for understanding ecological processes shaping community membership, but empirical evidence on this topic is still scarce. Ecological processes such as environmental filtering can decrease functional differences among species and promote functional clustering of species assemblages, whereas interspecific competition can do the opposite. These different ecological processes are expected to take place at different spatial scales, with competition being more likely at finer scales and environmental filtering most likely at coarser scales. We used a comprehensive dataset on species assemblages of a dominant ant genus, Pheidole, in the Cerrado (savanna) biodiversity hotspot to ask how functional richness relates to species richness gradients and whether such relationships vary across spatial scales. Functional richness of Pheidole assemblages decreased with increasing species richness, but such relationship did not vary across different spatial scales. Species were more functionally dissimilar at finer spatial scales, and functional richness increased less than expected with increasing species richness. Our results indicate a tighter packing of the functional volume as richness increases and point out to a primary role for environmental filtering in shaping membership of Pheidole assemblages in Neotropical savannas.

OPEN RESEARCH BADGES

This article has been awarded Open Materials, Open Data, Preregistered Research Designs Badges. All materials and data are publicly accessible via the Open Science Framework at https://doi.org/10.5061/dryad.31201jg.

Low levels of intraspecific trait variation in a keystone invertebrate group

The trait-based approach to ecology promises to provide a mechanistic understanding of species distributions and ecosystem functioning. Typically, trait analyses focus on average species trait values and assume that intraspecific variation is small or negligible. Recent work has shown, however, that intraspecific trait variation can often contribute substantially to total trait variation. Whilst many studies have investigated intraspecific variation in plants, very few have done so for invertebrates. There is no research on the level of intraspecific trait variation in ants (Hymenoptera: Formicidae), despite the fact that there is a growing body of literature using ant morphological trait data and demonstrating that these insects play important roles in many ecosystems and food webs. Here, we investigate the intraspecific variability of four commonly used ant morphological traits from 23 species from the Maloti-Drakensberg Mountains of southern Africa. In total, we measured 1145 different individuals and made 6870 trait measurements. Intraspecific variation accounted for only 1–4% of total trait variation for each of the four traits we analysed. We found no links between intraspecific variation, phylogeny and elevation. On average, six individuals generated robust species means but under biased sampling scenarios 20 individuals were needed. The low levels of intraspecific morphological variation that we find suggest that the approach of using mean species traits is valid, in this fauna at least. Regardless, we encourage ant trait ecologists to measure greater numbers of individuals, especially across gradients, to shed further light on intraspecific variation in this functionally important group of insects.

Amazonian deforestation and soil biodiversity

Clearance and perturbation of Amazonian forests are one of the greatest threats to tropical biodiversity conservation of our times. A better understanding of how soil communities respond to Amazonian deforestation is crucially needed to inform policy interventions that effectively protect biodiversity and the essential ecosystem services it provides. We assessed the impact of deforestation and ecosystem conversion to arable land on Amazonian soil biodiversity through a meta-analysis. We analyzed 274 pairwise comparisons of soil biodiversity in Amazonian primary forests and sites under different stages of deforestation and land-use conversion: disturbed (wildfire and selective logging) and slash-and-burnt forests, pastures, and cropping systems. Overall, 60% and 51% of responses of soil macrofauna and microbial community attributes (i.e., abundance, biomass, richness, and diversity indexes) to deforestation were negative, respectively. We found few studies on mesofauna (e.g., microarthropods) and microfauna (e.g., protozoa and nematodes), so those groups could not be analyzed. Macrofauna abundance and biomass were more vulnerable to the displacement of forests by pastures than by agricultural fields, whereas microbes showed the opposite pattern. Effects of Amazonian deforestation on macrofauna were more detrimental at sites with mean annual precipitation >1900 mm, and higher losses of microbes occurred in highly acidic soils (pH < 4.5). Limited geographic coverage, omission of meso- and microfauna, and low taxonomic resolution were main factors impairing generalizations from the data set. Few studies assessed the impacts of within-forest disturbance (wildfires and selective logging) on soil species in Amazonia, where logging operations rapidly expand across public lands and more frequent severe dry seasons are increasing the prevalence of wildfires.

Taxonomic and Functional Ant Diversity Along tropical, Subtropical, and Subalpine Elevational Transects in Southwest China

Although elevational gradients of biodiversity have long been the topic of scientific research, information on patterns of, and processes that shape insect community structure across elevation is still lacking. Addressing this gap requires the use of both taxonomic and functional approaches when studying diversity across elevational gradients. In this study, we examined taxonomic and functional alpha and beta diversity of ant assemblages sampled along tropical, subtropical, and subalpine elevational transects in Yunnan Province, southwest China. Species richness was used to quantify taxonomic alpha diversity, and two indices (FD and FRic) were calculated using morphological measurements to quantify functional alpha diversity. Taxonomic and functional beta diversity were partitioned into their turnover- and nestedness-resultant components. Though temperature and functional alpha diversity decreased linearly with increasing elevation, taxonomic alpha diversity showed a significant logarithmic decrease, with few species present at elevations greater than 3000 m a.s.l. The turnover-resultant component of taxonomic beta diversity increased with increasing elevational distance, while the nestedness-resultant component of functional beta diversity increased with increasing elevational distance in the subtropical transect. The observed patterns of taxonomic and functional diversity reflected ants’ thermophilic nature, implying functional adaptations (i.e., nested functional diversity) at higher elevations where environmental conditions were unfavorable.

Habitats shape taxonomic and functional composition of Neotropical ant assemblages

Determining assembly rules of co-occurring species persists as a fundamental goal in community ecology. At local scales, the relative importance of environmental filtering vs. competitive exclusion remains a subject of debate. In this study, we assessed the relative importance of habitat filtering and competition in structuring understory ant communities in tropical forests of French Guiana. Leaf-litter ants were collected using pitfall and Winkler traps across swamp, slope and plateau forests near Saül, French Guiana. We used a combination of univariate and multivariate analyses to evaluate trait response of ants to habitat characteristics. Null model analyses were used to investigate the effects of habitat filtering and competitive interactions on community assembly at the scale of assemblages and sampling points, respectively. Swamp forests presented a much lower taxonomic and functional richness compared to slope and plateau forests. Furthermore, marked differences in taxonomic and functional composition were observed between swamp forests and slope or plateau forests. We found weak evidence for competitive exclusion based on null models. Nevertheless, the contrasting trait composition observed between habitats revealed differences in the ecological attributes of the species in the different forest habitats. Our analyses suggest that competitive interactions may not play an important role in structuring leaf-litter ant assemblages locally. Rather, habitats are responsible for driving both taxonomic and functional composition of ant communities.

Co-occurrence Patterns in a Subtropical Ant Community Revealed by Complementary Sampling Methodologies

Ants are abundant and ecologically dominant insects in most terrestrial communities. In subtropical ecosystems, there is a high turnover of species from the canopy to the top layers of the soil. Additionally, ant communities are often influenced by inter-specific competition. Collectively, these two processes (abiotic filtering and competition) make ants ideal for studies of community structure. We examined composition, co-occurrence, and species interactions in a sub-tropical forest ant community to examine how ground-foraging ant species partition microhabitats. We used four methods: pitfall traps, litter samples, surface baits, and subterranean baits. Surface baiting was employed at three different time periods to examine how foraging activity and species interactions at baits varied with time of day and temperature. Each method sampled a particular assemblage of the 97 total ant species. Pitfall traps shared ~50% of species with surface baits and litter samples. Subterranean baits had the fewest total species but included some uncommonly sampled ants. The majority of interactions between species at baits were neutral, but a few agonistic interactions were also observed when bait occupancy was highest. Species co-occurrence patterns suggest that this ant community may not be heavily influenced by interspecific competition. Our results reinforce the advantages of applying complementary sampling techniques to examine ant community structure, and suggest that competition and dominance is best considered in the context of resource type, foraging strategy and time of sampling. Finally, we discuss the lack of two conspicuous Neotropical groups in our samples, leaf-cutting ant and army ants.

Unmasking the architecture of ant-diaspore networks in the Brazilian Savanna

Ant–diaspore interactions are directly related to fruit consumption, seed predation and dispersal, being determinant for the plant fitness. However, although abundant and diversified, these ecological interactions have been neglected in network studies. Understanding the structure of these networks is the first step in preserving these ecological functions. However, describing the network structure is not enough; we need to understand what mechanisms are behind the network patterns. In this study, for the first time, we describe the structure of the ant–diaspore network, considering only the interactions that can benefit plants, separating it into fruit consumption and diaspore removal networks in the Brazilian Savanna. We postulated that ant–diaspore interactions tend to be more specialized in the diaspore removal network compared to the fruit consumption network. Furthermore, we tested whether morphological features, such as size of mandibles of ants and diaspores, could modulate these ecological networks. Overall, we recorded 24 ant and 29 plant species interacting. We found that fruit consumption and diaspore removal networks exhibited similar patterns of interactions (i.e., non-modular), although only the diaspore removal network was nested. The diaspore removal network did not show a more specialized pattern than the fruit consumption network, since both networks consisted of opportunistic interactions. We found that ant mandible and diaspore size does not explain the structure of ecological networks, but in diaspore removal networks the relationship between these morphological traits may explain the pattern of interactions. Thus, we showed that mandible size of ants may have implications on seedling recruitment, suggesting that mandible size can predict possible effects on plant fitness within in diaspore removal networks. Overall, ant–diaspore networks maintain important ecological functions, such as fruit consumption and seed dispersal, which often implies an increase in reproductive success of the plants.

Ninhos de Atta sexdens (Hymenoptera: Formicidae) podem afetar a estrutura da assembleia de artrópodes do solo na Mata Atlântica?

RESUMO: As formigas-cortadeiras são consideradas os herbívoros dominantes da Região Neotropical e, portanto, estudos a respeito dos seus múltiplos efeitos sobre outros organismos e processos ecossistêmicos são relevantes. O presente estudo tem como objetivo determinar se ninhos de Atta sexdens (Linnaeus, 1758) podem afetar a estrutura da assembleia de artrópodes do solo em um fragmento de Mata Atlântica. Além disso, a fim de determinar os prováveis mecanismos que explicam a possível modificação na estrutura da fauna de artrópodes, foram testadas duas hipóteses: I) Hipótese da Serrapilheira: A. sexdens reduz a disponibilidade de serrapilheira nas proximidades do ninho; II) Hipótese dos Fatores Abióticos: A. sexdens modifica as condições microclimáticas ao redor do seu sítio de nidificação causando aumento da temperatura e luminosidade e redução da umidade relativa do ar. O estudo foi conduzido na Reserva Ecológica de Guapiaçu, junto à cidade do Rio de Janeiro, Brasil. Coletamos amostras de serrapilheira a intervalos de oito metros da borda dos ninhos de A. sexdens, ao longo de um transecto linear de 32 metros, para extração da assembleia de artrópodes e para estudar a estrutura da serrapilheira. Também medimos as temperaturas do ar e do solo, a luminosidade e a umidade relativa do ar onde coletamos as amostras de serrapilheira. Não detectamos qualquer efeito da presença do ninho sobre a riqueza, abundância e composição de artrópodes do solo no fragmento florestal estudado. Esse resultado foi provavelmente influenciado pelo fato de que os ninhos de A. sexdens estudados não afetam a disponibilidade de serrapilheira e as condições microclimáticas ao seu redor. Assim, concluímos que os múltiplos efeitos que as formigas-cortadeiras podem ter em uma floresta devem ser dependentes da espécie.

Homogenization and impoverishment of taxonomic and functional diversity of ants in Eucalyptus plantations

Despite its negative impacts on the environment and biodiversity, tree plantations can contribute to biodiversity conservation in fragmented landscapes, as they harbor many native species. In this study, we investigated the impact of Eucalyptus plantations on the taxonomic and functional diversity of ant communities, comparing ant communities sampled in managed and unmanaged (abandoned for 28 years) Eucalyptus plantations, and native Atlantic rain forests. Eucalyptus plantations, both managed and unmanaged, reduced the functional diversity and increased the similarity between ant communities leading to functional homogenization. While communities in managed plantations had the lowest values of both taxonomic and functional ant diversities, ant communities from unmanaged plantations had similar values of species richness, functional redundancy and Rao's Q compared to ant communities from forest patches (although functional richness was lower). In addition, communities in unmanaged Eucalyptus plantations were taxonomically and functionally more similar to communities located in managed plantations, indicating that Eucalyptus plantations have a severe long-term impact on ant communities. These results indicate that natural regeneration may mitigate the impact of Eucalyptus management, particularly regarding the functional structure of the community (α diversity), although it does not attenuate the effects of long term homogenization in community composition (β diversity).

Raimundo M, B. Cavalheiro EM, F. P. Salles L, Lyra C, J. Von Zuben F. Ant genera identification using an ensemble of convolutional neural networks

Works requiring taxonomic knowledge face several challenges, such as arduous identification of many taxa and an insufficient number of taxonomists to identify a great deal of collected organisms. Machine learning tools, particularly convolutional neural networks (CNNs), are then welcome to automatically generate high-performance classifiers from available data. Supported by the image datasets available at the largest online database on ant biology, the AntWeb (www.antweb.org), we propose here an ensemble of CNNs to identify ant genera directly from the head, profile and dorsal perspectives of ant images. Transfer learning is also considered to improve the individual performance of the CNN classifiers. The performance achieved by the classifiers is diverse enough to promote a reduction in the overall classification error when they are combined in an ensemble, achieving an accuracy rate of over 80% on top-1 classification and an accuracy of over 90% on top-3 classification.

Genetic Diversity of Urban Camponotus Mayr (Hymenoptera: Formicidae) Ants Revealed by Capture of Alates and DNA Sequencing

The Camponotus Mayr genus of carpenter ants is one of the largest in species number and widely represented in the Neotropical Region. Most species are generalists and capable of exploiting diverse habitats including urban environments. Urban green areas can act as a repository of regional biodiversity, thus we investigated whether this is valid for the largest city in South America. We compared the richness of Camponotus spp. in two green areas in regions with distinct urbanization profiles and also with previous surveys made in smaller cities and in natural areas of the original Atlantic Forest. Besides the usual capture of worker specimens, we included capture of alates to improve the species richness sampling. Morphological identification of Camponotus spp. is challenging, even more when alates are included. To assist in specimen identification, we performed DNA sequencing of mitochondrial and nuclear markers. The richness observed in the less stressed urban area was higher than in the more stressed one. Camponotus spp. reported in natural areas are largely represented in the urban area. DNA sequencing for specimen identification is hampered by the lack of corresponding sequences in the GenBank, but it helped to associate workers and alates of the same species and indicated the existence of cryptic species in the genus. Capture of alates allowed detection of several species for which workers were not sampled; therefore, it is a valuable tool for surveying diversity of Camponotus or other ant taxa with arboreal or hypogeic habits.

The surrounding landscape influences the diversity of leaf-litter ants in riparian cloud forest remnants

Riparian vegetation is a distinctive and ecologically important element of landscapes worldwide. However, the relative influence of the surrounding landscape on the conservation of the biodiversity of riparian remnants in human-modified tropical landscapes is poorly understood. We studied the surrounding landscape to evaluate its influence on leaf-litter-ant alpha and beta diversity in riparian remnants in the tropical montane cloud forest region of central Veracruz, Mexico. Sampling was carried out in 12 sites with riparian vegetation during both rainy (2011) and dry (2012) seasons. Ten leaf-litter samples were collected along a 100-m transect per site and processed with Berlese-Tullgren funnels and Winkler sacks. Using remotely-sensed and ground-collected data, we characterized the landscape around each site according to nine land cover types and computed metrics of landscape composition and configuration. We collected a total of 8,684 ant individuals belonging to 53 species, 22 genera, 11 tribes, and 7 subfamilies. Species richness and the diversity of Shannon and Simpson increased significantly in remnants immersed in landscapes with a high percentage of riparian land cover and a low percentage of land covers with areas reforested with Pinus, cattle pastures, and human settlements and infrastructure. The composition of ant assemblages was a function of the percentage of riparian land cover in the landscape. This study found evidence that leaf-litter ants, a highly specialized guild of arthropods, are mainly impacted by landscape composition and the configuration of the focal remnant. Maintaining or improving the surrounding landscape quality of riparian vegetation remnants can stimulate the movement of biodiversity among forest and riparian remnants and foster the provision of ecosystem services by these ecosystems. Effective outcomes may be achieved by considering scientific knowledge during the early stages of riparian policy formulation, in addition to integrating riparian management strategies with broader environmental planning instruments.

Inventário da fauna de formigas (Hymenoptera, Formicidae) no Mato Grosso do Sul, Brasil

RESUMO Formicidae inclui cerca de 16.000 nomes de espécies válidas em todo o mundo, com estimativas que excedem mais de 20.000 espécies. Atualmente 16 subfamílias foram descritas, sendo que na Região Neotropical são conhecidas 14 delas, representadas por mais de 4.000 espécies. Apresentamos a listagem de Formicidae para o estado de Mato Grosso do Sul, contemplada em inventários recentes realizados na Serra da Bodoquena, Pantanal, Chaco Brasileiro, Complexo Aporé-Sucuriú, Serra do Amolar e em uma Floresta Estacional Semidecidual Atlântica de Dourados, MS. Os dados aqui apresentados são referentes às coletas realizadas entre os anos de 2004 a 2012. O conjunto das amostras não foi padronizado para as respectivas áreas devido aos objetivos de cada estudo realizado. Até o momento foram identificadas para o estado 306 espécies em 71 gêneros de 11 subfamílias. Foram registradas pela primeira vez no estado as seguintes espécies consideradas raras para as fitofisionomias amostradas: Acanthostichus longinodis, Atta saltensis, Cryptomyrmex boltoni, Cylindromyrmex brasiliensis, Prionopelta punctulata, Probolomyrmex boliviensis, Probolomyrmex petiolatus, Procryptocerus montanus, Stegomyrmex olindae, Strumigenys xenochelyna e Tranopelta gilva. Três novas espécies foram registradas no estado: Asphinctanilloides sp. nov., Stigmatomma sp. nov. e Probolomyrmex sp. nov., em processo de descrição. Nossos estudos indicam a Serra da Bodoquena como a região mais diversa no estado para a fauna de Formicidae. Este trabalho tenta preencher a grande lacuna de conhecimento sobre a fauna de formigas neste mosaico de ecossistemas na região.

Value of Riparian Vegetation Remnants for Leaf-Litter Ants (Hymenoptera: Formicidae) in a Human-Dominated Landscape in Central Veracruz, Mexico

Riparian remnants are linear strips of vegetation immediately adjacent to rivers that may act as refuges for biodiversity, depending on their habitat quality. In this study, we evaluated the role of riparian remnants in contributing to the diversity of leaf-litter ants by determining the relationship between ant diversity and several riparian habitat characteristics within a human-dominated landscape in Veracruz, Mexico. Sampling was carried out in 2012 during both dry and rainy seasons at 12 transects 100 m in length, where 10 leaf-litter samples were collected along each transect and processed with Berlese-Tullgren funnels and Winkler sacks. A total of 8,684 individuals belonging to 53 species, 22 genera, and seven subfamilies were collected. The observed mean alpha diversity accounted for 34.4% of the total species recorded and beta diversity for 65.6%. Species richness and composition were significantly related to litter-layer depth and soil compaction, which could limit the distribution of ant species depending on their nesting, feeding, and foraging habits. Riparian remnants can contribute toward the conservation of ant assemblages and likely other invertebrate communities that are threatened by anthropogenic pressures. In human-dominated landscapes where remnants of riparian vegetation give refuge to a diverse array of myrmecofauna, the protection of the few remaining and well-preserved riparian sites is essential for the long-term maintenance of biodiversity.

Contrasting species and functional beta diversity in montane ant assemblages

AIM

Beta diversity describes the variation in species composition between sites and can be used to infer why different species occupy different parts of the globe. It can be viewed in a number of ways. First, it can be partitioned into two distinct patterns: turnover and nestedness. Second, it can be investigated from either a species identity or a functional-trait point of view. We aim to document for the first time how these two aspects of beta diversity vary in response to a large environmental gradient.

LOCATION

Maloti-Drakensberg Mountains, southern Africa.

METHODS

We sampled ant assemblages along an extensive elevational gradient (900-3000 m a.s.l.) twice yearly for 7 years, and collected functional-trait information related to the species' dietary and habitat-structure preferences. We used recently developed methods to partition species and functional beta diversity into their turnover and nestedness components. A series of null models were used to test whether the observed beta diversity patterns differed from random expectations.

RESULTS

Species beta diversity was driven by turnover, but functional beta diversity was composed of both turnover and nestedness patterns at different parts of the gradient. Null models revealed that deterministic processes were likely to be responsible for the species patterns but that the functional changes were indistinguishable from stochasticity.

MAIN CONCLUSIONS

Different ant species are found with increasing elevation, but they tend to represent an increasingly nested subset of the available functional strategies. This finding is unique and narrows down the list of possible factors that control ant existence across elevation. We conclude that diet and habitat preferences have little role in structuring ant assemblages in montane environments and that some other factor must be driving the non-random patterns of species turnover. This finding also highlights the importance of distinguishing between different kinds of beta diversity.

Effect of Carbohydrate Supplementation on Investment into Offspring Number, Size, and Condition in a Social Insect

Resource availability can determine an organism's investment strategies for growth and reproduction. When nutrients are limited, there are potential tradeoffs between investing into offspring number versus individual offspring size. In social insects, colony investment in offspring size and number may shift in response to colony needs and the availability of food resources. We experimentally manipulated the diet of a polymorphic ant species (Solenopsis invicta) to test how access to the carbohydrate and amino acid components of nectar resources affect colony investment in worker number, body size, size distributions, and individual percent fat mass. We reared field-collected colonies on one of four macronutrient treatment supplements: water, amino acids, carbohydrates, and amino acid and carbohydrates. Having access to carbohydrates nearly doubled colony biomass after 60 days. This increase in biomass resulted from an increase in worker number and mean worker size. Access to carbohydrates also altered worker body size distributions. Finally, we found a negative relationship between worker number and size, suggesting a tradeoff in colony investment strategies. This tradeoff was more pronounced for colonies without access to carbohydrate resources. The monopolization of plant-based resources has been implicated in the ecological success of ants. Our results shed light on a possible mechanism for this success, and also have implications for the success of introduced species. In addition to increases in colony size, our results suggest that having access to plant-based carbohydrates can also result in larger workers that may have better individual fighting ability, and that can withstand greater temperature fluctuations and periods of food deprivation.

Does morphology predict trophic position and habitat use of ant species and assemblages?

A functional traits-based theory of organismal communities is critical for understanding the principles underlying community assembly, and predicting responses to environmental change. This is particularly true for terrestrial arthropods, of which only 20% are described. Using epigaeic ant assemblages, we asked: (1) can we use morphological variation among species to predict trophic position or preferred microhabitat; (2) does the strength of morphological associations suggest recent trait divergence; (3) do environmental variables at site scale predict trait sets for whole assemblages? We pitfall-trapped ants from a revegetation chronosequence and measured their morphology, trophic position [using C:N stoichiometry and stable isotope ratios (δ)] and characteristics of microhabitat and macrohabitat. We found strong associations between high trophic position (low C:N and high δ(15)N) in body tissue and morphological traits: predators were larger, had more laterally positioned eyes, more physical protection and tended to be monomorphic. In addition, morphological traits were associated with certain microhabitat features, e.g. smaller heads were associated with the bare ground microhabitat. Trait-microhabitat relationships were more pronounced when phylogenetic adjustments were used, indicating a strong influence of recent trait divergences. At the assemblage level, our fourth corner analysis revealed associations between the prevalence of traits and macrohabitat, although these associations were not the same as those based on microhabitat associations. This study shows direct links between species-level traits and both diet and habitat preference. Trait-based prediction of ecological roles and community structure is thus achievable when integrating stoichiometry, morphology and phylogeny, but scale is an important consideration in such predictions.