Atta Cephalotes Research Articles

Leafcutter ants enhance microbial drought resilience in tropical forest soil.

We conducted a research campaign in a neotropical rainforest in Costa Rica throughout the drought phase of an El-Nino Southern Oscillation event to determine microbial community dynamics and soil C fluxes. Our study included nests of the leafcutter ant Atta cephalotes, as soil disturbances made by these ecosystem engineers may influence microbial drought response. Drought decreased the diversity of microbes and the abundance of core microbiome taxa, including Verrucomicrobial bacteria and Sordariomycete fungi. Despite initial responses of decreasing diversity and altered composition, 6 months post-drought the microbiomes were similar to pre-drought conditions, demonstrating the resilience of soil microbial communities to drought events. A. cephalotes nests altered fungal composition in the surrounding soil, and reduced both fungal mortality and growth of Acidobacteria post-drought. Drought increased CH4 consumption in soils due to lower soil moisture, and A. cephalotes nests decrease the variability of CH4 emissions in some soil types. CH4 emissions were tracked by the abundance of methanotrophic bacteria and fungal composition. These results characterize the microbiome of tropical soils across both time and space during drought and provide evidence for the importance of leafcutter ant nests in shaping soil microbiomes and enhancing microbial resilience during climatic perturbations.

Mapping microhabitats of lignocellulose decomposition by a microbial consortium.

The leaf-cutter ant fungal garden ecosystem is a naturally evolved model system for efficient plant biomass degradation. Degradation processes mediated by the symbiotic fungus Leucoagaricus gongylophorus are difficult to characterize due to dynamic metabolisms and spatial complexity of the system. Herein, we performed microscale imaging across 12-µm-thick adjacent sections of Atta cephalotes fungal gardens and applied a metabolome-informed proteome imaging approach to map lignin degradation. This approach combines two spatial multiomics mass spectrometry modalities that enabled us to visualize colocalized metabolites and proteins across and through the fungal garden. Spatially profiled metabolites revealed an accumulation of lignin-related products, outlining morphologically unique lignin microhabitats. Metaproteomic analyses of these microhabitats revealed carbohydrate-degrading enzymes, indicating a prominent fungal role in lignocellulose decomposition. Integration of metabolome-informed proteome imaging data provides a comprehensive view of underlying biological pathways to inform our understanding of metabolic fungal pathways in plant matter degradation within the micrometer-scale environment.

Atta cephalotes (Hymenoptera: Myrmicinae) is colonizing urban areas in Cali, Colombia

Numerous studies have examined the effect of invasive species on biodiversity in urban environments, however, few of them have investigated the role of native species while turning into invasive pests. In Colombia, Atta cephalotes, a native leaf-cutting ant (LCA), has responded successfully to the conversion of natural ecosystems to agricultural-rural environments and, most recently, to residential and urban development. In this study, we illustrate the incidence and distribution of this native ant species in an environment where animal life must face urban disturbs in the physical environment, resource availability, and ecosystem processes associated with human urbanization in Cali, the third most important city in Colombia. For this, A. cephalotes nests were georeferenced in public green areas located in 12 communes across the city of Cali, southern Colombia. Vegetation and soil cover, urban settings, foraging trails and plants foraged by the ants were recorded. A. cephalotes nests were present in all green areas and, even in human dwellings; the ants harvested both native and introduced plant species. Despite being well adapted to strongly modified urban environments, this ant species appears to be dependent on human-subsidized resources. Given the wide distribution of leaf-cutting ants in Latin America, it is plausible to expect that similar processes are underway in other countries where these ants are found. Hence, this study also proposes to alert the academic and social communities to direct future research towards evaluating both the responses and impacts of these ants in relation to changes in the urban landscape.

Leaf-cutter ants - mycorrhizal fungi: observations and research questions from an unexpected mutualism.

Leaf-cutter ants (LCAs) are widely distributed and alter the physical and biotic architecture above and below ground. In neotropical rainforests, they create aboveground and belowground disturbance gaps that facilitate oxygen and carbon dioxide exchange. Within the hyperdiverse neotropical rainforests, arbuscular mycorrhizal (AM) fungi occupy nearly all of the forest floor. Nearly every cubic centimeter of soil contains a network of hyphae of Glomeromycotina, fungi that form arbuscular mycorrhizae. Our broad question is as follows: how can alternative mycorrhizae, which are-especially ectomycorrhizae-essential for the survival of some plant species, become established? Specifically, is there an ant-mycorrhizal fungus interaction that facilitates their establishment in these hyperdiverse ecosystems? In one lowland Costa Rican rainforest, nests of the LCA Atta cephalotes cover approximately 1.2% of the land surface that is broadly scattered throughout the forest. On sequencing the DNA from soil organisms, we found the inocula of many AM fungi in their nests, but the nests also contained the inocula of ectomycorrhizal, orchid mycorrhizal, and ericoid mycorrhizal fungi, including Scleroderma sinnamariense, a fungus critical to Gnetum leyboldii, an obligate ectomycorrhizal plant. When the nests were abandoned, new root growth into the nest offered opportunities for new mycorrhizal associations to develop. Thus, the patches created by LCAs appear to be crucial sites for the establishment and survival of shifting mycorrhizal plant-fungal associations, in turn facilitating the high diversity of these communities. A better understanding of the interactions of organisms, including cross-kingdom and ant-mycorrhizal fungal interactions, would improve our understanding of how these ecosystems might tolerate environmental change.

Bacterial microbiota associated with the leaf‐cutting ant Atta cephalotes (Hymenoptera: Myrmicinae): Dynamics during development and potential role in defence

AbstractThe biological complexity of leaf‐cutting ants is determined in part by both positive and negative associations with microorganisms. These ants constantly face microorganisms that can compromise workers’ survival and the integrity of their symbiont fungus. The ability to produce antimicrobial compounds within the colony, both by the workers and by associated microorganisms, is an adaptive response that protects against these natural enemies. Atta cephalotes (Linnaeus, 1758) is an ecologically successful species with a great capacity to overcome pathogenic microorganisms. In contrast to the Acromyrmex genus, the evidence suggests that it does not maintain an association with antibiotic‐producing actinobacteria raising the question of whether this species maintains associations with bacterial communities that can potentially protect the colony against prejudicial microorganisms. In this direction, the diversity and composition of the culturable bacterial microbiota associated with A. cephalotes developmental stages were evaluated, as well as their potential to inhibit the growth of the entomopathogenic fungus Metarhizium anisopliae and the mycoparasite Trichoderma sp. Six nests were collected, of which a total of 900 larvae, 900 pupae and 900 adult workers were analysed. Culture‐dependent and molecular methods were used to identify the strains to genus level. To determine differences in bacterial composition in the development stages, analysis of the contribution to dissimilarity (SIMPER) were performed. Seventy‐seven strains corresponding to 18 genera were documented. Acinetobacter was the dominant one. On the other hand, Acinetobacter, Bacillus, Enterobacter, Serratia and Microbacterium were maintained from the larval to the adult stage. Furthermore, except for Acinetobacter, different strains of these bacterial groups significantly inhibited pathogenic fungi growth. The results suggest the existence of a persistent association of A. cephalotes with strains of these bacterial genera and a potential role in defence at the collective level.

Potential present and future distributions of the genus Atta of Mexico.

Temperature and precipitation influence insect distribution locally and drive large-scale biogeographical patterns. We used current and future climate data from the CHELSA database to create ensemble species distribution models for three Atta leaf-cutting ant species (Atta cephalotes, A. mexicana, and A. texana) found in Mexico. These models were used to estimate the potential impact of climate change on the distribution of these species in the future. Our results show that bioclimatic variables influence the distribution of each Atta species occupying a unique climatic niche: A. cephalotes is affected by temperature seasonality, A. mexicana by isothermality, and A. texana by the minimum temperature of the coldest month. Atta texana and A. mexicana are expected to decline their range by 80% and 60%, respectively, due to rising temperatures, decreased rainfall, and increased drought. Due to rising temperatures and increased humidity, Atta cephalotes is expected to expand its range by 30%. Since Atta species are important pests, our coexistence with them requires knowledge of their ecological functions and potential future distribution changes. In addition, these insects serve as bioindicators of habitat quality, and they can contribute to the local economy in rural areas since they are eaten as food for the nutritional value of the queens. In this sense, presenting a future perspective of these species' distribution is important for forest and crop management. Education programs also are necessary to raise awareness of the importance of these ants and the challenges they face because of climate change. Our results offer a perspective of climate change studies to define conservation and adaptation strategies for protecting vulnerable areas such as high-elevation remnant forests.

Three cuticular amides in the tripartite symbiosis of leafcutter ants.

Cuticular hydrocarbons (CHCs) play various roles in insects' chemical ecology. As leafcutter ants live in a specific symbiosis with fungi, they harvest and with different bacteria, some of these CHCs might be associated with a mutualistic function within this symbiosis. To obtain a more precise picture in that respect we compared the CHC profiles of the leafcutter ants, Atta sexdens, Atta cephalotes, and Acromyrmex octospinosus inhabited by mutualistic bacteria with the profiles of Polyrhachis dives and Messor aciculatus by GC-EI-MS analysis and 28 other ant species by data from the literature. We were able to identify three alkyl amides (hexadecanamide, hexadecenamide, and tetradecanamide), occurring only in the CHC profiles of leafcutter ants inhabited by symbiotic bacteria. Our results lead to the conclusion that those alkyl amides could have a function in the tripartite symbiosis of leafcutter ants.

Morphological evolution and the behavioral organization of agricultural division of labor in the leafcutter ant Atta cephalotes

Morphological evolution and the behavioral organization of agricultural division of labor in the leafcutter ant Atta cephalotes

Transcriptomic analysis of mosaic brain differentiation underlying complex division of labor in a social insect

Concerted developmental programming may constrain changes in component structures of the brain, thus limiting the ability of selection to form an adaptive mosaic of size-variable brain compartments independent of total brain size or body size. Measuring patterns of gene expression underpinning brain scaling in conjunction with anatomical brain atlases can aid in identifying influences of concerted and/or mosaic evolution. Species exhibiting exceptional size and behavioral polyphenisms provide excellent systems to test predictions of brain evolution models by quantifying brain gene expression. We examined patterns of brain gene expression in a remarkably polymorphic and behaviorally complex social insect, the leafcutter ant Atta cephalotes. The majority of significant differential gene expression observed among three morphologically, behaviorally, and neuroanatomically differentiated worker size groups was attributable to body size. However, we also found evidence of differential brain gene expression unexplained by worker morphological variation and transcriptomic analysis identified patterns not linearly correlated with worker size but sometimes mirroring neuropil scaling. Additionally, we identified enriched gene ontology terms associated with nucleic acid regulation, metabolism, neurotransmission, and sensory perception, further supporting a relationship between brain gene expression, brain mosaicism, and worker labor role. These findings demonstrate that differential brain gene expression among polymorphic workers underpins behavioral and neuroanatomical differentiation associated with complex agrarian division of labor in A. cephalotes.

Landscape genetics across the Andes mountains: Environmental variation drives genetic divergence in the leaf-cutting ant Atta cephalotes.

Distinguishing among the mechanisms underlying the spatial distribution of genetic variation resulting from the environmental or physical barriers from those arising due to simple geographic distance is challenging in complex landscapes. The Andean uplift represents one of the most heterogeneous habitats where multiple mechanisms may interact, confounding their relative roles. We explore this broad question in the leaf-cutting ant Atta cephalotes, a species that is distributed across the Andes mountains, using nuclear microsatellite markers and mtCOI gene sequences. We investigate spatial genetic divergence across the western range of the northern Andes in Colombia by testing the relative role of alternative scenarios of population divergence, including isolation by geographic distance (IBD), climatic conditions (IBE), and the physical barriers presented by the Andes mountains (IBB). Our results reveal substantial genetic differentiation among A. cephalotes populations for both types of markers, but only nuclear divergence followed a hierarchical pattern with multiple models of genetic divergence imposed by the western range. Model selection showed that the IBD, IBE (temperature and precipitation), and IBB (Andes mountains) models, often proposed as individual drivers of genetic divergence, interact, and explain up to 33% of the genetic divergence in A. cephalotes. The IBE model remained significant after accounting for IBD, suggesting that environmental factors play a more prominent role than IBB. These factors, in combination with the idiosyncratic dispersal patterns of ants, appear to determine the hierarchical patterns of gene flow. This study enriches our understanding of the forces shaping population divergence in complex habitat landscapes.

Karyotype conservation and genomic organization of repetitive sequences in the leaf-cutting ant Atta cephalotes (Linnaeus, 1758) (Formicidae: Myrmicinae).

Leaf-cutting ants are among the New World's most conspicuous and studied ant species due to their notable ecological and economic roles. Cytogenetic studies carried out in Atta show remarkable karyotype conservation among the species. We performed classical cytogenetics and physical mapping of repetitive sequences in the leaf-cutting ant Atta cephalotes (Linnaeus, 1758), the type species of the genus. Our goal was to test the karyotype conservation in Atta and to understand the genomic organization and diversity regarding repetitive sequences in leaf-cutting ants. Atta cephalotes showed 2n = 22 (18m + 2sm + 2st) chromosomes. The heterochromatin followed a centromeric pattern, and the GC-rich regions and 18S rDNA clusters were co-located interstitially in the 4th metacentric pair. These cytogenetic characteristics were observed in other Atta species that had previously been studied, confirming the karyotype conservation in Atta. Evolutionary implications regarding the conservation of the chromosome number in leaf-cutting ants are discussed. Telomeric motif (TTAGG)n was detected in A. cephalotes as observed in other ants. Five out of the 11 microsatellites showed a scattered distribution exclusively on euchromatic areas of the chromosomes. Repetitive sequences mapped on the chromosomes of A. cephalotes are the first insights into genomic organization and diversity in leaf-cutting ants, useful in further comparative studies.

Functional significance of the leaf-cutting ant Atta cephalotes (Formicidae) in coffee plantations: An enemy or an ally?

Leaf-cutter ants are appreciated as ecosystem engineers. Conversely, under agricultural scenarios, they are considered serious pests. Coffee is one of the crops selectively foraged by this species either under traditional shading or unshaded intensified systems. Despite the economic importance of coffee in Neotropical regions, there are few observational field studies on the impact of leaf-cutter ants on coffee plantation soils and how impact may differ in response to shade management. Three hypotheses were tested in coffee plantations in presence of Atta cephalotes: (1) bioturbation activity by leaf-cutter ants depends on the soil properties, which in turn, are affected by agronomic management of the coffee plantations; (2) a relatively higher concentration of resources (i.e., coffee plants) results in greater leaf-cutter ant activity in unshaded plantations than in shaded plantations; and (3) the effect of ant defoliation on fruit production depends on the level of foliar damage. Ten active ant nests were selected from each management system in ten farm plots. Soil samples were collected from nests and from outside the nests (control), physical, chemical and biological properties were analysed, and leaf-cutter ant herbivory was also assessed. No significant differences in microbial activity, evaluated through respiration, were found between nest and control soils. Nest soils had higher and lower percentages of sand and silt, respectively, than the control soils. Nest soils contained significantly higher amounts of sulphur, regardless of shade management. A. cephalotes translocated mineral soils and improved water infiltration in nest soils. The herbivory index and proportion of damage were greater in unshaded coffee, although fruit production tended to increase, possibly due to a compensatory effect as coffee plants responded to low levels of foliar damage. Therefore, the first hypothesis was only partially supported since bioturbation depended on soil properties, and certain soil properties were affected by coffee management, while the second and third hypotheses were supported by the data, suggesting that leaf-cutter ants differentially affect coffee plantations based on their shade management and on the moment the coffee plants are affected. Our results form the basis for the development of future studies that evaluate production impacts and economic damage in coffee varieties by leaf-cutter ants. Depending on the ecological context of the agroecosystem and management practices used, leaf-cutter ants can have positive or negative impacts for coffee production.

Bacteria associated with leaf-cutter ants drive natural antibiotic resistance in soil bacteria

AbstractActinobacteria that live mutualistically with leaf-cutter ants secrete antibiotics that may induce antibiotic resistance in nearby soil bacteria. We tested for the first time whether soil bacteria near and inside Atta cephalotes nests in Costa Rica show higher levels of antibiotic resistance than bacteria collected farther away. We collected soil samples 0 m to 50 m away from ant nests and grew bacteria from them on agar with paper discs treated with antibiotics of common veterinary use. As a proxy for antibiotic resistance, we measured the distance from the edge of each disc to the closest bacterial colonies. In general, resistance to oxytetracycline increased with proximity to leaf-cutter ant nests. Antibiotic resistance to oxytetracycline was also higher in samples collected inside the nest than in samples from the nest mound; not all antibiotics demonstrated the same trend. A preliminary exploratory morphological analysis suggests bacterial communities between 0 m and 50 m from ant nests were similar in diversity and abundance, indicating the pattern of antibiotic resistance described above may not be caused by differences in community composition. We conclude that actinobacteria living mutualistically with A. cephalotes drive natural antibiotic resistance to tetracycline in proximal bacterial communities.

Hygienic behavior and antimicrobial peptide expression of the leaf-cutting ant Atta cephalotes (Hymenoptera, Formicidae) to Metharhizium anisopliae

Leaf-cutting ants depend on mutualisticfungi to survive. An infection that massively affects the workers compromising the proper maintenance of the fungus, or that can attack the fungus garden, can be fatal to the colony. Thus, leaf-cutting ants have evolved a complex defense system composed of both innate individual immunity and collective immunity to protect the colony against potential threats. To characterize the collective and individual immunity of Atta cephalotes workers to Metarizhium anisopliae we assessed the hygienic behavior and the expression of antimicrobial peptides of A. cephalotes workers triggered by Metarizhium anisopliae spores. As a control challenge, workers were treated with water. Regardless of whether the challenge was with water or spore suspension, A. cephalotes workers displayed an immediate response characterized by an increase in time spent both self-grooming and collective grooming along with a reduction in time spent fungus-grooming. The individual immunity triggered the expression of abaecin as early as 24 hours post-infection, exclusively in workers challenged with M. anisopliae. In contrast, the level of expression of defensin remained constant. These results suggest that upon being challenged with a suspension of M. anisopliae spores, A. cephalotes workers deploy both collective and individual immunity to produce a response against the invader. However, when the spores of M. anisopliae are applied as liquid suspension collective immunity deploys a generic strategy, while individual immunity shows a specific response against this entomopathogen.

Yeasts associated with the worker caste of the leaf-cutting ant Atta cephalotes under experimental conditions in Colombia.

Yeasts isolated from the worker caste of the Colombian leaf-cutting ant, Atta cephalotes (Hymenoptera: Myrmicinae) were cultured and identified by molecular methods. Abundant, persistent, and omnipresent species were classified as "prevalent". Experimental data were compared with information gathered from published reports on the yeast species composition in other leaf-cutting ant species. Diversity analysis was conducted using diversity values (q0, q1, and q2) to compare the richness and abundance of yeasts present in different leaf-cutting ant species. Clustering analysis was carried out to assess the similarity of yeast community according to ant species. The yeast species composition was highly variable among the ant species. A. laevigata and A. capiguara showed the highest degree of similarity and differed from the group composed by A. cephalotes, A. sexdens, A. sexdens rubropilosa, and A. texana. The isolation of dominant yeasts in different ant castes within the different compartments of a colony strongly suggests that the identified microorganisms are not transient but are native to the soil surrounding ant colonies and the substrates used by the ants to grow their fungal cultivars. It is apparent that the ant-fungus mutualism does not operate in an environment devoid of other microbes, but rather that the association must be seen within the context of a background of other microorganisms, particularly the dominant yeasts.

Behavioral performance and division of labor influence brain mosaicism in the leafcutter ant Atta cephalotes.

Brain evolution is hypothesized to be driven by behavioral selection on neuroarchitecture. We developed a novel metric of relative neuroanatomical investments involved in performing tasks varying in sensorimotor and processing demands across polymorphic task-specialized workers of the leafcutter ant Atta cephalotes and quantified brain size and structure to examine their correlation with our computational approximations. Investment in multisensory and motor integration for task performance was estimated to be greatest for media workers, whose highly diverse repertoire includes leaf-quality discrimination and leaf-harvesting tasks that likely involve demanding sensory and motor processes. Confocal imaging revealed that absolute brain volume increased with worker size and functionally specialized compartmental scaling differed among workers. The mushroom bodies, centers of sensory integration and learning and memory, and the antennal lobes, olfactory input sites, were larger in medias than in minims (gardeners) and significantly larger than in majors ("soldiers"), both of which had lower scores for involvement of olfactory processing in the performance of their characteristic tasks. Minims had a proportionally larger central complex compared to other workers. These results support the hypothesis that variation in task performance influences selection for mosaic brain structure, the independent evolution of proportions of the brain composed of different neuropils.

Atta cephalotes (leaf cutting ant)

Atta cephalotes (leaf cutting ant)

How can Blue and White Light Pulses Stimulate Atta Cephalotes in Trails Below Fruit Trees?

Modern Concepts & Developments in Agronomy How can Blue and White Light Pulses Stimulate Atta Cephalotes in Trails Below Fruit Trees? Federico Hahn Schlam1* and Claudia Bolaños Sánchez2 1Irrigation Department, Universidad Autónoma Chapingo, Carr Km. 38.5, Carretera México- Texcoco, C.P. 56230, Chapingo, México 2IAUIA, Universidad Autónoma Chapingo, Km. 38.5, Carretera México-Texcoco, C.P.56230, Chapingo, México *Corresponding author: Federico Hahn Schlam, 1Irrigation Department, Universidad Autónoma Chapingo, Carr Km. 38.5, Carretera México-Texcoco, C.P. 56230, Chapingo, México Submission: November 16, 2021 Published: December 16, 2021 DOI: 10.31031/MCDA.2021.09.000725 ISSN 2637-7659Volume9 Issue 5

Role of the Andean uplift as an asymmetrical barrier to gene flow in the neotropical leaf‐cutting ant Atta cephalotes

AbstractNeotropical diversification by the Andean uplift is typically addressed on a large evolutionary scale (e.g., speciation), even though many species are still distributed in both sides of the mountains. The three parallel mountain ranges in the northern Andes (Colombia) impose a major geographical barrier to species’ migration from South to Central America. How important these barriers are for conspecific diversification of cross‐Andean species such as the leaf‐cutting ants remains largely unknown. To answer this question, we studied the mtCOI gene of Atta cephalotes, the most widely distributed leaf‐cutting ant species. Our hierarchical analyses evidenced substantial genetic structure among regions and populations, suggesting a more complex biogeographical history of Andean populations than previously thought. These mountains seem to isolate Central American and Western Colombian populations from the rest of A. cephalotes in South America. Population and migration modeling are consistent with the origin of this species in South America and a major role of the Eastern cordillera as a geographical barrier to historical gene flow, restricting dispersion from north to south. These findings provide insights into the role of the Andean uplift as barrier to gene flow in species of leaf‐cutting ants.Abstract in Spanish is available with online material.

Traditional knowledge regarding entomophagy in San Martín, Peruvian Amazon

The consumption of insects is a widespread practice among indigenous or native peoples of the Amazon. To assess the knowledge of the diversity of resources for entomophagy from the perspective of these peoples, testimonies or references about knowledge and feeding traditions of 100 people were collected in 37 localities in seven provinces of the department of San Martín in the basin of the Huallaga River. One cumulative species curve and the probability function of new species were estimated, then the probability of not finding a new species (99.5 %) to n100 was determined. The specimens that were captured in the field (54 %) were compared with representative specimens and databases, and the information provided by the participants was analysed to approximate the preliminary taxonomic locations of the remaining part of the sample. We found 46 resources for entomophagy and reported for first time in the Peruvian Amazon, the feeding with Chrysophora chrysochlora, Podalia sp., Lusura chera, and Cymothoidae, among others. Entomophagy is a deeply rooted practice in the native and riverine populations of the Huallaga basin, where Rhynchophorus palmarum, Rhinostomus barbirostris, Atta cephalotes sspp. and Brassolis sophorae were the most consumed for 78 % – 97 % of people. The least consumed species have the common characteristic of being scarce and they were part of the diet of the oldest segment in previous decades. At least 10 resources ceased to be consumed by the members of the sample. In addition to nutritional potential, the diversity of edible arthropod fauna represents complementary values for community health and cultural identity; however, most of these resources (87 %) are threatened and could disappear in brief time, as is the knowledge related to their use.