Acromyrmex Subterraneus Research Articles

Harmony under threat: does resource-mediated stress affect the (caste-based) social network of leaf-cutting ant colonies?

Managing pest species of eusocial insects, such as leaf-cutting ants, poses significant challenges. Controlling them requires understanding of how toxic plant substrates and ant baits are recognized by foragers, transported to the nest, shared among workers and managed by gardeners cultivating the symbiont fungus garden. Despite this, little is known about how unsuitable resources might impact social interactions within ant colonies. This study aims to investigate whether the provision of a suitable substrate (copperleaf) and a toxic substrate (nasturtium leaves) affects the social network dynamics within colonies of two leaf-cutting ant species: Acromyrmex molestans and Acromyrmex subterraneus. The interactions between castes were recorded and subjected to social network analyses. Initial foraging duration increased for A. subterraneus provided with copperleaf, although no difference was observed for the other species and resource combinations. The social network structure was similar for both species when copperleaf leaves were provided as a substrate. However, notable alterations occurred with nasturtium leaf provision, leading to higher integration of gardeners in interactions and noticeable changes in the generalist worker network centrality, particularly in A. subterraneus. The observed changes in social interactions, particularly in A. subterraneus, suggest that increasing gardener interactions with other castes expedites the movement of the substrate within the colony. This maximizes the potential toxic effect on the colony. © 2024 Society of Chemical Industry.

Repellent potential of agroecological extracts: Exploring their efficacy against the leaf‐cutting ant Acromyrmex subterraneus in the laboratory

AbstractThe increasing restrictions on commercial toxic baits for controlling leaf‐cutting ants have started a “gold rush” for alternative compounds, with agroecological extracts emerging as a promising option. Here, we tested for the first time the repellent effects of concentrated and diluted ant extracts and cow urine solution on laboratory colonies of Acromyrmex subterraneus (Forel) (Hymenoptera: Formicidae). The agroecological extracts preparation and application followed the information provided by peasants from the Movimento dos Trabalhadores Rurais Sem Terra in Brazil who carry out agroecology. First, we applied the agroecological extracts in the middle segment of the upper path of a foraging trail to determine whether they act as a chemical barrier. All agroecological extracts induced the deviation of the foraging flow from the upper path to the lateral path. However, only the concentrated ant extract reduced the leaf delivery rate. Also, we applied the agroecological extracts directly on the leaf disks and conducted a paired selection test. The proportion of transported leaf disks with concentrated ant extract and cow urine solution was lower than that of control disks. We suggest that the observed repellent efficacy of the concentrated ant extract may stem from its content of chemical compounds belonging to the same chemical group as the alarm pheromones found by other Acromyrmex species. As for the cow urine solution, we attribute its repellent effect to the presence of urea. Our findings highlight a significant repellent potential of the concentrated ant extract and cow urine solution for leaf‐cutting ants, which may be applied both on foraging trails and on leaves of cultivated plants.

Ant identity determines the fungi richness and composition of a myrmecochorous seed.

Myrmecochory-seed dispersal by ants-is a mutualistic interaction in which ants attracted by seed appendices take them away from the parental plant location, where seeds usually have better development odds. Not all ant species benefit plants, and the mechanisms of those divergent outcomes are still unclear, especially from the perspective of microbial third parties. Here, we explore the effects of seed manipulation on fungi communities promoted by two ant species with contrasting effects on seed germination and antimicrobial cleaning strategies. We hypothesize that: i) fungi richness is higher in seeds manipulated by Acromyrmex subterraneus (species that negatively affect seed germination), followed by unmanipulated seeds and seeds manipulated by Atta sexdens (ant species that increase seed germination) and ii) seeds manipulated by A. sexdens, Ac. subterraneus and unmanipulated seeds present dissimilar fungi compositions. We identified fungal morphotypes in three groups of seeds: i) manipulated by A. sexdens; ii) manipulated by Ac. subterraneus; iii) unmanipulated. Seeds manipulated by Ac. subterraneus exhibited higher fungal richness than those manipulated by A. sexdens and unmanipulated seeds, indicating that the ant species known to impair germination increases the fungal load on seeds. Additionally, we found that A. sexdens ants were unable to reduce fungal richness compared to unmanipulated seeds. Furthermore, fungal composition differed among all three treatments. Our results underscore the significance of ant species identity in shaping the fungal communities associated with myrmecochorous seeds. Given the potential influence of microbial infection on seed fate, we suggest considering manipulation strategies when evaluating the overall quality of an ant as a seed disperser.

Performance and efficiency in leaf transport: unveiling the task allocation puzzle in Acromyrmex subterraneus

Performance and efficiency in leaf transport: unveiling the task allocation puzzle in Acromyrmex subterraneus

Production of Escovopsis weberi (Ascomycota: Hypocreales) Mycelial Pellets and Their Effects on Leaf-Cutting Ant Fungal Gardens

The maintenance of the symbiosis between leaf-cutting ants and their mutualistic fungus Leucoagaricus gongylophorus Singer (Moller) is vital for the survival of both species. The specialist fungal parasite Escovopsis weberi Muchovej & Della Lucia is a threat to this symbiosis, causing severe damage to the fungal garden. Mycelial pellets are resistant fungal structures that can be produced under laboratory conditions. These structures were studied for use in biological pest control, but the production of mycelial pellets has not previously been documented in Escovopsis. One of the aims of this study was to induce Escovopsis weberi to produce mycelial pellets and investigate the potential of these pellets for the control of leaf-cutting ants. We compared the pathogenicity of Escovopsis weberi mycelial pellets and conidia against mini-colonies of Acromyrmex subterraneus subterraneus Forel when applied in the form of baits. Worker ants were able to distinguish mycelial pellets from conidia, as baits with mycelial pellets were more attractive to workers than those with conidia, causing a greater negative impact on colony health. All types of baits containing Escovopsis weberi influenced the foraging activity but only treatments with viable fungal propagules resulted in an increase in the quantity of waste material, with a significant negative impact on the fungal garden biomass. The results provided novel information regarding Escovopsis recognition by worker ants and differences between conidia and mycelial pellet dynamics in leaf-cutting ant colonies, with new perspectives for the biological control of these important pests.

Foraging for the fungus: why do Acromyrmex subterraneus (Formicidae) queens need to forage during the nest foundation phase?

1. Semiclaustral ant queens must pay the price of foraging to guarantee their survival and also that of their brood through the nest foundation phase. For leaf‐cutting ant species, the challenge is even greater, as they also need to cultivate their symbiont fungus.2. We hypothesised that suppressing foraging activity could reflect in larger offspring and higher survival, as queens would be entirely dedicated to rearing the brood and initial fungus.3. By providing easy access to leaves or completely denying it, we evaluated how foraging runs interfere in Acromyrmex subterraneus queens' survival, productivity, and variation of body mass components.4. Three foraging conditions were simulated: Starved – no leaves, Spoiled – leaves inside the nest chamber, and Walker – leaves 3 m away from the nest chamber. We registered the number of dead queens, offspring, weight of the fungus garden, fresh and lean dry mass of the queens, as well as their lipid and water contents.5. Survival of Starved queens, which did not oviposit, was lower than that of Spoiled and Walker queens, although weight loss, water content, and lean dry mass were similar. While lipid content reduction was similar for Spoiled and Walker queens, the former had more larvae and pupae, and a heavier fungus garden than the latter, suggesting a greater rearing effort of Spoiled queens toward them both.6. The simulated foraging conditions provided novel data for a semiclaustral leaf‐cutting ant species that evidences that fungus garden cultivation is definitively the main driving force for the colony founding success.

Cytogenetic studies on the social parasite Acromyrmex ameliae (Formicidae: Myrmicinae: Attini) and its hosts reveal chromosome fusion in Acromyrmex

The ant Acromyrmex ameliae is a social parasite of two leaf-cutting ant subspecies: Acromyrmex subterraneus subterraneus and A. subterraneus brunneus. Cytogenetic data are available for 14 species of Acromyrmex and all of them possess 2n = 38 chromosomes. In this study, chromosome number, heterochromatin detection, and detection of AT and GC-rich blocks of colonies of A. ameliae and its hosts were carried out. Additionally, the detection of nucleolus organizer regions and 18S rDNA clusters in chromosomes of the parasite and physical mapping of telomeres were undertaken. The same chromosome number and morphology were detected for the hosts 2n = 38 (10m + 14sm + 12st + 2a), while the females and males of the social parasite A. ameliae presented 2n = 36 (10m + 16sm + 8st + 2a) and n = 18 (5m + 8sm + 4st + 1a). In both A. ameliae and its hosts, the terminal region on the short arm of the largest subtelocentric pair is heterochromatic GC-rich, and this region corresponded to the 18S rDNA clusters in the parasite. The short arms of several chromosomes were heterochromatin-rich. The telomeric probe hybridized telomeres on all chromosomes of the parasite and was not detected in intrachromosomal regions. Through a comparative cytogenetic analysis, we hypothesize that the karyotype of A. ameliae (2n = 36) originated from a chromosomal rearrangement that reduced the number of chromosomes from 38 to 36; as available data on the genus Acromyrmex show that all other species possess 38 chromosomes, representing 45% of the 33 valid species in this genus. The mechanism of the chromosome rearrangement is discussed. Thus, the chromosome number observed in A. ameliae is a derivation from the genus. Our data show variation in the chromosomal number in Acromyrmex and suggest that analyses of the karyotypes of parasite species can yield novel insights with regards to the evolution of this genus.

Corrigendum

BiotropicaVolume 53, Issue 3 p. 976-976 CORRIGENDUMFree Access Corrigendum This article corrects the following: Does mining waste concentration in the soil interfere with leaf selection by Acromyrmex subterraneus (Formicidae)? Felipe dos Santos Nascimento, Antônio Marcos Oliveira Toledo, Maria de Paula Pimenta, Cristiano Ferrara de Resende, Paulo Henrique Pereira Peixoto, Arthur Zimerer, Juliane Floriano Santos Lopes, Volume 53Issue 2Biotropica pages: 487-495 First Published online: January 20, 2021 First published: 18 May 2021 https://doi.org/10.1111/btp.12960AboutSectionsPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat In the article by Nascimento et al. (2021), one of the research financing agents has been missed. The missing information is given below: “Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) Grant/Award Number: APQ-01187-16." Reference Nascimento, F. D. S., Toledo, A. M. O., Pimenta, M. D. P. et al. (2021). Does mining waste concentration in the soil interfere with leaf selection by Acromyrmex subterraneus (Formicidae)? Biotropica, 53(2), 487– 495. https://doi.org/10.1111/btp.12892Wiley Online LibraryWeb of Science®Google Scholar Volume53, Issue3May 2021Pages 976-976 ReferencesRelatedInformation

Immune Defense Strategies of Queens of the Social Parasite Ant Acromyrmex ameliae and Queens of Its Natural Hosts

Social parasitism is well known in ants, but many aspects of this social phenomenon remain mysterious and unexplored. In some cases, parasite queens, who are able to mate very rarely end up producing brood and, thus, depend virtually on the labor of host ants. In this work, we sought to test the occurrence of grooming by host workers of Acromyrmex subterraneus subterraneus Forel, to their own queens and queens of the parasite Acromyrmex ameliae De Souza, Soares and Della Lucia and to compare the immune defense responses of parasite queens and queens of A. subterraneus subterraneus and Acromyrmex subterraneus brunneus Forel, the natural hosts. Duration and frequency of behavioral acts were recorded. The relative size of the bulla and the encapsulation response to a standardized antigen were analyzed. Regarding behavioral acts, self-grooming (duration and frequency) and allogrooming (duration) were statistically different between the species; the first is more frequent and lasted longer in parasite queens, while the second act lasted longer in host ants than in parasite ants. The bulla of A. ameliae was approximately 50% wider than those of its hosts. Parasite queens exhibited a stronger immune response than host queens. The results of this work contribute to elucidate potential mechanisms involved in the parasitism capacity of A. ameliae queens such as their strategies of immune defense.

Does mining waste concentration in the soil interfere with leaf selection by Acromyrmex subterraneus (Formicidae)?

AbstractRevegetation programs are proposed to recover the soil and biodiversity of disturbed sites, this being the case of the Rio Doce basin, Brazil. This region was hugely affected by a mining waste dam disruption, whose leakage on the soil altered its chemical and physical characteristics, and consequently the physiology and performance of plants. The expected alterations of the plants can make them more attractive for leaf‐cutting ants, as lower water content induces an increase of non‐structural carbohydrates. In this context, we evaluated whether Acromyrmex subterraneus workers differentiate among plants grown on soil with different mining waste concentrations. Leaf disks from plants grown in soil containing 0, 25, 50, 75, and 100% of mining waste were simultaneously offered to workers from laboratory ant colonies. The number of transported disks from each mining waste concentration was recorded until all disks of any concentration had been transported. Leaf selection assays were repeated after 30 days due to the novelty effect phenomenon. Leaf thickness, water, starch, and total soluble carbohydrates (TSC) contents were determined. Leaf disks from plants grown in soil with 100% of mining waste concentration were preferentially selected in both selection assays. Leaf thickness and water content were significantly lower in plants from the aforementioned treatment, while starch and TSC were higher. Results suggest that seedlings implanted in sites with high mining waste concentration are under high predation risk. Revegetation programs must measure the impact of leaf‐cutting ants as both herbivorous and soil ecosystem engineers, for the best management of these insects.Abstract in Portuguese is available with online material

The Biology of <i>Szelenyiopria talitae</i> (Hymenoptera: Diapriidae): Larval Parasitoid of the Leaf-Cutting Ant <i>Acromyrmex subterraneus</i> (Hymenoptera: Formicidae)

The biology of a koinobiont parasitoid of leaf-cutting ant larvae, Szelenyiopria talitae (Hymenoptera: Diapriidae), was studied from naturally infested Acromyrmex subterraneus (Hymenoptera: Formicidae) nests. Nests were collected in the field from the Atlantic rainforest biome in the state of Rio de Janeiro. A total of fifty-three nests were collected from 2015 to 2018. Parasitized nests were only found during the months of September and October. Approximately 22% of the nests collected over a four-year period were found to have been parasitized by S. talitae. The mean within-nest parasitism rate was 66.3%. This diapriid displayed both solitary (14%) and gregarious parasitism (86%), with up to a maximum of 12 parasitoids developing within a single host. Gregarious parasitism with two (29%) or three (21%) S. talitae per host was most frequently observed. There was a positive correlation between the number of parasitoids per host and host size (dry weight), indicating that S. talitae females oviposited a higher number of eggs in larger hosts. There was also a negative correlation between S. talitae pharate adult size and the number of parasitoids per host, which could have been caused by sibling competition for limited host resources. The high levels of parasitism seen here had a debilitating effect on the colonies. Acromyrmex subterraneus is a serious pest in Brazil, and these studies lay the foundation for understanding the impact of S. talitae on ant populations.

Does resource-mediated stress affect colony personality in leaf-cutting ants?

Animal personality refers to behavioral consistency and propensity. In social insects, little is known about the interplay between colony personality and colony foraging. This study aimed to assess personality traits among colonies of the leaf-cutting ants Acromyrmex subterraneus subterraneus and Acromyrmex subterraneus molestans and examine their behavioral consistency when provided with a toxic substrate, nasturtium leaves [Tropaeolum majus L. (Tropaeolaceae)], with potential as a management tool against these pest species. The association between colony behavioral traits and fungus garden growth was also examined, and thus the efficacy of the colony suppression. Behavioral variation was higher between colonies than between subspecies. Behavioral traits were correlated before and after exposure to resource-mediated stress in both subspecies, indicating the existence of behavioral syndrome. The dimensions that contributed most to colony personality (activity, aggressiveness, and boldness) are directly related to colony resource searching and foraging. However, these dimensions diverged in their contribution before and after exposure to nasturtium. Colony activity was the major determinant of fungus garden growth, which is probably a consequence of its relationship with foraging behaviors and maintenance of the fungus garden. As the personality of a colony is unequally defined by its constituent castes, the relationship and network of interactions are determinants of foraging behaviors with relevant consequences for colony suppression using toxic foraging substrates that impair these relationships and interactions, as nasturtium leaves do. Therefore, it is plausible to say that resource-mediated stress affects colonies personality exhibiting control potential against these species.

Potential damage by Acromyrmex ant species in pine plantations in southern Brazil

Abstract Acromyrmex species primarily attack Pinus taeda plantations during the first months after planting, with more intense damage in the first 30 days. We evaluated potential damage by Acromyrmex crassispinus and Acromyrmex subterraneus in 30‐day‐old P. taeda plantations in southern Brazil by assessing the number of attacked plants and the distance reached by each colony, along with the losses in plant development resulting from different levels of defoliation. Both species were significant pests in newly established pine plantations. A single colony can attack a substantial number of seedlings (up to 453 seedlings). Colonies with larger nests attacked more plants and ranged farther; A. crassispinus reached 59 m and A. subterraneus 87 m. After 10 years, no significant losses in plant development were seen in seedlings defoliated less than 50% at 30 days after planting. But when defoliation of the young plants attained 75%, 100%, and 100%, including the cut of the apical meristem, volume losses reached 32%, 37%, and 43%, respectively. Leaf‐cutting ant controls should be carried out in plantations of P. taeda within 30 days of planting to avoid attacks. When seedlings are defoliated more than 75%, they should be replanted to avoid future losses in final wood volume.

Survey of leaf-cutting ant species in native vegetation and monocultures in the State of Goiás, Brazil

Leaf-cutting ants are distributed exclusively in the Americas. For this study, we sampled different areas of native vegetation and monocultures to survey the leaf-cutting ants that occur in the State of Goiás, and to what environments they are associated. We recorded six species of leaf-cutting ants: Atta sexdens, Atta laevigata, Acromyrmex subterraneus, Acromyrmex disciger, Acromyrmex ambiguus, and Acromyrmex hispidus. The last four were registered for the first time for the State of Goiás.

Correction to: Social Organization and Subcaste Specialization in the Leaf-Cutting Ant Acromyrmex subterraneus (Formicidae: Myrmicinae)

The original version of this article unfortunately contained some mistakes for the greek letter “Ɵ” in the proof manuscript.

Effect of azadirachtin on mortality and immune response of leaf-cutting ants.

Leaf-cutting ants are difficult pests to control because they have numerous defense strategies and are highly selective in their plant harvesting choices. The search for effective pest control methods that have minimal negative effects on the environment has been continuous. Azadirachtin, a compound extracted from the neem tree (Azadirachta indica), is a promising alternative for the control of various pests, as it is toxic to some insects but readily degrades in the environment. In this study, we evaluated the effects of azadirachtin on the mortality, through topical exposure to the compound, and immune response, by introducing an artificial antigen into leaf-cutting ants Atta sexdens and Acromyrmex subterraneus subterraneus. Azadirachtin caused death to minor and major workers of both species in a concentration-dependent manner. Topical application of the compound did not diminish the immune response of ants in a microfilament encapsulation assay. Azadirachtin showed no effect on the immune response of workers but increased worker mortality, which indicates its potential as an ant control agent.

Social Organization and Subcaste Specialization in the Leaf-Cutting Ant Acromyrmex subterraneus (Formicidae: Myrmicinae)

Several worker subcastes may occur in ant colonies, including physiological, morphological, and temporal subcastes. Leaf-cutting ants present intricate division of labor among worker subcastes during brood care, fungus garden maintenance, substrate foraging and processing. For colony survival, the fungus garden must be healthy, and tasks efficiently shared among worker subcastes. Therefore, worker behavior is key for colony maintenance in fungus-farming ants. Here we provide a qualitative and quantitative account of intracolonial behavior in Acromyrmex subterraneus, a common leaf-cutter in Brazilian Cerrado savanna. Quantitative ethograms showed that performance of major behavioral categories (e.g., “Brood and Queen Care,” “Foraging,” “Fungus Care”) and the composition of behavioral repertoires are important parameters distinguishing labor among A. subterraneus worker subcastes. Media and major subcastes are behaviorally more similar to one another than to minors. Minors regularly executed brood- and fungus-related tasks, whereas media and majors executed mostly foraging-related tasks. Grooming was frequent in all subcastes. Overall, the behavioral patterns reported in A. subterraneus are similar to those reported for other leaf-cutters. The tasks executed by different subcastes of A. subterraneus closely resemble the division of labor observed in Atta colonies, suggesting that alongside the use of fresh leaves as culturing substrates, a highly conserved set of worker behaviors persist since the origin of the leaf-cutting lineage. Our work highlights the importance of detailed analyses of the composition of behavioral repertoires in polymorphic fungus-farming ants to better understand their social organization, and the mechanisms mediating division of labor among worker subcastes in the Attina.

Foraging Ecology of the Leaf-Cutter Ant, Acromyrmex subterraneus (Hymenoptera: Formicidae), in a Neotropical Cerrado Savanna

Fungus-farming ants cultivate a fungal symbiont inside the nest that serves as a food source. Leaf-cutter ants are distinctive among fungus-farmers because they forage for fresh plant material to nurture the fungus. Here we investigate the foraging ecology of Acromyrmex subterraneus (Forel) in the Brazilian cerrado savanna. We examined the species activity pattern, forage material collected, and the relationship between load mass and forager size. Ant activity peaked at night and was negatively related to temperature but positively related to relative air humidity. The majority of the items collected by ants was plant material: dry and fresh leaves, flowers, and fruits. Trunk trails ranged from 0.7 to 13 m and colony home ranged from 2 to 28 m2, indicating that ants collect material nearby the nest. Total load mass was positively associated with forager size, especially in the case of leaves. The negative relationship between ant size and burden suggests that ants might optimize their delivery rate by collecting lighter substrates more frequently. Given their pest status, most studies on leaf-cutters are undertaken in human-altered environments. Information on A. subterraneus in native cerrado is imperative given the threatened status of this vegetation. Leaf-cutters thrive in disturbed cerrado and severe seedling herbivory may hinder vegetation recovery. Our fieldwork may provide insights for management techniques of Acromyrmex colonies in agroecosystems, as well as for restoration programs of degraded cerrado areas.

Do Workers from Subspecies Acromyrmex subterraneus Prepare Leaves and Toxic Baits in Similar Ways for Their Fungus Garden?

Toxic baits are the most efficient method to control leaf-cutter ants in eucalyptus forests for paper and cellulose production. For the proper use of these baits, insecticide compounds must reach workers and contaminate them. Thus, understanding how these baits are processed inside the nests is vital for a successful control, especially when it comes to genus Acromyrmex. Lack of information on toxic baits and on contamination of Acromyrmex workers raises the question: do workers from subspecies Acromyrmex subterraneus (Forel) prepare leaves and toxic baits in similar ways for their fungus garden? To answer it, this study described and analyzed the behavioral repertoire executed by A. subterraneus workers during the preparation of leaf disks and baits and their incorporation into the fungus garden. Results show that the act of licking the substrate was the most frequently executed behavior, regardless of subspecies or size categories. Moreover, additional behaviors have been observed when workers processed the baits, such as licking and scraping their jaws on the surface of the bait pellet, as well as licking and biting fragments of bait pellets, moistening them. Thus, it is concluded that the preparation of baits is different from that of leaves; baits are more processed and can therefore contribute to contaminating workers via insecticides.

Structure and Absolute Configuration of Secondary Metabolites from Two Strains of Streptomyces chartreusis Associated with Attine Ants

The antibiotic streptazolin (1), its E-isomer (2), along with the stereoisomers strepchazolin A (3) and strepchazolin B (4) and the inorganic compound cyclooctasulfur (5) were produced in solid culture by Streptomyces chartreusis ICBG377, which was isolated from the fungal garden of the leaf-cutter ant Acromyrmex subterraneus brunneus. This is the first time compound 2 is reported as a natural product. Compound 5, which showed antagonist activity against the specialized pathogenic fungus Escovopsis sp., was also produced by Streptomyces chartreusis ICBG323, isolated from the exoskeleton of winged male of Mycocepurus goeldii. The absolute configurations of 3 and 4 were confirmed by the combination of vibrational circular dichroism (VCD) spectroscopy and density functional theory (DFT) calculations. These results clearly demostrate the power of VCD to tell apart epimeric natural products. Compounds 1, 3 and 4 were produced by geographically distant but phylogenetically close strains, S. chartreusis ICBG 377 isolated in Brazil, and S. chartreusis NA02069, a marine sediment strain isolated in China.