Two +ssRNA mycoviruses cohabiting the fungal cultivar of leafcutter ants.

Leafcutter ants are dominant herbivores in the Neotropics and rely on a fungus (Leucoagaricus gongylophorus) to transform freshly gathered leaves into a source of nourishment rather than consuming the vegetation directly. Here we report two virus-like particles that were isolated from L. gongylophorus and observed using transmission electron microscopy. RNA sequencing identified two +ssRNA mycovirus strains, Leucoagaricus gongylophorus tymo-like virus 1 (LgTlV1) and Leucoagaricus gongylophorus magoulivirus 1 (LgMV1). Genome annotation of LgTlV1 (7401 nt) showed conserved domains for methyltransferase, endopeptidase, viral RNA helicase, and RNA-dependent RNA polymerase (RdRp). The smaller genome of LgMV1 (2636 nt) contains one open reading frame encoding an RdRp. While we hypothesize these mycoviruses function as symbionts in leafcutter farming systems, further study will be needed to test whether they are mutualists, commensals, or parasites.

Molecular identification of predation on the Dubas bug (Hemiptera: Tropiduchidae) in Oman date palms: density-dependent response to prey.

The date palm (Phoenix dactylifera L.) (Arecales: Arecaceae) is the most economically important crop in Oman with an annual production of >360,000 tons of fruit. The Dubas bug (Ommatissus lybicus de Bergevin) (Hemiptera: Tropiduchidae) is one of the major pests of date palms, causing up to a 50% reduction in fruit production. Across the course of 2 seasons, a variety of arthropod predators living in the date palm canopy were investigated for possible biological control of Dubas bugs, given the growing interest in nonchemical insect pest control in integrated pest management. We collected ~6,900 arthropod predators directly from date palm fronds from 60 Omani date palm plantations and tested them for Dubas bug predation using PCR-based molecular gut content analysis. We determined that ≥56 species of arthropod predators feed on the Dubas bug. We found that predatory mites, ants, and the entire predator community combined showed a positive correlation between predation detection frequency and increasing Dubas bug density. Additionally, there was a significant impact of season on gut content positives, with the spring season having a significantly higher percentage of predators testing positive for Dubas bug, suggesting this season could be the most successful time to target conservation biological control programs utilizing a diverse suite of predators.

Comparative transcriptomics and phylostratigraphy of Argentine ant odorant receptors.

Nestmate recognition in ants is regulated through the detection of cuticular hydrocarbons by odorant receptors (ORs) in the antennae. These ORs are crucial for maintaining colony cohesion that allows invasive ant species to dominate colonized environments. In the invasive Argentine ant, Linepithema humile, ORs regulating nestmate recognition are thought to be present in a clade of nine-exon odorant receptors, but the identity of the specific genes remains unknown. We sought to narrow down the list of candidate genes using transcriptomics and phylostratigraphy. Comparative transcriptomic analyses were conducted on the antennae, head, thorax, and legs of Argentine ant workers. We have identified a set of twenty-one nine-exon odorant receptors enriched in the antennae compared to the other tissues, allowing for downstream verification of whether they can detect Argentine ant cuticular hydrocarbons. Further investigation of these ORs could allow us to further understand the mechanisms underlying nestmate recognition and colony cohesion in ants.

[Effects of ant nesting on seasonal dynamics of soil CH4 emissions in a tropical rubber-plantation forest]. / 蚂蚁筑巢对热带橡胶人工林土壤甲烷排放季节动态的影响.

Ant nests can affect the process and seasonal dynamics of forest soil methane emissions through mediating methane oxidation/reduction microorganisms and physicochemical environments. To explore the process and mechanism by which ant nests affect soil methane emissions from Hevea brasiliensis plantation in Xishuangbanna, we measured the seasonal dynamics of methane emissions from ant nest and non-nest soils by using static chamber-gas chromatography method, and analyzed the effect of ant nesting on the changes in functional microbial diversity, microhabitats, and soil nutrients in the plantations. The results showed that: 1) Ant nests significantly affected the mean annual soil methane emissions in tropical plantation. Methane emissions in ant nest were decreased by 59.9% than the non-nest soil. In the dry season, ant nest soil was a methane sink (-1.770 µg·m-2·h-1), which decreased by 87.2% compared with the non-nest soil, while it was a methane source (0.703 µg·m-2·h-1) that increased by 152.7% in the wet season. 2) Ant nesting affected methane emissions via changing soil temperature, humidity, carbon and nitrogen concentrations. In contrast to the control, the mean annual temperature, humidity, and carbon and nitrogen content increased by 4.9%-138.5% in ant nest soils, which explained 90.1%, 97.3%, 27.3%-90.0% of the variation in methane emissions, respectively. 3) Ant nesting affected the emission dynamics through changing the diversity and community structure of methane functional microbe. Compared with the control, the average annual methanogen diversity (Ace, Chao1, Shannon, and Simpson indices) in the ant nest ranged from -9.9% to 61.2%, which were higher than those (-8.7%-31.2%) of the methane-oxidising bacterial communities. The relative abundance fluctuations of methanogens and methanotrophic bacteria were 46.76% and -6.33%, respectively. The explaining rate of methanogen diversity to methane emissions (78.4%) was higher than that of oxidizing bacterial diversity (54.5%), the relative abundance explained by the dominant genus of methanogens was 68.9%. 4) The structural equation model showed that methanogen diversity, methanotroph diversity, and soil moisture were the main factors controlling methane emissions, contributing 95.6%, 95.0%, and 91.2% to the variations of emissions, respectively. The contribution (73.1%-87.7%) of soil temperature and carbon and nitrogen components to the emission dynamics was ranked the second. Our results suggest that ant nesting mediates the seasonal dynamics of soil methane emissions, primarily through changing the diversity of methane-function microorganisms and soil water conditions. The research results deepen the understanding of the mechanism of biological regulation of methane emission in tropical forest soil.

Leaderless consensus decision-making determines cooperative transport direction in weaver ants.

Animal groups need to achieve and maintain consensus to minimize conflict among individuals and prevent group fragmentation. An excellent example of a consensus challenge is cooperative transport, where multiple individuals cooperate to move a large item together. This behaviour, regularly displayed by ants and humans only, requires individuals to agree on which direction to move in. Unlike humans, ants cannot use verbal communication but most likely rely on private information and/or mechanical forces sensed through the carried item to coordinate their behaviour. Here, we investigated how groups of weaver ants achieve consensus during cooperative transport using a tethered-object protocol, where ants had to transport a prey item that was tethered in place with a thin string. This protocol allows the decoupling of the movement of informed ants from that of uninformed individuals. We showed that weaver ants pool together the opinions of all group members to increase their navigational accuracy. We confirmed this result using a symmetry-breaking task, in which we challenged ants with navigating an open-ended corridor. Weaver ants are the first reported ant species to use a 'wisdom-of-the-crowd' strategy for cooperative transport, demonstrating that consensus mechanisms may differ according to the ecology of each species.

Impact of environmental pollution on ant (Camponotus japonicus) development and labial gland disease.

Metallic pollutants can have harmful impacts on ant morphology and physiology. We studied the occurrence of labial gland disease in Camponotus japonicus from two polluted areas (traffic pollution and industrial pollution) and one non-polluted area. We further analyzed the metal levels (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn) and morphological characteristics (head width, body mass, and other morphological traits) of both diseased and healthy workers. Our results showed that labial gland disease was only present in polluted areas, indicating that pollution stress makes ants more vulnerable to infections. Our research revealed that diseased ants in polluted areas accumulate higher levels of metals in their bodies and have lower dry weight and residual body mass compared to healthy ants in non-polluted environments, negatively impacting their development. We evaluated the importance of these elements and found that Cu has the greatest impact on the health risk of C. japonicus. Our study underscores the significant impact of environmental pollution on ant morphology and physiology and raises concerns about the broader ecological implications.

Long-term strict ant-plant mutualism identity characterises growth rate and leaf shearing resistance of an Amazonian myrmecophyte.

Over 125 million years of ant-plant interactions have culminated in one of the most intriguing evolutionary outcomes in life history. The myrmecophyte Duroia hirsuta (Rubiaceae) is known for its mutualistic association with the ant Myrmelachista schumanni and several other species, mainly Azteca, in the north-western Amazon. While both ants provide indirect defences to plants, only M. schumanni nests in plant domatia and has the unique behaviour of clearing the surroundings of its host tree from heterospecific plants, potentially increasing resource availability to its host. Using a 12-year survey, we asked how the continuous presence of either only M. schumanni or only Azteca spp. benefits the growth and defence traits of host trees. We found that the continuous presence of M. schumanni improved relative growth rates and leaf shearing resistance of Duroia better than trees with Azteca. However, leaf herbivory, dry matter content, trichome density, and secondary metabolite production were the same in all trees. Survival depended directly on ant association (> 94% of trees died when ants were absent). This study extends our understanding of the long-term effects of strict ant-plant mutualism on host plant traits in the field and reinforces the use of D. hirsuta-M. schumanni as a model system suitable for eco-co-evolutionary research on plant-animal interactions.

Ant colony optimization for the identification of dysregulated gene subnetworks from expression data.

BACKGROUND: High-throughput experimental technologies can provide deeper insights into pathway perturbations in biomedical studies. Accordingly, their usage is central to the identification of molecular targets and the subsequent development of suitable treatments for various diseases. Classical interpretations of generated data, such as differential gene expression and pathway analyses, disregard interconnections between studied genes when looking for gene-disease associations. Given that these interconnections are central to cellular processes, there has been a recent interest in incorporating them in such studies. The latter allows the detection of gene modules that underlie complex phenotypes in gene interaction networks. Existing methods either impose radius-based restrictions or freely grow modules at the expense of a statistical bias towards large modules. We propose a heuristic method, inspired by Ant Colony Optimization, to apply gene-level scoring and module identification with distance-based search constraints and penalties, rather than radius-based constraints. RESULTS: We test and compare our results to other approaches using three datasets of different neurodegenerative diseases, namely Alzheimer's, Parkinson's, and Huntington's, over three independent experiments. We report the outcomes of enrichment analyses and concordance of gene-level scores for each disease. Results indicate that the proposed approach generally shows superior stability in comparison to existing methods. It produces stable and meaningful enrichment results in all three datasets which have different case to control proportions and sample sizes. CONCLUSION: The presented network-based gene expression analysis approach successfully identifies dysregulated gene modules associated with a certain disease. Using a heuristic based on Ant Colony Optimization, we perform a distance-based search with no radius constraints. Experimental results support the effectiveness and stability of our method in prioritizing modules of high relevance. Our tool is publicly available at github.com/GhadiElHasbani/ACOxGS.git.

Disproportional fraction of inactive components leads to the variation in metabolic scaling.

In biological systems, solitary organisms or eusocial groups, the metabolic rate often scales allometrically with systems' size, when they are inactive, and the scaling becomes nearly isometric when the systems are active. Here I propose a hypothesis attempting to offer a departing point for a general joint understanding of the difference in the scaling powers between inactive and active states. When the system is inactive, there exist inactive components, which consume less energy than the active ones, and the larger the system is, the larger the fraction of the inactive components, which leads to sublinear scaling. When the system is active, most inactive components are activated, which leads to nearly isometric scaling. I hypothesize that the disproportional fraction of the inactive components is caused by the diffusants screening in the complex transportation network. I.e., when metabolites or information diffuses in the system, due to the physical limitation of the network structure and the diffusant's physical feature, not all the components can equally receive the diffusants so that these components are inactive. Using the mammalian pulmonary system, ant colonies, and other few systems as examples, I discuss how the screening leads to the allometric and isometric metabolic scaling powers in inactive and active states respectively. It is noteworthy that there are a few exceptions, in which the metabolic rate of the system has an isometric scaling relationship with size at rest. I show that these exceptions not only do not disapprove the hypothesis, but actually support it.

Species-specific behavioural responses to environmental variation as a potential species coexistence mechanism in ants.

A fundamental question of ecology is why species coexist in the same habitat. Coexistence can be enabled through niche differentiation, mediated by trait differentiation. Here, behaviour constitutes an often-overlooked set of traits. However, behaviours such as aggression and exploration drive intra- and interspecific competition, especially so in ants, where community structure is usually shaped by aggressive interactions. We studied behavioural variation in three ant species, which often co-occur in close proximity and occupy similar dominance ranks. We analysed how intra- and allospecific aggression, exploration and foraging activity vary under field conditions, namely with temperature and over time. Behaviours were assessed for 12 colonies per species, and four times each during several months. All behavioural traits consistently differed among colonies, but also varied over time and with temperature. These temperature-dependent and seasonal responses were highly species-specific. For example, foraging activity decreased at high temperatures in Formica rufibarbis, but not in Lasius niger; over time, it declined strongly in L. niger but much less in F. rufibarbis. Our results suggest that, owing to these species-specific responses, no species is always competitively superior. Thus, environmental and temporal variation effects a dynamic dominance hierarchy among the species, facilitating coexistence via the storage effect.

Ant mimicry in Australian plant bugs: a new genus (Heteroptera: Miridae: Austromirini: Carenotus gen. nov.), eight new species, myrmecomorphic traits, host plants and distribution.

The Australian plant bug tribe Austromirini consists of ant-mimetic taxa which are poorly known, with no information of their phylogenetic relationships and ant-mimetic traits. In this study, we examined nearly 1000 ingroup specimens and developed a comprehensive morphological dataset comprising 37 characters, which was analysed both weighted and unweighted, using 'Tree analysis using New Technology' (TNT ) software. A single minimal length phylogenetic tree was found, comprising a monophyletic group of ant-mimetic taxa, that included Myrmecoroides rufescens , Myrmecoridea sp., Kirkaldyella spp. and eight species of a new genus, Carenotus gen. nov. The myrmecomorphic traits of Carenotus and allied ant-mimetic taxa are documented and analysed phylogenetically, in conjunction with genitalic characters. Carenotus is defined by the myrmecomorphic colour patterning of the abdominal venter, whereas the ingroup species relationships are supported by genitalic characters alone. Carenotus is described as new with eight included species as follows: C. arltunga sp. nov., C. louthensis sp. nov., C. luritja sp. nov., C. pullabooka sp. nov., C. scaevolaphilus sp. nov., C. schwartzi sp. nov., C. tanami sp. nov. and C. yuendumu sp. nov. Host plant associations are also documented, ranging from host plant specificity and genus-group preferences to host plant generalism. The distribution of Carenotus species is documented with reference to phytogeographic subregions, with all species being semi-arid and arid dwelling. The male and female genitalia of Kirkaldyella pilosa and K. rugosa are described and illustrated, for comparative and phylogenetic purposes. This research expands our knowledge on the plant bug tribe Austromirini and has broader implications for myrmecomorphic research in the suborder Heteroptera. ZooBank: urn:lsid:zoobank.org:pub:2FF9BE23-38A6-42B4-8488-74F216D8237F.

How online pro-environmental games affect users' pro-environmental behavioural intentions? - Insights from Ant Forest.

Information technology has created new ways for people to participate in environmental protection. Ant Forest, a pro-environmental game that actively encourages users to take part in offline environmental activities through online gaming content, has gained great popularity. However, research in this area is still limited, and the effect of playing such games on users' pro-environmental intentions in real life and the underlying mechanisms are unknown. Therefore, this research draws from Persuasive Systems Design model and value theory and examines the relationships between design features of Ant Forest, users' values and their pro-environmental behavioural intentions. The research model is empirically tested by survey data from 428 Ant Forest users. Results indicate that users' self-enhancement values, including utilitarian, hedonic and social values, and self-transcendence values, including altruistic and biospheric values, all positively affect their continued gameplay intentions and therefore affect their pro-environmental behavioural intentions. Additionally, the primary task support, social support, dialogue support, and system credibility of Ant Forest have varying positive effects on users' perceived values.

Ant impacts on global patterns of bird elevational diversity.

Using data on bird species elevational distributions from the world's mountain ranges, bird diets, and the distribution of the ant genus Oecophylla, we report that global patterns in bird elevational diversity show signals of competition with ants. Oecophylla is an abundant and effective predator of invertebrates, preying on the same species that invertivorous birds feed on. In mountain ranges with Oecophylla present in the foothills, the maximum species richness of invertivorous birds (but not other trophic guilds) occurs, on average, at 960 m, ca. 450 m higher than in mountain ranges without Oecophylla, resulting in a mid-elevation peak in bird species richness. Where Oecophylla is absent, bird species richness for all guilds generally show monotonic declines with increasing elevation. We argue that Oecophylla reduces prey density for invertivorous birds and that low prey abundance reduces invertivorous bird density, which in turn is correlated with lower bird species richness. These findngs suggest that competition between distantly related taxa can set range limits, leading to emergent diversity patterns over large scales.

Male genitalia, hierarchical homology, and the anatomy of the bullet ant (Paraponera clavata; Hymenoptera, Formicidae).

The male genitalia of insects are among the most variable, complex, and informative character systems for evolutionary analysis and taxonomic purposes. Because of these general properties, many generations of systematists have struggled to develop a theory of homology and alignment of parts. This struggle continues to the present day, where fundamentally different models and nomenclatures for the male genitalia of Hymenoptera, for example, are applied. Here, we take a multimodal approach to digitalize and comprehensively document the genital skeletomuscular anatomy of the bullet ant (Paraponera clavata; Hymenoptera: Formicidae), including hand dissection, synchrotron radiation microcomputed tomography, microphotography, scanning electron microscopy, confocal laser scanning microscopy, and 3D-printing. Through this work, we generate several new concepts for the structure and form of the male genitalia of Hymenoptera, such as for the endophallic sclerite (=fibula ducti), which we were able to evaluate in detail for the first time for any species. Based on this phenomic anatomical study and comparison with other Holometabola and Hexapoda, we reconsider the homologies of insect genitalia more broadly, and propose a series of clarifications in support of the penis-gonopod theory of male genital identity. Specifically, we use the male genitalia of Paraponera and insects more broadly as an empirical case for hierarchical homology by applying and refining the 5-category classification of serial homologs from DiFrisco et al. (2023) (DLW23) to all of our formalized concepts. Through this, we find that: (1) geometry is a critical attribute to account for in ontology, especially as all individually identifiable attributes are positionally indexed hence can be recognized as homomorphic; (2) the definition of "structure" proposed by DLW23 is difficult to apply, and likely heterogeneous; and (3) formative elements, or spatially defined foldings or in- or evaginations of the epidermis and cuticle, are an important yet overlooked class of homomorphs. We propose a morphogenetic model for male and female insect genitalia, and a model analogous to gene-tree species-tree mappings for the hierarchical homology of male genitalia specifically. For all of the structures evaluated in the present study, we provide 3D-printable models - with and without musculature, and in various states of digital dissection - to facilitate the development of a tactile understanding. Our treatment of the male genitalia of P. clavata serves as a basic template for future phenomic studies of male insect genitalia, which will be substantially improved with the development of automation and collections-based data processing pipelines, that is, collectomics. The Hymenoptera Anatomy Ontology will be a critical resource to include in this effort, and in best practice concepts should be linked.

Genotypes and phenotypes in a Wolbachia-ant symbiosis.

The fitness effects of overt parasites, and host resistance to them, are well documented. Most symbionts, however, are more covert and their interactions with their hosts are less well understood. Wolbachia, an intracellular symbiont of insects, is particularly interesting because it is thought to be unaffected by the host immune response and to have fitness effects mostly focussed on sex ratio manipulation. Here, we use quantitative PCR to investigate whether host genotype affects Wolbachia infection density in the leaf-cutting ant Acromyrmex echinatior, and whether Wolbachia infection density may affect host morphology or caste determination. We found significant differences between host colonies in the density of Wolbachia infections, and also smaller intracolonial differences in infection density between host patrilines. However, the density of Wolbachia infections did not appear to affect the morphology of adult queens or likelihood of ants developing as queens. The results suggest that both host genotype and environment influence the host-Wolbachia relationship, but that Wolbachia infections carry little or no physiological effect on the development of larvae in this system.

Cretaceous crown male ant reveals the rise of modern lineages.

Most described Mesozoic ants belong to stem groups that existed only during the Cretaceous period. Previously, the earliest known crown ants were dated to the Turonian (Late Cretaceous, ca. 94-90 million years ago (Ma)) deposits found in the USA, Kazakhstan, and Botswana. However, the recent discovery of an alate male ant in Kachin amber from the earliest Cenomanian (ca. 99 Ma), representing a new genus and species, Antiquiformica alata, revises the narrative on ant diversification. Antiquiformica can be distinctly differentiated from all known male stem ants by its geniculate antennae with elongated scape, extending far beyond the occipital margin of the head and half the length of the funiculus, as well as its partly reduced forewing venation. Furthermore, the combination of a one-segmented waist with a well-developed node, elongated scape extending beyond the occipital margin, and reduced forewing venation, particularly the completely reduced m-cu and rs-m crossveins and absence of rm and mcu closed cells, firmly places the fossil within the extant subfamily Formicinae. Fourier transform infrared spectroscopy (FTIR) confirmed that the amber containing Antiquiformica alata originated from the Kachin mines in Myanmar. This discovery significantly revises our understanding of the early evolution of Formicinae. The presence of Antiquiformica in Cenomanian amber indicates that the subfamily Formicinae emerged at least by the start of the Late Cretaceous, with crown ants likely originating earlier during the earliest Cretaceous or possibly the Late Jurassic, although paleontological evidence is lacking to support the latter hypothesis.

Ant social network structure is highly conserved across species.

The ecological success of social insects makes their colony organization fascinating to scientists studying collective systems. In recent years, the combination of automated behavioural tracking and social network analysis has deepened our understanding of many aspects of colony organization. However, because studies have typically worked with single species, we know little about interspecific variation in network structure. Here, we conduct a comparative network analysis across five ant species from five subfamilies, separated by more than 100 Myr of evolution. We find that social network structure is highly conserved across subfamilies. All species studied form modular networks, with two social communities, a similar distribution of individuals between the two communities, and equivalent mapping of task performance onto the communities. Against this backdrop of organizational similarity, queens of the different species occupied qualitatively distinct network positions. The deep conservation of the two community structure implies that the most fundamental behavioural division of labour in social insects is between workers that stay in the nest to rear brood, and those that leave the nest to forage. This division has parallels across the animal kingdom in systems of biparental care and probably represents the most readily evolvable form of behavioural division of labour.

Random walks with spatial and temporal resets can explain individual and colony-level searching patterns in ants.

Central place foragers, such as many ants, exploit the environment around their nest. The extent of their foraging range is a function of individual movement, but how the movement patterns of large numbers of foragers result in an emergent colony foraging range remains unclear. Here, we introduce a random walk model with stochastic resetting to depict the movements of searching ants. Stochastic resetting refers to spatially resetting at random times the position of agents to a given location, here the nest of searching ants. We investigate the effect of a range of resetting mechanisms and compare the macroscopic predictions of our model to laboratory and field data. We find that all returning mechanisms very robustly ensure that scouts exploring the surroundings of a nest will be exponentially distributed with distance from the nest. We also find that a decreasing probability for searching ants to return to their nest is compatible with empirical data, resulting in scouts going further away from the nest as the number of foraging trips increases. Our findings highlight the importance of resetting random walk models for depicting the movements of central place foragers and nurture novel questions regarding the searching behaviour of ants.

Co-inheritance of recombined chromatids maintains heterozygosity in a parthenogenetic ant.

According to Mendel's second law, chromosomes segregate randomly in meiosis. Non-random segregation is primarily known for cases of selfish meiotic drive in females, in which particular alleles bias their own transmission into the oocyte. Here we report a rare example of unselfish meiotic drive for crossover inheritance in the clonal raider ant, Ooceraea biroi, in which both alleles are co-inherited at all loci across the entire genome. This species produces diploid offspring parthenogenetically via fusion of two haploid nuclei from the same meiosis. This process should cause rapid genotypic degeneration due to loss of heterozygosity, which results if crossover recombination is followed by random (Mendelian) segregation of chromosomes. However, by comparing whole genomes of mothers and daughters, we show that loss of heterozygosity is exceedingly rare, raising the possibility that crossovers are infrequent or absent in O. biroi meiosis. Using a combination of cytology and whole-genome sequencing, we show that crossover recombination is, in fact, common but that loss of heterozygosity is avoided because crossover products are faithfully co-inherited. This results from a programmed violation of Mendel's law of segregation, such that crossover products segregate together rather than randomly. This discovery highlights an extreme example of cellular 'memory' of crossovers, which could be a common yet cryptic feature of chromosomal segregation.

Social evolution: Limb amputation prevents infection in ants.

Social insect workers, renowned for their altruism, are frequently perceived as 'disposable'. A new study finds that ants amputate the limbs of nestmates, which saves them from infection, and indicates that worker care is as critical to colony success as sacrifice.