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Season length and its associated variables can influence the expression of social behaviours, including the occurrence of eusociality in insects. Eusociality can vary widely across environmental gradients, both within and between different species. Numerous theoretical models have been developed to examine the life history traits that underlie the emergence and maintenance of eusociality, yet the impact of seasonality on this process is largely uncharacterized. Here, we present a theoretical model that incorporates season length and offspring development time into a single, individual-focused model to examine how these factors can shape the costs and benefits of social living. We find that longer season lengths and faster brood development times are sufficient to favour the emergence and maintenance of a social strategy, while shorter seasons favour a solitary one. We also identify a range of season lengths where social and solitary strategies can coexist. Moreover, our theoretical predictions are well matched to the natural history and behaviour of two flexibly eusocial bee species, suggesting that our model can make realistic predictions about the evolution of different social strategies. Broadly, this work reveals the crucial role that environmental conditions can have in shaping social behaviour and its evolution and it underscores the need for further models that explicitly incorporate such variation to study the evolutionary trajectories of eusociality. [ABSTRACT FROM AUTHOR]

The naked mole-rat (Heterocephalus glaber) is a mouse-sized rodent species, notable for its eusociality and long lifespan. Previously, we reported that demographic aging, i.e., the exponential increase of mortality hazard that accompanies advancing age in mammals and other organisms, does not occur in naked mole-rats (Ruby et al., 2018), a finding that has potential implications for human healthy aging. The demographic data supporting that conclusion had taken over three decades to accumulate, starting with the original rearing of H. glaber in captivity. This finding was controversial since many of the animals in that study were relatively young. In the 5 years following that study, we have doubled our quantity of demographic data. Here, we re-evaluated our prior conclusions in light of these new data and found them to be not only supported but indeed strengthened. We additionally provided insight into the social dynamics of captive H. glaber with data and analyses of body weight and colony size versus mortality. Finally, we provide a phylogenetically proximal comparator in the form of lifespan data from our Damaraland mole-rat (Fukomys damarensis) colony and demographic meta-analysis of those data along with published data from Ansell's mole-rat (Fukomys anselli). We found Fukomys mortality hazard to increase gradually with age, an observation with inferences on the evolution of exceptional lifespan among mole-rats and the ecological factors that may have accompanied that evolution. [ABSTRACT FROM AUTHOR]

Communication is essential for social organisms. In eusocial insects, olfaction facilitates communication and recognition between nestmates. The study of certain model organisms has led to the hypothesis that odorant receptors are expanded in eusocial Hymenoptera. This has become a widely mentioned idea in the literature, albeit with conflicting reports, and has not been tested with a broad comparative analysis. Here we combined existing genomic and new neuroanatomical data, including from an approximately 100 Myr old fossil ant, across a phylogenetically broad sample of hymenopteran lineages. We find no evidence that variation in the size and evolutionary tempo of odorant receptor repertoires is related to eusociality. Post hoc exploration of our data hinted at loss of flight as a possible factor shaping some of the variation in OR repertoires in Hymenoptera. Nevertheless, our analyses revealed a complex pattern of evolutionary variation, and raise new questions about the ecological, behavioural and social factors that shape olfactory abilities. [ABSTRACT FROM AUTHOR]

Animal collective behavior produces group‐level patterns that emerge from individual‐level interactions among members. Such sophisticated behavioral coordination can be observed across various taxa, indicating evolutionary convergence. Among the most striking examples are two social insect lineages: ants and termites. Ants and termites evolved socially independently, inhabit terrestrial and subterranean environments, and face a similar collective task of maintaining their colonies with many individuals. This results in the convergent evolution of collective phenomena, such as constructing complex nest structures or movement coordination based on chemical and tactile cues. However, although the striking similarity attracts the most attention, little research has focused on how ants and termites differ in collective behaviors at individual and group levels. Here, we review the similarities and distinctions of collective behaviors in ants and termites. Even with similarities in group‐level patterns, rich diversity exists in mechanisms of behavioral coordination and the functions of collective patterns. Comparative analysis of collective behavior is challenging, but recent advances in automatic movement tracking methodologies have greatly expanded the potential for generating further insights. Finally, we conclude that comparative collective behavioral analysis can enhance our ability to understand biodiversity and provide alternative solutions for collective problem‐solving in many fields. [ABSTRACT FROM AUTHOR]

Eusocial organisms typically live in colonies with one reproductive queen supported by thousands of sterile workers. It is widely believed that monogamous mating is a precondition for the evolution of eusociality. Here, we present a theoretical model that simulates a realistic scenario for the evolution of eusociality. In the model, mothers can evolve control over resource allocation to offspring, affecting offspring's body size. The offspring can evolve body-size-dependent dispersal, by which they disperse to breed or stay at the nest as helpers. We demonstrate that eusociality can evolve even if mothers are not strictly monogamous, provided that they can constrain their offspring's reproduction through manipulation. We also observe the evolution of social polymorphism with small individuals that help and larger individuals that disperse to breed. Our model unifies the traditional kin selection and maternal manipulation explanations for the evolution of eusociality and demonstrates that--contrary to current consensus belief--eusociality can evolve despite highly promiscuous mating. [ABSTRACT FROM AUTHOR]

Eusociality, where units that previously reproduced independently function as one entity, is of major interest in evolutionary biology. Obligate eusociality is characterized by morphologically differentiated castes and reduced conflict. We explore conditions under which morphological castes may arise in the Hymenoptera and factors constraining their evolution. Control over offspring morphology and behaviour seems likely to be decoupled. Provisioners (queens and workers) can influence offspring morphology directly through the nutrition they provide, while adult offspring control their own behaviour. Provisioners may, however, influence worker behaviour indirectly if offspring modify their behaviour in response to their morphology. If manipulation underlies helping, we should not see helping evolve before specialized worker morphology, yet empirical observations suggest that behavioural castes precede morphological castes. We use evolutionary invasion analyses to show how the evolution of a morphologically differentiated worker caste depends on the prior presence of a behavioural caste: specialist worker morphology will be mismatched with behaviour unless some offspring already choose to work. A mother's certainty about her offspring's behaviour is also critical—less certainty results in greater mismatch. We show how baseline worker productivity can affect the likelihood of a morphological trait being favoured by natural selection. We then show how under a decoupled control scenario, morphologically differentiated castes should be less and less likely to be lost as they become more specialized. We also suggest that for eusociality to be evolutionarily irreversible, workers must be unable to functionally replace reproductives and reproductives must be unable to reproduce without help from workers. Graphical Abstract [ABSTRACT FROM AUTHOR]

Eusocial insects, such as ants and termites, are characterized by high levels of coordinated social organization. This is contrasted by solitary insects that display more limited forms of collective behavior. It has been hypothesized that this gradient in sociobehavioral sophistication is positively correlated with chemical profile complexity, due to a potentially increased demand for diversity in chemical communication mechanisms in insects with higher levels of social complexity. However, this claim has rarely been assessed empirically. Here, we compare different levels of chemical and transcriptomic complexity in selected species of the order Blattodea that represent different levels of social organization, from solitary to eusocial. We primarily focus on cuticular hydrocarbon (CHC) complexity, since it has repeatedly been demonstrated that CHCs are key signaling molecules conveying a wide variety of chemical information in solitary as well as eusocial insects. We assessed CHC complexity and divergence between our studied taxa of different social complexity levels as well as the differentiation of their respective repertoires of CHC biosynthesis gene transcripts. Surprisingly, we did not find any consistent pattern of chemical complexity correlating with social complexity, nor did the overall chemical divergence or transcriptomic repertoire of CHC biosynthesis genes reflect on the levels of social organization. Our results challenge the assumption that increasing social complexity is generally reflected in more complex chemical profiles and point toward the need for a more cautious and differentiated view on correlating complexity on a chemical, genetic, and social level. [ABSTRACT FROM AUTHOR]

In eusocial insects, worker longevity is essential to ensure colony survival in brood-free periods. Trade-offs between longevity and other traits may render long-living workers in brood-free periods more susceptible to pesticides compared to short-lived ones. Further, colony environment (e.g., adequate nutrition) may enable workers to better cope with pesticides, yet data comparing long vs. short-living workers and the role of the colony environment for pesticide tolerance are scarce. Here, we show that long-living honey bee workers, Apis mellifera, are less susceptible to the neonicotinoid thiamethoxam than short-lived workers, and that susceptibility was further reduced when workers were acclimatized under colony compared to laboratory conditions. Following an OECD protocol, freshly-emerged workers were exposed to thiamethoxam in summer and winter and either acclimatized within their colony or in the laboratory. Mortality and sucrose consumption were measured daily and revealed that winter workers were significantly less susceptible than summer workers, despite being exposed to higher thiamethoxam dosages due to increased food consumption. Disparencies in fat body activity, which is key for detoxification, may explain why winter bees were less susceptible. Furthermore, colony acclimatization significantly reduced susceptibility towards thiamethoxam in winter workers likely due to enhanced protein nutrition. Brood absence and colony environment seem to govern workers' ability to cope with pesticides, which should be considered in risk assessments. Since honey bee colony losses occur mostly over winter, long-term studies assessing the effects of pesticide exposure on winter bees are required to better understand the underlying mechanisms. [ABSTRACT FROM AUTHOR]

Domains as functional protein units and their rearrangements along the phylogeny can shed light on the functional changes of proteomes associated with the evolution of complex traits like eusociality. This complex trait is associated with sterile soldiers and workers, and long-lived, highly fecund reproductives. Unlike in Hymenoptera (ants, bees, and wasps), the evolution of eusociality within Blattodea, where termites evolved from within cockroaches, was accompanied by a reduction in proteome size, raising the question of whether functional novelty was achieved with existing rather than novel proteins. To address this, we investigated the role of domain rearrangements during the evolution of termite eusociality. Analysing domain rearrangements in the proteomes of three solitary cockroaches and five eusocial termites, we inferred more than 5,000 rearrangements over the phylogeny of Blattodea. The 90 novel domain arrangements that emerged at the origin of termites were enriched for several functions related to longevity, such as protein homeostasis, DNA repair, mitochondrial activity, and nutrient sensing. Many domain rearrangements were related to changes in developmental pathways, important for the emergence of novel castes. Along with the elaboration of social complexity, including permanently sterile workers and larger, foraging colonies, we found 110 further domain arrangements with functions related to protein glycosylation and ion transport. We found an enrichment of caste-biased expression and splicing within rearranged genes, highlighting their importance for the evolution of castes. Furthermore, we found increased levels of DNA methylation among rearranged compared to non-rearranged genes suggesting fundamental differences in their regulation. Our findings indicate the importance of domain rearrangements in the generation of functional novelty necessary for termite eusociality to evolve. Graphical Abstract [ABSTRACT FROM AUTHOR]

Ant physiology has been fashioned by 100 million years of social evolution. Ants perform many sophisticated social and collective behaviors yet possess nervous systems similar in schematic and scale to that of the fruit fly Drosophila melanogaster, a popular solitary model organism. Ants are thus attractive complementary subjects to investigate adaptations pertaining to complex social behaviors that are absent in flies. Despite research interest in ant behavior and the neurobiological foundations of sociality more broadly, our understanding of the ant nervous system is incomplete. Recent technical advances have enabled cutting-edge investigations of the nervous system in a fashion that is less dependent on model choice, opening the door for mechanistic social insect neuroscience. In this review, we revisit important aspects of what is known about the ant nervous system and behavior, and we look forward to how functional circuit neuroscience in ants will help us understand what distinguishes solitary animals from highly social ones. [ABSTRACT FROM AUTHOR]

Societies of social Hymenoptera usually consist of groups of closely related females in which the dominant female(s) is specialized for reproduction and subordinate females care for immature offspring. Studying simple societies allows the identification of factors responsible for early stages of evolution of sociality. Here, we examined facultative social nesting in the species Ceratina chalybea using nest dissection, observation of nests, and evaluation of relatedness using microsatellite loci. Social nests were composed of an old female and on average 3.38 young adults and 2.05 newly provisioned brood cells. Social nests had a smaller number of brood cells, and empty cells made up a smaller proportion of the nest in comparison with solitary nests. Moreover, social nesting was strongly associated with nest reuse. Almost all of the young adults present were males, and about half of them were unrelated to the old female. The old female was the only member of the society who performed regular foraging. Feeding of mature offspring by the mother is typical for Ceratina bees. We suppose that social nests emerge when the mother begins provisioning new brood cells in the same nest where young adults are still present. As young adults do not perform physically demanding or risky activities, they incur little or no cost, but they can benefit from the food they obtain from the old female. Our results suggest that relatedness may be unimportant for eusociality maintenance when costs of helping behaviour are small. [ABSTRACT FROM AUTHOR]

This article explores the use of social insects, like ants, bees, and wasps, as models for studying reproductive longevity. Social insect queens have long lifespans and high fertility, which challenges the typical trade-off between lifespan and reproduction. These insects provide valuable insights into the molecular and cellular mechanisms that allow for high fecundity and long lifespans. The article also discusses the plasticity of senescence and fertility in social insects and raises questions about the deviations from conventional aging theories. Further research in social insects could provide important insights into reproductive senescence and aging. Additionally, the article mentions the relevance of non-insect eusocial species, like mole rats, in bridging the gap between social insects and humans. Overall, social insects offer valuable perspectives and potential applications for studying reproductive longevity in diverse species. [Extracted from the article]

Social insects are arthropods that lives in a community with other members of the same species. Eusocial insects frequently lose colony members as a result of living in big groupings. They perform cooperative corpse management to maintain the hygiene of the nest, exhibiting behavioural and physiological responses that promote disease resistance, nutrient reallocating and colony protection. Undertaking behaviour is most common in social insects belonging to Hymenoptera and Isoptera which adopts various mechanisms of death recognition, convergent and divergent behavioural responses towards dead items. Corpse removal, burial, cannibalism and avoidance are different solutions evolved by social insects, independently towards the problem of corpse management. Genetic studies and gene expression analysis related to social immune systems gives a better knowledge on behavioural and physiological disease defense in insects which could be considered a novel access to biological pest control. This article provides a comprehensive understanding of corpse management in social insects. [ABSTRACT FROM AUTHOR]

If we are to reckon Ursula K. Le Guin as the architect of several liminal ecotopian landscapes, what is most noticeable is her pervasive attitude toward the evolutionary ethic of speculative fiction, which clearly encompasses experimentation on several mind-bending ideas, such as the veracity of accessing other-than-human contexts and models of communication, as well as the examination of complex multisensorial modalities backing such phenomena. As a result, it is evident that Le Guin passionately pronounced the ecocultural imperative as the yardstick of her creative sorties, while she explored radical possibilities for networking life and relationships in fictional geographies. On these lines, the three short stories chosen for discussion--Direction of the Road, The Author of the Acacia Seeds, and Texts--are based on the premise of one perceiving and interpreting what otherwise cannot be easily shaped in words. Can a rhizomatic entity claim sentience and chronicle its saga of psycho-ambulatory movement? Can the eusocial ant be deemed an authentic antiquarian scribe on par with a human? Can the ocean's spatial language of ebb and flow be adequately deciphered? These are earth-centered thematic questions raised and answered by Le Guin in the vein of imaginative realism. So too, we observe, the distinctive feature that characterizes the author's narratives is her emphasis on the subject of geo-linguistics and eco-historicism, whereupon every rock, tree, bird, and insect is deemed the hero of one's own story. [ABSTRACT FROM AUTHOR]

Genetic changes that enabled the evolution of eusociality have long captivated biologists. More recently, attention has focussed on the consequences of eusociality on genome evolution. Studies have reported higher molecular evolutionary rates in eusocial hymenopteran insects compared with their solitary relatives. To investigate the genomic consequences of eusociality in termites, we analysed nine genomes, including newly sequenced genomes from three non-eusocial cockroaches. Using a phylogenomic approach, we found that termite genomes have experienced lower rates of synonymous substitutions than those of cockroaches, possibly as a result of longer generation times. We identified higher rates of non-synonymous substitutions in termite genomes than in cockroach genomes, and identified pervasive relaxed selection in the former (24–31% of the genes analysed) compared with the latter (2–4%). We infer that this is due to reductions in effective population size, rather than gene-specific effects (e.g. indirect selection of caste-biased genes). We found no obvious signature of increased genetic load in termites, and postulate efficient purging of deleterious alleles at the colony level. Additionally, we identified genomic adaptations that may underpin caste differentiation, such as genes involved in post-translational modifications. Our results provide insights into the evolution of termites and the genomic consequences of eusociality more broadly. [ABSTRACT FROM AUTHOR]

The shift to a pollen diet and the evolution of more highly organized societies, i.e. eusocial, were key milestones in bee diversification over their evolutionary history, culminating in a high dependence on feeding broods with a large variety of floral resources. Here, we hypothesized that obligatory eusocial bees have a wider diet diversity than their relatives with solitary lifestyles, and this would be related to colony size. To test both hypotheses, we surveyed diet breadth data (palynological analysis) based on the Shannon–Wiener index (Hʹ) for 85 bee taxa. We also obtained colony size for 47 eusocial bee species. These data were examined using phylogenetic comparative methods. The results support the generalist strategy as a derived trait for the bee taxa evaluated here. The dietary diversity of eusocial bees (Hʹ: 2.1, on average) was 67.5% higher than that of noneusocial bees (Hʹ: 1.21, on average). There was, however, no relationship between diet breadth and colony size, indicating that smaller colonies can harvest a pollen variety as diverse as larger colonies. Taken together, these results provide new insights into the impact of lifestyle on the diversity of collected pollen. Furthermore, this work sheds light on an advantage of living in more highly structured societies irrespective of the size of the colony. [ABSTRACT FROM AUTHOR]

Insurance-based mechanisms, where surviving group-members can complete parental care after the death of a nestmate, are key to the origin of cooperative group formation in insects. Selection for group living via these models is proposed to be dependent on the life expectancy of adult carers relative to the duration of offspring dependency on parental care. Progressive provisioning, where adults feed offspring gradually as they grow, is thought to extend this period of dependency and is therefore suggested to be an important factor promoting the evolution of sociality. In contrast, mass-provisioning species provide offspring with all the food they need to reach maturity at the beginning of their development. Since offspring are then nutritionally independent, the applicability of insurance models is less clear. In this paper we experimentally demonstrate that adult presence on the nest, even after the end of provisioning, is critical for brood survival in the mass provisioning silk wasp Microstigmus rosae. After 10 days, experimentally orphaned nests contained 65% fewer healthy offspring than controls. Adult females were also recorded performing post-provisioning parental care behaviours including nest maintenance and repair, putative hygienic brood care and aggressive nest defence against both ants and parasitoid wasps. By demonstrating the potential applicability of insurance advantages our results highlight how, even in mass provisioners, insurance-based mechanisms may be part of what favours group living. Significance statement: Extended parental care is an important precursor to the evolution of eusociality. In this context, group living can serve as a form of "life insurance", ensuring that dependent offspring receive the care they need to reach maturity should the mother die. Such mechanisms are especially important to our understanding of social evolution as they are able to account for the origins of cooperative group formation, not just its maintenance. However, for mass-provisioning species, where all food items are provided upfront, the significance of insurance advantages remains unclear. In this study, we experimentally demonstrate that adult attendance is critical for brood survival in the mass provisioning wasp, Microstigmus rosae. Our results reveal the applicability of insurance advantages to M. rosae with important implications for our understanding of the potential adaptive value of group living in mass provisioning species. [ABSTRACT FROM AUTHOR]

William Morton Wheeler (1865–1937) was among the greatest experts on ants and his influence on the field of sociobiology, along with that of his academic grandson E. O. Wilson, is second to none. In 1923, Wheeler published his landmark book "Social Life Among the Insects" [1], which marked the beginning of the modern study of insect societies. In this centenary year of its publication, we are honoured and proud to pay tribute to William Morton Wheeler. [ABSTRACT FROM AUTHOR]

Major evolutionary transitions (METs) across Earth's biological history describe fusions of lower-level entities into higher-level individuals (evolutionary transitions in individuality: ETIs) as well as novel forms of information storage and transmission (Information Leaps). Obligate eusociality is frequently listed as a MET—most often in the context of being an ETI and with an extrapolation that the ETI requires inclusive fitness maximization for all parties. However, obligate eusociality neither fundamentally alters how information is stored and transmitted nor meets the various criteria proposed for an ETI. We argue that rather than representing a higher-level individual, the evolution of non-reproductive worker castes is more analogous to a novel 'organ' that maintains homeostasis and nurtures the gonadal tissue of mated queens. Worker castes benefit queens by performing dangerous but necessary functions such as foraging, while enabling the gamete-producing functions to be kept relatively safe. This is an ecologically successful and significant evolutionary innovation, which can be thought of as a major competitive transition (MCT). In this context, we hypothesize that worker castes are most likely to evolve through parental manipulation. Employing such a MCT perspective generates a broad series of predictions about eusocial life histories. [ABSTRACT FROM AUTHOR]

Social insect reproductives and non‐reproductives represent ideal models with which to understand the expression and regulation of alternative phenotypes. Most research in this area has focused on the developmental regulation of reproductive phenotypes in obligately social taxa such as honey bees, while relatively few studies have addressed the molecular correlates of reproductive differentiation in species in which the division of reproductive labour is established only in plastic dominance hierarchies. To address this knowledge gap, we generate the first genome for any stenogastrine wasp and analyse brain transcriptomic data for non‐reproductives and reproductives of the facultatively social species Liostenogaster flavolineata, a representative of one of the simplest forms of social living. By experimentally manipulating the reproductive 'queues' exhibited by social colonies of this species, we show that reproductive division of labour in this species is associated with transcriptomic signatures that are more subtle and variable than those observed in social taxa in which colony living has become obligate; that variation in gene expression among non‐reproductives reflects their investment into foraging effort more than their social rank; and that genes associated with reproductive division of labour overlap to some extent with those underlying division of labour in the separate polistine origin of wasp sociality but only explain a small portion of overall variation in this trait. These results indicate that broad patterns of within‐colony transcriptomic differentiation in this species are similar to those in Polistinae but offer little support for the existence of a strongly conserved 'toolkit' for sociality. [ABSTRACT FROM AUTHOR]

A well-established field of research in vertebrates focuses on the variability of cognitive abilities within species. From mammals to fish, numerous studies have revealed remarkable differences in the cognitive phenotype among individuals, particularly in terms of sex or personality. However, many aspects of the mechanisms, genetics, and selective pressures that underlie individual cognitive variation remain unclear. Surprisingly, intraspecific variability in cognition has received much less attention in invertebrates, despite the increasing evidence of remarkable cognitive abilities in this group and the insights that could be gained from examining simultaneously two distinct taxa, namely vertebrates and invertebrates. In this review, we provide evidence that certain invertebrate species exhibit all the key features of cognitive variation observed in vertebrates, including differences related to sex and personality. In many cases, invertebrate studies have provided insights into the genetic basis, evolvability and response to selection of cognitive variability. Moreover, we highlight evidence for caste differences in eusocial insects, which are linked to task specialisation within the colony. This makes insect eusociality a valuable system for understanding how selection influences cognitive variation. We propose that cognitive variation in invertebrates may be more widespread than currently thought, and that selection may operate in a similar manner on two distantly related cognitive systems (vertebrates and invertebrates). Finally, we suggest that invertebrates hold the potential to serve both as alternative and complementary models to vertebrates, contributing to a deeper understanding of cognitive evolution. [ABSTRACT FROM AUTHOR]

The coexistence of multiple reproductives in eusocial insects is widespread, yet the decisions leading to additional queen acceptance are not well understood. Unlike in vertebrates, acceptance decisions are likely controlled by the more numerous helper population rather than the parent reproductive. Yet there are likely to be queen-worker differences in acceptance criteria because workers and queens differ in their relatedness to a secondary queen. We develop a model that examines queen-worker conflict in two scenarios: accepting a queen's sister or daughter. We additionally ask how the mating frequency and split sex ratios affect the outcomes of these conflicts. Our results reveal that conflict over queen acceptance is highest in monandrous mating systems. We identify a "window of conflict" in which a queen is selected to accept her sister but her workers do not. Our result, that polyandry neutralizes conflict over acceptance thresholds, suggests that conflict suppression may be an additional contributor to the maintenance of polyandrous mating systems. [ABSTRACT FROM AUTHOR]

Evolutionary psychology (EP) has become an important metatheory over the past three decades. EP is centered upon Darwin's theory of natural selection and how this process has played an important role in the development of the human brain and behavior. Evolutionary psychology attempts to explain biological phenomena in terms of evolutionary forces, in this case brain structure and function, which directly impacts human behavior. There has been a remarkable increase in empirical evidence in regards to the merits of this theory and it has been able to partially explain certain features of aggression, sexual behavior, anxiety, depression, and numerous other aspects of cognition, emotions, and psychopathology. This literature review examines the origins, actors, principles, and evidence in the development of this theory and how evolutionary psychology can be applied to the social work profession. [ABSTRACT FROM AUTHOR]

In the first description of evolution, the fundamental mechanism is the natural selection favoring the individuals best suited for survival and reproduction (selection at the individual level or classical Darwinian selection). However, this is a very reductive description of natural selection that does not consider or explain a long series of known phenomena, including those in which an individual sacrifices or jeopardizes his life on the basis of genetically determined mechanisms (i.e., phenoptosis). In fact, in addition to (i) selection at the individual level, it is essential to consider other types of natural selection such as those concerning: (ii) kin selection and some related forms of group selection; (iii) the interactions between the innumerable species that constitute a holobiont; (iv) the origin of the eukaryotic cell from prokaryotic organisms; (v) the origin of multicellular eukaryotic organisms from unicellular organisms; (vi) eusociality (e.g., in many species of ants, bees, termites); (vii) selection at the level of single genes, or groups of genes; (viii) the interactions between individuals (or more precisely their holobionts) of the innumerable species that make up an ecosystem. These forms of natural selection, which are all effects and not violations of the classical Darwinian selection, also show how concepts as life, species, individual, and phenoptosis are somewhat not entirely defined and somehow arbitrary. Furthermore, the idea of organisms selected on the basis of their survival and reproduction capabilities is intertwined with that of organisms also selected on the basis of their ability to cooperate and interact, even by losing their lives or their distinct identities. [ABSTRACT FROM AUTHOR]

The standard evolutionary theory of aging predicts a negative relationship (trade-off) between fecundity and longevity. However, in principle, the fecundity–longevity relationship can become positive in populations in which individuals have unequal resources. Positive fecundity–longevity relationships also occur in queens of eusocial insects such as ants and bees. Developmental diet is likely to be central to determining trade-offs as it affects key fitness traits, but its exact role remains uncertain. For example, in Drosophila melanogaster , changes in adult diet can affect fecundity, longevity, and gene expression throughout life, but it is unknown how changes in developmental (larval) diet affect fecundity–longevity relationships and gene expression in adults. Using D. melanogaster , we tested the hypothesis that varying developmental diets alters the directionality of fecundity–longevity relationships in adults, and characterized associated gene expression changes. We reared larvae on low (20%), medium (100%), and high (120%) yeast diets, and transferred adult females to a common diet. We measured fecundity and longevity of individual adult females and profiled gene expression changes with age. Adult females raised on different larval diets exhibited fecundity–longevity relationships that varied from significantly positive to significantly negative, despite minimal differences in mean lifetime fertility or longevity. Treatments also differed in age-related gene expression, including for aging-related genes. Hence, the sign of fecundity–longevity relationships in adult insects can be altered and even reversed by changes in larval diet quality. By extension, larval diet differences may represent a key mechanistic factor underpinning positive fecundity–longevity relationships observed in species such as eusocial insects. [ABSTRACT FROM AUTHOR]

Representatives of species of alpheid shrimps included in Synalpheus Spence Bate, 1888 exhibit spectacular and distinct behaviors such as eusociality. The wide range of morphological variations in these taxa makes taxonomic understanding difficult. The phylogenetic relationships of the species that comprise the Synalpheus brevicarpus (Herrick, 1891) complex are little known, especially for individuals from South America. Our investigation represents an additional approach to elucidate some aspects of the phylogeny of this species complex. Morphological and molecular evidence resulting from our analyses revealed the existence of a cryptic entity within the S. brevicarpus complex in southeastern Brazil. [ABSTRACT FROM AUTHOR]

In evolutionary terms, life is about reproduction. Yet, in some species, individuals forgo their own reproduction to support the reproductive efforts of others. Social insect colonies for example, can contain up to a million workers that actively cooperate in tasks such as foraging, brood care and nest defence, but do not produce offspring. In such societies the division of labour is pronounced, and reproduction is restricted to just one or a few individuals, most notably the queen(s). This extreme eusocial organisation exists in only a few mammals, crustaceans and insects, but strikingly, it evolved independently up to nine times in the order Hymenoptera (including ants, bees and wasps). Transitions from a solitary lifestyle to an organised society can occur through natural selection when helpers obtain a fitness benefit from cooperating with kin, owing to the indirect transmission of genes through siblings. However, this process, called kin selection, is vulnerable to parasitism and opportunistic behaviours from unrelated individuals. An ability to distinguish kin from non‐kin, and to respond accordingly, could therefore critically facilitate the evolution of eusociality and the maintenance of non‐reproductive workers. The question of how the hymenopteran brain has adapted to support this function is therefore a fundamental issue in evolutionary neuroethology. Early neuroanatomical investigations proposed that social Hymenoptera have expanded integrative brain areas due to selection for increased cognitive capabilities in the context of processing social information. Later studies challenged this assumption and instead pointed to an intimate link between higher social organisation and the existence of developed sensory structures involved in recognition and communication. In particular, chemical signalling of social identity, known to be mediated through cuticular hydrocarbons (CHCs), may have evolved hand in hand with a specialised chemosensory system in Hymenoptera. Here, we compile the current knowledge on this recognition system, from emitted identity signals, to the molecular and neuronal basis of chemical detection, with particular emphasis on its evolutionary history. Finally, we ask whether the evolution of social behaviour in Hymenoptera could have driven the expansion of their complex olfactory system, or whether the early origin and conservation of an olfactory subsystem dedicated to social recognition could explain the abundance of eusocial species in this insect order. Answering this question will require further comparative studies to provide a comprehensive view on lineage‐specific adaptations in the olfactory pathway of Hymenoptera. [ABSTRACT FROM AUTHOR]

Background: Venoms, which have evolved numerous times in animals, are ideal models of convergent trait evolution. However, detailed genomic studies of toxin-encoding genes exist for only a few animal groups. The hyper-diverse hymenopteran insects are the most speciose venomous clade, but investigation of the origin of their venom genes has been largely neglected. Results: Utilizing a combination of genomic and proteo-transcriptomic data, we investigated the origin of 11 toxin genes in 29 published and 3 new hymenopteran genomes and compiled an up-to-date list of prevalent bee venom proteins. Observed patterns indicate that bee venom genes predominantly originate through single gene co-option with gene duplication contributing to subsequent diversification. Conclusions: Most Hymenoptera venom genes are shared by all members of the clade and only melittin and the new venom protein family anthophilin1 appear unique to the bee lineage. Most venom proteins thus predate the mega-radiation of hymenopterans and the evolution of the aculeate stinger. [ABSTRACT FROM AUTHOR]

Conflict and conflict resolution have been argued to be fundamental to the major transitions in evolution. These were key events in life's history in which previously independently living individuals cooperatively formed a higher-level individual, such as a multicellular organism or eusocial colony. Conflict has its central role because, to proceed stably, the evolution of individuality in each major transition required within-individual conflict to be held in check. This review revisits the role of conflict and conflict resolution in the major transitions, addressing recent work arguing for a minor role. Inclusive fitness logic suggests that differences between the kin structures of clones and sexual families support the absence of conflict at the origin of multicellularity but, by contrast, suggest that key conflicts existed at the origin of eusociality. A principal example is conflict over replacing the founding queen (queen replacement). Following the origin of each transition, conflict remained important, because within-individual conflict potentially disrupts the attainment of maximal individuality (organismality) in the system. The conclusion is that conflict remains central to understanding the major transitions, essentially because conflict arises from differences in inclusive fitness optima while conflict resolution can help the system attain a high degree of coincidence of inclusive fitness interests. [ABSTRACT FROM AUTHOR]

An ant colony is the epitome of social organization where up to millions of individuals cooperate to survive, compete, and reproduce as a single superorganism, Female members of ant colonies typically are categorized into a reproductive queen caste and a non-reproductive worker caste. The queen(s) conveys her fertility condition and in cases, genotype status, via a suite of queen pheromones whose various functions are crucial to the superorganismal nature of ant colonies. Knowledge of these functional properties is fundamental for identifying constituent chemicals and understanding corresponding modes of actions. In this review, I summarize functional properties of ant queen pheromones learned from seven decades of behavioral experiments, and contextualize this knowledge within the broader understanding of queen pheromones in other major groups of social insects. The effects include promotion of colony integrity and coherence, maintenance of reproductive dominance of the queen, and regulation of colony social structure. Additionally, general characteristics of queen pheromones are discussed and potential avenues for future research are highlighted. [ABSTRACT FROM AUTHOR]

Distinctive chemical signatures have the potential to serve as discriminatory cues for olfactory recognition mechanisms. Cuticular hydrocarbon (CHC) profiles are among the most prominent chemical signatures in insects that can be highly diverse even among closely related species and between populations with similar ecology. Particularly within the major insect order Hymenoptera, CHC profiles are characterized by high complexity and variation with the potential to evolve rapidly. In this study, we found two very distinct CHC chemotypes distinguishing sympatric colonies of the African carpenter ant Camponotus maculatus (Hymenoptera: Formicinae). These chemotypic differences were mainly detected on the surface profiles of eggs produced by either queens or isolated worker groups. In one chemotype, queen- and worker-laid eggs are very similar. This is largely contrasted by the other chemotype, where queen-laid eggs clearly differ from worker-laid eggs with several prominent queen-exclusive compounds. However, workers display a stable behavior of discriminating against and selectively disposing of worker-laid eggs i.e., worker policing, independent of egg chemotype. Furthermore, genetic barcoding of workers revealed a clear separation between colonies characterized by producing these two distinct egg chemotypes, which may indicate that these colonies belong to a cryptic species complex. Interestingly, worker policing behaviour appears to be evolutionarily conserved, despite the strikingly different egg surface profiles. [ABSTRACT FROM AUTHOR]

Eusocial species live in colonies with a reproductive division of labour into fertile reproductive castes and sterile non-reproductive castes, an overlap of generations and cooperative brood care. A further distinction can be usefully made between primitively eusocial species which do not have morphological caste differentiation and highly eusocial species which do. Ropalidia marginata is a tropical primitively eusocial wasp that has been extensively studied, especially compared to other tropical social wasps. R. marginata has several distinct traits, such as a docile queen, well-developed age polyethism, and decentralized work regulation, which makes it different from other primitively eusocial wasps and reminiscent of highly eusocial species. Since tropical wasps, especially those belonging to the genus Ropalidia have been poorly studied, we cannot be sure whether R. marginata is unique or its traits are more common among tropical Ropalidia species. To begin to overcome this problem, we have extended our research to the congeneric and sympatric Ropalidia cyathiformis. Here, we compare and contrast what we now know about these two species, especially concerning their reproductive and non-reproductive division of labour. We find that R. cyathiformis, unlike R. marginata, has a behaviourally dominant queen, weak and rigid age polyethism, likely uses behavioural dominance to regulate worker reproduction and individual workers self-regulate their own non-reproductive activities. We, therefore, conclude that R. marginata is indeed unique and argue that R. marginata is intermediate between primitively and highly eusocial wasps. [ABSTRACT FROM AUTHOR]

Background: The standard evolutionary theory of ageing proposes that ageing occurs because of a trade-off between reproduction and longevity. Eusocial insect queens exhibit positive fecundity-longevity associations and so have been suggested to be counter-examples through not expressing costs of reproduction and through remodelling conserved genetic and endocrine networks regulating ageing and reproduction. If so, eusocial evolution from solitary ancestors with negative fecundity-longevity associations must have involved a stage at which costs of reproduction were suppressed and fecundity and longevity became positively associated. Using the bumblebee (Bombus terrestris), we experimentally tested whether queens in annual eusocial insects at an intermediate level of eusocial complexity experience costs of reproduction, and, using mRNA-seq, the extent to which they exhibit a remodelling of relevant genetic and endocrine networks. Specifically, we tested whether costs of reproduction are present but latent, or whether a remodelling of relevant genetic and endocrine networks has already occurred allowing queens to reproduce without costs. Results: We experimentally increased queens’ costs of reproduction by removing their eggs, which caused queens to increase their egg-laying rate. Treatment queens had significantly reduced longevity relative to control queens whose egg-laying rate was not increased. Reduced longevity in treatment queens was not caused by increased worker-to-queen aggression or by increased overall activity in queens. In addition, treatment and control queens differed in age-related gene expression based on mRNA-seq in both their overall expression profiles and the expression of ageing-related genes. Remarkably, these differences appeared to occur principally with respect to relative age, not chronological age. Conclusions: This study represents the first simultaneously phenotypic and transcriptomic experimental test for a longevity cost of reproduction in eusocial insect queens. The results support the occurrence of costs of reproduction in annual eusocial insects of intermediate social complexity and suggest that reproductive costs are present but latent in queens of such species, i.e. that these queens exhibit condition-dependent positive fecundity-longevity associations. They also raise the possibility that a partial remodelling of genetic and endocrine networks underpinning ageing may have occurred in intermediately eusocial species such that, in unmanipulated conditions, age-related gene expression depends more on chronological than relative age. [ABSTRACT FROM AUTHOR]

One of the major evolutionary transitions is the shift from solitary to social lifestyle, which involved a plethora of behavioral and physiological changes in social entities. Group living has several advantages as the evolution of collective defense mechanisms. It may also affect the individual immune system either due to the efficiency of social immune defenses or because of the high transmission frequency of pathogens. Individual defense consists of the innate and acquired immune components. In insects, there are two signaling pathways (Toll and Jak/Stat) that result in the expression of specific immune genes, which, in their turn, encode peptides, proteins and activate innate immune responses like encapsulation. The main aim of our study was to verify whether transition to eusocial lifestyle is reflected in proteins involved in immune responses. We carried out phylogenetic analyses of 15 proteins involved in encapsulation signaling pathways in ants. We also included four other social insect groups, bees, sweat bees, social wasps, and termites, and three solitary insect groups, as fruit flies, braconid wasps, and megachilid bees. Ants grouped separately from other insect groups in most cases, however, there were some notable exceptions mostly in the case of pattern recognition proteins, probably correlating with differences in potential pathogens. No major differences were revealed though between solitary and social insects with respect to proteins involved in encapsulation. [ABSTRACT FROM AUTHOR]

One of the major evolutionary transitions is the shift from solitary to social lifestyle, which involved a plethora of behavioral and physiological changes in social entities. Group living has several advantages as the evolution of collective defense mechanisms. It may also affect the individual immune system either due to the efficiency of social immune defenses or because of the high transmission frequency of pathogens. Individual defense consists of the innate and acquired immune components. In insects, there are two signaling pathways (Toll and Jak/Stat) that result in the expression of specific immune genes, which, in their turn, encode peptides, proteins and activate innate immune responses like encapsulation. The main aim of our study was to verify whether transition to eusocial lifestyle is reflected in proteins involved in immune responses. We carried out phylogenetic analyses of 15 proteins involved in encapsulation signaling pathways in ants. We also included four other social insect groups, bees, sweat bees, social wasps, and termites, and three solitary insect groups, as fruit flies, braconid wasps, and megachilid bees. Ants grouped separately from other insect groups in most cases, however, there were some notable exceptions mostly in the case of pattern recognition proteins, probably correlating with differences in potential pathogens. No major differences were revealed though between solitary and social insects with respect to proteins involved in encapsulation. [ABSTRACT FROM AUTHOR]

Eusociality in insects has evolved independently many times. One of the most notable characteristics of eusociality is the reproductive division of labor. In social insects, the reproductive division of labor is accomplished by queens and workers. Transcriptome analyses of queens and workers have been conducted for various eusocial species. However, the genes that regulate the reproductive division of labor across all or multiple eusocial species have not yet been fully elucidated. Therefore, we conducted a meta-analysis using publicly available RNA-sequencing data from four major groups of social insects. In this meta-analysis, we collected 258 pairs (queen vs. worker) of RNA-sequencing data from 34 eusocial species. The meta-analysis identified a total of 20 genes that were differentially expressed in queens or workers. Out of these, 12 genes have not previously been reported to be involved in the reproductive division of labor. Functional annotation of these 20 genes in other organisms revealed that they could be regulators of behaviors and physiological states related to the reproductive division of labor. These 20 genes, revealed using massive datasets of numerous eusocial insects, may be key regulators of the reproductive division of labor. [ABSTRACT FROM AUTHOR]

Termites (Insecta, Blattodea, Termitoidae) are a widespread and diverse group of eusocial insects known for their ability to digest wood matter. Herein, we report the draft genome of the subterranean termite Reticulitermes lucifugus, an economically important species and among the most studied taxa with respect to eusocial organization and mating system. The final assembly (~813 Mb) covered up to 88% of the estimated genome size and, in agreement with the Asexual Queen Succession Mating System, it was found completely homozygous. We predicted 16,349 highly supported gene models and 42% of repetitive DNA content. Transposable elements of R. lucifugus show similar evolutionary dynamics compared to that of other termites, with two main peaks of activity localized at 25% and 8% of Kimura divergence driven by DNA, LINE and SINE elements. Gene family turnover analyses identified multiple instances of gene duplication associated with R. lucifugus diversification, with significant lineage‐specific gene family expansions related to development, perception and nutrient metabolism pathways. Finally, we analysed P450 and odourant receptor gene repertoires in detail, highlighting the large diversity and dynamical evolutionary history of these proteins in the R. lucifugus genome. This newly assembled genome will provide a valuable resource for further understanding the molecular basis of termites biology as well as for pest control. [ABSTRACT FROM AUTHOR]

Genomic imprinting is known from flowering plants and mammals but has not been confirmed for the Hymenoptera even though the eusocial Hymenoptera are prime candidates for this peculiar form of gene expression. Here, the kin selection theory of genomic imprinting is reviewed and applied to the eusocial Hymenoptera. The evidence for imprinting in eusocial Hymenoptera with the typical mode of reproduction, involving the sexual production of diploid female offspring, which develop into workers or gynes, and the arrhenotokous parthenogenesis of haploid males, is also reviewed briefly. However, the focus of this review is how atypical modes of reproduction, involving thelytokous parthenogenesis, hybridisation and androgenesis, may also select for imprinting. In particular, naturally occurring hybridisation in several genera of ants may provide useful tests of the role of kin selection in the evolution of imprinting. Hybridisation is expected to disrupt the coadaptation of antagonistically imprinted loci, and thus affect the phenotypes of hybrids. Some of the limited data available on hybrid worker reproduction and on colony sex ratios support predictions about patterns of imprinting derived from kin selection theory. [ABSTRACT FROM AUTHOR]

That humans might undergo future evolutionary transitions in individuality (ETIs) seems fanciful. However, drawing upon recent thinking concerning the origins of properties that underpin ETIs, I argue that certain ETIs are imminently realizable. Central to my argument is recognition that heritable variance in fitness at higher levels of organization can be externally imposed (scaffolded) by specific ecological structures and cultural practices. While ETIs to eusociality seem highly improbable, ETIs involving symbioses between humans and artificial intelligence (AI) can be readily envisaged. A necessary requirement is that fitness-affecting interactions between humans and AI devices are inherited by offspring. The Mendelian nature of human reproduction ensures that offspring resemble parents. Reproduction of AI devices requires nothing more than transference of algorithms from parental AI devices to devices that are assigned to offspring. This simple copying, combined with societal structures that require humans to carry AI devices, ensures heritable variance in fitness at the level of both interacting partners. Selection at the collective level will drive alignment of replicative fates and increase co-dependency, thus alleviating need for continual imposition of externally imposed scaffolds. I conclude by drawing attention to the immediacy of such transitions and express concern over possibilities for malevolent manipulation. [ABSTRACT FROM AUTHOR]

Living in nests is an almost universal feature of eusocial animals. In some aphids, however, sterile soldier castes have evolved in open colonies without a nest. To clarify the factors promoting the evolution of eusociality in these colonies, we used newly developed microsatellite markers to compare the kin structure of the open colonies of two aphid species on bamboo: the non-eusocial colonies of Astegopteryx bambucifoliae and the eusocial colonies of Pseudoregma alexanderi on Dendrocalamus latiflorus. Our samples, from over 1000 hectares, contained 99 clones of A. bambucifoliae and 19 of P. alexanderi. Clonal mixing occurred in both species: average pairwise relatedness within a colony was 0.54 in A. bambucifoliae and 0.71 in P. alexanderi. Each clone of A. bambucifoliae occurred in a unique location, whereas those of P. alexanderi occurred in multiple locations and more than 90% of individuals came from just four clones. There was significant genetic variation among different colonies in the same clump (stem-cluster) in A. bambucifoliae but not in P. alexanderi, indicating that P. alexanderi colonies in a single clump are genetically homogenised, functioning as a large colony. In P. alexanderi, the proportion of sterile soldiers to normal first-instar nymphs was significantly different across the four clones. Our results indicate that the lack of input of migrants from the primary host and feeding on a large, stable host plant are important ecological factors that might favour the evolution of eusociality, enabling the production of genetically homogenised, large, and long-lived colonies. After eusociality evolves on the secondary host, the optimal strategy of soldier production might vary between different clones. Significance statement: Nest living has often been considered to be a necessary condition for the evolution of eusociality. In a small number of aphid species, however, sterile soldier castes have evolved in open colonies without a nest. To understand why these aphids are unique, we examined the kin structure and genetic relatedness of individuals within eusocial and non-eusocial open colonies of two aphid species on bamboo. We found that clonal mixing occurred in both species, but the eusocial colonies are more genetically homogenised, functioning as a large colony. Our results suggest that ecological conditions that promote genetically homogenised, large and long-lived colonies are important for the evolution of eusociality in these aphids. We propose that the open colonies of social aphids provide an ideal model system in which to study the evolution of altruism. [ABSTRACT FROM AUTHOR]

Nutrition is an important component of oogenesis and ovarian development in insects. In social insect colonies where a large proportion of females are sterile, suppression of reproduction caused by differential acquisition and retention of nutrition has been hypothesized to cause worker sterility. This study, using the primitively eusocial wasp Ropalidia marginata (Lepeletier) (Hymenoptera: Vespidae), show that worker ovarian development in naturally foraging colonies is more similar to experimentally food-limited colonies than to surplus-fed colonies, indicating nutritional castration in workers whose ovaries are inhibited by food availability. Further, experimental provisioning of surplus nutrition led to higher ovarian development in workers as compared to naturally foraging and food-limited workers. Surplus feeding also led to higher nest desertion by workers, leading to a breakdown of the colony’s social structure, whereas food-limited colonies retained workers. [ABSTRACT FROM AUTHOR]

Simple Summary: The naked mole-rat is a small, long-lived mammal that lives in large colonies in subterranean burrows. The lifestyle of naked mole-rats makes their study difficult, and many details about their biology remain enigmatic. For evolutionary biologists and ecologists, a special trait exhibited by this species, their eusocial lifestyle, is of particular interest. In this study, we explored the determinants of early offspring survival using data from observations of 14 captive colonies over a total period of seven years. Our study revealed that early pup survival was significantly improved by higher pup body mass and maternal number of mammae and significantly reduced by increased maternal body mass and colony size. The latter negative effect may, however, be an artifact of the captive conditions in which colonies were kept. We further discuss the implications of the similarities and differences of naked mole-rats to eusocial insects and cooperatively breeding mammals in these determinants to shed light on the origin and maintenance of eusociality in mammals. In eusocial insects, offspring survival strongly depends on the quality and quantity of non-breeders. In contrast, the influence of social factors on offspring survival is more variable in cooperatively breeding mammals since maternal traits also play an important role. This difference between cooperative insects and mammals is generally attributed to the difference in the level of sociality. Examining offspring survival in eusocial mammals should, therefore, clarify to what extent social organization and taxonomic differences determine the relative contribution of non-breeders and maternal effects to offspring survival. Here, we present the first in-depth and long-term study on the influence of individual, maternal, social and environmental characteristics on early offspring survival in a eusocial breeding mammal, the naked mole-rat (Heterocephalus glaber). Similarly to other mammals, pup birth mass and maternal characteristics such as body mass and the number of mammae significantly affected early pup survival. In this eusocial species, the number of non-breeders had a significant influence on early pup survival, but this influence was negative—potentially an artifact of captivity. By contrasting our findings with known determinants of survival in eusocial insects we contribute to a better understanding of the origin and maintenance of eusociality in mammals. [ABSTRACT FROM AUTHOR]

To maintain the eusociality of a colony, ants recognize subtle differences in colony-specific sets of cuticular hydrocarbons (CHCs). The CHCs are received by female-specific antennal basiconic sensilla and processed in specific brain regions. However, it is controversial whether a peripheral or central neural mechanism is mainly responsible for discrimination of CHC blends. In the Japanese carpenter ant, Camponotus japonicus, about 140 sensory neurons (SNs) are co-housed in a single basiconic sensillum and receive colony-specific blends of 18 CHCs. The complexity of this CHC sensory process makes the neural basis of peripheral nestmate recognition difficult to understand. Here, we electrophysiologically recorded responses of single basiconic sensilla to each of 18 synthesized CHCs, and identified CHC responses of each SN co-housed in a single sensillum. Each CHC activated different sets of SNs and each SN was broadly tuned to CHCs. Multiple SNs in a given sensillum fired in synchrony, and the synchronicity of spikes was impaired by treatment with a gap junction inhibitor. These results indicated that SNs in single basiconic sensilla were electrically coupled. Quantitative analysis indicated that the Japanese carpenter ants have the potential to discriminate chemical structures of CHCs based on the combinational patterns of activated SNs. SNs of ants from different colonies exhibited different CHC response spectra. In addition, ants collected from the same colony but bred in separate groups also exhibited different CHC response spectra. These results support the hypothesis that the peripheral sensory mechanism is important for discrimination between nestmate and non-nestmate ants. [ABSTRACT FROM AUTHOR]

Simple Summary: Termites are eusocial insects that live in large colonies made up of queens, kings, workers, and soldiers. Queens and kings start new colonies and continually reproduce. Workers are responsible for many crucial roles, including colony husbandry, foraging, and nest construction. Soldiers are adapted for colony defense, usually with large heads and mandibles to ward off predators, but their defensive adaptations prevent them from caring for themselves or performing tasks within the nest. The soldiers of some termite species participate in foraging, either directly by scouting food sources and recruiting workers, or indirectly by influencing worker foraging behavior through their presence. Colonies of the Formosan subterranean termite maintain relatively large soldier proportions compared to termites in their invasive range, but the potential soldier influence on foraging workers has not yet been studied. Since the soldiers of other termite species can influence food exploration, we hypothesized that soldier presence also influences foraging behavior in this species. We compared the exploratory behavior of foraging groups of 100 workers and either 0, 2, 10, or 30 soldiers to determine whether soldier concentration influenced tunnel complexity, tunnel speed, food location, or food collection. In the context of this study, soldier presence did not influence worker foraging behavior, which suggests that workers of the Formosan subterranean termite can maintain foraging efficiency regardless of fluctuations in soldier presence. Termites are eusocial insects that live in organized colonies consisting of reproductives, workers, and soldiers. Soldiers are specialized for defense but are expensive to maintain, as they are incapable of husbandry and must be fed and groomed by workers. The soldiers of several species influence foraging behavior by acting as scouts that initiate foraging or by mediating worker behavioral plasticity during food exploration. These behaviors imply that soldiers may play a keystone role in termite colony function, apart from defense. Subterranean termite workers tunnel through soil in search of food while accompanied by varying proportions of soldiers, depending on the species and colony conditions. Previous studies have shown that soldiers accelerate worker exploratory tunneling behavior in two Reticulitermes species, the colonies of which contain fewer than 2% soldiers. This effect, however, is unknown in other subterranean species with different soldier proportions. In this study, we examined the influence of soldiers on exploratory foraging behavior in the Formosan subterranean termite, Coptotermes formosanus Shiraki, which is an economically devastating invasive species that maintains a relatively high soldier proportion (about 10%). When 100 foraging workers were grouped with 0, 2, 10, or 30 soldiers in two-dimensional foraging arenas, we found no significant effect of soldiers on the tunnel length, branch pattern, food source interception, or food collected within 96 h. These results suggest that C. formosanus colonies maintain food exploration efficiency regardless of soldier proportion variation. [ABSTRACT FROM AUTHOR]

How the role of dopamine differs according to the evolution of eusociality and how it is required in the flexible society of Polistes paper wasps need further clarification. In the present study, we compared the storage and usage of dopamine-related substances in brains between the castes of paper wasps. The head widths, lipid stores in the abdomen, and levels of biogenic amines in the brains were measured in newly emerged females before male emergence (workers) and after male emergence (gynes) in four Polistes species. The head widths and the lipid stores were significantly larger in gynes than workers in P. snelleni, P. rothneyi, and P. jokahamae, whereas they did not differ between castes in P. chinensis. The levels of dopamine precursors in the brains were significantly higher in gynes than workers in P. snelleni, P. chinensis, and P. rothneyi, whereas those of dopamine and its metabolites did not differ between castes in these species. In P. jokahamae, the levels of dopamine precursors and dopamine in the brains did not differ between castes, but those of a dopamine metabolite were significantly higher in gynes than workers. Thus, the caste differences in the levels of dopamine-related substances did not always match body sizes and nutritional reserves. Foundresses in P. rothneyi had significantly lower levels of dopamine precursors and higher levels of dopamine and its metabolite than newly emerged gynes. These results suggested that in several Polistes species, dopamine precursors were stored in the brain without dopamine biosynthesis at emergence, and then converted into dopamine in foundresses during colony founding. These neuroendocrinal states in Polistes species largely differed from those in eusocial bees. [ABSTRACT FROM AUTHOR]

Termites (Blattodea: Isoptera) have evolved specialized defensive strategies for colony protection. Alarm communication enables workers to escape threats while soldiers are recruited to the source of disturbance. Here, we study the vibroacoustic and chemical alarm communication in the wood roach Cryptocercus and in 20 termite species including seven of the nine termite families, all life-types, and all feeding and nesting habits. Our multidisciplinary approach shows that vibratory alarm signals represent an ethological synapomorphy of termites and Cryptocercus. In contrast, chemical alarms have evolved independently in several cockroach groups and at least twice in termites. Vibroacoustic alarm signaling patterns are the most complex in Neoisoptera, in which they are often combined with chemical signals. The alarm characters correlate to phylogenetic position, food type and hardness, foraging area size, and nesting habits. Overall, species of Neoisoptera have developed the most sophisticated communication system amongst termites, potentially contributing to their ecological success. The vibroacoustic and chemical alarm communication in the wood roach Cryptocercus and in 20 termite species are studied to reveal that the Neoisoptera species have developed the most sophisticated communication system, which could contribute towards their ecological success. [ABSTRACT FROM AUTHOR]

Background: Eusociality is widely considered to evolve through kin selection, where the reproductive success of an individual's close relative is favored at the expense of its own. High genetic relatedness is thus considered a prerequisite for eusociality. While ants are textbook examples of eusocial animals, not all ants form colonies of closely related individuals. One such example is the ectatommine ant Rhytidoponera metallica, which predominantly forms queen-less colonies that have such a low intra-colony relatedness that they have been proposed to represent a transient, unstable form of eusociality. However, R. metallica is among the most abundant and widespread ants on the Australian continent. This apparent contradiction provides an example of how inclusive fitness may not by itself explain the maintenance of eusociality and raises the question of what other selective advantages maintain the eusocial lifestyle of this species. Results: We provide a comprehensive portrait of the venom of R. metallica and show that the colony-wide venom consists of an exceptionally high diversity of functionally distinct toxins for an ant. These toxins have evolved under strong positive selection, which is normally expected to reduce genetic variance. Yet, R. metallica exhibits remarkable intra-colony variation, with workers sharing only a relatively small proportion of toxins in their venoms. This variation is not due to the presence of chemical castes, but has a genetic foundation that is at least in part explained by toxin allelic diversity. Conclusions: Taken together, our results suggest that the toxin diversity contained in R. metallica colonies may be maintained by a form of group selection that selects for colonies that can exploit more resources and defend against a wider range of predators. We propose that increased intra-colony genetic variance resulting from low kinship may itself provide a selective advantage in the form of an expanded pharmacological venom repertoire. These findings provide an example of how group selection on adaptive phenotypes may contribute to maintaining eusociality where a prerequisite for kin selection is diminished. [ABSTRACT FROM AUTHOR]

Bees provide important ecosystem services and are subjects of extensive studies on their α‐diversity, which is generally calculated with indices that integrate the number of species with their abundances. Variation in social behaviour, though expected to impact genetic diversity, is still largely neglected in such studies.We propose a simple method to show how sociality may affect diversity indices, when a surrogate of genetic diversity is taken into account. This method weighs the number of sampled females (N) to obtain new abundance values (NW), by taking into account relevant biological traits affecting genetic structure of populations, that is, the number of (natal) nests from which the sampled females originated (which depends on brood productivity and sex ratio) and the genetic relatedness among such females.Solitary species tend to have greater NW than eusocial ones especially at larger sample sizes. Across studies on 121 bee communities, we found that Taxonomic distinctness, Shannon–Wiener diversity and Gini–Simpson dominance tended to be greater when based on NW rather than on N. Such differences increased in communities with decreasing number of eusocial species and with increasing proportion of individuals from eusocial species.The results suggest that taking into account the social organisation of wild bees may have important consequences in estimating α‐diversity, thus claiming for future efforts in collecting biological data on as many wild bee species as possible to improve the precision of NW estimations. For example, stressors affecting more solitary bees could impoverish communities dominated by few but abundant eusocial species, more than expected by using unweighted abundances. [ABSTRACT FROM AUTHOR]

The neotropical apoid wasp genus Microstigmus is of particular interest biologically because it represents an origin of eusociality independent of vespid wasps and bees, and is part of the only eusocial lineage among the approximately 10,000 solitary species of apoid wasps. Females construct nests made of silk and the species exhibit an unusual diversity of nesting strategies. However, research is hampered because many species remain undescribed and the basic nesting biology of only a few species is known. I describe three new species from north-west Ecuador related to M. bicolor Richards, including diagnostic morphological characters, altitudinal ranges and molecular data as well as descriptions of their nests and nesting biologies. M. rosae sp. nov. is a mass provisioner that preys on nymphal Thysanoptera, while M. lydiae sp. nov. and M. mirandae sp. nov. are progressive provisioners that prey on nymphal leafhoppers (Cicadellidae). Nests of all three species can contain multiple adult females but more than half of nests contain only a single female. [ABSTRACT FROM AUTHOR]