Insectes Sociaux最新文献

Abstract

Insects are the most diverse group on earth, providing a vast array of essential functions for people and nature. Yet, our appreciation of their contributions is biased towards a few economically important taxa, especially pollinating insects like honeybees. Other taxa are less well appreciated despite the important roles they play, and these taxa are rarely (if ever) the focus of conservation initiatives. Here, we explore the role that scientists play through their interactions with the media in shaping our attitudes towards one of the least appreciated insects—the aculeate (stinging) wasps. Vespine wasps are an excellent taxonomic group for such a study as they are important predators in native ecosystems (e.g., the Northern Hemisphere—in Europe and North America) but ecologically devastating as invasive species in many regions of the Southern Hemisphere (e.g., New Zealand, Australia, South America). Despite this, global media coverage of wasps invariably focuses on and emotively exaggerates the negative defensive stinging behaviour of wasps, and almost entirely overlooks their beneficial positive roles (as pest controllers and pollinators). Wasp and bee scientists from around the world were surveyed about their interactions with the media and how they considered these interactions to influence public perceptions and insect conservation. Our surveys capture the negative-wasp and positive-bee biases experienced by scientists through their interactions with the media. We consider the implications of such biases on wasp populations, their conservation and management, and make recommendations for a more balanced portrayal of this important and diverse group of insects.

Abstract

Colonies of the queenless ponerine ant Dinoponera quadriceps are characterized by a social hierarchy among the workers, in which the gamergate occupies the alpha rank. She may be challenged, however, by a beta worker in an attempt to take over reproductive control in the colony. The gamergate does not engage in a direct conflict, however, but only smears secretion from her Dufour gland onto the beta worker. This secretion then stimulates the low-ranked workers to immobilize the beta worker and thus prevent it from overthrowing the gamergate. Our histological and ultrastructural examination of the Dufour gland in gamergates, one-week-old workers that still have reproductive potential and low-ranked foragers clearly shows that the gamergate has the most developed gland containing secretory cells displaying abundant smooth endoplasmic reticulum and an obvious microvillar differentiation of the apical cell membrane. These findings are in line with the already existing chemical and behavioral observations of the peculiar pretender punishment in this species.

Organisms face the fundamental ecological question of when to switch resources from growth to reproduction or allocate resources between the two. Social wasps, including Vespula species (the yellowjackets), must crucially decide to transition from colony growth to reproductive production before the onset of winter. The timing of this transition could be influenced by worker numbers and environmental factors that affect the fitness of the colony. Early initiation of reproductive production has the advantage that a few reproductives can emerge if the colony collapses prematurely. In contrast, once reproductive production begins, nest growth terminates and the increase of future reproductives should be limited. This study investigated the group decision-making process regarding when and under what circumstances Vespula shidai initiates its reproductive phase. During the early reproductive period, we estimated the number of workers and new queens that emerged from the meconia in the cells. Significantly, a positive correlation was observed between the number of workers and the production of new queens during the early reproductive period. To examine the benefits of early reproduction, we reared V. shidai colonies in a plastic greenhouse, allowed males and new queens to fly and mate freely, and allowed the queens to begin overwintering at their timing. In our experimental environment, new queens that emerged earlier in the reproductive period had a higher survival rate during overwintering and higher dry and fat weights in the following spring. The higher dry and fat weights of the queens suggested better survival during the founding phase of the nest.

Abstract

Somatic mutations originate from both exogenous (e.g. UV radiation, chemical agents) and endogenous (e.g., DNA replication, defective DNA repair) sources and can have significant impacts on an animal’s reproductive success. This may be especially true for haploid organisms that are susceptible to any deleterious alleles inherited from their parent and any that arise over their lifetime. Unfortunately, little is known about the rate of somatic mutation accumulation across individuals and tissues of haplodiploid animal populations, the functional processes through which they arise, and their distribution across tissues and the genome. Here, we generated short-read whole-genome sequencing data for four tissues of haploid honey bee males. We paired this with estimates of telomere length and tissue-specific DNA content to address three major questions: is there variance in somatic mutational load across haploid individuals and specific tissues therein, does increased DNA content in a tissue contribute to somatic mutational load, and does telomere length correlate with mutational load? Our results suggest that variance in somatic mutational load is better captured across individuals than across tissues, that tissue-specific DNA content is not associated with somatic mutation load, and that variance in telomere length does not correlate with somatic mutation loads across tissues. To our knowledge, this is the first observational study on somatic mutational load in Apoidea and likely Hymenoptera. It serves as a useful advent for additional studies understanding the processes through which haploids tolerate or repair somatic mutations.

The so-called “acorn ants” (i.e., the Formicoxenus genus group, comprised of the closely related genera Formicoxenus, Harpagoxenus, Temnothorax, Leptothorax, Vombisidris, and Gauromyrmex) are model systems for studying collective decision-making. This is because of the well-understood algorithms workers use to select nests during relocation. However, the details of these algorithms are based on data from relatively few species. This taxonomic neglect threatens to provide a distorted sense of how colonies in general execute collective decision-making and the obscure variation in algorithms that can be used to accomplish this task. We observed nest relocations in 18 species of acorn ants and compared our data to previously collected data from emigrations in T. curvispinosus to obtain a more thorough survey of nest relocation behavior in this group of ants. We found that the basic sequence of emigration behaviors in most species was no different from those reported in previous studies. However, we found a few notable deviations from standard Temnothorax emigration behavior that appear to be common in Leptothorax. Compared to Temnothorax, species of Leptothorax showed elevated rates of worker participation in scouting for a new nest and fewer adults were carried to the new nest. This difference could not be explained by colony size, the latitude of colony origin, or whether colonies were social parasites that captured workers from colonies of other species. Furthermore, we found that the timing of transports in Leptothorax is structured so that brood transports are prioritized; adults are carried to the new nest near the end of emigrations after all brood items have already been relocated.

Abstract

Workers of the red imported fire ant Solenopsis invicta are repeatedly claimed in the literature not to have ovaries. Here, we demonstrate that we cannot find a source publication that proves the statement, and we show how publications are erroneously citing this statement. To remedy this gap, we dissected 87 S. invicta workers over a range of worker sizes, and demonstrate that S. invicta workers do not have reproductive organs. To the best of our knowledge, this is the first time such a demonstration has been published in the scientific literature. We flag that the same issue of a lack of published evidence for the same statement likely exists for many other species and genera, precluding the ability for appropriate referencing of such details.

Eusocial insects, such as ants and honeybees, are characterized by the sophisticated division of labor among workers. In addition to age polyethism, the division of labor is maintained by task shifting of workers in fluctuating environments. While task experience is considered a key factor in realizing the task shifting, our previous study suggests that the experience promotes the task shifting of not nurses but foragers in a queenless ant, Diacamma cf. indicum from Japan. Therefore, we hypothesize that different mechanisms, e.g., reproductive potential, underlie task shifting between the nurse and the forager. In this study, we examined the relationship between the ovarian development of workers and their task shifting, using D. cf. indicum. We also examined the relationships between the expression levels of Vitellogenin (Vg), VgR, Vg-like A, Vg-like B, Vg-like C, and foraging gene and the task shifting of the nurses. Our results showed that more than half of the nurses maintained their reproductive potential—as evidenced by their well-developed ovaries—even when they had shifted to the foraging task. In contrast, the foragers—whether they had shifted to the nursing task or not—remained with regressed ovaries. Finally, we found that the nurses who shifted to the foraging task exhibited low expression levels of Vg, VgR, and Vg-like A. In conjunction with previous studies, our results suggest that this physiological contradiction may underlie the different mechanisms that lead to the task shifting between the nurse and the forager in this species.

Joining a social group entails a range of possible costs and benefits, with the balance of pros and cons potentially dependent on the specific conditions present in the local environment. In the third-instar stage of fruit fly (Drosophila melanogaster) development, individuals may join together into clusters that can increase access to buried food resources, but this collaboration comes with the possible risks of kleptoparasitism or slowed development. Cluster feeding in D. melanogaster larvae has the potential to be a valuable model for studying the dynamics of social and group behaviours, but little is currently known about the plasticity of its expression. In this study, we set out to explore how this collective behaviour might be shaped by the nutritional quality of the environment and/or the spatial distribution of resources by manipulating the nutritional quality of the larval environment and the configuration of available resources. By tracking the timing, frequency, composition, and size of any feeding clusters that subsequently developed, we could better understand the factors that influenced the expression of this social behaviour. We found that cluster expression varied temporally and with the type of resources present in the environment. When possible, larvae formed clusters more frequently to take advantage of otherwise inaccessible resources. The increased clustering patterns were most dramatically manifested as deeper feeding mines. This work expands our understanding of the plastic nature of this collective behaviour, given that discrete environmental changes elicited dynamic changes in larval behaviours.

Subterranean termites rely on chemical and vibroacoustic communication as they live enclosed in tunnels in the soil or wood. While social context is known to influence colony-level behaviors in many social insects, its influence on alarm communication remains unstudied. We tested the influence of the soldier caste on worker behavioral plasticity for subterranean termites: two species of Reticulitermes and Coptotermes formosanus. We altered the group composition according to soldier proportion or their replacement by chemical signals (hexane extracts). The responses of termites to stimuli known to provoke alarm responses, such as human breath simulating a breech in the nest or crushed soldier head (CSH) containing the chemical alarm cues, comprised increased movement and increased vibroacoustic alarm signaling. Species differed in the intensity of their responses, which were generally stronger in Reticulitermes. Groups of Reticulitermes with soldiers responded more strongly to CSH, while groups of R. virginicus only responded to human breath in the presence of soldier extracts. The responses of Coptotermes formosanus showed no effect of group composition on responses to stimuli, suggesting that soldier presence does not affect vibroacoustic behavior in this species. Our results highlight how alarm behavior changes quickly in closely related species as part of finely tuned behavioral mechanisms optimizing a species’ response in each environment including in the presence of natural predators and competitors.

An important question in evolutionary biology is to identify the mechanisms that control the number of reproductives in social groups. Ants are appropriate models to address this question because of the variety of their social structures both within and between species, making this taxon suitable for initiating comparative studies to examine the drivers of this diversity. In this study, we developed a comparative approach between populations of the ponerine ant Odontomachus hastatus from Brazil and French Guiana. In Brazil, monogynous and polygynous colonies coexist in the same populations, whereas only monogynous colonies are present in French Guiana. We combined ecological, behavioural and chemical analyses to identify the factors associated with the expression of this social polymorphism. In Brazil, nest densities were higher than in French Guiana, but nesting sites were available in large quantities in both areas, indicating that habitat saturation is probably not the cause of social polymorphism. We did not detect any difference in queen size, regardless of the social structure of the colonies, suggesting that dispersal strategies may be similar between monogynous and polygynous populations. We found no influence of social structure on aggression intensity in dyadic encounters between workers. Last, we showed that the level of aggression increased with both geographical and chemical distance, but we did not find any difference in cuticular profiles between monogynous and polygynous colonies. Overall, the determinism of social polymorphism in O. hastatus still eludes us and calls for further field experiments coupled with genetic approaches.