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Simple Summary The spotted wing drosophila, Drosophila suzukii, is an invasive pest species from Southeast Asia that was recently introduced in parts of Europe and North America. As D. suzukii lays its eggs in ripening soft-skinned fruit, it causes significant damage to a wide variety of summer fruit, including cherries, blueberries, blackberries, raspberries, grapes, plums and strawberries. Therefore, there is a need for an effective attractant to improve monitoring or allow for mass trapping of this fly. Because blackberry is one of the preferred host crops of D. suzukii, the volatiles which this berry emits were analyzed via GC-MS in order to identify the key compounds with an attractive effect. In total, 33 volatiles were tested of which six proved to be significantly attractive to D. suzukii. Of these compounds, acetaldehyde, hexyl acetate, linalool and myrtenol proved to be most attractive. Overall, these results can form a valuable basis to further develop more effective and selective lures to monitor or mass trap this pest. Abstract The spotted wing drosophila, Drosophila suzukii, is an invasive pest species from Southeast Asia that was recently introduced in Europe and North America. As this fruit fly lays its eggs in ripening soft-skinned fruit, it causes great damage to a variety of crops, including cherries, blueberries, blackberries, raspberries, grapes, plums and strawberries. Consequently, there is a great demand for an effective and species-specific lure, which requires the development of successful attractants. Until now, there is no lure available that is species-specific and can detect the presence of D. suzukii before infestation. As blackberry (Rubus fruticosus) is one of the preferred host crops of D. suzukii, the volatile compounds of R. fruticosus berries are here identified and quantified using multiple headspace SPME (solid phase micro extraction) GC-MS (gas chromatography–mass spectrometry). Subsequently, the attractivity of 33 of the identified compounds was tested with a two-choice laboratory bioassay. Acetaldehyde, hexyl acetate, linalool, myrtenol, L-limonene and camphene came out as significantly attractive to D. suzukii. The first four attractive compounds induced the strongest effect and therefore provided the best prospects to be implemented in a potential lure. These findings could contribute towards the development of more effective attractants for monitoring and mass trapping D. suzukii.

ispartof: Encyclopedia of Social Insects status: Published online

Invasive species cause severe ecological and economic impacts in their introduced ranges. Vespula wasps, native to Eurasia, are a major threat to New Zealand native ecosystems. Understanding factors that influence the success of wasp invasion is pivotal for the development of control strategies. Here, we compare genetic diversity and structure of Vespula germanica and Vespula vulgaris between regions of their native and introduced ranges using microsatellite markers. Our study found lower diversity and lack of genetic structure for both invasive Vespula species within New Zealand. The significant reduction in allelic richness, gene diversity and effective population size illustrate a major bottleneck in New Zealand V. germanica and V. vulgaris populations. Strong signatures of population structure were found for both Vespula species with two clusters being identified as optimal k, approximately corresponding to the native and the invaded ranges. Our results highlight the fact that the lack of genetic diversity does not impede successful invasions in V. germanica and V. vulgaris and encourage further research into mechanisms that promote the success of invasive social insects. Overall, this study provides insights into the genetics of invasive Vespula wasps that can be useful for the development of efficient management strategies.

Despite the mitochondrion's long-recognized role in energy production, mitochondrial DNA (mtDNA) variation commonly found in natural populations was assumed to be effectively neutral. However, variation in mtDNA has now been increasingly linked to phenotypic variation in life history traits and fitness. We examined whether the relative fitness in native and invasive common wasp (Vespula vulgaris) populations in Belgium and New Zealand (NZ), respectively, can be linked to mtDNA variation. Social wasp colonies in NZ were smaller with comparatively fewer queen cells, indicating a reduced relative fitness in the invaded range. Interestingly, queen cells in this population were significantly larger leading to larger queen offspring. By sequencing 1,872 bp of the mitochondrial genome, we determined mitochondrial haplotypes and detected reduced genetic diversity in NZ. Three common haplotypes in NZ frequently produced many queens, whereas the four rare haplotypes produced significantly fewer or no queens. The entire mitochondrial genome for each of these haplotypes was sequenced to identify polymorphisms associated with fitness reduction. We found 16 variable sites; however, no nonsynonymous mutation that was clearly causing impaired mitochondrial function was detected. We discuss how detected variants may alter secondary structures, gene expression or mito-nuclear interactions, or could be associated with nuclear-encoded variation. Whatever the ultimate mechanism, we show reduced fitness and mtDNA variation in an invasive wasp population as well as specific mtDNA variants associated with fitness variation within this population. Ours is one of only a few studies that confirm fitness impacts of mtDNA variation in wild nonmodel populations.

In social Hymenoptera, fertility and fertility signalling are often under identical hormonal control, and it has been suggested that such hormonal pleiotropies can help to maintain signal honesty. In the common wasp Vespula vulgaris, for example, fertile queens have much higher juvenile hormone (JH) titers than workers, and JH also controls the production of chemical fertility cues present on the females' cuticle. To regulate reproductive division of labour, queens use these fertility cues in two distinct ways: as queen pheromones that directly suppress the workers' reproduction as well as to mark queen eggs and enable the workers to recognize and police eggs laid by other workers. Here, we investigated the hormonal pleiotropy hypothesis by testing if experimental treatment with the JH analogue methoprene could enable the workers to lay eggs that evade policing. In support of this hypothesis, we find that methoprene-treated workers laid more eggs, and that the chemical profiles of their eggs were more queen-like, thereby causing fewer of their eggs to be policed compared to in the control. Overall, our results identify JH as a key regulator of both reproduction and the production of egg marking pheromones that mediate policing behaviour in eusocial wasps. ispartof: SCIENTIFIC REPORTS vol:10 issue:1 ispartof: location:England status: published

Enmeshed in various social structures, humans must often weigh their own interest against the interest of others-including the common interest of groups they belong to. The Public Goods Game (PGG), which succinctly pits individual interest against group interest, has been a staple of research into how people make such decisions. It has been studied in many variations, in the laboratory and (increasingly) online. One of the defining parameters of the PGG is the marginal per capita return of the group project (MPCR), which determines the incentive for contributing to the group project relative to the incentive of keeping points in the personal account. The effect of MPCR on contributions has been investigated before, but its effects have never been characterised with high resolution. Here, we present a systematic and high-resolution investigation of the effect of MPCR in groups of three. We do this in a large-scale online decision making experiment recruiting participants from Amazon Mechanical Turk. Our results provide a fine-grained account of the relationship between incentive to cooperate on the one hand and cooperation on the other, and can help to provide a basis for choosing MPCR magnitudes for future research endeavours using online PGG studies. ispartof: SCIENTIFIC REPORTS vol:10 issue:1 ispartof: location:England status: published

Genomic imprinting is the differential expression of alleles in diploid individuals, with the expression being dependent upon the sex of the parent from which it was inherited. Haig’s kinship theory hypothesizes that genomic imprinting is due to an evolutionary conflict of interest between alleles from the mother and father. In social insects, it has been suggested that genomic imprinting should be widespread. One recent study identified parent-of-origin expression in honeybees and found evidence supporting the kinship theory. However, little is known about genomic imprinting in insects and multiple theoretical predictions must be tested to avoid single-study confirmation bias. We, therefore, tested for parent-of-origin expression in a primitively eusocial bee. We found equal numbers of maternally and paternally biased expressed alleles. The most highly biased alleles were maternally expressed, offering support for the kinship theory. We also found low conservation of potentially imprinted genes with the honeybee, suggesting rapid evolution of genomic imprinting in Hymenoptera.Impact summaryGenomic imprinting is the differential expression of alleles in diploid individuals, with the expression being dependent upon the sex of the parent from which it was inherited. Genomic imprinting is an evolutionary paradox. Natural selection is expected to favour expression of both alleles in order to protect against recessive mutations that render a gene ineffective. What then is the benefit of silencing one copy of a gene, making the organism functionally haploid at that locus? Several explanations for the evolution of genomic imprinting have been proposed. Haig’s kinship theory is the most developed and best supported.Haig’s theory is based on the fact that maternally (matrigene) and paternally (patrigene) inherited genes in the same organism can have different interests. For example, in a species with multiple paternity, a patrigene has a lower probability of being present in siblings that are progeny of the same mother than does a matrigene. As a result, a patrigene will be selected to value the survival of the organism it is in more highly, compared to the survival of siblings. This is not the case for a matrigene.Kinship theory is central to our evolutionary understanding of imprinting effects in human health and plant breeding. Despite this, it still lacks a robust, independent test. Colonies of social bees consist of diploid females (queens and workers) and haploid males created from unfertilised eggs. This along with their social structures allows for novel predictions of Haig’s theory.In this paper, we find parent of origin allele specific expression in the important pollinator, the buff-tailed bumblebee. We also find, as predicted by Haig’s theory, a balanced number of genes showing matrigenic or patrigenic bias with the most extreme bias been found in matrigenically biased genes.

The division of labour between reproductive queens and mostly sterile workers is among the defining characteristics of social insects. Queen-produced chemical signals advertising her presence and fertility status, i.e. queen pheromones, are normally used to assert the queen's reproductive dominance in the colony. Most queen pheromones identified to date are chemicals that stop the daughter workers from reproducing. Nevertheless, it has long been suggested that queen pheromones could also regulate reproduction in different ways. In some multiple-queen ants with obligately sterile workers, for example—such as fire ants and pharaoh ants—queen pheromones are thought to regulate reproduction by inhibiting the rearing of new sexuals. Here, we identify the first such queen pheromone in the pharaoh ant Monomorium pharaonis and demonstrate its mode of action via bioassays with the pure biosynthesized compound. In particular, we show that the monocyclic diterpene neocembrene, which in different Monomorium species is produced solely by fertile, egg-laying queens, strongly inhibits the rearing of new sexuals (queens and males) and also exerts a weakly attractive ‘queen retinue’ effect on the workers. This is the first time that a queen pheromone with such a dual function has been identified in a social insect species with obligately sterile workers.

ispartof: Encyclopedia of Social Insects status: Published online

Sphecophaga vesparum often parasitizes nests of vespid wasps such as Vespula vulgaris and Vespula germanica. Inside the colonies, the ectoparasitic larvae feed on the immature forms of the wasps. There are two adult forms of S. vesparum. The large, winged adults emerge from either rigid yellow cocoons or the orange cocoons used for overwintering. The small, brachypterous females emerge from soft, white cocoons. The species is facultative deuterotokous, producing mostly parthenogenic females and infrequently producing males. Here, we describe the production of chemical compounds related to the different developmental forms of the parasitoid S. vesparum (larvae, pupae and adults). We also compare the chemical profiles of the parasitoid wasp adults to those of their two main host species, Vespula vulgaris and Vespula germanica. The results show differences in hydrocarbon composition of larvae, pupae and adults of S. vesparum. Our results also suggest a partial mimicry of each of the two host species, mostly relating to linear alkanes present in both parasitoids and the host vespid wasp species. This matching is likely due to the recycling of the prey&rsquo, s hydrocarbons, as has been found in other species of parasitoids.

Indirect interactions occur when a species affects another species by altering the density (density-mediated interactions) or influencing traits (trait-mediated interactions) of a third species. We studied variation in these two types of indirect interactions in a network of red wood ants and symbiotic arthropods living in their nests. We tested whether the ant workers indirectly affected survival of a symbiotic prey species (Cyphoderus albinus) by changing the density and/or traits of three symbiotic predators, i.e., Mastigusa arietina, Thyreosthenius biovatus and Stenus aterrimus, provoking, respectively, low, medium and high ant aggression. An ant nest is highly heterogeneous in ant worker density and the number of aggressive interactions towards symbionts increases with worker density. We, therefore, hypothesized that varying ant density could indirectly impact prey-predator interactions of the associated symbiont community. Ants caused trait-mediated indirect effects in all three prey-predator interactions, by affecting the prey capture rate of the symbiotic predators at different worker densities. Prey capture rate of the highly and moderately aggressed spider predators M. arietina and T. biovatus decreased with ant density, whereas the prey capture rate of the weakly aggressed beetle predator S. aterrimus increased. Ants also induced density-mediated indirect interactions as high worker densities decreased the survival rate of the two predatory spider species. These results demonstrate for the first time that a host can indirectly mediate the trophic interactions between associated symbionts. In addition, we show that a single host can induce opposing indirect effects depending on its degree of aggression towards the symbionts. ispartof: OECOLOGIA vol:188 issue:4 pages:1145-1153 ispartof: location:Germany status: published

Individuals face many types of social interactions throughout their lives, but they often cannot perfectly assess what the consequences of their actions will be. Although it is known that unpredictable environments can profoundly affect the evolutionary process, it remains unclear how uncertainty about the nature of social interactions shapes the evolution of social behaviour. Here, we present an evolutionary simulation model, showing that even intermediate uncertainty leads to the evolution of simple cooperation strategies that disregard information about the social interaction (‘social heuristics’). Moreover, our results show that the evolution of social heuristics can greatly affect cooperation levels, nearly doubling cooperation rates in our simulations. These results provide new insight into why social behaviour, including cooperation in humans, is often observed to be seemingly suboptimal. More generally, our results show that social behaviour that seems maladaptive when considered in isolation may actually be well-adapted to a heterogeneous and uncertain world., Humans are known to use social heuristics to make intuitive decisions on whether to cooperate. Here, the authors show with evolutionary simulations that social heuristics can be an adaptive solution to uncertainties about the consequences of cooperation and can greatly increase cooperation levels.

BACKGROUND Historically, inert insecticidal powders such as diatomaceous earth were researched for pest management applications, and it was revealed that these types of powders killed insects by desiccation. However, data on the critical material properties that affect their efficacy are sparse. The present study investigated the insecticidal effect of powdered materials on the pharaoh ant, a notorious domestic pest. RESULTS The insecticidal activity of 24 porous materials was tested. Eight of these materials performed better than the benchmark, diatomaceous earth. Zeolite Y and carbon black II performed best, inducing 50% mortality within 40 and 55 minutes, respectively. Statistical analysis of seven material properties revealed that macroporous surface area and Brunauer-Emmett-Teller (BET) specific surface area were most predictive of insecticidal activity. For zeolites and ordered mesoporous silica materials, the most important parameters were, respectively, BET and large mesopore surface area. Finally, gas chromatography-mass spectrometry (GC-MS) analysis confirmed the adsorption of epicuticular hydrocarbons onto the zeolite powders. CONCLUSION This study shows clear potential for the use of environmentally friendly, inert porous materials as insecticides against the pharaoh ant and identified the key material properties influencing insecticidal activity. The GC-MS data support the hypothesis that the mortality was caused by the removal of the protective epicuticular hydrocarbons. © 2017 Society of Chemical Industry.

Social insect colonies provide a valuable resource that attracts and offers shelter to a large community of arthropods. Previous research has suggested that many specialist parasites of social insects chemically mimic their host in order to evade aggression. In the present study, we carry out a systematic study to test how common such chemical deception is across a group of 22 arthropods that are associated with red wood ants (Formica rufa group). In contrast to the examples of chemical mimicry documented in some highly specialized parasites in previous studies, we find that most of the rather unspecialized red wood ant associates surveyed did not use mimicry of the cuticular hydrocarbon recognition cues to evade host detection. Instead, we found that myrmecophiles with lower cuticular hydrocarbon concentrations provoked less host aggression. Therefore, some myrmecophiles with low hydrocarbon concentrations appear to evade host detection via a strategy known as chemical insignificance. Others showed no chemical disguise at all and, instead, relied on behavioral adaptations such as particular defense or evasion tactics, in order to evade host aggression. Overall, this study indicates that unspecialized myrmecophiles do not require the matching of host recognition cues and advanced strategies of chemical mimicry, but can integrate in a hostile ant nest via either chemical insignificance or specific behavioral adaptations. ispartof: Journal of Chemical Ecology vol:43 issue:7 pages:644-661 ispartof: location:United States status: published

Cooperation in biological systems is frequently maintained by social enforcement mechanisms, where individually egoistic and group-costly behaviour is mutually suppressed by other group members. One of the best examples in nature is worker policing in the honeybee, where workers selectively remove or “police” eggs laid by workers that egoistically try to produce their own offspring instead of working for the good of the colony. It has long been suggested that worker policing behaviour should be genetically determined, as theory has shown that queen polyandry in the honeybee would be expected to give rise to clear indirect genetic or "inclusive fitness" benefits of worker policing, thereby causing genes for policing to spread in the population. In the present study we test the theory that worker policing should have a genetic component by determining if workers belonging to different patrilines, derived from different fathers, show differences in their tendency to police eggs. This analysis shows that variation in policing behaviour indeed has a genetic basis, with the trait having an estimated broad-sense heritability of 0.24 ([0.013-0.46] 95% C.L.s). In addition, there was clear individual specialization in policing, as just a few individuals within each patriline were observed to police. Remarkably though, there was no evidence for age specialisation, as workers of all ages except those younger than 10 days and older than ca. 40 days engaged in policing. This contrasts with most other behaviours in the honeybee, which usually follow a strict age-linked pattern of division of labour. Overall, we conclude that worker policing behaviour in the honeybee is genetically heritable and that workers of all ages engage in policing to help maintain the social order in the colony. ispartof: Animal Behaviour vol:128 pages:95-102 status: published

Viruses are one of the major threats for honeybees and until now more than 20 different viruses have been discovered. Viruses and their hosts are engaged in a continuous arms race in which viral defense mechanisms drive the adaptive evolution of host immune genes, which in turn results in counter-adaptations of the viral immune antagonists. The honeybee immune responses to non-viral pathogens have been extensively studied, but little is known about the antiviral responses. Recent evidence suggests that the main mechanism of antiviral defense in insects is the RNA interference (RNAi) pathway. Furthermore, there is evidence that some viruses suppress this RNAi pathway in order to evade antiviral immunity. In the present study, we test this hypothesis by comparing the gene expression levels of some key components of the RNAi response of honeybees that were naturally infected with at least five viruses with those who were infected with only two or three viruses using a colorimetric microarray developed in-house, called BeeClinic, and subsequently confirmed by quantitative reverse-transcription-polymerase chain reaction (qRT-PCR). Our results show that key components of the RNAi pathway are indeed downregulated in highly infected bees. We were able to show that high virus loads suppress key RNAi components, which results in a counteraction of the host RNAi antiviral defense. As the RNAi is a primary defense against viruses, these findings shed new light on pathogen-host interactions and can help mitigate escalating colony losses worldwide.

The radiation of Palearctic green toads (Bufotes) holds great potential to evaluate the role of hybridization in phylogeography at multiple stages along the speciation continuum. With fifteen species representing three ploidy levels, this model system is particularly attractive to examine the causes and consequences of allopolyploidization, a prevalent yet enigmatic pathway towards hybrid speciation. Despite substantial efforts, the evolutionary history of this species complex remains largely blurred by the lack of consistency among the corresponding literature. To get a fresh, comprehensive view on Bufotes phylogeography, here we combined genome-wide multilocus analyses (RAD-seq) with an extensive compilation of mitochondrial, genome size, niche modelling, distribution and phenotypic (bioacoustics, morphometrics, toxin composition) datasets, representing hundreds of populations throughout Eurasia. We provide a fully resolved nuclear phylogeny for Bufotes and highlight exceptional cyto-nuclear discordances characteristic of complete mtDNA replacement (in 20% of species), mitochondrial surfing during post-glacial expansions, and the formation of homoploid hybrid populations. Moreover, we traced the origin of several allopolyploids down to species level, showing that all were exclusively fathered by the West Himalayan B. latastii but mothered by several diploid forms inhabiting Central Asian lowlands, an asymmetry consistent with hypotheses on mate choice and Dobzhansky-Muller incompatibilities. Their intermediate call phenotypes potentially allowed for rapid reproductive isolation, while toxin compositions converged towards the ecologically-closest parent. Across the radiation, we pinpoint a stepwise progression of reproductive isolation through time, with a threshold below which hybridizability is irrespective of divergence (15My). Finally, we clarified the taxonomy of Bufotes (including genetic analyses of type series) and formally described two new species, B. cypriensis sp. nov. (endemic to Cyprus) and B. perrini sp. nov. (endemic to Central Asia). Embracing the genomic age, our framework marks the advent of a new exciting era for evolutionary research in these iconic amphibians. ispartof: MOLECULAR PHYLOGENETICS AND EVOLUTION vol:141 ispartof: location:United States status: published

The evolutionary origin of queen pheromones (QPs), which regulate reproductive division of labor in insect societies, has been explained by two evolutionary scenarios: the sender-precursor hypothesis and the sensory exploitation hypothesis. These scenarios differ in terms of whether the signaling system was built on preadaptations on the part of either the sender queens or the receiver workers. While some social insect QPs—such as cuticular hydrocarbons—were likely derived from ancestral fertility cues and evolved according to the former theory, the honeybee’s queen mandibular pheromone (QMP) has been suggested to act directly on preexisting gene-regulatory networks linked with reproduction. This is evidenced by the fact that QMP has been shown to also inhibit ovary activation in fruit flies, thereby implying exploitation of conserved physiological pathways. To verify whether QMP has similar effects on more closely related eusocial species, we here tested for QMP cross-activity in the bumblebee Bombus terrestris. Interestingly, we found that the non-native QMP blend significantly inhibited egg laying in both worker and queen bumblebees and caused accompanying shifts in ovary activation. The native bumblebee QP pentacosane, by contrast, only inhibited the reproduction of the workers. Overall, these findings support the hypothesis that honeybee QMP likely evolved via a route of sensory exploitation. We argue that such exploitation could allow social insect queens to produce compounds that manipulate the workers to remain sterile, but that a major hurdle would be that the queens themselves would have to be immune to such compounds. ispartof: Behavioral Ecology vol:31 issue:2 status: published

In several highly eusocial insect species with morphologically distinct castes, queen-characteristic cuticular hydrocarbons (CHCs) have been shown to act as queen signals that suppress the reproduction of nestmate workers. However, it is not known whether such queen pheromones might also play a role in regulating reproductive division of labour in primitively eusocial insects that lack morphologically defined castes. Here, we experimentally tested whether a blend of CHCs which occurred in higher concentrations in the dominant breeding female act as a queen pheromone, and inhibit reproduction by subordinate females in the primitively eusocial paper wasp Polistes satan. In contrast to earlier findings with highly eusocial species, our results show that although specific compounds were enhanced in dominant, reproductively active females, a blend of five of these compounds did not inhibit development of the ovaries of female nestmates. Instead, the dominant female had to be physically present to prevent subordinate females from reproducing. Our results are in line with earlier evidence suggesting that fertility-linked compounds in primitively eusocial wasps act only as cues and help to regulate reproduction when used in conjunction with aggressive dominance behaviour, meaning the physical presence of the dominant female. Alternatively, our results support the hypothesis that queen pheromones in highly eusocial insects were co-opted from fertility cues that were already present in primitively eusocial ancestors, even when initially, such compounds were merely produced as by-products of ovarian activation, without actually serving to signal reproductive status.

Paternity testing using genetic markers has shown that extra-pair paternity (EPP) is common in many pair-bonded species [1, 2]. Evolutionary theory and empirical data show that extra-pair copulations can increase the fitness of males as well as females [3, 4]. This can carry a significant fitness cost for the social father, who then invests in rearing offspring that biologically are not his own [5]. In human populations, the incidence and correlates of extra-pair paternity remain highly contentious [2, 6, 7]. Here, we use a population-level genetic genealogy approach [6, 8] to reconstruct spatiotemporal patterns in human EPP rates. Using patrilineal genealogies from the Low Countries spanning a period of over 500 years and Y chromosome genotyping of living descendants, our analysis reveals that historical EPP rates, while low overall, were strongly impacted by socioeconomic and demographic factors. Specifically, we observe that estimated EPP rates among married couples varied by more than an order of magnitude, from 0.4% to 5.9%, and peaked among families with a low socioeconomic background living in densely populated cities of the late 19 century. Our results support theoretical predictions that social context can strongly affect the outcomes of sexual conflict in human populations by modulating the incentives and opportunities for engaging in extra-pair relationships [9–11]. These findings show how contemporary genetic data combined with in-depth genealogies open up a new window on the sexual behavior of our ancestors. Larmuseau et al. combine genetic data with family trees to reconstruct historical patterns of human extra-pair paternity (EPP). They show that EPP rates in Western society were low overall (∼1%) but varied in function of social context, peaking at ∼6% among families with low socioeconomic status in densely populated cities of the 19 century., Funding was provided by KU Leuven (BOF-C1 grant C12/15/013) and the Fund for Scientific Research – Flanders (Research grant number 1503216N and postdoc grants of M.H.D.L. and P.v.d.B.). F.C. was supported by Agencia Estatal de Investigación and Fondo Europeo de Desarollo Regional (FEDER) (grant CGL2016-75389-P), Agència de Gestió d’Ajuts Universitaris i de la Recerca (Generalitat de Catalunya) grant 2017 SGR00702, and “Unidad de Excelencia María de Maeztu,” funded by the MINECO (ref: MDM-2014-0370).

Aphid species can be polyphagous, feeding on multiple host plants across genera. As host plant species can have large variation in their phloem composition, this can affect aphid fitness and honeydew composition. Previous research showed significant intraspecific genotype variation in the composition of the honeydew carbohydrates of the black bean aphid Aphis fabae, with the ant attractant trisaccharide melezitose showing especially large variation across different genotypes. In this study, we test if variation in melezitose and carbohydrate composition of aphid honeydew could be linked to the adaptation of specific aphid genotypes to particular host plants. To this end, 4 high and 5 low melezitose secreting genotypes of the black bean aphid Aphis fabae were reared on 4 common host plants: broad bean, goosefoot, beet, and poppy. The carbohydrate composition, and in particular melezitose secretion, showed important aphid genotype and host plant interactions, with some genotypes being high melezitose secreting on 1 host plant but not on another. However, the interaction effects were not paralleled in the fitness measurements, even though there were significant differences in the average fitness across the different host plants. On the whole, this study demonstrates that aphid honeydew composition is influenced by complex herbivore-plant interactions. We discuss the relevance of these findings in the context of ant-aphid mutualisms and adaptive specialization in aphids.

Insect societies display a remarkable level of cooperation, but their colonies also represent a valuable resource that can be taken advantage of by genetically unrelated individuals. Indeed, several recent studies have documented cases of intraspecific reproductive parasitism, whereby workers penetrate and lay eggs in unrelated colonies in order to have their brood raised by the host workers. Previously, it has been predicted that queenless colonies should be a prime target of such intraspecific worker parasitism, as in such colonies the parasite workers would be able to reproduce without interference from either the queen or other workers. So far, this prediction has been supported with data from the honeybee, but evidence from other social insect groups is currently lacking. Here we present the first such test in the common wasp, Vespula vulgaris. In particular, workers from queenright colonies left the natal nest at a higher rate than those from queenless colonies. However, contrary to our predictions, drifter workers targeted queenless and queenright colonies equally. Chemical data suggest that this lack of discrimination may be linked to recognition constraints and the lack of volatile signals that reliably indicate the presence or absence of the queen. In addition, in queenright colonies, drifters activated their ovaries at a rate that was ca. five times higher than the natal workers. Overall, our results suggest that also in wasps, workers can gain inclusive fitness by drifting to unrelated nests, even if the chances of successfully reproducing there may be very slim.

The division of labour between reproductive queens and mostly sterile workers is among the defining characteristics of social insects. Queen-produced chemical signals advertising her presence and fertility status, i.e. queen pheromones, are normally used to assert the queen's reproductive dominance in the colony. Most queen pheromones identified to date are chemicals that stop the daughter workers from reproducing. Nevertheless, it has long been suggested that queen pheromones could also regulate reproduction in different ways. In some multiple-queen ants with obligately sterile workers, for example—such as fire ants and pharaoh ants—queen pheromones are thought to regulate reproduction by inhibiting the rearing of new sexuals. Here, we identify the first such queen pheromone in the pharaoh ant Monomorium pharaonis and demonstrate its mode of action via bioassays with the pure biosynthesized compound. In particular, we show that the monocyclic diterpene neocembrene, which in different Monomorium species is produced solely by fertile, egg-laying queens, strongly inhibits the rearing of new sexuals (queens and males) and also exerts a weakly attractive ‘queen retinue’ effect on the workers. This is the first time that a queen pheromone with such a dual function has been identified in a social insect species with obligately sterile workers.

© 2018 The Author(s). Many parasites display complex strategies to evade host detection. The principal view is that the parasites of social insects deceive their host by means of advanced chemical adaptations such as mimicking the cuticular host recognition cues, being chemically odorless, or emitting manipulative volatiles. Apart from these chemical adaptations, parasites of social insects may also use simpler behavioral strategies to evade host detection. As yet, such a behavior has rarely been studied. Here we tested which chemical and behavioral strategies the unspecialized parasitic rove beetle Thiasophila angulata uses to avoid detection by its aggressive Formica rufa red wood ant host. Chemical comparisons of the beetle's and the host ants' cuticular hydrocarbons showed that the beetle carried an idiosyncratic cuticular profile that was clearly different from that of its host. Beetles that were isolated from their host or were placed in the nests of another Formica species perfectly retained their original cuticular profiles and provoked equal levels of aggression. These results suggest that the beetles do not avoid host detection through chemical deception. In contrast, the beetle adapted its behavior to avoid aggression by the ants. In the presence of ants, the beetle behaved much more prudently by hiding more frequently and engaging in less risky runs. Overall, these results highlight that for relatively unspecialized parasites, general strategies such as prudent behavior can be equally effective as more specialized deception strategies to evade host detection. ispartof: BEHAVIORAL ECOLOGY vol:29 issue:6 pages:1225-1233 status: published

ETHNOPHARMACOLOGICAL RELEVANCE: Semen Torreyae, the seeds of Torreya grandis Fortune ex Lindley (Cephalotaxaceae) is a well-known traditional Chinese medicinal plant recorded in the Chinese Pharmacopeia (2010 version). It is widely used for treating intestinal parasites in China, owing to its desirable efficacy and safety. However, the anthelmintic compounds in Semen Torreyae have not yet been identified. AIM OF THE STUDY: This study aims to identify the compounds active against helminths from Semen Torreyae. In addition, we tested whether C. elegans strains resistant to currently-used anthelmintic drugs showed cross-resistance to these compounds. METHODS: A bioassay-guided isolation of anthelmintic compounds from Semen Torreyae was performed using a Caenorhabditis elegans (C. elegans) testing model. The structures of active compounds were elucidated by a combination of GC-MS, high resolution MS, and NMR. The median-effect method was employed to generate a combination index (CI) to evaluate the synergistic effect of the anthelmintic compounds. A panel of C. elegans mutant strains resistant against the major anthelmintic drug classes was used to study the cross-resistance to currently-used anthelmintic drugs. A panel of transient receptor potential (TRP) channel mutant strains was also tested to explore the possible mechanisms of action of the anthelmintic compounds. RESULTS: The bioassay-guided isolation led to two active compounds, i.e. galangal acetate (IC50: 58.5 ± 8.9 μM) and miogadial (IC50: 25.1 ± 5.4 μM). The combination of galangal acetate and miogadial resulted in a synergistic effect at IC50, IC70, and IC90 levels (CIs < 1). Galangal acetate and miogadial demonstrated similar activity against drug-resistant C. elegans strains compared to the wild-type strain. In addition, none of the TRP mutants was significantly resistant to galangal acetate or miogadial compared to wild type worms. CONCLUSIONS: We identified the bioactive compounds from Semen Torreyae responsible for its anthelmintic activity: galangal acetate and miogadial. The two anthelmintic compounds demonstrated a synergistic effect against C. elegans. Galangal acetate and miogadial are unlikely to act on the targets of currently-used anthelmintics (ivermectin, levamisole, benomyl and aldicarb), and an action on TRP channels appears to be ruled out as well. In summary, galangal acetate and miogadial are promising anthelmintic hits worth further investigation. ispartof: JOURNAL OF ETHNOPHARMACOLOGY vol:224 pages:421-428 ispartof: location:Ireland status: published

The pharaoh ant is a notorious and hard to eradicate pest, which poses a threat in hospitals, spreading pathogens and contaminating sterile equipment. When applied on ants, zeolites adsorb part of their epicuticular wax layer. The ants are then vulnerable to desiccation, since this layer regulates water exchange. We analyzed the chemical composition of this wax layer using GC-MS (Gas Chromatography-Mass Spectrometry). A hexane wash of M. pharaonis foragers resulted in the identification of 53 components, four of which were not previously defined in Monomorium species. Selective adsorption of specific compounds on zeolites assisted in the identification of compounds which could not be separated on the GC column and allowed for the identification of three additional compounds. Zeolites show different affinities for the wax compounds depending on pore structure and chemical composition. Selective adsorption of alkanes on zeolites is also investigated in the fields of refinery processes and catalysis. Pore mouth and key lock adsorption mechanisms and selectivity according to molecular weight and branching, investigated in these fields, are also involved in adsorption processes of epicuticular waxes. The insecticidal activity of a zeolite is related to adsorption selectivity rather than capacity. One of the best adsorbing zeolites showed limited insecticidal activity and can be considered as a non-lethal alternative for epicuticular wax sampling.

Non-toxic and environmentally friendly insecticidal powders have grown in popularity as pest control products to substitute traditional pesticide-based methods. The pharaoh ant is an ideal test species for insecticidal dusts and it is an indoor pest, mostly found in heated buildings where it can pose severe risks because of its ability to destroy electrical equipment and transfer diseases in hospitals. The use of commercially available activated carbon and carbon black materials as insecticidal dust is of great interest, since these types of materials proved effective in previous research and they have been little researched in the past. In the present study, we compared the effectiveness of 11 different carbon materials to reveal the key material properties defining the insecticidal action. All of the materials, with the exception of Printex U, performed better than the benchmark diatomaceous earth, which is presently the most widely used insecticidal dust. The shortest median survival time, 25 min, was observed upon exposure to activated carbon powder, which was significantly shorter than the 95 min observed for diatomaceous earth. Model selection revealed that particle size was the most important parameter determining insecticidal activity for activated carbon materials. Overall, our findings highlight the potential for the use of carbon materials as insecticidal agents, not just for the control of the pharaoh ant, but potentially also to control other domestic or agricultural pests in confined spaces, such as stored grain pests or bed bugs. ispartof: JOURNAL OF PEST SCIENCE vol:92 issue:2 pages:1-10 status: Published online

Animal gut microbiota affect host physiology and behaviour. In eusocial Hymenoptera, where colony-level integrity is preserved via a nestmate discrimination system based on cuticular hydrocarbon mixtures, microorganismal effects may influence social dynamics. Although nestmate recognition has undergone a thorough exploration during the last four decades, few studies have investigated the putative role of gut microbes. Here we integrate metagenomic, chemical and behavioural approaches to test whether gut microbes affect nestmate recognition inAcromyrmex echinatiorleaf-cutting ants. Treating workers with a sterile diet or with antibiotics resulted in a substantial alteration of their gut microbial communities. In pairwise social interactions, untreated vs. antibiotic-treated nestmates behaved more aggressively than other nestmate and non-nestmate pairs, suggesting that the suppression of microbes indirectly alters chemical social cues and triggers aggressive behaviour. Chemical analyses on treated individuals revealed a decrease in the abundance of two metapleural gland antifungal compounds, and we confirmed the correspondence between aggression levels and chemical profile differences. Feeding microbiota-remodelled ants with conspecific faecal droplets partially restored the original bacterial communities. Furthermore, non-nestmates fed with faecal droplets from different colonies were unusually aggressive compared to pairs fed with faecal droplets from the same colony. This suggests that chemicals derived from microbial strains may shape nestmate recognition, opening novel questions about the role of microorganisms in the evolution of social behaviour.

Persisters are transiently antibiotic-tolerant cells that complicate the treatment of bacterial infections. Both theory and experiments have suggested that persisters facilitate genetic resistance by constituting an evolutionary reservoir of viable cells. Here, we provide evidence for a strong positive correlation between persistence and the likelihood to become genetically resistant in natural and lab strains of E. coli. This correlation can be partly attributed to the increased availability of viable cells associated with persistence. However, our data additionally show that persistence is pleiotropically linked with mutation rates. Our theoretical model further demonstrates that increased survival and mutation rates jointly affect the likelihood of evolving clinical resistance. Overall, these results suggest that the battle against antibiotic resistance will benefit from incorporating anti-persister therapies.

The lag phase is arguably one of the prime characteristics of microbial growth. Longer lag phases result in lower competitive fitness in variable environments, and the duration of the lag phase is also important in many industrial processes where long lag phases lead to sluggish, less efficient fermentations. Despite the immense importance of the lag phase, surprisingly little is known about the exact molecular processes that determine its duration. Our study uses the molecular toolbox of S. cerevisiae combined with detailed growth experiments to reveal how the transition from fermentative to respirative metabolism is a key bottleneck for cells to overcome the lag phase. Together, our findings not only yield insight into the key molecular processes and genes that influence lag duration but also open routes to increase the efficiency of industrial fermentations and offer an experimental framework to study other types of lag behavior., When faced with environmental changes, microbes often enter a temporary growth arrest during which they reprogram the expression of specific genes to adapt to the new conditions. A prime example of such a lag phase occurs when microbes need to switch from glucose to other, less-preferred carbon sources. Despite its industrial relevance, the genetic network that determines the duration of the lag phase has not been studied in much detail. Here, we performed a genome-wide Bar-Seq screen to identify genetic determinants of the Saccharomyces cerevisiae glucose-to-galactose lag phase. The results show that genes involved in respiration, and specifically those encoding complexes III and IV of the electron transport chain, are needed for efficient growth resumption after the lag phase. Anaerobic growth experiments confirmed the importance of respiratory energy conversion in determining the lag phase duration. Moreover, overexpression of the central regulator of respiration, HAP4, leads to significantly shorter lag phases. Together, these results suggest that the glucose-induced repression of respiration, known as the Crabtree effect, is a major determinant of microbial fitness in fluctuating carbon environments.

Living in close association with other organisms has proven to be a widespread and successful strategy in nature. Some communities are completely driven by symbiotic associations and therefore, intimate relationships among the partners can be expected. Here, we analyzed in-depth the food web of a particularly rich community of arthropods found in strict association with European red wood ants (Formica rufa group). We studied the trophic links between different ant-associated myrmecophiles and food sources associated with the host ant, but also tested predator-prey links among myrmecophiles themselves. Our approach combined direct feeding tests and stable carbon and nitrogen isotope analyses for a large number of myrmecophiles. The results of the direct feeding tests reveal a complex food web. Most myrmecophiles were found to parasitize on ant brood. Moreover, we encountered multiple trophic predator-prey links among the myrmecophiles. The results of the stable isotope analyses complement these findings and indicate the existence of multiple trophic levels and trophic isotopic niche compartmentalization. delta N-15 values were strongly correlated with the trophic levels based on the direct tests, reflecting that delta N-15 values of myrmecophiles increased with higher trophic levels. This strong correlation underlines the strength of stable isotopes as a powerful tool to assess trophic levels. In addition, the stable isotope data suggest that most species only facultatively prey on ant brood. The presence of numerous trophic interactions among symbionts clearly contrasts with the traditional view of social insects nests as offering an enemy-free space for symbionts. Interestingly, the ant host can indirectly benefit from these interactions because brood predators are also preyed upon by other myrmecophiles. Overall, this study provides unique insights into the complex interactions in a small symbiont microcosm system and suggests that the interactions between host and symbiont might be mediated by other symbionts in the same community.

© 2015 Gesellschaft für Ökologie. Red wood ants support a diverse community of myrmecophiles in their nest mounds. Given that nest mounds provide fairly constant and distinct habitat patches for myrmecophiles, metapopulation and metacommunity dynamics can be expected to play an important role in structuring myrmecophile communities. Here, we investigate how site, site size (i.e. number of mounds per site), mound isolation, mound size, moisture, pH and red wood ant host (Formica rufa and Formica polyctena) affect the (meta)community composition and species richness. We demonstrate that community composition is structured by site and within-site isolation. In addition, species richness per unit volume is negatively correlated with increasing nest mound isolation. Mound size and site size at a higher spatial scale had no effect on community composition or diversity. The latter suggests that few mounds are required to support the minimum viable metapopulation size. We did not find support that the environmental variables mound moisture and pH affect the myrmecophile community or its species richness. Finally, the communities of the two closely related wood ant species F. rufa and F. polyctena were very similar. Overall, our results demonstrate, in accordance with metapopulation theory, that isolated mounds support fewer myrmecophile species. Diverse myrmecophile metacommunities also occur in small red wood ant sites, with well connected nest mounds. We discuss the powerful potential of ant nests, and particularly red wood ant mounds, for metapopulation and metacommunity research. publisher: Elsevier articletitle: Metapopulation processes affecting diversity and distribution of myrmecophiles associated with red wood ants journaltitle: Basic and Applied Ecology articlelink: http://dx.doi.org/10.1016/j.baae.2015.04.008 content_type: article copyright: Copyright © 2015 Gesellschaft für Ökologie. Published by Elsevier GmbH All rights reserved. ispartof: Basic and Applied Ecology vol:16 issue:6 pages:553-562 status: published

The aphid Aphis fabae (Scopoli) is facultatively tended by Lasius niger (Linnaeus) ants. Previously, we found that A. fabae colonies can be made up of several clones, and that clones display significant differences in the composition of their honeydew sugars, especially in the amount of the ant attractant sugar melezitose that they produce. 2. These clonal differences could greatly impact the strength of the mutualistic interaction with ants as well as the aphids' fitness. 3. Hence, the aim of this study was to compare the fitness of different A. fabae clones that differed in their melezitose secretion, and whether or not they were tended by ants. 4. Individual fitness indices, colony growth, and alate production of single-clone aphid colonies were analysed. 5. The results demonstrate that the fitness consequences of ant attendance critically depend on an interaction between levels of melezitose production. In particular, we show that high-melezitose secreting clones produce fewer alates and hence might have a lower dispersal ability in the presence of ants. 6. Furthermore, these data confirm previous evidence that ant attendance is costly and results in the production of fewer apterae.

In many species, specialized defence traits and strategies are crucial for surviving enemy attacks or securing resources. In numerous social insect lineages, a morphologically and behaviourally distinct soldier caste specializes in colony defence, with larger foragers typically engaging most in the aggressive defence of the colony against external threats. We hypothesized, however, that specialization in aggression could show vastly different patterns in the context of the defence against small intranidal parasites that prey on brood. This is because we expected that small, intranidal nurse workers could be better suited to defend against these parasitic myrmecophiles (=ant associates) due to their better matching size, high encounter rate and the high task switching costs that would occur if foragers had to carry out this task. Here, we present data that support this hypothesis from a study on specialization in defence against two parasites in the red wood ant Formica rufa. In particular, we show that small workers displayed the strongest aggressive behaviour towards the parasitic rove beetle Thiasophila angulata and the spider Thyreosthenius biovatus, and present evidence that small workers were better at preventing brood predation than larger workers. In addition, there was worker task specialization in defensive behaviour, with nurses and workers at nest entrances being more aggressive towards T. angulata than extranidal foragers. We argue that this context-dependent specialization in aggression and nest defence was likely to be important in favouring the pronounced worker polymorphism observed in both this and other ant species and discuss our findings in relation to models for the evolution of division of labour and caste polymorphism in insect societies.

Queen pheromones, which signal the presence of a fertile queen and induce daughter workers to remain sterile, are considered to play a key role in regulating the reproductive division of labor of insect societies. Although queen pheromones were long thought to be highly taxon-specific, recent studies have shown that structurally related long-chain hydrocarbons act as conserved queen signals across several independently evolved lineages of social insects. These results imply that social insect queen pheromones are very ancient and likely derived from an ancestral signalling system that was already present in their common solitary ancestors. Based on these new insights, we here review the literature and speculate on what signal precursors social insect queen pheromones may have evolved from. Furthermore, we provide compelling evidence that these pheromones should best be seen as honest signals of fertility as opposed to suppressive agents that chemically sterilize the workers against their own best interests.

a b s t r a c t Honey bees (Apis mellifera) are susceptible to a wide range of pathogens, including a broad set of viruses. Recently, next-generation sequencing has expanded the list of viruses with, for instance, two strains of Lake Sinai Virus. Soon after its discovery in the USA, LSV was also discovered in other countries and in other hosts. In the present study, we assemble four almost complete LSV genomes, and show that there is remarkable sequence heterogeneity based on the Orf1, RNA-dependent RNA polymerase and capsid protein sequences in comparison to the previously identified LSV 1 and 2 strains. Phylogenetic analyses of LSV sequences obtained from single honey bee specimens further revealed that up to three distinctive clades could be present in a single bee. Such superinfections have not previously been identified for other honey bee viruses. In a search for the putative routes of LSV transmission, we were able to demonstrate the presence of LSV in pollen pellets and in Varroa destructor mites. However, negative-strand analyses demonstrated that the virus only actively replicates in honey bees and mason bees (Osmia cornuta) and not in Varroa mites. © 2015 Elsevier B.V. All rights reserved.

This study investigated the variation in growth/no growth boundaries of 188 Escherichia coli strains. Experiments were conducted in Luria–Bertani media under 36 combinations of lactic acid (LA) (0 and 25 mM), pH (3.8, 3.9, 4.0, 4.1, 4.2 and 4.3 for 0 mM LA and 4.3, 4.4, 4.5, 4.6, 4.7 and 4.8 for 25 mM LA) and temperature (20, 25 and 30 °C). After 3 days of incubation, growth was monitored through optical density measurements. For each strain, a so-called purposeful selection approach was used to fit a logistic regression model that adequately predicted the likelihood for growth. Further, to assess the growth/no growth variability for all the strains at once, a generalized linear mixed model was fitted to the data. Strain was fitted as a fixed factor and replicate as a random blocking factor. E. coli O157:H7 strain ATCC 43888 was used as reference strain allowing a comparison with the other strains. Out of the 188 strains tested, 140 strains (∼75%) presented a significantly higher probability of growth under low pH conditions than the O157:H7 strain ATCC 43888, whereas 20 strains (∼11%) showed a significantly lower probability of growth under high pH conditions. publisher: Elsevier articletitle: Variability in growth/no growth boundaries of 188 different Escherichia coli strains reveals that approximately 75 % have a higher growth probability under low pH conditions than E. coli O157:H7 strain ATCC 43888 journaltitle: Food Microbiology articlelink: http://dx.doi.org/10.1016/j.fm.2014.06.024 content_type: article copyright: Copyright © 2014 Elsevier Ltd. ispartof: Food Microbiology vol:45 issue:Pt B pages:222-230 ispartof: location:FRANCE, Paris status: published

Contemporary data of extra-pair paternity (EPP) in human populations may be biased by the use of modern contraceptives. Studies have now estimated historical EPP rates in several human populations. The observed low EPP rates challenge the idea that women routinely ‘shop around’ for good genes by engaging in extra-pair copulations. ispartof: Trends in Ecology & Evolution vol:31 issue:5 pages:327-329 ispartof: location:England status: published

Historically, inert insecticidal powders such as diatomaceous earth were researched for pest management applications, and it was revealed that these types of powders killed insects by desiccation. However, data on the critical material properties that affect their efficacy are sparse. The present study investigated the insecticidal effect of powdered materials on the pharaoh ant, a notorious domestic pest.The insecticidal activity of 24 porous materials was tested. Eight of these materials performed better than the benchmark, diatomaceous earth. Zeolite Y and carbon black II performed best, inducing 50% mortality within 40 and 55 minutes, respectively. Statistical analysis of seven material properties revealed that macroporous surface area and Brunauer-Emmett-Teller (BET) specific surface area were most predictive of insecticidal activity. For zeolites and ordered mesoporous silica materials, the most important parameters were, respectively, BET and large mesopore surface area. Finally, gas chromatography-mass spectrometry (GC-MS) analysis confirmed the adsorption of epicuticular hydrocarbons onto the zeolite powders.This study shows clear potential for the use of environmentally friendly, inert porous materials as insecticides against the pharaoh ant and identified the key material properties influencing insecticidal activity. The GC-MS data support the hypothesis that the mortality was caused by the removal of the protective epicuticular hydrocarbons. © 2017 Society of Chemical Industry.

A key question in evolutionary biology is to explain the causes and consequences of the so-called “major transitions in evolution,” which resulted in the progressive evolution of cells, organisms, and animal societies (1⇓–3). Several studies, for example, have now aimed to determine which suite of adaptive changes occurred following the evolution of sociality in insects (4). In this context, a long-standing hypothesis is that the evolution of the spectacular sociality seen in insects, such as ants, bees, or wasps, should have gone hand in hand with the evolution of more complex chemical communication systems, to allow them to coordinate their complex social behavior (5). Indeed, whereas solitary insects are known to use pheromone signals mainly in the context of mate attraction and species-recognition, social insects use chemical signals in a wide variety of contexts: to communicate their caste or reproductive status, recognize nestmates from invaders, mark the way to food sources, or alarm nestmates about imminent danger (5). Well-controlled studies of the change in investment in chemical communication systems in highly eusocial insects, such as ants, termites, or Corbiculate bees, however, have proven hard to conduct, because eusociality in these taxa evolved long ago in the Cretaceous (6) and closely related solitary species are no longer around (Fig. 1). In PNAS, Wittwer et al. (7) now provide an elegant solution to this problem. By studying Halictinae sweat bees—a group of primitively eusocial insects that evolved sociality more recently and on several occasions reverted back to a solitary lifestyle (8) (Fig. 1)—they succeed in making an accurate comparison of the investment in chemosensory systems made by social and derived, closely related, nonsocial species. Fig. 1. Cladogram showing the independent origins and secondary losses of sociality in the Hymenoptera (after refs. 6 and 20⇓⇓⇓–24). For clarity, … [↵][1]1To whom correspondence should be addressed. Email: tom.wenseleers{at}kuleuven.be. [1]: #xref-corresp-1-1

As in most Hymenoptera, the eusocial stingless bees (Meliponini) have a complementary sex determination (CSD) system. When a queen makes a "matched mating" with a male that shares a CSD allele with her, half of their diploid offspring are diploid males rather than females. Matched mating imposes a cost, since diploid male production reduces the colony workforce. Hence, adaptations preventing the occurrence or attenuating its effects are likely to arise. Here we provide clear evidence that in the stingless bee Scaptotrigona depilis, the emergence of diploid males induces queen death, and this usually occurs within 10-20 days of the emergence of diploid male offspring from their pupae. Queens that have not made a matched mating die when introduced into a colony in which diploid males are emerging. This shows that the adult diploid males, and not the queen that has made a matched mating herself, are the proximate cause of queen death. Analysis of the cuticular hydrocarbon profiles of adult haploid and diploid males shows six compounds with significant differences. Moreover, the diploid and haploid males only acquire distinct cuticular hydrocarbon profiles 10 days after emergence. Our data shows that the timing of queen death occurs when the cuticular hydrocarbons of haploid and diploid males differ significantly, suggesting that these chemical differences could be used as cues or signals to trigger queen death. ispartof: JOURNAL OF CHEMICAL ECOLOGY vol:43 issue:4 pages:403-410 ispartof: location:United States status: published

© 2017, Springer-Verlag Berlin Heidelberg. Abstract: Social insects have a highly developed nestmate and species recognition system that is quite effective at keeping out unwanted intruders. Rare cases of “parabiosis,” however, are known in some ants where two species apparently live peacefully alongside each other within the same nest. Here, we report on such an association between the tiny Afrotropical ant Strumigenys maynei and the large ant Platythyrea conradti. We demonstrated that both ants peacefully share the same arboreal nests in spite of the presence of clearly distinct nestmate recognition cues. Because of the large size differences, we hypothesized that each of the two species would benefit from specializing in carrying out particular tasks, in analogy to the size-related division of labor observed in species with size-polymorphic workers. In line with this theory, we found that the tiny ant S. maynei was highly efficient at nest defense against intranidal arthropods and alien ant intruders, whereas the large ant P. conradti was highly skilled in nest engineering. We argue that the described association is likely mutualistic, as P. conradti clearly benefited from the supreme defense capabilities of S. maynei, and that, conversely, S. maynei took advantage of small prey thriving in the organic nest material collected by P. conradti. Significance statement: Associations between social insects are typically parasitic in nature. A few cases, however, are known of beneficial associations between social insects. Here, we report such a rare association between two Afrotropical species that share the same nest even though they lack matching colony odors. The large ant Platythyrea conradti benefited from the presence of Strumigenys maynei as this tiny, but highly aggressive, ant was much more efficient in attacking intranidal and extranidal enemies. S. maynei in turn took advantage of P. conradti as this ant constructs a unique nest which attracts suitable prey. ispartof: Behavioral Ecology and Sociobiology vol:71 issue:3 status: published

In a recent study, Amsalem, Orlova & Grozinger (2015) performed experiments withBombus impatiensbumblebees to test the hypothesis that saturated cuticular hydrocarbons are evolutionarily conserved signals used to regulate reproductive division of labor in many Hymenopteran social insects. They concluded that the cuticular hydrocarbon pentacosane (C25), previously identified as a queen pheromone in a congeneric bumblebee, does not affect worker reproduction inB. impatiens. Here we discuss some shortcomings of Amsalem et al.’s study that make its conclusions unreliable. In particular, several confounding effects may have affected the results of both experimental manipulations in the study. Additionally, the study’s low sample sizes (mean n per treatment = 13.6, range: 4–23) give it low power, not 96–99% power as claimed, such that its conclusions may be false negatives. Inappropriate statistical tests were also used, and our reanalysis found that C25substantially reduced and delayed worker egg laying inB. impatiens. We review the evidence that cuticular hydrocarbons act as queen pheromones, and offer some recommendations for future queen pheromone experiments.

In insect societies, both queens and workers produce chemicals that reliably signal caste membership and reproductive status. The mechanisms that help to maintain the honesty of such queen and fertility signals, however, remain poorly studied. Here we test if queen signal honesty could be based on the shared endocrine control of queen fertility and the production of specific signals. In support of this “hormonal pleiotropy” hypothesis, we find that in the common wasp, application of methoprene (a juveline hormone analogue) caused workers to acquire a queen-like cuticular hydrocarbon profile, resulting in the overproduction of known queen pheromones as well as of some compounds typically linked to worker fertility. By contrast, administration of precocene-I (a JH inhibitor) had a tendency to have the opposite effect. Furthermore, a clear gonadotropic effect of JH in queens was suggested by the fact that circulating levels of JH were ca. 2 orders of magnitude higher in queens than those in workers and virgin, non-egglaying queens, even if methoprene or precocene treatment did not affect the ovary development of workers. Overall, these results suggest that queen signal honesty in this system is maintained by queen fertility and queen signal production being under shared endocrine control. ispartof: Scientific Reports vol:7 issue:1 ispartof: location:England status: published

We consider a model of self-propelled agents with spring-like interactions that depend only on relative positions, and not on relative orientations. We observe that groups of these agents self-organize to achieve collective motion (CM) through a mechanism based on the cascading of self-propulsion energy towards lower elastic modes. By computing the correlation functions of the speed and velocity fluctuations for different group sizes, we show that the corresponding correlation lengths are proportional to the linear size of the group and have no intrinsic length scale. We argue that such scale-free correlations are a natural consequence of the position-based interactions and associated CM dynamics. We hypothesize that this effect, acting in the context of more complex realistic interactions, could be at the origin of the scale-free correlations measured experimentally in flocks of starlings, instead of the previously argued proximity to a critical regime.

A state-of-the-art phylogeny of the human Y-chromosome is an essential tool for forensic genetics. The explosion of whole genome sequencing (WGS) data due to the rapid progress of next-generation sequencing facilities is useful to optimize and to increase the resolution of the phylogenetic Y-chromosomal tree. The most interesting Y-chromosomal variants to increase the phylogeny are SNPs (Y-SNPs) especially since the software to call them in WGS data and to genotype them in forensic assays has been optimized over the past years. The PENNY software presented here detects potentially phylogenetic interesting Y-SNPs in silico based on SNP calling data files and classifies them into different types according to their position in the currently used Y-chromosomal tree. The software utilized 790 available male WGS samples of which 172 had a high SNP calling quality. In total, 1269 Y-SNPs potentially capable of increasing the resolution of the Y-chromosomal phylogenetic tree were detected based on a first run with PENNY. Based on a test panel of 57 high-quality and 618 low-quality WGS samples, we could prove that these newly added Y-SNPs indeed increased the resolution of the phylogenetic Y-chromosomal analysis substantially. Finally, we performed a second run with PENNY whereby all samples including those of the test panel are used and this resulted in 509 additional phylogenetic promising Y-SNPs. By including these additional Y-SNPs, a final update of the present phylogenetic Y-chromosomal tree which is useful for forensic applications was generated. In order to find more convincing forensic interesting Y-SNPs with this PENNY software, the number of samples and variety of the haplogroups to which these samples belong needs to increase. The PENNY software (inclusive the user manual) is freely available on the website http://bio.kuleuven.be/eeb/lbeg/software.

Long Live the Queen Eusociality is often considered to have arisen, at least in part, due to the inclusive fitness that workers gain through helping their queen sister to raise her offspring. Van Oystaeyen et al. (p. 287 ; see the Perspective by Chapuisat ) characterized the sterility-inducing queen pheromone across three distantly related eusocial hymenopterans (a wasp, a bumblebee, and a desert ant) and synthesized data across 69 other species. Queen pheromones appear to be remarkably conserved, which suggests that reproductive manipulation has ancient roots.

Over the past decade, the spotted-wing drosophila, Drosophila suzukii Matsumara has become one of the most important pests of soft- and stone fruits throughout Europe. Currently, the majority of growers still rely heavily on a limited portfolio of chemical foliar spray insecticides. Alternative strategies such as attract and kill (pull) or behavioral control systems that repel or deter D. suzukii from damaging fruits (push) are less common. We evaluated the potential of hop (Humulus lupulus L.), as a repellent for the Integrated Pest Management of D. suzukii, in controlled greenhouse conditions as well as at commercial field sites. In greenhouse cage tests on fruit or attractant medium, the positive controls thymol and 1-octen-3-ol as well as certain hops significantly reduced larval infestation levels compared to an untreated control, while other hop products showed only numerical reduction in infestation. A controlled field trial on raspberries (Rubus idaeus L.) failed to replicate these results, both for the positive control repellents as for the hop samples. In field experiments in commercial raspberry and blackberry (Rubus fruticosus L.) plantations, no significant reduction in oviposition or differences in population density could be observed for the hop treated plots as compared to the untreated. Through SPME headspace analysis of the hops, a number of compounds were associated with the efficacy observed in the greenhouse, even though different hop varieties were found to have notably different volatile profiles.