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Kao AB, Hund AK, Santos FP, Young JG, Bhat D, Garland J, Oomen RA, McCreery HF. Opposing Responses to Scarcity Emerge from Functionally Unique Sociality Drivers. Am Nat 2023; 202:302-321. [PMID: 37606948 DOI: 10.1086/725426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
AbstractFrom biofilms to whale pods, organisms across taxa live in groups, thereby accruing numerous diverse benefits of sociality. All social organisms, however, pay the inherent cost of increased resource competition. One expects that when resources become scarce, this cost will increase, causing group sizes to decrease. Indeed, this occurs in some species, but there are also species for which group sizes remain stable or even increase under scarcity. What accounts for these opposing responses? We present a conceptual framework, literature review, and theoretical model demonstrating that differing responses to sudden resource shifts can be explained by which sociality benefit exerts the strongest selection pressure on a particular species. We categorize resource-related benefits of sociality into six functionally distinct classes and model their effect on the survival of individuals foraging in groups under different resource conditions. We find that whether, and to what degree, the optimal group size (or correlates thereof) increases, decreases, or remains constant when resource abundance declines depends strongly on the dominant sociality mechanism. Existing data, although limited, support our model predictions. Overall, we show that across a wide diversity of taxa, differences in how group size shifts in response to resource declines can be driven by differences in the primary benefits of sociality.
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2
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Metzler S, Kirchner J, Grasse AV, Cremer S. Trade-offs between immunity and competitive ability in fighting ant males. BMC Ecol Evol 2023; 23:37. [PMID: 37550612 PMCID: PMC10405452 DOI: 10.1186/s12862-023-02137-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 06/16/2023] [Indexed: 08/09/2023] Open
Abstract
BACKGROUND Fighting disease while fighting rivals exposes males to constraints and trade-offs during male-male competition. We here tested how both the stage and intensity of infection with the fungal pathogen Metarhizium robertsii interfere with fighting success in Cardiocondyla obscurior ant males. Males of this species have evolved long lifespans during which they can gain many matings with the young queens of the colony, if successful in male-male competition. Since male fights occur inside the colony, the outcome of male-male competition can further be biased by interference of the colony's worker force. RESULTS We found that severe, but not yet mild, infection strongly impaired male fighting success. In late-stage infection, this could be attributed to worker aggression directed towards the infected rather than the healthy male and an already very high male morbidity even in the absence of fighting. Shortly after pathogen exposure, however, male mortality was particularly increased during combat. Since these males mounted a strong immune response, their reduced fighting success suggests a trade-off between immune investment and competitive ability already early in the infection. Even if the males themselves showed no difference in the number of attacks they raised against their healthy rivals across infection stages and levels, severely infected males were thus losing in male-male competition from an early stage of infection on. CONCLUSIONS Males of the ant C. obscurior have a well-developed immune system that raises a strong immune response very fast after fungal exposure. This allows them to cope with mild pathogen exposures without compromising their success in male-male competition, and hence to gain multiple mating opportunities with the emerging virgin queens of the colony. Under severe infection, however, they are weak fighters and rarely survive a combat already at early infection when raising an immune response, as well as at progressed infection, when they are morbid and preferentially targeted by worker aggression. Workers thereby remove males that pose a future disease threat by biasing male-male competition. Our study thus reveals a novel social immunity mechanism how social insect workers protect the colony against disease risk.
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Affiliation(s)
- Sina Metzler
- ISTA (Institute of Science and Technology Austria), Am Campus 1, Klosterneuburg, 3400, Austria
| | - Jessica Kirchner
- ISTA (Institute of Science and Technology Austria), Am Campus 1, Klosterneuburg, 3400, Austria
| | - Anna V Grasse
- ISTA (Institute of Science and Technology Austria), Am Campus 1, Klosterneuburg, 3400, Austria
| | - Sylvia Cremer
- ISTA (Institute of Science and Technology Austria), Am Campus 1, Klosterneuburg, 3400, Austria.
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3
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Stock M, Milutinović B, Hoenigsberger M, Grasse AV, Wiesenhofer F, Kampleitner N, Narasimhan M, Schmitt T, Cremer S. Pathogen evasion of social immunity. Nat Ecol Evol 2023; 7:450-460. [PMID: 36732670 PMCID: PMC9998270 DOI: 10.1038/s41559-023-01981-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Accepted: 01/04/2023] [Indexed: 02/04/2023]
Abstract
Treating sick group members is a hallmark of collective disease defence in vertebrates and invertebrates alike. Despite substantial effects on pathogen fitness and epidemiology, it is still largely unknown how pathogens react to the selection pressure imposed by care intervention. Using social insects and pathogenic fungi, we here performed a serial passage experiment in the presence or absence of colony members, which provide social immunity by grooming off infectious spores from exposed individuals. We found specific effects on pathogen diversity, virulence and transmission. Under selection of social immunity, pathogens invested into higher spore production, but spores were less virulent. Notably, they also elicited a lower grooming response in colony members, compared with spores from the individual host selection lines. Chemical spore analysis suggested that the spores from social selection lines escaped the caregivers' detection by containing lower levels of ergosterol, a key fungal membrane component. Experimental application of chemically pure ergosterol indeed induced sanitary grooming, supporting its role as a microbe-associated cue triggering host social immunity against fungal pathogens. By reducing this detection cue, pathogens were able to evade the otherwise very effective collective disease defences of their social hosts.
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Affiliation(s)
- Miriam Stock
- ISTA (Institute of Science and Technology Austria), Klosterneuburg, Austria
| | - Barbara Milutinović
- ISTA (Institute of Science and Technology Austria), Klosterneuburg, Austria. .,Laboratory of Evolutionary Genetics, Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia.
| | | | - Anna V Grasse
- ISTA (Institute of Science and Technology Austria), Klosterneuburg, Austria
| | | | - Niklas Kampleitner
- ISTA (Institute of Science and Technology Austria), Klosterneuburg, Austria
| | | | - Thomas Schmitt
- Department of Animal Ecology and Tropical Biology, University of Würzburg, Würzburg, Germany
| | - Sylvia Cremer
- ISTA (Institute of Science and Technology Austria), Klosterneuburg, Austria.
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4
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Sanmartín-Villar I. Social buffer or avoidance depends on the similarity of stress between queen ants. Curr Zool 2022; 69:181-191. [PMID: 37091993 PMCID: PMC10120981 DOI: 10.1093/cz/zoac031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 04/18/2022] [Indexed: 11/13/2022] Open
Abstract
Abstract
The association of unrelated ant queens (pleometrosis) is supposed to improve nest foundation and competitiveness under environmental stress, but its evolutionary maintenance is difficult to explain because only one of the queens survives after nest foundation. My aim was to test the potential effect of queen association as a social buffer, i.e. as a mechanism reducing stress and improving fitness due to the benefits of social contact. I analysed the survival, fecundity, and behaviour of isolated and paired Lasius flavus queens exposed and not exposed to stressors (disturbing environmental conditions). I found no difference in survivorship between isolated and paired queens or between stressed and unstressed isolated queens. Groups in which one or two paired queens were stressed showed higher mortality. Unstressed queens died similarly to their stressed nestmates, suggesting stress transmission. A trend suggested that paired queens produced eggs more quickly, but eggs were produced similarly between isolated and paired queens. Social avoidance was observed in groups with one stressed and one unstressed queen. However, the groups with two stressed queens showed the expected behaviours according to social buffering: lower mobility and more interindividual inspection. My findings suggest the synergistic effect of pleometrosis and stress and the dependence of stress level similarity between nestmates on social buffering or rejection on ant queens.
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Affiliation(s)
- Iago Sanmartín-Villar
- ECOEVO Lab, Escola de Enxeñaría Forestal, Campus A Xunqueira, Universidade de Vigo, Pontevedra, Galiza, Spain
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5
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Casillas-Pérez B, Pull CD, Naiser F, Naderlinger E, Matas J, Cremer S. Early queen infection shapes developmental dynamics and induces long-term disease protection in incipient ant colonies. Ecol Lett 2021; 25:89-100. [PMID: 34725912 PMCID: PMC9298059 DOI: 10.1111/ele.13907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 10/04/2021] [Accepted: 10/04/2021] [Indexed: 11/30/2022]
Abstract
Infections early in life can have enduring effects on an organism's development and immunity. In this study, we show that this equally applies to developing 'superorganisms'--incipient social insect colonies. When we exposed newly mated Lasius niger ant queens to a low pathogen dose, their colonies grew more slowly than controls before winter, but reached similar sizes afterwards. Independent of exposure, queen hibernation survival improved when the ratio of pupae to workers was small. Queens that reared fewer pupae before worker emergence exhibited lower pathogen levels, indicating that high brood rearing efforts interfere with the ability of the queen's immune system to suppress pathogen proliferation. Early-life queen pathogen exposure also improved the immunocompetence of her worker offspring, as demonstrated by challenging the workers to the same pathogen a year later. Transgenerational transfer of the queen's pathogen experience to her workforce can hence durably reduce the disease susceptibility of the whole superorganism.
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Affiliation(s)
| | - Christopher D Pull
- IST Austria (Institute of Science and Technology Austria), Klosterneuburg, Austria
| | - Filip Naiser
- Department of Cybernetics, Faculty of Electrical Engineering, Czech Technical University in Prague, Czech Republic
| | | | - Jiri Matas
- Department of Cybernetics, Faculty of Electrical Engineering, Czech Technical University in Prague, Czech Republic
| | - Sylvia Cremer
- IST Austria (Institute of Science and Technology Austria), Klosterneuburg, Austria
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6
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Phillips ZI, Reding L, Farrior CE. The early life of a leaf-cutter ant colony constrains symbiont vertical transmission and favors horizontal transmission. Ecol Evol 2021; 11:11718-11729. [PMID: 34522335 PMCID: PMC8427574 DOI: 10.1002/ece3.7900] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 05/24/2021] [Accepted: 06/22/2021] [Indexed: 01/05/2023] Open
Abstract
Colonial organisms host a large diversity of symbionts (collectively, parasites, mutualists, and commensals) that use vertical transmission (from parent colony to offspring colony) and/or horizontal transmission to disperse between host colonies. The early life of some colonies, characterized by the dispersal and establishment of solitary individuals, may constrain vertical transmission and favor horizontal transmission between large established colonies. We explore this possibility with the miniature cockroach Attaphila fungicola, a symbiont of leaf-cutter ants and the mutualist fungal gardens they cultivate. The early life of a leaf-cutter colony is characterized by the dispersal of a female alate (winged "queen") carrying a fungal pellet, and the subsequent establishment of a foundress (workerless "queen") raising her incipient fungal garden and colony. Roaches hitchhike on female alates during leaf-cutter nuptial flights, which strongly suggests that roaches are vertically transmitted to foundresses and their incipient colonies; however, weak compatibility between roaches and incipient gardens may constrain roach vertical transmission. Reciprocally, opportunities for horizontal transmission between large established colonies with abundant fungal gardens may weaken selection against roach-induced harm (virulence) of incipient gardens. We use a laboratory experiment, behavioral observations, field surveys, and a transmission model to estimate the effect roaches have on the survivorship of incipient gardens and the frequency of roach vertical transmission. Contrary to traditional assumptions, our results indicate that roaches harm incipient gardens and predominantly use horizontal transmission between established leaf-cutter colonies. Ultimately, "costs of generalism" associated with infecting disparate stages of a host's lifecycle (e.g., incipient vs. established colonies) may constrain the vertical transmission of roaches and a broad range of symbionts.
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Affiliation(s)
| | - Luke Reding
- Department of Integrative BiologyUniversity of TexasAustinTexasUSA
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7
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Heneberg P, Svoboda J, Pech P. Claustral colony founding does not prevent sensitivity to the detrimental effects of azole fungicides on the fecundity of ants. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 280:111740. [PMID: 33272659 DOI: 10.1016/j.jenvman.2020.111740] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 11/08/2020] [Accepted: 11/21/2020] [Indexed: 06/12/2023]
Abstract
Azole fungicides (benzimidazoles, triazoles and imidazoles) are among the most widely used agrochemicals in the world. Unfortunately, azole fungicides are increasingly recognized for playing the role of endocrine disruptors in non-target organisms. Previously, the fecundity of ants with semi-claustral colony founding was found to be severely decreased in response to field-realistic concentrations of azole fungicides. However, during claustral colony founding, the ant queens do not feed and could therefore be protected against effects of agrochemicals applied during the colony founding. In the present study, we hypothesized that claustral colony founding is associated with a lower risk of oral exposure of ant queens to azole fungicides. We exposed queens of a common farmland ant species with claustral colony founding, Lasius niger, to four azole fungicides (epoxiconazole, flusilazole, prochloraz and thiophanate-methyl) that are commonly used in foliar applications and analyzed the differences in fecundity between fungicide-treated groups and the control water-treated group. We found that oral exposure to all four tested formulations of azole fungicides decreased the fecundity of L. niger queens. The decreases in fecundity ranged from 30.5% (epoxiconazole) to 40.3% (prochloraz), although the concentrations of fungicides used were several times lower than the minimum effective concentrations used to eliminate the target fungi by foliar applications of examined fungicides on various crops. Ants with both claustral and semi-claustral colony founding are highly vulnerable to field-realistic concentrations of azole fungicides that are sprayed in foliar applications. Azole fungicides substantially decrease the fitness of ant queens and may explain part of the recently observed decreases in farmland insect abundance and diversity.
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Affiliation(s)
- Petr Heneberg
- Charles University, Third Faculty of Medicine, Prague, Czech Republic.
| | - Jakub Svoboda
- University of Hradec Králové, Faculty of Science, Hradec Králové, Czech Republic
| | - Pavel Pech
- University of Hradec Králové, Faculty of Science, Hradec Králové, Czech Republic
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8
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Fecundity determines the outcome of founding queen associations in ants. Sci Rep 2021; 11:2986. [PMID: 33542354 PMCID: PMC7862224 DOI: 10.1038/s41598-021-82559-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 01/18/2021] [Indexed: 11/08/2022] Open
Abstract
Animal cooperation evolved because of its benefits to the cooperators. Pleometrosis in ants-the cooperation of queens to found a colony-benefits colony growth, but also incurs costs for some of the cooperators because only one queen usually survives the association. While several traits in queens influence queen survival, they tend to be confounded and it is unclear which factor specifically determines the outcome of pleometrosis. In this study, we used the ant Lasius niger to monitor offspring production in colonies founded by one or two queens. Then, we experimentally paired queens that differed in fecundity but not in size, and vice versa, to disentangle the effect of these factors on queen survival. Finally, we investigated how fecundity and size differed between queens depending on whether they were chosen as pleometrotic partners. Our results indicate that pleometrosis increased and accelerated worker production via a nutritional boost to the larvae. The most fecund queens more frequently survived the associations, even when controlling for size and worker parentage, and queens selected as pleometrotic partners were less fecund. Our results are consistent with fecundity being central to the onset and outcome of pleometrosis, a classic example of cooperation among unrelated animals.
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9
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Aron S, Deneubourg JL. Colony co-founding in ants is an active process by queens. Sci Rep 2020; 10:13539. [PMID: 32782254 PMCID: PMC7419493 DOI: 10.1038/s41598-020-70497-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 07/29/2020] [Indexed: 11/08/2022] Open
Abstract
Cooperative breeding may be selected for in animals when, on average, it confers greater benefits than solitary breeding. In a number of eusocial insects (i.e., ants, bees, wasps, and termites), queens join together to co-create new nests, a phenomenon known as colony co-founding. It has been hypothesised that co-founding evolved because queens obtain several fitness benefits. However, in ants, previous work has suggested that co-founding is a random process that results from high queen density and low nest-site availability. We experimentally examined nest-founding behaviour in the black garden ant, Lasius niger. We gave newly mated queens the choice between two empty nesting chambers, and compared their distribution across the two chambers with that expected under random allocation. We found that queens formed associations of various sizes; in most instances, queens group together in a single chamber. Across all experiments, the frequency of larger groups of queens was significantly higher than expected given random assortment. These results indicate colony co-founding in ants may actually be an active process resulting from mutual attraction among queens. That said, under natural conditions, ecological constraints may limit encounters among newly mated queens.
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Affiliation(s)
- Serge Aron
- Evolutionary Biology and Ecology, Université Libre de Bruxelles, Brussels, Belgium.
| | - Jean-Louis Deneubourg
- Center for Nonlinear Phenomena and Complex Systems, Université Libre de Bruxelles, Brussels, Belgium
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10
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Milutinović B, Stock M, Grasse AV, Naderlinger E, Hilbe C, Cremer S. Social immunity modulates competition between coinfecting pathogens. Ecol Lett 2020; 23:565-574. [PMID: 31950595 DOI: 10.1111/ele.13458] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 10/31/2019] [Accepted: 12/14/2019] [Indexed: 12/18/2022]
Abstract
Coinfections with multiple pathogens can result in complex within-host dynamics affecting virulence and transmission. While multiple infections are intensively studied in solitary hosts, it is so far unresolved how social host interactions interfere with pathogen competition, and if this depends on coinfection diversity. We studied how the collective disease defences of ants - their social immunity - influence pathogen competition in coinfections of same or different fungal pathogen species. Social immunity reduced virulence for all pathogen combinations, but interfered with spore production only in different-species coinfections. Here, it decreased overall pathogen sporulation success while increasing co-sporulation on individual cadavers and maintaining a higher pathogen diversity at the community level. Mathematical modelling revealed that host sanitary care alone can modulate competitive outcomes between pathogens, giving advantage to fast-germinating, thus less grooming-sensitive ones. Host social interactions can hence modulate infection dynamics in coinfected group members, thereby altering pathogen communities at the host level and population level.
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Affiliation(s)
- Barbara Milutinović
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
| | - Miriam Stock
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
| | - Anna V Grasse
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
| | - Elisabeth Naderlinger
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
| | - Christian Hilbe
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
| | - Sylvia Cremer
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
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11
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Stroeymeyt N, Grasse AV, Crespi A, Mersch DP, Cremer S, Keller L. Social network plasticity decreases disease transmission in a eusocial insect. Science 2019; 362:941-945. [PMID: 30467168 DOI: 10.1126/science.aat4793] [Citation(s) in RCA: 142] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 10/22/2018] [Indexed: 12/19/2022]
Abstract
Animal social networks are shaped by multiple selection pressures, including the need to ensure efficient communication and functioning while simultaneously limiting disease transmission. Social animals could potentially further reduce epidemic risk by altering their social networks in the presence of pathogens, yet there is currently no evidence for such pathogen-triggered responses. We tested this hypothesis experimentally in the ant Lasius niger using a combination of automated tracking, controlled pathogen exposure, transmission quantification, and temporally explicit simulations. Pathogen exposure induced behavioral changes in both exposed ants and their nestmates, which helped contain the disease by reinforcing key transmission-inhibitory properties of the colony's contact network. This suggests that social network plasticity in response to pathogens is an effective strategy for mitigating the effects of disease in social groups.
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Affiliation(s)
- Nathalie Stroeymeyt
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland.
| | - Anna V Grasse
- Institute of Science and Technology Austria (IST Austria), Am Campus 1, A-3400 Klosterneuburg, Austria
| | - Alessandro Crespi
- Biorobotics Laboratory, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Danielle P Mersch
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Sylvia Cremer
- Institute of Science and Technology Austria (IST Austria), Am Campus 1, A-3400 Klosterneuburg, Austria.
| | - Laurent Keller
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland.
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12
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Giehr J, Heinze J. Queens stay, workers leave: caste-specific responses to fatal infections in an ant. BMC Evol Biol 2018; 18:202. [PMID: 30587108 PMCID: PMC6307282 DOI: 10.1186/s12862-018-1320-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 12/04/2018] [Indexed: 01/13/2023] Open
Abstract
Background The intense interactions among closely related individuals in animal societies provide perfect conditions for the spread of pathogens. Social insects have therefore evolved counter-measures on the cellular, individual, and social level to reduce the infection risk. One striking example is altruistic self-removal, i.e., lethally infected workers leave the nest and die in isolation to prevent the spread of a contagious disease to their nestmates. Because reproductive queens and egg-laying workers behave less altruistically than non-laying workers, e.g., when it comes to colony defense, we wondered whether moribund egg-layers would show the same self-removal as non-reproductive workers. Furthermore, we investigated how a lethal infection affects reproduction and studied if queens and egg-laying workers intensify their reproductive efforts when their residual reproductive value decreases (“terminal investment”). Results We treated queens, egg-laying workers from queenless colonies, and non-laying workers from queenright colonies of the monogynous (single-queened) ant Temnothorax crassispinus either with a control solution or a solution containing spores of the entomopathogenic fungus Metarhizium brunneum. Lethally infected workers left the nest and died away from it, regardless of their reproductive status. In contrast, infected queens never left the nest and were removed by workers only after they had died. The reproductive investment of queens strongly decreased after the treatment with both, the control solution and the Metarhizium brunneum suspension. The egg laying rate in queenless colonies was initially reduced in infected colonies but not in control colonies. Egg number increased again with decreasing number of infected workers. Conclusions Queens and workers of the ant Temnothorax crassispinus differ in their reaction to an infection risk and a reduced life expectancy. Workers isolate themselves to prevent contagion inside the colony, whereas queens stay in the nest. We did not find terminal investment; instead it appeared that egg-layers completely shut down egg production in response to the lethal infection. Workers in queenless colonies resumed reproduction only after all infected individuals had died, probably again to minimize the risk of infecting the offspring. Electronic supplementary material The online version of this article (10.1186/s12862-018-1320-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Julia Giehr
- Department of Zoology/ Evolutionary Biology, University of Regensburg, 93053, Regensburg, Germany.
| | - Jürgen Heinze
- Department of Zoology/ Evolutionary Biology, University of Regensburg, 93053, Regensburg, Germany
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13
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Liutkevičiūtė Z, Gil-Mansilla E, Eder T, Casillas-Pérez B, Di Giglio MG, Muratspahić E, Grebien F, Rattei T, Muttenthaler M, Cremer S, Gruber CW. Oxytocin-like signaling in ants influences metabolic gene expression and locomotor activity. FASEB J 2018; 32:fj201800443. [PMID: 29939785 PMCID: PMC6174076 DOI: 10.1096/fj.201800443] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 06/04/2018] [Indexed: 01/12/2023]
Abstract
Ants are emerging model systems to study cellular signaling because distinct castes possess different physiologic phenotypes within the same colony. Here we studied the functionality of inotocin signaling, an insect ortholog of mammalian oxytocin (OT), which was recently discovered in ants. In Lasius ants, we determined that specialization within the colony, seasonal factors, and physiologic conditions down-regulated the expression of the OT-like signaling system. Given this natural variation, we interrogated its function using RNAi knockdowns. Next-generation RNA sequencing of OT-like precursor knock-down ants highlighted its role in the regulation of genes involved in metabolism. Knock-down ants exhibited higher walking activity and increased self-grooming in the brood chamber. We propose that OT-like signaling in ants is important for regulating metabolic processes and locomotion.-Liutkevičiūtė, Z., Gil-Mansilla, E., Eder, T., Casillas-Pérez, B., Di Giglio, M. G., Muratspahić, E., Grebien, F., Rattei, T., Muttenthaler, M., Cremer, S., Gruber, C. W. Oxytocin-like signaling in ants influences metabolic gene expression and locomotor activity.
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Affiliation(s)
- Zita Liutkevičiūtė
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Esther Gil-Mansilla
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Thomas Eder
- Division of Computational Systems Biology (CUBE), Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria
- Ludwig Boltzmann Institute for Cancer Research, Vienna, Austria
| | | | | | - Edin Muratspahić
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Florian Grebien
- Ludwig Boltzmann Institute for Cancer Research, Vienna, Austria
| | - Thomas Rattei
- Division of Computational Systems Biology (CUBE), Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria
| | - Markus Muttenthaler
- Faculty of Chemistry, Institute of Biological Chemistry, University of Vienna, Vienna, Austria
- Institute for Molecular Biosciences, The University of Queensland, St. Lucia, Queensland, Australia
| | - Sylvia Cremer
- Institute of Science and Technology (IST) Austria, Klosterneuburg, Austria
| | - Christian W. Gruber
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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14
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Turner J, Hughes WOH. The effect of parasitism on personality in a social insect. Behav Processes 2018; 157:532-539. [PMID: 29898416 DOI: 10.1016/j.beproc.2018.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 05/31/2018] [Accepted: 06/04/2018] [Indexed: 10/14/2022]
Abstract
Individuals are known to differ consistently in various aspects of their behaviour in many animal species, a phenomenon that has come to be referred to as animal personalities. These individual differences are likely to have evolutionary and ecological significance, and it is therefore important to understand the precise nature of how environmental and physiological factors affect animal personalities. One factor which may affect personality is disease, but while the effects of disease on many aspects of host behaviour are well known, the effects on animal personalities have been little studied. Here we show that wood ants, Formica rufa, exhibit consistent individual differences in three personality traits: boldness, sociability and aggressiveness. However, experimental exposure to a virulent fungal parasite, Metarhizium pingshaense, had surprisingly little effect on the personality traits. Parasite-challenged ants showed marginal changes in sociability at high doses of parasite but no change in boldness or aggressiveness even when close to death. There was similarly little effect of other physiological stresses on ant personalities. The results suggest that individual personality in ants can be remarkably resilient to physiological stress, such as that caused by parasite infection. Future studies are needed to determine whether there is a similar resilience in solitary animals, as well as in other social species.
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Affiliation(s)
- Joe Turner
- School of Life Sciences, University of Sussex, Brighton, BN1 9QG, UK.
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Dávila F, Botteaux A, Bauman D, Chérasse S, Aron S. Antibacterial activity of male and female sperm-storage organs in ants. ACTA ACUST UNITED AC 2018; 221:jeb.175158. [PMID: 29444845 DOI: 10.1242/jeb.175158] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 02/05/2018] [Indexed: 01/08/2023]
Abstract
Bacteria can damage sperm and thus reduce the reproductive success of both males and females; selection should therefore favour the evolution of antimicrobial protection. Eusocial hymenopterans might be particularly affected by such bacterial infections because of their mating ecology. In both sexes, mating is restricted to a short window early in the adult stage; there are no further chances to mate later in life. Males die shortly after mating, but queens use the acquired sperm to fertilise their eggs for years, sometimes decades. The reproductive success of both sexes is, thus, ultimately sperm-limited, which maintains strong selection for high sperm viability before and after storage. We tested the antibacterial activity of the contents of the male and female sperm-storage organs - the accessory testes and the spermatheca, respectively. As our study species, we used the bacterium Escherichia coli and the garden ant Lasius niger, whose queens can live for several decades. Our results provide the first empirical evidence that male and female sperm-storage organs display different antibacterial activity. While the contents of the accessory testes actually enhanced bacterial growth, the contents of the spermatheca strongly inhibited it. Furthermore, mating appears to activate the general immune system in queens. However, antimicrobial activity in both the spermatheca and the control tissue (head-thorax homogenate) declined rapidly post-mating, consistent with a trade-off between immunity and reproduction. Overall, this study suggests that ejaculates undergo an immune 'flush' at the time of mating, allowing storage of sperm cells free of bacteria.
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Affiliation(s)
- Francisco Dávila
- Evolutionary Biology and Ecology, Université Libre de Bruxelles, 1050 Brussels, Belgium
| | - Anne Botteaux
- Laboratory of Molecular Bacteriology, Université Libre de Bruxelles, 1070 Brussels, Belgium
| | - David Bauman
- Laboratory of Plant Ecology and Biogeochemistry, Université Libre de Bruxelles, 1050 Brussels, Belgium
| | - Sarah Chérasse
- Evolutionary Biology and Ecology, Université Libre de Bruxelles, 1050 Brussels, Belgium
| | - Serge Aron
- Evolutionary Biology and Ecology, Université Libre de Bruxelles, 1050 Brussels, Belgium
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Konrad M, Pull CD, Metzler S, Seif K, Naderlinger E, Grasse AV, Cremer S. Ants avoid superinfections by performing risk-adjusted sanitary care. Proc Natl Acad Sci U S A 2018; 115:2782-2787. [PMID: 29463746 PMCID: PMC5856517 DOI: 10.1073/pnas.1713501115] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Being cared for when sick is a benefit of sociality that can reduce disease and improve survival of group members. However, individuals providing care risk contracting infectious diseases themselves. If they contract a low pathogen dose, they may develop low-level infections that do not cause disease but still affect host immunity by either decreasing or increasing the host's vulnerability to subsequent infections. Caring for contagious individuals can thus significantly alter the future disease susceptibility of caregivers. Using ants and their fungal pathogens as a model system, we tested if the altered disease susceptibility of experienced caregivers, in turn, affects their expression of sanitary care behavior. We found that low-level infections contracted during sanitary care had protective or neutral effects on secondary exposure to the same (homologous) pathogen but consistently caused high mortality on superinfection with a different (heterologous) pathogen. In response to this risk, the ants selectively adjusted the expression of their sanitary care. Specifically, the ants performed less grooming and more antimicrobial disinfection when caring for nestmates contaminated with heterologous pathogens compared with homologous ones. By modulating the components of sanitary care in this way the ants acquired less infectious particles of the heterologous pathogens, resulting in reduced superinfection. The performance of risk-adjusted sanitary care reveals the remarkable capacity of ants to react to changes in their disease susceptibility, according to their own infection history and to flexibly adjust collective care to individual risk.
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Affiliation(s)
- Matthias Konrad
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Christopher D Pull
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Sina Metzler
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Katharina Seif
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Elisabeth Naderlinger
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Anna V Grasse
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Sylvia Cremer
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
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Brütsch T, Avril A, Chapuisat M. No evidence for social immunity in co-founding queen associations. Sci Rep 2017; 7:16262. [PMID: 29176649 PMCID: PMC5701228 DOI: 10.1038/s41598-017-16368-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 10/31/2017] [Indexed: 12/02/2022] Open
Abstract
Ant queens often associate to found new colonies, yet the benefits of this behaviour remain unclear. A major hypothesis is that queens founding in groups are protected by social immunity and can better resist disease than solitary queens, due to mutual grooming, sharing of antimicrobials, or higher genetic diversity among their workers. We tested this hypothesis by manipulating the number of queens in incipient colonies of Lasius niger and measuring their resistance to the fungal entomopathogen Metarhizium brunneum. We found no evidence for social immunity in associations of founding queens. First, co-founding queens engaged in self-grooming, but performed very little allo-grooming or trophallaxis. Second, co-founding queens did not exhibit higher pathogen resistance than solitary queens, and their respective workers did not differ in disease resistance. Finally, queens founding in groups increased their investment in a component of individual immunity, as expected if they do not benefit from social immunity but respond to a higher risk of disease. Overall, our results provide no evidence that joint colony founding by L. niger queens increases their ability to resist fungal pathogens.
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Affiliation(s)
- Timothée Brütsch
- Department of Ecology and Evolution, Biophore, UNIL-Sorge, University of Lausanne, 1015, Lausanne, Switzerland.
| | - Amaury Avril
- Department of Ecology and Evolution, Biophore, UNIL-Sorge, University of Lausanne, 1015, Lausanne, Switzerland
| | - Michel Chapuisat
- Department of Ecology and Evolution, Biophore, UNIL-Sorge, University of Lausanne, 1015, Lausanne, Switzerland
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Pull CD, Cremer S. Co-founding ant queens prevent disease by performing prophylactic undertaking behaviour. BMC Evol Biol 2017; 17:219. [PMID: 29025392 PMCID: PMC5639488 DOI: 10.1186/s12862-017-1062-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 09/18/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Social insects form densely crowded societies in environments with high pathogen loads, but have evolved collective defences that mitigate the impact of disease. However, colony-founding queens lack this protection and suffer high rates of mortality. The impact of pathogens may be exacerbated in species where queens found colonies together, as healthy individuals may contract pathogens from infectious co-founders. Therefore, we tested whether ant queens avoid founding colonies with pathogen-exposed conspecifics and how they might limit disease transmission from infectious individuals. RESULTS Using Lasius niger queens and a naturally infecting fungal pathogen Metarhizium brunneum, we observed that queens were equally likely to found colonies with another pathogen-exposed or sham-treated queen. However, when one queen died, the surviving individual performed biting, burial and removal of the corpse. These undertaking behaviours were performed prophylactically, i.e. targeted equally towards non-infected and infected corpses, as well as carried out before infected corpses became infectious. Biting and burial reduced the risk of the queens contracting and dying from disease from an infectious corpse of a dead co-foundress. CONCLUSIONS We show that co-founding ant queens express undertaking behaviours that, in mature colonies, are performed exclusively by workers. Such infection avoidance behaviours act before the queens can contract the disease and will therefore improve the overall chance of colony founding success in ant queens.
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Affiliation(s)
- Christopher D Pull
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria. .,Present address: School of Biological Sciences, Royal Holloway University of London, Egham, TW20 0EX, UK.
| | - Sylvia Cremer
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
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Disease Dynamics in Ants: A Critical Review of the Ecological Relevance of Using Generalist Fungi to Study Infections in Insect Societies. ADVANCES IN GENETICS 2016; 94:287-306. [PMID: 27131328 DOI: 10.1016/bs.adgen.2015.12.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
It is assumed that social life can lead to the rapid spread of infectious diseases and outbreaks. In ants, disease outbreaks are rare and the expression of collective behaviors is invoked to explain the absence of epidemics in natural populations. Here, we address the ecological approach employed by many studies that have notably focused (89% of the studies) on two genera of generalist fungal parasites (Beauveria and Metarhizium). We ask whether these are the most representative models to study the evolutionary ecology of ant-fungal parasite interactions. To assess this, we critically examine the literature on ants and their interactions with fungal parasites from the past 114years (1900-2014). We discuss how current evolutionary ecology approaches emerged from studies focused on the biological control of pest ants. We also analyzed the ecological relevance of the laboratory protocols used in evolutionary ecology studies employing generalist parasites, as well as the rare natural occurrence of these parasites on ants. After a detailed consideration of all the publications, we suggest that using generalist pathogens such as Beauveria and Metarhizium is not an optimal approach if the goal is to study the evolutionary ecology of disease in ants. We conclude by advocating for approaches that incorporate greater realism.
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Pamminger T, Treanor D, Hughes WOH. Pleiotropic effects of juvenile hormone in ant queens and the escape from the reproduction-immunocompetence trade-off. Proc Biol Sci 2016; 283:20152409. [PMID: 26763704 PMCID: PMC4721097 DOI: 10.1098/rspb.2015.2409] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 12/09/2015] [Indexed: 12/27/2022] Open
Abstract
The ubiquitous trade-off between survival and costly reproduction is one of the most fundamental constraints governing life-history evolution. In numerous animals, gonadotropic hormones antagonistically suppressing immunocompetence cause this trade-off. The queens of many social insects defy the reproduction-survival trade-off, achieving both an extraordinarily long life and high reproductive output, but how they achieve this is unknown. Here we show experimentally, by integrating quantification of gene expression, physiology and behaviour, that the long-lived queens of the ant Lasius niger have escaped the reproduction-immunocompetence trade-off by decoupling the effects of a key endocrine regulator of fertility and immunocompetence in solitary insects, juvenile hormone (JH). This modification of the regulatory architecture enables queens to sustain a high reproductive output without elevated JH titres and suppressed immunocompetence, providing an escape from the reproduction-immunocompetence trade-off that may contribute to the extraordinary lifespan of many social insect queens.
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Affiliation(s)
- Tobias Pamminger
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK
| | - David Treanor
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK
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Manfredini F, Shoemaker D, Grozinger CM. Dynamic changes in host-virus interactions associated with colony founding and social environment in fire ant queens (Solenopsis invicta). Ecol Evol 2016; 6:233-44. [PMID: 26811788 PMCID: PMC4716520 DOI: 10.1002/ece3.1843] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 10/27/2015] [Accepted: 10/28/2015] [Indexed: 11/10/2022] Open
Abstract
The dynamics of host-parasite interactions can change dramatically over the course of a chronic infection as the internal (physiological) and external (environmental) conditions of the host change. When queens of social insects found a colony, they experience changes in both their physiological state (they develop their ovaries and begin laying eggs) and the social environment (they suddenly stop interacting with the other members of the mother colony), making this an excellent model system for examining how these factors interact with chronic infections. We investigated the dynamics of host-viral interactions in queens of Solenopsis invicta (fire ant) as they transition from mating to colony founding/brood rearing to the emergence of the first workers. We examined these dynamics in naturally infected queens in two different social environments, where queens either founded colonies as individuals or as pairs. We hypothesized that stress associated with colony founding plays an important role in the dynamics of host-parasite interactions. We also hypothesized that different viruses have different modalities of interaction with the host that can be quantified by physiological measures and genomic analysis of gene expression in the host. We found that the two most prevalent viruses, SINV-1 and SINV-2, are associated with different fitness costs that are mirrored by different patterns of gene expression in the host. In fact SINV-2, the virus that imposes the significant reduction of a queen's reproductive output is also associated with larger changes of global gene expression in the host. These results show the complexity of interactions between S. invicta and two viral parasites. Our findings also show that chronic infections by viral parasites in insects are dynamic processes that may pose different challenges in the host, laying the groundwork for interesting ecological and evolutionary considerations.
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Affiliation(s)
- Fabio Manfredini
- School of Biological SciencesRoyal Holloway University of LondonEghamUK
- Department of Entomology and Center for Pollinator ResearchThe Pennsylvania State UniversityUniversity ParkPennsylvania
| | | | - Christina M. Grozinger
- Department of Entomology and Center for Pollinator ResearchThe Pennsylvania State UniversityUniversity ParkPennsylvania
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Meunier J. Social immunity and the evolution of group living in insects. Philos Trans R Soc Lond B Biol Sci 2015; 370:20140102. [PMID: 25870389 PMCID: PMC4410369 DOI: 10.1098/rstb.2014.0102] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/02/2014] [Indexed: 01/25/2023] Open
Abstract
The evolution of group living requires that individuals limit the inherent risks of parasite infection. To this end, group living insects have developed a unique capability of mounting collective anti-parasite defences, such as allogrooming and corpse removal from the nest. Over the last 20 years, this phenomenon (called social immunity) was mostly studied in eusocial insects, with results emphasizing its importance in derived social systems. However, the role of social immunity in the early evolution of group living remains unclear. Here, I investigate this topic by first presenting the definitions of social immunity and discussing their applications across social systems. I then provide an up-to-date appraisal of the collective and individual mechanisms of social immunity described in eusocial insects and show that they have counterparts in non-eusocial species and even solitary species. Finally, I review evidence demonstrating that the increased risks of parasite infection in group living species may both decrease and increase the level of personal immunity, and discuss how the expression of social immunity could drive these opposite effects. By highlighting similarities and differences of social immunity across social systems, this review emphasizes the potential importance of this phenomenon in the early evolution of the multiple forms of group living in insects.
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Affiliation(s)
- Joël Meunier
- Zoological Institute, Evolutionary Biology, Johannes Gutenberg University Mainz, Mainz, Germany
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Bengston SE, Jandt JM. The development of collective personality: the ontogenetic drivers of behavioral variation across groups. Front Ecol Evol 2014. [DOI: 10.3389/fevo.2014.00081] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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