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Barrajon-Santos V, Nepel M, Hausmann B, Voglmayr H, Woebken D, Mayer VE. Dynamics and drivers of fungal communities in a multipartite ant-plant association. BMC Biol 2024; 22:112. [PMID: 38745290 PMCID: PMC11093746 DOI: 10.1186/s12915-024-01897-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 04/18/2024] [Indexed: 05/16/2024] Open
Abstract
BACKGROUND Fungi and ants belong to the most important organisms in terrestrial ecosystems on Earth. In nutrient-poor niches of tropical rainforests, they have developed steady ecological relationships as a successful survival strategy. In tropical ant-plant mutualisms worldwide, where resident ants provide the host plants with defense and nutrients in exchange for shelter and food, fungi are regularly found in the ant nesting space, inhabiting ant-made dark-colored piles ("patches"). Unlike the extensively investigated fungus-growing insects, where the fungi serve as the primary food source, the purpose of this ant-fungi association is less clear. To decipher the roles of fungi in these structures within ant nests, it is crucial to first understand the dynamics and drivers that influence fungal patch communities during ant colony development. RESULTS In this study, we investigated how the ant colony age and the ant-plant species affect the fungal community in the patches. As model we selected one of the most common mutualisms in the Tropics of America, the Azteca-Cecropia complex. By amplicon sequencing of the internal transcribed spacer 2 (ITS2) region, we analyzed the patch fungal communities of 93 Azteca spp. colonies inhabiting Cecropia spp. trees. Our study demonstrates that the fungal diversity in patches increases as the ant colony grows and that a change in the prevalent fungal taxa occurs between initial and established patches. In addition, the ant species significantly influences the composition of the fungal community in established ant colonies, rather than the host plant species. CONCLUSIONS The fungal patch communities become more complex as the ant colony develops, due to an acquisition of fungi from the environment and a substrate diversification. Our results suggest a successional progression of the fungal communities in the patches during ant colony growth and place the ant colony as the main driver shaping such communities. The findings of this study demonstrate the unexpectedly complex nature of ant-plant mutualisms in tropical regions at a micro scale.
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Affiliation(s)
- Veronica Barrajon-Santos
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria.
- Department of Microbiology and Ecosystem Science, Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria.
- Doctoral School in Microbiology and Environmental Science, University of Vienna, Vienna, Austria.
| | - Maximilian Nepel
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
- Present Address: Plant Health and Environment Laboratory, Ministry for Primary Industries, Auckland, New Zealand
| | - Bela Hausmann
- Joint Microbiome Facility of the Medical University of Vienna and the University of Vienna, Vienna, Austria
- Department of Laboratory Medicine Division of Clinical Microbiology, Medical University of Vienna, Vienna, Austria
| | - Hermann Voglmayr
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
| | - Dagmar Woebken
- Department of Microbiology and Ecosystem Science, Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Veronika E Mayer
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria.
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2
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Frank ET, Kesner L, Liberti J, Helleu Q, LeBoeuf AC, Dascalu A, Sponsler DB, Azuma F, Economo EP, Waridel P, Engel P, Schmitt T, Keller L. Targeted treatment of injured nestmates with antimicrobial compounds in an ant society. Nat Commun 2023; 14:8446. [PMID: 38158416 PMCID: PMC10756881 DOI: 10.1038/s41467-023-43885-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 11/20/2023] [Indexed: 01/03/2024] Open
Abstract
Infected wounds pose a major mortality risk in animals. Injuries are common in the ant Megaponera analis, which raids pugnacious prey. Here we show that M. analis can determine when wounds are infected and treat them accordingly. By applying a variety of antimicrobial compounds and proteins secreted from the metapleural gland to infected wounds, workers reduce the mortality of infected individuals by 90%. Chemical analyses showed that wound infection is associated with specific changes in the cuticular hydrocarbon profile, thereby likely allowing nestmates to diagnose the infection state of injured individuals and apply the appropriate antimicrobial treatment. This study demonstrates that M. analis ant societies use antimicrobial compounds produced in the metapleural glands to treat infected wounds and reduce nestmate mortality.
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Affiliation(s)
- Erik T Frank
- Department of Ecology and Evolution, Biophore, University of Lausanne, CH-1015, Lausanne, Switzerland.
- Department of Animal Ecology and Tropical Biology, Biocenter, University of Würzburg, D-97074, Würzburg, Germany.
| | - Lucie Kesner
- Department of Fundamental Microbiology, Biophore, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Joanito Liberti
- Department of Ecology and Evolution, Biophore, University of Lausanne, CH-1015, Lausanne, Switzerland
- Department of Fundamental Microbiology, Biophore, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Quentin Helleu
- Department of Ecology and Evolution, Biophore, University of Lausanne, CH-1015, Lausanne, Switzerland
- Structure et Instabilité des Génomes, Muséum National d'Histoire Naturelle, CNRS UMR 7196, INSERM U1154, 43 rue Cuvier, F-75005, Paris, France
| | - Adria C LeBoeuf
- Department of Biology, University of Fribourg, CH-1700, Fribourg, Switzerland
| | - Andrei Dascalu
- Department of Ecology and Evolution, Biophore, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Douglas B Sponsler
- Department of Animal Ecology and Tropical Biology, Biocenter, University of Würzburg, D-97074, Würzburg, Germany
| | - Fumika Azuma
- Biodiversity and Biocomplexity Unit, Okinawa Institute of Science and Technology Graduate University, Onna, 904-0495, Japan
| | - Evan P Economo
- Biodiversity and Biocomplexity Unit, Okinawa Institute of Science and Technology Graduate University, Onna, 904-0495, Japan
- Radcliffe Institute for Advanced Study, Harvard University, Cambridge, 02138, USA
| | - Patrice Waridel
- Protein Analysis Facility, Génopode, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Philipp Engel
- Department of Fundamental Microbiology, Biophore, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Thomas Schmitt
- Department of Animal Ecology and Tropical Biology, Biocenter, University of Würzburg, D-97074, Würzburg, Germany
| | - Laurent Keller
- Department of Ecology and Evolution, Biophore, University of Lausanne, CH-1015, Lausanne, Switzerland.
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3
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Goes AC, Kooij PW, Culot L, Bueno OC, Rodrigues A. Distinct and enhanced hygienic responses of a leaf-cutting ant toward repeated fungi exposures. Ecol Evol 2022; 12:e9112. [PMID: 35866016 PMCID: PMC9288931 DOI: 10.1002/ece3.9112] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 06/06/2022] [Accepted: 06/23/2022] [Indexed: 11/10/2022] Open
Abstract
Leaf-cutting ants and their fungal crops are a textbook example of a long-term obligatory mutualism. Many microbes continuously enter their nest containing the fungal cultivars, destabilizing the symbiosis and, in some cases, outcompeting the mutualistic partners. Preferably, the ant workers should distinguish between different microorganisms to respond according to their threat level and recurrence in the colony. To address these assumptions, we investigated how workers of Atta sexdens sanitize their fungal crop toward five different fungi commonly isolated from the fungus gardens: Escovopsis sp., Fusarium oxysporum, Metarhizium anisopliae, Trichoderma spirale, and Syncephalastrum sp. Also, to investigate the plasticity of these responses toward recurrences of these fungi, we exposed the colonies with each fungus three times fourteen days apart. As expected, intensities in sanitization differed according to the fungal species. Ants significantly groom their fungal crop more toward F. oxysporum, M. anisopliae, and Syncephalastrum sp. than toward Escovopsis sp. and T. spirale. Weeding, self-, and allogrooming were observed in less frequency than fungus grooming in all cases. Moreover, we detected a significant increase in the overall responses after repeated exposures for each fungus, except for Escovopsis sp. Our results indicate that A. sexdens workers are able to distinguish between different fungi and apply distinct responses to remove these from the fungus gardens. Our findings also suggest that successive exposures to the same antagonist increase hygiene, indicating plasticity of ant colonies' defenses to previously encountered pathogens.
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Affiliation(s)
- Aryel C. Goes
- Department of General and Applied BiologySão Paulo State University (UNESP)Rio ClaroBrazil
| | - Pepijn W. Kooij
- Department of General and Applied BiologySão Paulo State University (UNESP)Rio ClaroBrazil
| | - Laurence Culot
- Department of BiodiversitySão Paulo State University (UNESP)Rio ClaroBrazil
| | - Odair C. Bueno
- Department of General and Applied BiologySão Paulo State University (UNESP)Rio ClaroBrazil
| | - Andre Rodrigues
- Department of General and Applied BiologySão Paulo State University (UNESP)Rio ClaroBrazil
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4
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Social microbiota and social gland gene expression of worker honey bees by age and climate. Sci Rep 2022; 12:10690. [PMID: 35739206 PMCID: PMC9226125 DOI: 10.1038/s41598-022-14442-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Accepted: 06/07/2022] [Indexed: 11/08/2022] Open
Abstract
Winter forage dearth is a major contributor to honey bee colony loss and can influence disease susceptibility. Honey bees possess a secretory head gland that interfaces with the social environment on many levels. During winter or forage dearth, colonies produce a long-lived (diutinus) worker phenotype that survives until environmental conditions improve. We used a known-age worker cohort to investigate microbiome integrity and social gene expression of workers in early and late winter. We provide additional context by contrasting host-microbial interactions from warm outdoor and cold indoor environments. Our results provide novel evidence that social immune gene expression is associated with worker longevity, and highlight the midgut as a target of opportunistic disease during winter. Host microbial interactions suggest opportunistic disease progression and resistance in long-lived workers, but susceptibility to opportunistic disease in younger workers that emerged during the winter, including increases in Enterobacteriaceae, fungal load and non-core bacterial abundance. The results are consistent with increased social immunity, including host associations with the social microbiota, and a social immune response by long-lived workers to combat microbial opportunism. The cost/benefit ratio associated with limited expression of the diutinus phenotype may be a strong determinant of colony survival during winter forage dearth.
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Symbiont-Mediated Protection of Acromyrmex Leaf-Cutter Ants from the Entomopathogenic Fungus Metarhizium anisopliae. mBio 2021; 12:e0188521. [PMID: 34933458 PMCID: PMC8689564 DOI: 10.1128/mbio.01885-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Many fungus-growing ants engage in a defensive symbiosis with antibiotic-producing ectosymbiotic bacteria in the genus Pseudonocardia, which help protect the ants' fungal mutualist from a specialized mycoparasite, Escovopsis. Here, using germfree ant rearing and experimental pathogen infection treatments, we evaluate if Acromyrmex ants derive higher immunity to the entomopathogenic fungus Metarhizium anisopliae from their Pseudonocardia symbionts. We further examine the ecological dynamics and defensive capacities of Pseudonocardia against M. anisopliae across seven different Acromyrmex species by controlling Pseudonocardia acquisition using ant-nonnative Pseudonocardia switches, in vitro challenges, and in situ mass spectrometry imaging (MSI). We show that Pseudonocardia protects the ants against M. anisopliae across different Acromyrmex species and appears to afford higher protection than metapleural gland (MG) secretions. Although Acromyrmex echinatior ants with nonnative Pseudonocardia symbionts receive protection from M. anisopliae regardless of the strain acquired compared with Pseudonocardia-free conditions, we find significant variation in the degree of protection conferred by different Pseudonocardia strains. Additionally, when ants were reared in Pseudonocardia-free conditions, some species exhibit more susceptibility to M. anisopliae than others, indicating that some ant species depend more on defensive symbionts than others. In vitro challenge experiments indicate that Pseudonocardia reduces Metarhizium conidiospore germination area. Our chemometric analysis using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) reveals that Pseudonocardia-carrying ants produce more chemical signals than Pseudonocardia-free treatments, indicating that Pseudonocardia produces bioactive metabolites on the Acromyrmex cuticle. Our results indicate that Pseudonocardia can serve as a dual-purpose defensive symbiont, conferring increased immunity for both the obligate fungal mutualist and the ants themselves. IMPORTANCE In some plants and animals, beneficial microbes mediate host immune response against pathogens, including by serving as defensive symbionts that produce antimicrobial compounds. Defensive symbionts are known in several insects, including some leaf-cutter ants where antifungal-producing Actinobacteria help protect the fungal mutualist of the ants from specialized mycoparasites. In many defensive symbioses, the extent and specificity of defensive benefits received by the host are poorly understood. Here, using "aposymbiotic" rearing, symbiont switching experiments, and imaging mass spectrometry, we explore the ecological and chemical dynamics of the model defensive symbiosis between Acromyrmex ants and their defensive symbiotic bacterium Pseudonocardia. We show that the defensive symbiont not only protects the fungal crop of Acromyrmex but also provides protection from fungal pathogens that infect the ant workers themselves. Furthermore, we reveal that the increased immunity to pathogen infection differs among strains of defensive symbionts and that the degree of reliance on a defensive symbiont for protection varies across congeneric ant species. Taken together, our results suggest that Acromyrmex-associated Pseudonocardia have evolved broad antimicrobial defenses that promote strong immunity to diverse fungal pathogens within the ancient fungus-growing ant-microbe symbiosis.
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6
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de Mendonça DMF, Caixeta MCS, Martins GL, Moreira CC, Kloss TG, Elliot SL. Low Virulence of the Fungi Escovopsis and Escovopsioides to a Leaf-Cutting Ant-Fungus Symbiosis. Front Microbiol 2021; 12:673445. [PMID: 34394025 PMCID: PMC8358438 DOI: 10.3389/fmicb.2021.673445] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 07/06/2021] [Indexed: 01/22/2023] Open
Abstract
Eusocial insects interact with a diversity of parasites that can threaten their survival and reproduction. The amount of harm these parasites cause to their hosts (i.e., their virulence) can be influenced by numerous factors, such as the ecological context in which the parasite and its host are inserted. Leaf-cutting ants (genera Atta, Acromyrmex and Amoimyrmex, Attini: Formicidae) are an example of a eusocial insect whose colonies are constantly threatened by parasites. The fungi Escovopsis and Escovopsioides (Ascomycota: Hypocreales) are considered a highly virulent parasite and an antagonist, respectively, to the leaf-cutting ants' fungal cultivar, Leucoagaricus gongylophorus (Basidiomycota: Agaricales). Since Escovopsis and Escovopsioides are common inhabitants of healthy colonies that can live for years, we expect them to have low levels of virulence. However, this virulence could vary depending on ecological context. We therefore tested two hypotheses: (i) Escovopsis and Escovopsioides are of low virulence to colonies; (ii) virulence increases as colony complexity decreases. For this, we used three levels of complexity: queenright colonies (fungus garden with queen and workers), queenless colonies (fungus garden and workers, without queen) and fungus gardens (without any ants). Each was inoculated with extremely high concentrations of conidia of Escovopsis moelleri, Escovopsioides nivea, the mycoparasitic fungus Trichoderma longibrachiatum or a blank control. We found that these fungi were of low virulence to queenright colonies. The survival of queenless colonies was decreased by E. moelleri and fungus gardens were suppressed by all treatments. Moreover, E. nivea and T. longibrachiatum seemed to be less aggressive than E. moelleri, observed both in vivo and in vitro. The results highlight the importance of each element (queen, workers and fungus garden) in the leaf-cutting ant-fungus symbiosis. Most importantly, we showed that Escovopsis may not be virulent to healthy colonies, despite commonly being described as such, with the reported virulence of Escovopsis being due to poor colony conditions in the field or in laboratory experiments.
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Affiliation(s)
| | | | | | - Camila Costa Moreira
- Department of Entomology, Federal University of Viçosa, Viçosa, Brazil.,Department of Entomology and Acarology, Luiz de Queiroz College of Agriculture, University of São Paulo, Piracicaba, Brazil
| | - Thiago Gechel Kloss
- Department of Biological Sciences, Minas Gerais State University, Ubá, Brazil
| | - Simon Luke Elliot
- Department of Entomology, Federal University of Viçosa, Viçosa, Brazil
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7
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Christopher Y, Wcislo WT, Martínez‐Luis S, Hughes WO, Gerardo NM, Fernández‐Marín H. Disease management in two sympatric Apterostigma fungus-growing ants for controlling the parasitic fungus Escovopsis. Ecol Evol 2021; 11:6041-6052. [PMID: 34141201 PMCID: PMC8207340 DOI: 10.1002/ece3.7379] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 01/31/2021] [Accepted: 02/16/2021] [Indexed: 12/25/2022] Open
Abstract
Antagonistic interactions between host and parasites are often embedded in networks of interacting species, in which hosts may be attacked by competing parasites species, and parasites may infect more than one host species. To better understand the evolution of host defenses and parasite counterdefenses in the context of a multihost, multiparasite system, we studied two sympatric species, of congeneric fungus-growing ants (Attini) species and their symbiotic fungal cultivars, which are attacked by multiple morphotypes of parasitic fungi in the genus, Escovopsis. To assess whether closely related ant species and their cultured fungi are evolving defenses against the same or different parasitic strains, we characterized Escovopsis that were isolated from colonies of sympatric Apterostigma dentigerum and A. pilosum. We assessed in vitro and in vivo interactions of these parasites with their hosts. While the ant cultivars are parasitized by similar Escovopsis spp., the frequency of infection by these pathogens differs between the two ant species. The ability of the host fungi to suppress Escovopsis growth, as well as ant defensive responses toward the parasites, differs depending on the parasite strain and on the host ant species.
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Affiliation(s)
- Yuliana Christopher
- Centro de Biodiversidad y Descubrimiento de DrogasInstituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP)ClaytonRepública de Panamá
- Department of BiotechnologyAcharya Nagarjuna UniversityGunturIndia
- Smithsonian Tropical Research InstitutePanamaRepública de Panamá
| | | | - Sergio Martínez‐Luis
- Centro de Biodiversidad y Descubrimiento de DrogasInstituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP)ClaytonRepública de Panamá
| | | | | | - Hermógenes Fernández‐Marín
- Centro de Biodiversidad y Descubrimiento de DrogasInstituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP)ClaytonRepública de Panamá
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8
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Gandra LC, Amaral KD, Couceiro JC, Dângelo RAC, De Souza DJ, Della Lucia TMC. Immune Defense Strategies of Queens of the Social Parasite Ant Acromyrmex ameliae and Queens of Its Natural Hosts. NEOTROPICAL ENTOMOLOGY 2021; 50:229-236. [PMID: 33555562 DOI: 10.1007/s13744-020-00838-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 12/07/2020] [Indexed: 06/12/2023]
Abstract
Social parasitism is well known in ants, but many aspects of this social phenomenon remain mysterious and unexplored. In some cases, parasite queens, who are able to mate very rarely end up producing brood and, thus, depend virtually on the labor of host ants. In this work, we sought to test the occurrence of grooming by host workers of Acromyrmex subterraneus subterraneus Forel, to their own queens and queens of the parasite Acromyrmex ameliae De Souza, Soares and Della Lucia and to compare the immune defense responses of parasite queens and queens of A. subterraneus subterraneus and Acromyrmex subterraneus brunneus Forel, the natural hosts. Duration and frequency of behavioral acts were recorded. The relative size of the bulla and the encapsulation response to a standardized antigen were analyzed. Regarding behavioral acts, self-grooming (duration and frequency) and allogrooming (duration) were statistically different between the species; the first is more frequent and lasted longer in parasite queens, while the second act lasted longer in host ants than in parasite ants. The bulla of A. ameliae was approximately 50% wider than those of its hosts. Parasite queens exhibited a stronger immune response than host queens. The results of this work contribute to elucidate potential mechanisms involved in the parasitism capacity of A. ameliae queens such as their strategies of immune defense.
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Affiliation(s)
- Lailla C Gandra
- Instituto de Ciências Biológicas e da Saúde, Univ Federal de Viçosa, Florestal, MG, Brazil.
| | | | - Joel C Couceiro
- Escola Superior de Agricultura Luiz de Queiroz, Univ de São Paulo, São Paulo, Brazil
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9
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Halawani O, Dunn RR, Grunden AM, Smith AA. Bacterial exposure leads to variable mortality but not a measurable increase in surface antimicrobials across ant species. PeerJ 2020; 8:e10412. [PMID: 33344078 PMCID: PMC7719289 DOI: 10.7717/peerj.10412] [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: 06/05/2020] [Accepted: 11/02/2020] [Indexed: 11/20/2022] Open
Abstract
Social insects have co-existed with microbial species for millions of years and have evolved a diversity of collective defenses, including the use of antimicrobials. While many studies have revealed strategies that ants use against microbial entomopathogens, and several have shown ant-produced compounds inhibit environmental bacterial growth, few studies have tested whether exposure to environmental bacteria represents a health threat to ants. We compare four ant species’ responses to exposure to Escherichia coli and Staphylococcus epidermidis bacteria in order to broaden our understanding of microbial health-threats to ants and their ability to defend against them. In a first experiment, we measure worker mortality of Solenopsis invicta, Brachymyrmex chinensis, Aphaenogaster rudis, and Dorymyrmex bureni in response to exposure to E. coli and S. epidermidis. We found that exposure to E. coli was lethal for S. invicta and D. bureni, while all other effects of exposure were not different from experimental controls. In a second experiment, we compared the antimicrobial ability of surface extracts from bacteria-exposed and non-exposed S. invicta and B. chinensis worker ants, to see if exposure to E. coli or S. epidermidis led to an increase in antimicrobial compounds. We found no difference in the inhibitory effects from either treatment group in either species. Our results demonstrate the susceptibility to bacteria is varied across ant species. This variation may correlate with an ant species’ use of surface antimicrobials, as we found significant mortality effects in species which also were producing antimicrobials. Further exploration of a wide range of both bacteria and ant species is likely to reveal unique and nuanced antimicrobial strategies and deepen our understanding of how ant societies respond to microbial health threats.
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Affiliation(s)
- Omar Halawani
- Department of Applied Ecology, North Carolina State University, Raleigh, NC, USA
| | - Robert R Dunn
- Department of Applied Ecology, North Carolina State University, Raleigh, NC, USA
| | - Amy M Grunden
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, USA
| | - Adrian A Smith
- Department of Biological Sciences, North Carolina State University, Raleigh, NC, USA.,Research & Collections, North Carolina Museum of Natural Sciences, Raleigh, NC, USA
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10
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Lash CL, Fordyce JA, Kwit C. Nest substrate, more than ant activity, drives fungal pathogen community dissimilarity in seed-dispersing ant nests. Oecologia 2020; 194:649-657. [PMID: 33159541 DOI: 10.1007/s00442-020-04796-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Accepted: 10/24/2020] [Indexed: 11/30/2022]
Abstract
Myrmecochory is a widespread mutualism in which plants benefit from seed dispersal services by ants. Ants might also be providing seeds with an additional byproduct benefit via reduced plant pathogen loads in the ant nest environment through their antimicrobial glandular secretions. We investigate this byproduct benefit by identifying fungal communities in ant nests and surrounding environments and quantifying fungal community change (1) through time, (2) between different nest substrates, and (3) as a function of average ant activity levels within nests (based on observed ant activity at nest entrances throughout the summer). We split fungal communities by functional guild to determine seed-dispersing ant-induced changes in the overall fungal community, the animal pathogen fungal community, the plant pathogen fungal community, and the myrmecochore pathogen fungal community. Nest substrate (soil or log) explained much of the variation in fungal community dissimilarity, while substrate occupation (ant nest or control sample) and time had no influence on fungal community composition. Average ant activity had no effect on the community turnover in fungal communities except for the myrmecochore pathogenic fungal community. In this community, higher ant activity throughout the summer resulted in more fluctuation in the pathogenic community in the ant nest. Our results are not consistent with a byproduct benefit framework in myrmecochory, but suggest that nest substrate drives dissimilarity in fungal communities. The influence of nest substrate on fungal communities has important implications for seeds taken into ant nests, as well as ant nest location choice by queens and during nest relocation.
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Affiliation(s)
- Chloe L Lash
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, 37996, USA. .,Natural Sciences Department, University of St. Francis, Joliet, IL, 60435, USA.
| | - James A Fordyce
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, 37996, USA
| | - Charles Kwit
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, 37996, USA.,Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN, 37996, USA
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11
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Penick CA, Halawani O, Pearson B, Mathews S, López-Uribe MM, Dunn RR, Smith AA. External immunity in ant societies: sociality and colony size do not predict investment in antimicrobials. ROYAL SOCIETY OPEN SCIENCE 2018; 5:171332. [PMID: 29515850 PMCID: PMC5830739 DOI: 10.1098/rsos.171332] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 01/04/2018] [Indexed: 06/10/2023]
Abstract
Social insects live in dense groups with a high probability of disease transmission and have therefore faced strong pressures to develop defences against pathogens. For this reason, social insects have been hypothesized to invest in antimicrobial secretions as a mechanism of external immunity to prevent the spread of disease. However, empirical studies linking the evolution of sociality with increased investment in antimicrobials have been relatively few. Here we quantify the strength of antimicrobial secretions among 20 ant species that cover a broad spectrum of ant diversity and colony sizes. We extracted external compounds from ant workers to test whether they inhibited the growth of the bacterium Staphylococcus epidermidis. Because all ant species are highly social, we predicted that all species would exhibit some antimicrobial activity and that species that form the largest colonies would exhibit the strongest antimicrobial response. Our comparative approach revealed that strong surface antimicrobials are common to particular ant clades, but 40% of species exhibited no antimicrobial activity at all. We also found no correlation between antimicrobial activity and colony size. Rather than relying on antimicrobial secretions as external immunity to control pathogen spread, many ant species have probably developed alternative strategies to defend against disease pressure.
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Affiliation(s)
- Clint A. Penick
- The Biomimicry Center, Arizona State University, Tempe, AZ 85287, USA
| | - Omar Halawani
- Research & Collections, North Carolina Museum of Natural Sciences, Raleigh, NC 27601, USA
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Bria Pearson
- Research & Collections, North Carolina Museum of Natural Sciences, Raleigh, NC 27601, USA
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Stephanie Mathews
- Biological Sciences, Campbell University, Buies Creek, NC 27506, USA
| | - Margarita M. López-Uribe
- Department of Entomology, Center for Pollinator Research, Pennsylvania State University, University Park, PA 16802, USA
| | - Robert R. Dunn
- Department of Applied Ecology, North Carolina State University, Raleigh, NC 27695, USA
- Center for Macroecology, Evolution and Climate, University of Copenhagen, Copenhagen, 2100Denmark
| | - Adrian A. Smith
- Research & Collections, North Carolina Museum of Natural Sciences, Raleigh, NC 27601, USA
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
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Cremer S, Pull CD, Fürst MA. Social Immunity: Emergence and Evolution of Colony-Level Disease Protection. ANNUAL REVIEW OF ENTOMOLOGY 2018; 63:105-123. [PMID: 28945976 DOI: 10.1146/annurev-ento-020117-043110] [Citation(s) in RCA: 150] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Social insect colonies have evolved many collectively performed adaptations that reduce the impact of infectious disease and that are expected to maximize their fitness. This colony-level protection is termed social immunity, and it enhances the health and survival of the colony. In this review, we address how social immunity emerges from its mechanistic components to produce colony-level disease avoidance, resistance, and tolerance. To understand the evolutionary causes and consequences of social immunity, we highlight the need for studies that evaluate the effects of social immunity on colony fitness. We discuss the roles that host life history and ecology have on predicted eco-evolutionary dynamics, which differ among the social insect lineages. Throughout the review, we highlight current gaps in our knowledge and promising avenues for future research, which we hope will bring us closer to an integrated understanding of socio-eco-evo-immunology.
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Affiliation(s)
- Sylvia Cremer
- IST Austria (Institute of Science and Technology Austria), Klosterneuburg 3400, Austria; ,
| | - Christopher D Pull
- IST Austria (Institute of Science and Technology Austria), Klosterneuburg 3400, Austria; ,
- Current affiliation: School of Biological Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, United Kingdom;
| | - Matthias A Fürst
- IST Austria (Institute of Science and Technology Austria), Klosterneuburg 3400, Austria; ,
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13
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14
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Armitage SAO, Fernández-Marín H, Boomsma JJ, Wcislo WT. Slowing them down will make them lose: a role for attine ant crop fungus in defending pupae against infections? J Anim Ecol 2016; 85:1210-21. [PMID: 27136600 PMCID: PMC6084299 DOI: 10.1111/1365-2656.12543] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 04/12/2016] [Indexed: 02/05/2023]
Abstract
Fungus-growing ants (Attini) have evolved an obligate dependency upon a basidiomycete fungus that they cultivate as their food. Less well known is that the crop fungus is also used by many attine species to cover their eggs, larvae and pupae. The adaptive functional significance of this brood covering is poorly understood. One hypothesis to account for this behaviour is that it is part of the pathogen protection portfolio when many thousands of sister workers live in close proximity and larvae and pupae are not protected by cells, as in bees and wasps, and are immobile. We performed behavioural observations on brood covering in the leaf-cutting ant Acromyrmex echinatior, and we experimentally manipulated mycelial cover on pupae and exposed them to the entomopathogenic fungus Metarhizium brunneum to test for a role in pathogen resistance. Our results show that active mycelial brood covering by workers is a behaviourally plastic trait that varies temporally, and across life stages and castes. The presence of a fungal cover on the pupae reduced the rate at which conidia appeared and the percentage of pupal surface that produced pathogen spores, compared to pupae that had fungal cover experimentally removed or naturally had no mycelial cover. Infected pupae with mycelium had higher survival rates than infected pupae without the cover, although this depended upon the time at which adult sister workers were allowed to interact with pupae. Finally, workers employed higher rates of metapleural gland grooming to infected pupae without mycelium than to infected pupae with mycelium. Our results imply that mycelial brood covering may play a significant role in suppressing the growth and subsequent spread of disease, thus adding a novel layer of protection to their defence portfolio.
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Affiliation(s)
- Sophie A O Armitage
- Department of Biology, Centre for Social Evolution, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark
| | - Hermógenes Fernández-Marín
- Department of Biology, Centre for Social Evolution, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark.,Instituto de Investigaciones Científicas y Servicios de Alta Tecnología, Edificio 219, Ciudad del Saber, Clayton, Panamá City, Panamá,Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Panamá
| | - Jacobus J Boomsma
- Department of Biology, Centre for Social Evolution, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark
| | - William T Wcislo
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Panamá
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15
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Pereira JS, Costa RR, Nagamoto NS, Forti LC, Pagnocca FC, Rodrigues A. Comparative analysis of fungal communities in colonies of two leaf-cutting ant species with different substratum preferences. FUNGAL ECOL 2016. [DOI: 10.1016/j.funeco.2016.03.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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16
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Fernández-Marín H, Nash DR, Higginbotham S, Estrada C, van Zweden JS, d'Ettorre P, Wcislo WT, Boomsma JJ. Functional role of phenylacetic acid from metapleural gland secretions in controlling fungal pathogens in evolutionarily derived leaf-cutting ants. Proc Biol Sci 2016; 282:20150212. [PMID: 25925100 DOI: 10.1098/rspb.2015.0212] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Fungus-farming ant colonies vary four to five orders of magnitude in size. They employ compounds from actinomycete bacteria and exocrine glands as antimicrobial agents. Atta colonies have millions of ants and are particularly relevant for understanding hygienic strategies as they have abandoned their ancestors' prime dependence on antibiotic-based biological control in favour of using metapleural gland (MG) chemical secretions. Atta MGs are unique in synthesizing large quantities of phenylacetic acid (PAA), a known but little investigated antimicrobial agent. We show that particularly the smallest workers greatly reduce germination rates of Escovopsis and Metarhizium spores after actively applying PAA to experimental infection targets in garden fragments and transferring the spores to the ants' infrabuccal cavities. In vitro assays further indicated that Escovopsis strains isolated from evolutionarily derived leaf-cutting ants are less sensitive to PAA than strains from phylogenetically more basal fungus-farming ants, consistent with the dynamics of an evolutionary arms race between virulence and control for Escovopsis, but not Metarhizium. Atta ants form larger colonies with more extreme caste differentiation relative to other attines, in societies characterized by an almost complete absence of reproductive conflicts. We hypothesize that these changes are associated with unique evolutionary innovations in chemical pest management that appear robust against selection pressure for resistance by specialized mycopathogens.
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Affiliation(s)
- Hermógenes Fernández-Marín
- Centro de Biodiversidad y Descubrimiento de Drogas, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología, Edificio 219, Ciudad del Saber, Clayton, Panamá Centre for Social Evolution, Department of Biology, University of Copenhagen Universitetsparken 15, Copenhagen 2100, Denmark Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panamá
| | - David R Nash
- Centre for Social Evolution, Department of Biology, University of Copenhagen Universitetsparken 15, Copenhagen 2100, Denmark
| | - Sarah Higginbotham
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panamá
| | - Catalina Estrada
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panamá
| | - Jelle S van Zweden
- Centre for Social Evolution, Department of Biology, University of Copenhagen Universitetsparken 15, Copenhagen 2100, Denmark Laboratory of Socioecology and Social Evolution, Zoological Institute, University of Leuven, Naamsestraat 59, box 2466, Leuven 3000, Belgium
| | - Patrizia d'Ettorre
- Centre for Social Evolution, Department of Biology, University of Copenhagen Universitetsparken 15, Copenhagen 2100, Denmark Laboratoire d'Ethologie Expérimentale et Comparée (LEEC), University of Paris 13, Sorbonne Paris Cité, France
| | - William T Wcislo
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panamá
| | - Jacobus J Boomsma
- Centre for Social Evolution, Department of Biology, University of Copenhagen Universitetsparken 15, Copenhagen 2100, Denmark
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Tranter C, Fernández‐Marín H, Hughes WOH. Quality and quantity: transitions in antimicrobial gland use for parasite defense. Ecol Evol 2015; 5:5857-68. [PMID: 26811760 PMCID: PMC4717345 DOI: 10.1002/ece3.1827] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 10/09/2015] [Accepted: 10/09/2015] [Indexed: 11/09/2022] Open
Abstract
Parasites are a major force in evolution, and understanding how host life history affects parasite pressure and investment in disease resistance is a general problem in evolutionary biology. The threat of disease may be especially strong in social animals, and ants have evolved the unique metapleural gland (MG), which in many taxa produce antimicrobial compounds that have been argued to have been a key to their ecological success. However, the importance of the MG in the disease resistance of individual ants across ant taxa has not been examined directly. We investigate experimentally the importance of the MG for disease resistance in the fungus-growing ants, a group in which there is interspecific variation in MG size and which has distinct transitions in life history. We find that more derived taxa rely more on the MG for disease resistance than more basal taxa and that there are a series of evolutionary transitions in the quality, quantity, and usage of the MG secretions, which correlate with transitions in life history. These shifts show how even small clades can exhibit substantial transitions in disease resistance investment, demonstrating that host-parasite relationships can be very dynamic and that targeted experimental, as well as large-scale, comparative studies can be valuable for identifying evolutionary transitions.
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Affiliation(s)
| | - Hermógenes Fernández‐Marín
- Instituto de Investigaciones Científicas y Servicios de Alta TecnologíaEdificio 219, Panamá 5Ciudad del SaberClaytonPanama CityPO Box 0843‐01105Republic of Panama
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18
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Nepel M, Voglmayr H, Schönenberger J, Mayer VE. High diversity and low specificity of chaetothyrialean fungi in carton galleries in a neotropical ant-plant association. PLoS One 2014; 9:e112756. [PMID: 25398091 PMCID: PMC4232418 DOI: 10.1371/journal.pone.0112756] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 10/14/2014] [Indexed: 11/20/2022] Open
Abstract
New associations have recently been discovered between arboreal ants that live on myrmecophytic plants, and different groups of fungi. Most of the – usually undescribed – fungi cultured by the ants belong to the order Chaetothyriales (Ascomycetes). Chaetothyriales occur in the nesting spaces provided by the host plant, and form a major part of the cardboard-like material produced by the ants for constructing nests and runway galleries. Until now, the fungi have been considered specific to each ant species. We focus on the three-way association between the plant Tetrathylacium macrophyllum (Salicaceae), the ant Azteca brevis (Formicidae: Dolichoderinae) and various chaetothyrialean fungi. Azteca brevis builds extensive runway galleries along branches of T. macrophyllum. The carton of the gallery walls consists of masticated plant material densely pervaded by chaetothyrialean hyphae. In order to characterise the specificity of the ant–fungus association, fungi from the runway galleries of 19 ant colonies were grown as pure cultures and analyzed using partial SSU, complete ITS, 5.8S and partial LSU rDNA sequences. This gave 128 different fungal genotypes, 78% of which were clustered into three monophyletic groups. The most common fungus (either genotype or approximate species-level OTU) was found in the runway galleries of 63% of the investigated ant colonies. This indicates that there can be a dominant fungus but, in general, a wider guild of chaetothyrialean fungi share the same ant mutualist in Azteca brevis.
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Affiliation(s)
- Maximilian Nepel
- Division of Structural and Functional Botany, Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
| | - Hermann Voglmayr
- Division of Systematic and Evolutionary Botany, Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
- Institute of Forest Entomology, Forest Pathology and Forest Protection, Department of Forest and Soil Sciences, BOKU-University of Natural Resources and Life Sciences, Vienna, Austria
| | - Jürg Schönenberger
- Division of Structural and Functional Botany, Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
| | - Veronika E. Mayer
- Division of Structural and Functional Botany, Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
- * E-mail:
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Weiss K, Parzefall C, Herzner G. Multifaceted defense against antagonistic microbes in developing offspring of the parasitoid wasp Ampulex compressa (Hymenoptera, Ampulicidae). PLoS One 2014; 9:e98784. [PMID: 24886721 PMCID: PMC4041758 DOI: 10.1371/journal.pone.0098784] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 05/07/2014] [Indexed: 12/02/2022] Open
Abstract
Effective antimicrobial strategies are essential adaptations of insects to protect themselves, their offspring, and their foods from microbial pathogens and decomposers. Larvae of the emerald cockroach wasp, Ampulex compressa, sanitize their cockroach hosts, Periplaneta americana, with a cocktail of nine antimicrobials comprising mainly (R)-(-)-mellein and micromolide. The blend of these antimicrobials has broad-spectrum antimicrobial activity. Here we explore the spatio-temporal pattern of deployment of antimicrobials during the development from egg to adult as well as their physico-chemical properties to assess how these aspects may contribute to the success of the antimicrobial strategy. Using gas chromatography/mass spectrometry (GC/MS) we show that larvae start sanitizing their food as soon as they have entered their host to feed on its tissue. Subsequently, they impregnate the cockroach carcass with antimicrobials to create a hygienic substrate for cocoon spinning inside the host. Finally, the antimicrobials are incorporated into the cocoon. The antimicrobial profiles on cockroach and wasp cocoon differed markedly. While micromolide persisted on the cockroaches until emergence of the wasps, solid-phase microextraction sampling and GC/MS analysis revealed that (R)-(-)-mellein vaporized from the cockroaches and accumulated in the enclosed nest. In microbial challenge assays (R)-(-)-mellein in the headspace of parasitized cockroaches inhibited growth of entomopathogenic and opportunistic microbes (Serratia marcescens, Aspergillus sydowii, Metarhizium brunneum). We conclude that, in addition to food sanitation, A. compressa larvae enclose themselves in two defensive walls by impregnating the cocoon and the cockroach cuticle with antimicrobials. On top of that, they use vaporous (R)-(-)-mellein to sanitize the nest by fumigation. This multifaceted antimicrobial defense strategy involving the spatially and temporally coordinated deployment of several antimicrobials in solution and vapor form has apparently evolved to reliably protect the larvae themselves and their food against a broad range of antagonistic microbes.
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Affiliation(s)
- Katharina Weiss
- Evolutionary Ecology Group, Institute of Zoology, University of Regensburg, Regensburg, Germany
| | - Christopher Parzefall
- Evolutionary Ecology Group, Institute of Zoology, University of Regensburg, Regensburg, Germany
| | - Gudrun Herzner
- Evolutionary Ecology Group, Institute of Zoology, University of Regensburg, Regensburg, Germany
- * E-mail:
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Pull CD, Hughes WOH, Brown MJF. Tolerating an infection: an indirect benefit of co-founding queen associations in the ant Lasius niger. Naturwissenschaften 2013; 100:1125-36. [DOI: 10.1007/s00114-013-1115-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 10/22/2013] [Accepted: 10/25/2013] [Indexed: 10/26/2022]
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21
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Instability of novel ant-fungal associations constrains horizontal exchange of fungal symbionts. Evol Ecol 2013. [DOI: 10.1007/s10682-013-9665-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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22
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Yek SH, Boomsma JJ, Schiøtt M. Differential gene expression in Acromyrmex leaf-cutting ants after challenges with two fungal pathogens. Mol Ecol 2013; 22:2173-87. [PMID: 23480581 DOI: 10.1111/mec.12255] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 01/03/2013] [Accepted: 01/15/2013] [Indexed: 11/30/2022]
Abstract
Social insects in general and leaf-cutting ants in particular have increased selection pressures on their innate immune system due to their social lifestyle and monoclonality of the symbiotic fungal cultivar. As this symbiosis is obligate for both parties, prophylactic behavioural defences against infections are expected to increase either ant survival or fungus-garden survival, but also to possibly trade off when specific infections differ in potential danger. We examined the effectiveness of prophylactic behaviours and modulations of innate immune defences by a combination of inoculation bioassays and genome-wide transcriptomic studies (RNA-Seq), using an ant pathogen (Metarhizium brunneum) and a fungus-garden pathogen (Escovopsis weberi) and administering inoculations both directly and indirectly (via the symbiotic partner). Upon detection of pathogen conidia, ant workers responded by increasing both general activity and the frequency of specific defence behaviours (self-grooming, allo-grooming, garden-grooming) independent of the pathogen encountered. This trend was also evident in the patterns of gene expression change. Both direct and indirect (via fungus garden) inoculations with Metarhizium induced a general up-regulation of gene expression, including a number of well-known immune-related genes. In contrast, direct inoculation of the fungus garden by Escovopsis induced an overall down-regulation of ant gene expression, whereas indirect inoculation (via the ants) did not, suggesting that increased activity of ants to remove this fungus-garden pathogen is costly and involves trade-offs with the activation of other physiological pathways.
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Affiliation(s)
- Sze H Yek
- Department of Biology, Centre for Social Evolution, University of Copenhagen, Copenhagen, Denmark
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