1
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O'Neill X, White A, Boots M. The evolution of parasite virulence under targeted culling and harvesting in wildlife and livestock. Evol Appl 2023; 16:1697-1707. [PMID: 38020874 PMCID: PMC10660816 DOI: 10.1111/eva.13594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 07/27/2023] [Accepted: 09/01/2023] [Indexed: 12/01/2023] Open
Abstract
There is a clear need to understand the effect of human intervention on the evolution of infectious disease. In particular, culling and harvesting of both wildlife and managed livestock populations are carried out in a wide range of management practices, and they have the potential to impact the evolution of a broad range of disease characteristics. Applying eco-evolutionary theory we show that once culling/harvesting becomes targeted on specific disease classes, the established result that culling selects for higher virulence is only found when sufficient infected individuals are culled. If susceptible or recovered individuals are targeted, selection for lower virulence can occur. An important implication of this result is that when culling to eradicate an infectious disease from a population, while it is optimal to target infected individuals, the consequent evolution can increase the basic reproductive ratio of the infection, R 0 , and make parasite eradication more difficult. We show that increases in evolved virulence due to the culling of infected individuals can lead to excess population decline when sustainably harvesting a population. In contrast, culling susceptible or recovered individuals can select for decreased virulence and a reduction in population decline through culling. The implications to the evolution of virulence are typically the same in wildlife populations, that are regulated by the parasite, and livestock populations, that have a constant population size where restocking balances the losses due to mortality. However, the well-known result that vertical transmission selects for lower virulence and transmission in wildlife populations is less marked in livestock populations for parasites that convey long-term immunity since restocking can enhance the density of the immune class. Our work emphasizes the importance of understanding the evolutionary consequences of intervention strategies and the different ecological feedbacks that can occur in wildlife and livestock populations.
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Affiliation(s)
- Xander O'Neill
- Department of MathematicsMaxwell Institute for Mathematical Sciences, Heriot‐Watt UniversityEdinburghUK
| | - Andy White
- Department of MathematicsMaxwell Institute for Mathematical Sciences, Heriot‐Watt UniversityEdinburghUK
| | - Mike Boots
- Department of Integrative BiologyUniversity of CaliforniaBerkeleyCaliforniaUSA
- Centre for Ecology and Conservation, BiosciencesUniversity of ExeterCornwallUK
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2
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Wilson K, Grzywacz D, Cory JS, Donkersley P, Graham RI. Trans-generational viral transmission and immune priming are dose-dependent. J Anim Ecol 2021; 90:1560-1569. [PMID: 33724454 DOI: 10.1111/1365-2656.13476] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 03/08/2021] [Indexed: 12/30/2022]
Abstract
It is becoming increasingly apparent that trans-generational immune priming (i.e. the transfer of the parental immunological experience to its progeny resulting in offspring protection from pathogens that persist across generations) is a common phenomenon not only in vertebrates, but also invertebrates. Likewise, it is known that covert pathogenic infections may become 'triggered' into an overt infection by various stimuli, including exposure to heterologous infections. Yet, rarely have both phenomena been explored in parallel. Using as a model system the African armyworm Spodoptera exempta, an eruptive agricultural pest and its endemic dsDNA virus (Spodoptera exempta nucleopolyhedrovirus, SpexNPV), the aim of this study was to explore the impact of parental inoculating-dose on trans-generational pathogen transmission and immune priming (in its broadest sense). Larvae were orally challenged with one of five doses of SpexNPV and survivors from these treatments were mated and their offspring monitored for viral mortality. Offspring from parents challenged with low viral doses showed evidence of 'immune priming' (i.e. enhanced survival following SpexNPV challenge); in contrast, offspring from parents challenged with higher viral doses exhibited greater susceptibility to viral challenge. Most offspring larvae died of the virus they were orally challenged with; in contrast, most offspring from parents that had been challenged with the highest doses were killed by the vertically transmitted virus (90%) and not the challenge virus. These results demonstrate that the outcome of a potentially lethal virus challenge is critically dependent on the level of exposure to virus in the parental generation-either increasing resistance at very low parental viral doses (consistent with trans-generational immune priming) or increasing susceptibility at higher parental doses (consistent with virus triggering). We discuss the implications of these findings for understanding both natural epizootics of baculoviruses and for using them as biological control agents.
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Affiliation(s)
- Kenneth Wilson
- Lancaster Environment Centre, Lancaster University, Lancaster, UK
| | - David Grzywacz
- Department of Agriculture Health and Environment, Natural Resources Institute, University of Greenwich, Kent, UK
| | - Jenny S Cory
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
| | | | - Robert I Graham
- Lancaster Environment Centre, Lancaster University, Lancaster, UK
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3
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Abstract
AbstractA microbiome rife with enemies of the host should cause selection for defensive traits in symbionts, yet such complex environments are also predicted to select for greater symbiont virulence. Why then do we so often observe defensive mutualists that protect hosts while causing little to no damage? To address this question, we build a symbiont-centered model that incorporates the evolution of two independent symbiont traits: defense and virulence. Virulence is modeled as a continuous trait spanning parasitism (positive virulence) and mutualism (negative virulence), thus accounting for the entire range of direct effects that symbionts have on host mortality. Defense is modeled as a continuous trait that ameliorates the costs to the host associated with infection by a deleterious parasite. We show that the evolution of increased defense in one symbiont may lead to the evolution of lower virulence in both symbionts and even facilitate pathogens evolving to mutualism. However, results are context dependent, and when defensive traits are costly, the evolution of greater defense may also lead to the evolution of greater virulence, breaking the common expectation that defensive symbionts are necessarily mutualists toward the host.
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4
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Vorburger C, Perlman SJ. The role of defensive symbionts in host-parasite coevolution. Biol Rev Camb Philos Soc 2018; 93:1747-1764. [PMID: 29663622 DOI: 10.1111/brv.12417] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 03/20/2018] [Accepted: 03/23/2018] [Indexed: 02/06/2023]
Abstract
Understanding the coevolution of hosts and parasites is a long-standing goal of evolutionary biology. There is a well-developed theoretical framework to describe the evolution of host-parasite interactions under the assumption of direct, two-species interactions, which can result in arms race dynamics or sustained genotype fluctuations driven by negative frequency dependence (Red Queen dynamics). However, many hosts rely on symbionts for defence against parasites. Whilst the ubiquity of defensive symbionts and their potential importance for disease control are increasingly recognized, there is still a gap in our understanding of how symbionts mediate or possibly take part in host-parasite coevolution. Herein we address this question by synthesizing information already available from theoretical and empirical studies. First, we briefly introduce current hypotheses on how defensive mutualisms evolved from more parasitic relationships and highlight exciting new experimental evidence showing that this can occur very rapidly. We go on to show that defensive symbionts influence virtually all important determinants of coevolutionary dynamics, namely the variation in host resistance available to selection by parasites, the specificity of host resistance, and the trade-off structure between host resistance and other components of fitness. In light of these findings, we turn to the limited theory and experiments available for such three-species interactions to assess the role of defensive symbionts in host-parasite coevolution. Specifically, we discuss under which conditions the defensive symbiont may take over from the host the reciprocal adaptation with parasites and undergo its own selection dynamics, thereby altering or relaxing selection on the hosts' own immune defences. Finally, we address potential effects of defensive symbionts on the evolution of parasite virulence. This is an important problem for which there is no single, clear-cut prediction. The selection on parasite virulence resulting from the presence of defensive symbionts in their hosts will depend on the underlying mechanism of defence. We identify the evolutionary predictions for different functional categories of symbiont-conferred resistance and we evaluate the empirical literature for supporting evidence. We end this review with outstanding questions and promising avenues for future research to improve our understanding of symbiont-mediated coevolution between hosts and parasites.
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Affiliation(s)
- Christoph Vorburger
- Department of Aquatic Ecology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600, Dübendorf, Switzerland.,Institute of Integrative Biology, Department of Environmental Systems Science, ETH Zürich, Universitätsstrasse 16, 8092, Zürich, Switzerland
| | - Steve J Perlman
- Department of Biology, University of Victoria, 3800 Finnerty Road, Victoria, BC, V8P 5C2, Canada
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5
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Yang Y, Latorre J, Khatri B, Kwon Y, Kong B, Teague K, Graham L, Wolfenden A, Mahaffey B, Baxter M, Hernandez-Velasco X, Merino-Guzman R, Hargis B, Tellez G. Characterization and evaluation of lactic acid bacteria candidates for intestinal epithelial permeability and Salmonella Typhimurium colonization in neonatal turkey poults. Poult Sci 2018; 97:515-521. [DOI: 10.3382/ps/pex311] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2017] [Accepted: 09/25/2017] [Indexed: 12/13/2022] Open
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6
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Ashby B, King KC. Friendly foes: The evolution of host protection by a parasite. Evol Lett 2017; 1:211-221. [PMID: 30283650 PMCID: PMC6121858 DOI: 10.1002/evl3.19] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 06/28/2017] [Accepted: 07/24/2017] [Indexed: 01/25/2023] Open
Abstract
Hosts are often infected by multiple parasite species, yet the ecological and evolutionary implications of the interactions between hosts and coinfecting parasites are largely unknown. Most theoretical models of evolution among coinfecting parasites focus on the evolution of virulence, but parasites may also evolve to protect their hosts by reducing susceptibility (i.e., conferring resistance) to other parasites or reducing the virulence of coinfecting parasites (i.e., conferring tolerance). Here, we analyze the eco-evolutionary dynamics of parasite-conferred resistance and tolerance using coinfection models. We show that both parasite-conferred resistance and tolerance can evolve for a wide range of underlying trade-offs. The shape and strength of the trade-off qualitatively affects the outcome causing shifts between the minimisation or maximization of protection, intermediate stable strategies, evolutionary branching, and bistability. Furthermore, we find that a protected dimorphism can readily evolve for parasite-conferred resistance, but find no evidence of evolutionary branching for parasite-conferred tolerance, in general agreement with previous work on host evolution. These results provide novel insights into the evolution of parasite-conferred resistance and tolerance, and suggest clues to the underlying trade-offs in recent experimental work on microbe-mediated protection. More generally, our results highlight the context dependence of host-parasite relationships in complex communities.
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Affiliation(s)
- Ben Ashby
- Department of Mathematical SciencesUniversity of BathBathBA2 7AYUnited Kingdom
- Department of Integrative BiologyUniversity of California BerkeleyBerkeley94720California
| | - Kayla C. King
- Department of ZoologyUniversity of OxfordOxfordOX1 3PSUnited Kingdom
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7
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Williams T, Virto C, Murillo R, Caballero P. Covert Infection of Insects by Baculoviruses. Front Microbiol 2017; 8:1337. [PMID: 28769903 PMCID: PMC5511839 DOI: 10.3389/fmicb.2017.01337] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 07/03/2017] [Indexed: 12/19/2022] Open
Abstract
Baculoviruses (Baculoviridae) are occluded DNA viruses that are lethal pathogens of the larval stages of some lepidopterans, mosquitoes, and sawflies (phytophagous Hymenoptera). These viruses have been developed as biological insecticides for control of insect pests and as expression vectors in biotechnological applications. Natural and laboratory populations frequently harbor covert infections by baculoviruses, often at a prevalence exceeding 50%. Covert infection can comprise either non-productive latency or sublethal infection involving low level production of virus progeny. Latency in cell culture systems involves the expression of a small subset of viral genes. In contrast, covert infection in lepidopterans is associated with differential infection of cell types, modulation of virus gene expression and avoidance of immune system clearance. The molecular basis for covert infection may reside in the regulation of host-virus interactions through the action of microRNAs (miRNA). Initial findings suggest that insect nudiviruses and vertebrate herpesviruses may provide useful analogous models for exploring the mechanisms of covert infection by baculoviruses. These pathogens adopt mixed-mode transmission strategies that depend on the relative fitness gains that accrue through vertical and horizontal transmission. This facilitates virus persistence when opportunities for horizontal transmission are limited and ensures virus dispersal in migratory host species. However, when host survival is threatened by environmental or physiological stressors, latent or persistent infections can be activated to produce lethal disease, followed by horizontal transmission. Covert infection has also been implicated in population level effects on host-pathogen dynamics due to the reduced reproductive capacity of infected females. We conclude that covert infections provide many opportunities to examine the complexity of insect-virus pathosystems at the organismal level and to explore the evolutionary and ecological relationships of these pathogens with major crop and forest pests.
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Affiliation(s)
| | - Cristina Virto
- Bioinsecticidas Microbianos, Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Científicas, Universidad Pública de NavarraMutilva, Spain
- Laboratorio de Entomología Agrícola y Patología de Insectos, Departamento de Producción Agraria, Universidad Pública de NavarraPamplona, Spain
| | - Rosa Murillo
- Bioinsecticidas Microbianos, Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Científicas, Universidad Pública de NavarraMutilva, Spain
- Laboratorio de Entomología Agrícola y Patología de Insectos, Departamento de Producción Agraria, Universidad Pública de NavarraPamplona, Spain
| | - Primitivo Caballero
- Bioinsecticidas Microbianos, Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Científicas, Universidad Pública de NavarraMutilva, Spain
- Laboratorio de Entomología Agrícola y Patología de Insectos, Departamento de Producción Agraria, Universidad Pública de NavarraPamplona, Spain
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8
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Parratt SR, Frost CL, Schenkel MA, Rice A, Hurst GDD, King KC. Superparasitism Drives Heritable Symbiont Epidemiology and Host Sex Ratio in a Wasp. PLoS Pathog 2016; 12:e1005629. [PMID: 27322651 PMCID: PMC4920596 DOI: 10.1371/journal.ppat.1005629] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 04/22/2016] [Indexed: 02/06/2023] Open
Abstract
Heritable microbial symbionts have profound impacts upon the biology of their arthropod hosts. Whilst our current understanding of the dynamics of these symbionts is typically cast within a framework of vertical transmission only, horizontal transmission has been observed in a number of cases. For instance, several symbionts can transmit horizontally when their parasitoid hosts share oviposition patches with uninfected conspecifics, a phenomenon called superparasitism. Despite this, horizontal transmission, and the host contact structures that facilitates it, have not been considered in heritable symbiont epidemiology. Here, we tested for the importance of host contact, and resulting horizontal transmission, for the epidemiology of a male-killing heritable symbiont (Arsenophonus nasoniae) in parasitoid wasp hosts. We observed that host contact through superparasitism is necessary for this symbiont's spread in populations of its primary host Nasonia vitripennis, such that when superparasitism rates are high, A. nasoniae almost reaches fixation, causes highly female biased population sex ratios and consequently causes local host extinction. We further tested if natural interspecific variation in superparasitism behaviours predicted symbiont dynamics among parasitoid species. We found that A. nasoniae was maintained in laboratory populations of a closely related set of Nasonia species, but declined in other, more distantly related pteromalid hosts. The natural proclivity of a species to superparasitise was the primary factor determining symbiont persistence. Our results thus indicate that host contact behaviour is a key factor for heritable microbe dynamics when horizontal transmission is possible, and that 'reproductive parasite' phenotypes, such as male-killing, may be of secondary importance in the dynamics of such symbiont infections.
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Affiliation(s)
- Steven R. Parratt
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
| | - Crystal L. Frost
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Martijn A. Schenkel
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Annabel Rice
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Gregory D. D. Hurst
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Kayla C. King
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
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9
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Ford SA, King KC. Harnessing the Power of Defensive Microbes: Evolutionary Implications in Nature and Disease Control. PLoS Pathog 2016; 12:e1005465. [PMID: 27058881 PMCID: PMC4826280 DOI: 10.1371/journal.ppat.1005465] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Affiliation(s)
- Suzanne A. Ford
- Department of Zoology, University of Oxford, Oxford, United Kingdom
- * E-mail: (SAF); (KCK)
| | - Kayla C. King
- Department of Zoology, University of Oxford, Oxford, United Kingdom
- * E-mail: (SAF); (KCK)
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10
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Myers JH, Cory JS. Ecology and evolution of pathogens in natural populations of Lepidoptera. Evol Appl 2016; 9:231-47. [PMID: 27087850 PMCID: PMC4780379 DOI: 10.1111/eva.12328] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 08/19/2015] [Indexed: 01/25/2023] Open
Abstract
Pathogens are ubiquitous in insect populations and yet few studies examine their dynamics and impacts on host populations. We discuss four lepidopteran systems and explore their contributions to disease ecology and evolution. More specifically, we elucidate the role of pathogens in insect population dynamics. For three species, western tent caterpillars, African armyworm and introduced populations of gypsy moth, infection by nucleopolyhedrovirus (NPV) clearly regulates host populations or reduces their outbreaks. Transmission of NPV is largely horizontal although low levels of vertical transmission occur, and high levels of covert infection in some cases suggest that the virus can persist in a nonsymptomatic form. The prevalence of a mostly vertically transmitted protozoan parasite, Ophryocystis elektroscirrha, in monarch butterflies is intimately related to their migratory behaviour that culls highly infected individuals. Virulence and transmission are positively related among genotypes of this parasite. These systems clearly demonstrate that the interactions between insects and pathogens are highly context dependent. Not only is the outcome a consequence of changes in density and genetic diversity: environmental factors, particularly diet, can have strong impacts on virulence, transmission and host resistance or tolerance. What maintains the high level of host and pathogen diversity in these systems, however, remains a question.
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Affiliation(s)
- Judith H. Myers
- Department of ZoologyUniversity of British ColumbiaVancouverBCCanada
| | - Jenny S. Cory
- Department of Biological SciencesSimon Fraser UniversityBurnabyBCCanada
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11
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Abstract
Why is it that some parasites cause high levels of host damage (i.e. virulence) whereas others are relatively benign? There are now numerous reviews of virulence evolution in the literature but it is nevertheless still difficult to find a comprehensive treatment of the theory and data on the subject that is easily accessible to non-specialists. Here we attempt to do so by distilling the vast theoretical literature on the topic into a set of relatively few robust predictions. We then provide a comprehensive assessment of the available empirical literature that tests these predictions. Our results show that there have been some notable successes in integrating theory and data but also that theory and empiricism in this field do not ‘speak’ to each other very well. We offer a few suggestions for how the connection between the two might be improved.
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12
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Cory JS. Insect virus transmission: different routes to persistence. CURRENT OPINION IN INSECT SCIENCE 2015; 8:130-135. [PMID: 32846660 DOI: 10.1016/j.cois.2015.01.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 01/15/2015] [Accepted: 01/15/2015] [Indexed: 05/05/2023]
Abstract
Transmission is a fundamental process in disease ecology; however, the factors that modulate transmission and the dynamical and evolutionary consequences of these factors in host populations are difficult to study in natural settings. Much of our current knowledge comes from a limited number of virus groups and few ecological studies. Alternatively, progress has been made in the detection of new viruses and in probing the molecular basis of behavioural manipulation of hosts that might influence virus transmission. An expanding theoretical framework provides guidelines on the conditions under which particular transmission strategies might evolve, and their dynamical consequences, but empirical tests are lacking.
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Affiliation(s)
- Jenny S Cory
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6.
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13
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Duncan AB, Agnew P, Noel V, Michalakis Y. The consequences of co-infections for parasite transmission in the mosquito Aedes aegypti. J Anim Ecol 2014; 84:498-508. [PMID: 25311642 DOI: 10.1111/1365-2656.12302] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 10/01/2014] [Indexed: 11/29/2022]
Abstract
Co-infections may modify parasite transmission opportunities directly as a consequence of interactions in the within-host environment, but also indirectly through changes in host life history. Furthermore, host and parasite traits are sensitive to the abiotic environment with variable consequences for parasite transmission in co-infections. We investigate how co-infection of the mosquito Aedes aegypti with two microsporidian parasites (Vavraia culicis and Edhazardia aedis) at two levels of larval food availability affects parasite transmission directly, and indirectly through effects on host traits. In a laboratory infection experiment, we compared how co-infection, at low and high larval food availability, affected the probability of infection, within-host growth and the transmission potential of each parasite, compared to single infections. Horizontal transmission was deemed possible for both parasites when infected hosts died harbouring horizontally transmitting spores. Vertical transmission was judged possible for E. aedis when infected females emerged as adults. We also compared the total input number of spores used to seed infections with output number, in single and co-infections for each parasite. The effects of co-infection on parasite fitness were complex, especially for V. culicis. In low larval food conditions, co-infection increased the chances of mosquitoes dying as larvae or pupae, thus increasing opportunities for V. culicis' horizontal transmission. However, co-infection reduced larval longevity and hence time available for V. culicis spore production. Overall, there was a negative net effect of co-infection on V. culicis, whereby the number of spores produced was less than the number used to seed infection. Co-infections also negatively affected horizontal transmission of the more virulent parasite, E. aedis, through reduced longevity of pre-adult hosts. However, its potential transmission suffered less relative to V. culicis. Our results show that co-infection can negatively affect parasite transmission opportunities, both directly as well as indirectly via effects on host life history. We also find that transmission is contingent on the combined effect of the abiotic environment.
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Affiliation(s)
- Alison B Duncan
- MIVEGEC, UMR CNRS-IRD-UM1-UM2 5290, Centre IRD, 911 avenue Agropolis, 34394, Montpellier CEDEX 5, France
| | - Philip Agnew
- MIVEGEC, UMR CNRS-IRD-UM1-UM2 5290, Centre IRD, 911 avenue Agropolis, 34394, Montpellier CEDEX 5, France
| | - Valérie Noel
- MIVEGEC, UMR CNRS-IRD-UM1-UM2 5290, Centre IRD, 911 avenue Agropolis, 34394, Montpellier CEDEX 5, France
| | - Yannis Michalakis
- MIVEGEC, UMR CNRS-IRD-UM1-UM2 5290, Centre IRD, 911 avenue Agropolis, 34394, Montpellier CEDEX 5, France
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14
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Tellez G. Prokaryotes Versus Eukaryotes: Who is Hosting Whom? Front Vet Sci 2014; 1:3. [PMID: 26664911 PMCID: PMC4668860 DOI: 10.3389/fvets.2014.00003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 06/23/2014] [Indexed: 01/22/2023] Open
Abstract
Microorganisms represent the largest component of biodiversity in our world. For millions of years, prokaryotic microorganisms have functioned as a major selective force shaping eukaryotic evolution. Microbes that live inside and on animals outnumber the animals' actual somatic and germ cells by an estimated 10-fold. Collectively, the intestinal microbiome represents a "forgotten organ," functioning as an organ inside another that can execute many physiological responsibilities. The nature of primitive eukaryotes was drastically changed due to the association with symbiotic prokaryotes facilitating mutual coevolution of host and microbe. Phytophagous insects have long been used to test theories of evolutionary diversification; moreover, the diversification of a number of phytophagous insect lineages has been linked to mutualisms with microbes. From termites and honey bees to ruminants and mammals, depending on novel biochemistries provided by the prokaryotic microbiome, the association helps to metabolize several nutrients that the host cannot digest and converting these into useful end products (such as short-chain fatty acids), a process, which has huge impact on the biology and homeostasis of metazoans. More importantly, in a direct and/or indirect way, the intestinal microbiota influences the assembly of gut-associated lymphoid tissue, helps to educate immune system, affects the integrity of the intestinal mucosal barrier, modulates proliferation and differentiation of its epithelial lineages, regulates angiogenesis, and modifies the activity of enteric as well as the central nervous system. Despite these important effects, the mechanisms by which the gut microbial community influences the host's biology remain almost entirely unknown. Our aim here is to encourage empirical inquiry into the relationship between mutualism and evolutionary diversification between prokaryotes and eukaryotes, which encourage us to postulate: who is hosting whom?
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Affiliation(s)
- Guillermo Tellez
- The John Kirkpatrick Skeeles Poultry Health Laboratory, Department of Poultry Science, The Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR, USA
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15
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Gerardo NM, Parker BJ. Mechanisms of symbiont-conferred protection against natural enemies: an ecological and evolutionary framework. CURRENT OPINION IN INSECT SCIENCE 2014; 4:8-14. [PMID: 28043411 DOI: 10.1016/j.cois.2014.08.002] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 08/02/2014] [Accepted: 08/05/2014] [Indexed: 05/08/2023]
Abstract
Many vertically-transmitted microbial symbionts protect their insect hosts from natural enemies, including host-targeted pathogens and parasites, and those vectored by insects to other hosts. Protection is often achieved through production of inhibiting toxins, which is not surprising given that toxin production mediates competition in many environments. Classical models of macroecological interactions, however, demonstrate that interspecific competition can be less direct, and recent research indicates that symbiont-protection can be mediated through exploitation of limiting resources, and through activation of host immune mechanisms that then suppress natural enemies. Available data, though limited, suggest that effects of symbionts on vectored pathogens and parasites, as compared to those that are host-targeted, are more likely to result from symbiont activation of the host immune system. We discuss these different mechanisms in light of their potential impact on the evolution of host physiological processes.
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Affiliation(s)
- Nicole M Gerardo
- Department of Biology, Emory University, O. Wayne Rollins Research Center, 1510 E. Clifton Road N.E., Atlanta, GA 30322, USA.
| | - Benjamin J Parker
- Department of Zoology, The University of Oxford, The Tinbergen Building, South Parks Road, Oxford OX13PS, UK.
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16
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Cézilly F, Perrot-Minnot MJ, Rigaud T. Cooperation and conflict in host manipulation: interactions among macro-parasites and micro-organisms. Front Microbiol 2014; 5:248. [PMID: 24966851 PMCID: PMC4052506 DOI: 10.3389/fmicb.2014.00248] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 05/06/2014] [Indexed: 11/30/2022] Open
Abstract
Several parasite species are known to manipulate the phenotype of their hosts in ways that enhance their own transmission. Co-occurrence of manipulative parasites, belonging to the same species or to more than one species, in a single host has been regularly observed. Little is known, however, on interactions between co-occurring manipulative parasites with same or different transmission routes. Several models addressing this problem have provided predictions on how cooperation and conflict between parasites could emerge from multiple infections. Here, we review the empirical evidence in favor of the existence of synergistic or antagonistic interactions between co-occurring parasites, and highlight the neglected role of micro-organisms. We particularly discuss the actual importance of selective forces shaping the evolution of interactions between manipulative parasites in relation to parasite prevalence in natural populations, efficiency in manipulation, and type of transmission (i.e., horizontal versus vertical), and we emphasize the potential for future research.
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Affiliation(s)
- Frank Cézilly
- Equipe Ecologie Evolutive, UMR CNRS 6282 Biogéosciences, Université de BourgogneDijon, France
- Institut Universitaire de FranceStrasbourg, France
| | | | - Thierry Rigaud
- Equipe Ecologie Evolutive, UMR CNRS 6282 Biogéosciences, Université de BourgogneDijon, France
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Vorburger C. The evolutionary ecology of symbiont-conferred resistance to parasitoids in aphids. INSECT SCIENCE 2014; 21:251-264. [PMID: 24167113 DOI: 10.1111/1744-7917.12067] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 10/21/2013] [Indexed: 06/02/2023]
Abstract
Aphids may harbor a wide variety of facultative bacterial endosymbionts. These symbionts are transmitted maternally with high fidelity and they show horizontal transmission as well, albeit at rates too low to enable infectious spread. Such symbionts need to provide a net fitness benefit to their hosts to persist and spread. Several symbionts have achieved this by evolving the ability to protect their hosts against parasitoids. Reviewing empirical work and some models, I explore the evolutionary ecology of symbiont-conferred resistance to parasitoids in order to understand how defensive symbiont frequencies are maintained at the intermediate levels observed in aphid populations. I further show that defensive symbionts alter the reciprocal selection between aphids and parasitoids by augmenting the heritable variation for resistance, by increasing the genetic specificity of the host-parasitoid interaction, and by inducing environment-dependent trade-offs. These effects are conducive to very dynamic, symbiont-mediated coevolution that is driven by frequency-dependent selection. Finally I argue that defensive symbionts represent a problem for biological control of pest aphids, and I propose to mitigate this problem by exploiting the parasitoids' demonstrated ability to rapidly evolve counteradaptations to symbiont-conferred resistance.
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Affiliation(s)
- Christoph Vorburger
- Institute of Integrative Biology, ETH Zürich, Universitätstrasse 16, 8092 Zürich; EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland
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18
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Dittmer J, Beltran-Bech S, Lesobre J, Raimond M, Johnson M, Bouchon D. Host tissues as microhabitats forWolbachiaand quantitative insights into the bacterial community in terrestrial isopods. Mol Ecol 2014; 23:2619-35. [DOI: 10.1111/mec.12760] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 04/12/2014] [Indexed: 02/06/2023]
Affiliation(s)
- J. Dittmer
- Université de Poitiers; UMR CNRS 7267 Ecologie et Biologie des Interactions; Equipe Ecologie Evolution Symbiose; 6 rue Michel Brunet 86073 Poitiers France
| | - S. Beltran-Bech
- Université de Poitiers; UMR CNRS 7267 Ecologie et Biologie des Interactions; Equipe Ecologie Evolution Symbiose; 6 rue Michel Brunet 86073 Poitiers France
| | - J. Lesobre
- Université de Poitiers; UMR CNRS 7267 Ecologie et Biologie des Interactions; Equipe Ecologie Evolution Symbiose; 6 rue Michel Brunet 86073 Poitiers France
| | - M. Raimond
- Université de Poitiers; UMR CNRS 7267 Ecologie et Biologie des Interactions; Equipe Ecologie Evolution Symbiose; 6 rue Michel Brunet 86073 Poitiers France
| | - M. Johnson
- Université de Poitiers; UMR CNRS 7267 Ecologie et Biologie des Interactions; Equipe Ecologie Evolution Symbiose; 6 rue Michel Brunet 86073 Poitiers France
| | - D. Bouchon
- Université de Poitiers; UMR CNRS 7267 Ecologie et Biologie des Interactions; Equipe Ecologie Evolution Symbiose; 6 rue Michel Brunet 86073 Poitiers France
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19
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Zug R, Hammerstein P. Bad guys turned nice? A critical assessment of Wolbachia mutualisms in arthropod hosts. Biol Rev Camb Philos Soc 2014; 90:89-111. [PMID: 24618033 DOI: 10.1111/brv.12098] [Citation(s) in RCA: 191] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 02/05/2014] [Accepted: 02/07/2014] [Indexed: 12/21/2022]
Abstract
Wolbachia are the most abundant bacterial endosymbionts among arthropods. Although maternally inherited, they do not conform to the widespread view that vertical transmission inevitably selects for beneficial symbionts. Instead, Wolbachia are notorious for their reproductive parasitism which, although lowering host fitness, ensures their spread. However, even for reproductive parasites it can pay to enhance host fitness. Indeed, there is a recent upsurge of reports on Wolbachia-associated fitness benefits. Therefore, the question arises how such instances of mutualism are related to the phenotypes of reproductive parasitism. Here, we review the evidence of Wolbachia mutualisms in arthropods, including both facultative and obligate relationships, and critically assess their biological relevance. Although many studies report anti-pathogenic effects of Wolbachia, few actually prove these effects to be relevant to field conditions. We further show that Wolbachia frequently have beneficial and detrimental effects at the same time, and that reproductive manipulations and obligate mutualisms may share common mechanisms. These findings undermine the idea of a clear-cut distinction between Wolbachia mutualism and parasitism. In general, both facultative and obligate mutualisms can have a strong, and sometimes unforeseen, impact on the ecology and evolution of Wolbachia and their arthropod hosts. Acknowledging this mutualistic potential might be the key to a better understanding of some unresolved issues in the study of Wolbachia-host interactions.
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Affiliation(s)
- Roman Zug
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Invalidenstr. 43, 10115, Berlin, Germany
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20
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Rainey SM, Shah P, Kohl A, Dietrich I. Understanding the Wolbachia-mediated inhibition of arboviruses in mosquitoes: progress and challenges. J Gen Virol 2013; 95:517-530. [PMID: 24343914 DOI: 10.1099/vir.0.057422-0] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Arthropod-borne viruses (arboviruses) pose a considerable threat to human and animal health, yet effective control measures have proven difficult to implement, and novel means of controlling their replication in arthropod vectors, such as mosquitoes, are urgently required. One of the most exciting approaches to emerge from research on arthropods is the use of the endosymbiotic intracellular bacterium Wolbachia to control arbovirus transmission from mosquito to vertebrate. These α-proteobacteria propagate through insects, in part through modulation of host reproduction, thus ensuring spread through species and maintenance in nature. Since it was discovered that Wolbachia endosymbiosis inhibits insect virus replication in Drosophila species, these bacteria have also been shown to inhibit arbovirus replication and spread in mosquitoes. Importantly, it is not clear how these antiviral effects are mediated. This review will summarize recent work and discuss determinants of antiviral effectiveness that may differ between individual Wolbachia/vector/arbovirus interactions. We will also discuss the application of this approach to field settings and the associated risks.
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Affiliation(s)
- Stephanie M Rainey
- MRC - University of Glasgow Centre for Virus Research, 8 Church Street, Glasgow G11 5JR, UK
| | - Pranav Shah
- MRC - University of Glasgow Centre for Virus Research, 8 Church Street, Glasgow G11 5JR, UK
| | - Alain Kohl
- MRC - University of Glasgow Centre for Virus Research, 8 Church Street, Glasgow G11 5JR, UK
| | - Isabelle Dietrich
- MRC - University of Glasgow Centre for Virus Research, 8 Church Street, Glasgow G11 5JR, UK
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21
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Lélu M, Langlais M, Poulle ML, Gilot-Fromont E, Gandon S. When should a trophically and vertically transmitted parasite manipulate its intermediate host? The case of Toxoplasma gondii. Proc Biol Sci 2013; 280:20131143. [PMID: 23825211 DOI: 10.1098/rspb.2013.1143] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Parasites with complex life cycles are expected to manipulate the behaviour of their intermediate hosts (IHs), which increase their predation rate and facilitate the transmission to definitive hosts (DHs). This ability, however, is a double-edged sword when the parasite can also be transmitted vertically in the IH. In this situation, as the manipulation of the IH behaviour increases the IH death rate, it conflicts with vertical transmission, which requires healthy and reproducing IHs. The protozoan Toxoplasma gondii, a widespread pathogen, combines both trophic and vertical transmission strategies. Is parasite manipulation of host behaviour still adaptive in this situation? We model the evolution of the IH manipulation by T. gondii to study the conflict between these two routes of transmission under different epidemiological situations. Model outputs show that manipulation is particularly advantageous for virulent strains and in epidemic situations, and that different levels of manipulation may evolve depending on the sex of the IH and the transmission routes considered. These results may help to understand the variability of strain characteristics encountered for T. gondii and may extend to other trophically transmitted parasites.
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Affiliation(s)
- Maud Lélu
- National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville, TN 37996, USA.
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22
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Alizon S, de Roode JC, Michalakis Y. Multiple infections and the evolution of virulence. Ecol Lett 2013; 16:556-67. [PMID: 23347009 DOI: 10.1111/ele.12076] [Citation(s) in RCA: 270] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 10/30/2012] [Accepted: 12/17/2012] [Indexed: 12/13/2022]
Abstract
Infections that consist of multiple parasite strains or species are common in the wild and are a major public health concern. Theory suggests that these infections have a key influence on the evolution of infectious diseases and, more specifically, on virulence evolution. However, we still lack an overall vision of the empirical support for these predictions. We argue that within-host interactions between parasites largely determine how virulence evolves and that experimental data support model predictions. Then, we explore the main limitation of the experimental study of such 'mixed infections', which is that it draws conclusions on evolutionary outcomes from studies conducted at the individual level. We also discuss differences between coinfections caused by different strains of the same species or by different species. Overall, we argue that it is possible to make sense out of the complexity inherent to multiple infections and that experimental evolution settings may provide the best opportunity to further our understanding of virulence evolution.
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Affiliation(s)
- Samuel Alizon
- Laboratoire MIVEGEC (UMR CNRS 5290, UR IRD 224, UM1, UM2), Montpellier, France.
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23
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Łukasik P, van Asch M, Guo H, Ferrari J, Godfray HCJ. Unrelated facultative endosymbionts protect aphids against a fungal pathogen. Ecol Lett 2012; 16:214-8. [PMID: 23137173 DOI: 10.1111/ele.12031] [Citation(s) in RCA: 213] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 09/26/2012] [Accepted: 10/15/2012] [Indexed: 11/30/2022]
Abstract
The importance of microbial facultative endosymbionts to insects is increasingly being recognized, but our understanding of how the fitness effects of infection are distributed across symbiont taxa is limited. In the pea aphid, some of the seven known species of facultative symbionts influence their host's resistance to natural enemies, including parasitoid wasps and a pathogenic fungus. Here we show that protection against this entomopathogen, Pandora neoaphidis, can be conferred by strains of four distantly related symbionts (in the genera Regiella, Rickettsia, Rickettsiella and Spiroplasma). They reduce mortality and also decrease fungal sporulation on dead aphids which may help protect nearby genetically identical insects. Pea aphids thus obtain protection from natural enemies through association with a wider range of microbial associates than has previously been thought. Providing resistance against natural enemies appears to be a particularly common way for facultative endosymbionts to increase in frequency within host populations.
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Affiliation(s)
- Piotr Łukasik
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK.
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24
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Rouchet R, Vorburger C. Strong specificity in the interaction between parasitoids and symbiont-protected hosts. J Evol Biol 2012; 25:2369-75. [PMID: 22998667 DOI: 10.1111/j.1420-9101.2012.02608.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 07/09/2012] [Accepted: 08/07/2012] [Indexed: 11/28/2022]
Abstract
Coevolution between hosts and parasites may promote the maintenance of genetic variation in both antagonists by negative frequency-dependence if the host-parasite interaction is genotype-specific. Here we tested for specificity in the interaction between parasitoids (Lysiphlebus fabarum) and aphid hosts (Aphis fabae) that are protected by a heritable defensive endosymbiont, the γ-proteobacterium Hamiltonella defensa. Previous studies reported a lack of genotype specificity between unprotected aphids and parasitoids, but suggested that symbiont-conferred resistance might exhibit a higher degree of specificity. Indeed, in addition to ample variation in host resistance as well as parasitoid infectivity, we found a strong aphid clone-by-parasitoid line interaction on the rates of successful parasitism. This genotype specificity appears to be mediated by H. defensa, highlighting the important role that endosymbionts can play in host-parasite coevolution.
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Affiliation(s)
- Romain Rouchet
- Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland.
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25
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Graham RI, Grzywacz D, Mushobozi WL, Wilson K. Wolbachiain a major African crop pest increases susceptibility to viral disease rather than protects. Ecol Lett 2012; 15:993-1000. [DOI: 10.1111/j.1461-0248.2012.01820.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 05/21/2012] [Accepted: 05/22/2012] [Indexed: 12/22/2022]
Affiliation(s)
- Robert I. Graham
- Lancaster Environment Centre; Lancaster University; Lancaster; LA1 4YQ; UK
| | - David Grzywacz
- Natural Resources Institute; University of Greenwich; Central Avenue; Chatham Maritime; ME4 4TB; UK
| | - Wilfred L. Mushobozi
- Eco Agri Consultancy Services Ltd; Nairobi Road; Kwa Idd; PO Box 15040; Arusha; Tanzania
| | - Kenneth Wilson
- Lancaster Environment Centre; Lancaster University; Lancaster; LA1 4YQ; UK
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26
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Vavre F, Charlat S. Making (good) use of Wolbachia: what the models say. Curr Opin Microbiol 2012; 15:263-8. [DOI: 10.1016/j.mib.2012.03.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 03/15/2012] [Indexed: 01/22/2023]
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27
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Kwiatkowski M, Vorburger C. Modeling the Ecology of Symbiont-Mediated Protection against Parasites. Am Nat 2012; 179:595-605. [DOI: 10.1086/665003] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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28
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Rudgers JA, Miller TEX, Ziegler SM, Craven KD. There are many ways to be a mutualist: Endophytic fungus reduces plant survival but increases population growth. Ecology 2012; 93:565-74. [DOI: 10.1890/11-0689.1] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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29
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Koch H, Schmid-Hempel P. Socially transmitted gut microbiota protect bumble bees against an intestinal parasite. Proc Natl Acad Sci U S A 2011; 108:19288-92. [PMID: 22084077 PMCID: PMC3228419 DOI: 10.1073/pnas.1110474108] [Citation(s) in RCA: 540] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Populations of important pollinators, such as bumble bees and honey bees, are declining at alarming rates worldwide. Parasites are likely contributing to this phenomenon. A distinct resident community of bacteria has recently been identified in bumble bees and honey bees that is not shared with related solitary bee species. We now show that the presence of these microbiota protects bee hosts against a widespread and highly virulent natural parasite (Crithidia bombi) in an experimental setting. We add further support to this antagonistic relationship from patterns found in field data. For the successful establishment of these microbiota and a protective effect, exposure to feces from nest mates was needed after pupal eclosion. Transmission of beneficial gut bacteria could therefore represent an important benefit of sociality. Our results stress the importance of considering the host microbiota as an "extended immune phenotype" in addition to the host immune system itself and provide a unique perspective to understanding bees in health and disease.
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Affiliation(s)
- Hauke Koch
- Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH) Zürich, CH-8092 Zürich, Switzerland
| | - Paul Schmid-Hempel
- Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH) Zürich, CH-8092 Zürich, Switzerland
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