1
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Oliver MG, Best A. Parasite evolution of host manipulation strategies with fluctuating ecological dynamics. J Evol Biol 2024; 37:302-313. [PMID: 38300519 DOI: 10.1093/jeb/voae014] [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: 07/31/2023] [Revised: 10/27/2023] [Accepted: 01/19/2024] [Indexed: 02/02/2024]
Abstract
Trophically transmitted parasites often infect an intermediate prey host and manipulate their behaviour to make predation more likely, thus facilitating parasite transmission to the definitive host. However, it is unclear when such a manipulation strategy should be expected to evolve. We develop the first evolutionary invasion model to explore the evolution of manipulation strategies that are in a trade-off with parasite production of free-living spores. We find that the size of the susceptible prey population together with the threat of predation drives manipulation evolution. We find that it is only when the susceptible prey population is large and the threat of predation is relatively small that selection favours manipulation strategies over spore production. We also confirm that the system exhibits cyclic population dynamics, and this can influence the qualitative direction of selection.
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Affiliation(s)
- Megan Grace Oliver
- School of Mathematics and Statistics, University of Sheffield, Sheffield, United Kingdom
| | - Alex Best
- School of Mathematics and Statistics, University of Sheffield, Sheffield, United Kingdom
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2
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Albert L, Rumschlag S, Parker A, Vaziri G, Knutie SA. Elevated nest temperature has opposing effects on host species infested with parasitic nest flies. Oecologia 2023; 201:877-886. [PMID: 37012554 DOI: 10.1007/s00442-023-05343-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 02/20/2023] [Indexed: 04/05/2023]
Abstract
Environmental factors, such as elevated temperature, can have varying effects on hosts and their parasites, which can have consequences for the net outcome of this relationship. The individual direct effects of temperature must be disentangled to determine the net-effect in host-parasite relationships, yet few studies have determined the net-effects in a multi-host system. To address this gap, we experimentally manipulated temperature and parasite presence in the nests of two host species infested by parasitic blowflies (Protocalliphora sialia). We conducted a factorial experiment by increasing temperature (or not) and removing all parasites (or not) in the nests of eastern bluebirds (Sialia sialis) and tree swallows (Tachycineta bicolor). We then measured nestling morphometrics, blood loss, and survival and quantified parasite abundance. We predicted that if temperature had a direct effect on parasite abundance, then elevated temperature would cause similar directional effects on parasite abundance across host species. If temperature had a direct effect on hosts, and therefore an indirect effect on the parasite, parasite abundance would differ across host species. Swallow nests with elevated temperature had fewer parasites compared to nests without temperature manipulation. In contrast, bluebird nests with elevated temperatures had more parasites compared to nests without temperature manipulation. The results of our study demonstrate that elevated temperature can have differential effects on host species, which can impact infestation susceptibility. Furthermore, changing climates could have complex net-effects on parasite fitness and host health across multi-host-parasite interactions.
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Affiliation(s)
- Lauren Albert
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, USA.
- Department of Biology, Indiana University, Bloomington, IN, USA.
| | - Samantha Rumschlag
- Department of Biological Sciences, Environmental Change Initiative, University of Notre Dame, Notre Dame, IN, USA
| | - Alexandra Parker
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, USA
| | - Grace Vaziri
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, USA
| | - Sarah A Knutie
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, USA
- Institute for Systems Genomics, University of Connecticut, Storrs, CT, USA
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3
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Best A, Ashby B. How do fluctuating ecological dynamics impact the evolution of hosts and parasites? Philos Trans R Soc Lond B Biol Sci 2023; 378:20220006. [PMID: 36744565 PMCID: PMC9900711 DOI: 10.1098/rstb.2022.0006] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Theoretical models of the evolution of parasites and their hosts have shaped our understanding of infectious disease dynamics for over 40 years. Many theoretical models assume that the underlying ecological dynamics are at equilibrium or constant, yet we know that in a great many systems there are fluctuations in the ecological dynamics owing to a variety of intrinsic or extrinsic factors. Here, we discuss the challenges presented when modelling evolution in systems with fluctuating ecological dynamics and summarize the main approaches that have been developed to study host-parasite evolution in such systems. We provide an in-depth guide to one of the methods by applying it to two worked examples of host evolution that have not previously been studied in the literature: when cycles occur owing to seasonal forcing in competition, and when the presence of a free-living parasite causes cycles, with accompanying interactive Python code provided. We review the findings of studies that have explored host-parasite evolution when ecological dynamics fluctuate, and point to areas of future research. Throughout we stress the importance of feedbacks between the ecological and evolutionary dynamics in driving the outcomes of infectious disease systems. This article is part of the theme issue 'Infectious disease ecology and evolution in a changing world'.
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Affiliation(s)
- A. Best
- School of Mathematics and Statistics, University of Sheffield, Sheffield S3 7RH, UK,Integrative Biology, University of California - Berkeley, Berkeley, CA 94720-5800, USA
| | - B. Ashby
- Department of Mathematics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6,Department of Mathematics, University of Bath, Bath BA2 7AY, UK
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4
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Lion S, Gandon S. Evolution of class-structured populations in periodic environments. Evolution 2022; 76:1674-1688. [PMID: 35657205 PMCID: PMC9541870 DOI: 10.1111/evo.14522] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 04/17/2022] [Indexed: 01/22/2023]
Abstract
What is the influence of periodic environmental fluctuations on life-history evolution? We present a general theoretical framework to understand and predict the long-term evolution of life-history traits under a broad range of ecological scenarios. Specifically, we investigate how periodic fluctuations affect selection when the population is also structured in distinct classes. This analysis yields time-varying selection gradients that clarify the influence of the fluctuations of the environment on the competitive ability of a specific life-history mutation. We use this framework to analyse the evolution of key life-history traits of pathogens. We examine three different epidemiological scenarios and we show how periodic fluctuations of the environment can affect the evolution of virulence and transmission as well as the preference for different hosts. These examples yield new and testable predictions on pathogen evolution, and illustrate how our approach can provide a better understanding of the evolutionary consequences of time-varying environmental fluctuations in a broad range of scenarios.
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5
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Lion S, Boots M, Sasaki A. Multi-morph eco-evolutionary dynamics in structured populations. Am Nat 2022; 200:345-372. [DOI: 10.1086/720439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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6
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MacDonald H, Brisson D. Host phenology regulates parasite-host demographic cycles and eco-evolutionary feedbacks. Ecol Evol 2022; 12:e8658. [PMID: 35342586 PMCID: PMC8928868 DOI: 10.1002/ece3.8658] [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: 01/10/2022] [Revised: 01/25/2022] [Accepted: 01/30/2022] [Indexed: 01/26/2023] Open
Abstract
Parasite-host interactions can drive periodic population dynamics when parasites overexploit host populations. The timing of host seasonal activity, or host phenology, determines the frequency and demographic impact of parasite-host interactions, which may govern whether parasites sufficiently overexploit hosts to drive population cycles. We describe a mathematical model of a monocyclic, obligate-killer parasite system with seasonal host activity to investigate the consequences of host phenology on host-parasite dynamics. The results suggest that parasites can reach the densities necessary to destabilize host dynamics and drive cycling as they adapt, but only in some phenological scenarios such as environments with short seasons and synchronous host emergence. Furthermore, only parasite lineages that are sufficiently adapted to phenological scenarios with short seasons and synchronous host emergence can achieve the densities necessary to overexploit hosts and produce population cycles. Host-parasite cycles also generate an eco-evolutionary feedback that slows parasite adaptation to the phenological environment as rare advantageous phenotypes can be driven extinct due to a population bottleneck depending on when they are introduced in the cycle. The results demonstrate that seasonal environments can drive population cycling in a restricted set of phenological patterns and provide further evidence that the rate of adaptive evolution depends on underlying ecological dynamics.
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Affiliation(s)
| | - Dustin Brisson
- Department of BiologyUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
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7
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How seasonal variations in birth and transmission rates impact population dynamics in a basic SIR model. ECOLOGICAL COMPLEXITY 2021. [DOI: 10.1016/j.ecocom.2021.100949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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8
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Kirk D, Greischar M, Mideo N, Krkošek M. Environmental variability affects optimal trade‐offs in ecological immunology. Ecosphere 2021. [DOI: 10.1002/ecs2.3654] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Affiliation(s)
- Devin Kirk
- Department of Ecology and Evolutionary Biology University of Toronto Toronto OntarioM5S 1A1Canada
| | - Megan Greischar
- Department of Ecology and Evolutionary Biology University of Toronto Toronto OntarioM5S 1A1Canada
| | - Nicole Mideo
- Department of Ecology and Evolutionary Biology University of Toronto Toronto OntarioM5S 1A1Canada
| | - Martin Krkošek
- Department of Ecology and Evolutionary Biology University of Toronto Toronto OntarioM5S 1A1Canada
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9
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Evolutionarily stable strategies are well studied in periodically fluctuating populations. Proc Natl Acad Sci U S A 2021; 118:2102001118. [PMID: 33853857 DOI: 10.1073/pnas.2102001118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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10
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Walter A, Lion S. Epidemiological and evolutionary consequences of periodicity in treatment coverage. Proc Biol Sci 2021; 288:20203007. [PMID: 33715439 PMCID: PMC7944112 DOI: 10.1098/rspb.2020.3007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 02/15/2021] [Indexed: 12/16/2022] Open
Abstract
Host heterogeneity is a key driver of host-pathogen dynamics. In particular, the use of treatments against infectious diseases creates variation in quality among hosts, which can have both epidemiological and evolutionary consequences. We present a general theoretical model to highlight the consequences of different imperfect treatments on pathogen prevalence and evolution. These treatments differ in their action on host and pathogen traits. In contrast with previous studies, we assume that treatment coverage can vary in time, as in seasonal or pulsed treatment strategies. We show that periodic treatment strategies can limit both disease spread and virulence evolution, depending on the type of treatment. We also introduce a new method to analytically calculate the selection gradient in periodic environments, which allows our predictions to be interpreted using the concept of reproductive value, and can be applied more generally to analyse eco-evolutionary dynamics in class-structured populations and fluctuating environments.
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Affiliation(s)
- Alicia Walter
- CEFE, CNRS, Univ Montpellier, EPHE, IRD, Univ Paul Valéry Montpellier 3. 1919, route de Mende, Montpellier, France
| | - Sébastien Lion
- CEFE, CNRS, Univ Montpellier, EPHE, IRD, Univ Paul Valéry Montpellier 3. 1919, route de Mende, Montpellier, France
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11
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Xie X. Bistability of a two-species competition model with stage structure. INT J BIOMATH 2021. [DOI: 10.1142/s1793524520500771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In this paper, we focus on the dynamic behaviors of the bistability for a two-species Lotka–Volterra competition model with stage structure. Using the theory of generalized saddle-point behaviors, it is shown that there exists a [Formula: see text]-separatrix [Formula: see text] on its state space such that Species 2 wins the competition whenever the initial distribution is above [Formula: see text], while Species 1 wins the competition whenever the initial distribution is below [Formula: see text]. Combining with the previous conclusions of the system, we give a complete classification for global competitive dynamics. Furthermore, we carefully analyze the changes of the competition outcome after introducing the stage structure. Finally, some numerical simulations are provided to illustrate the effectiveness of the theoretical results.
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Affiliation(s)
- Xizhuang Xie
- School of Mathematical Sciences, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
- School of Mathematical Sciences, Huaqiao University, Quanzhou, Fujian 362021, P. R. China
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12
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Ferris C, Wright R, Brockhurst MA, Best A. The evolution of host resistance and parasite infectivity is highest in seasonal resource environments that oscillate at intermediate amplitudes. Proc Biol Sci 2020; 287:20200787. [PMID: 32453992 PMCID: PMC7287369 DOI: 10.1098/rspb.2020.0787] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 05/01/2020] [Indexed: 12/31/2022] Open
Abstract
Seasonal environments vary in their amplitude of oscillation but the effects of this temporal heterogeneity for host-parasite coevolution are poorly understood. Here, we combined mathematical modelling and experimental evolution of a coevolving bacteria-phage interaction to show that the intensity of host-parasite coevolution peaked in environments that oscillate in their resource supply with intermediate amplitude. Our experimentally parameterized mathematical model explains that this pattern is primarily driven by the ecological effects of resource oscillations on host growth rates. Our findings suggest that in host-parasite systems where the host's but not the parasite's population growth dynamics are subject to seasonal forcing, the intensity of coevolution will peak at intermediate amplitudes but be constrained at extreme amplitudes of environmental oscillation.
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Affiliation(s)
- Charlotte Ferris
- School of Mathematics and Statistics, University of Sheffield, Hicks Building, 226 Hounsfield Road, Sheffield S3 7RH, UK
| | - Rosanna Wright
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Michael A. Brockhurst
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Alex Best
- School of Mathematics and Statistics, University of Sheffield, Hicks Building, 226 Hounsfield Road, Sheffield S3 7RH, UK
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13
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Ferris C, Best A. The effect of temporal fluctuations on the evolution of host tolerance to parasitism. Theor Popul Biol 2019; 130:182-190. [PMID: 31415775 DOI: 10.1016/j.tpb.2019.07.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 05/29/2019] [Accepted: 07/29/2019] [Indexed: 11/19/2022]
Abstract
There are many mechanisms that hosts can evolve to defend against parasites, two of which are resistance and tolerance. These defences often have different evolutionary behaviours, and it is important to consider how each individual mechanism may respond to changes in environment. In particular, host defence through tolerance is predicted to be unlikely to lead to variation, despite many observations of diversity in both animal and plant systems. Hence understanding the drivers of diversity in host defence and parasite virulence is vital for predicting future evolutionary changes in infectious disease dynamics. It has been suggested that heterogeneous environments might generally promote diversity, but the effect of temporal fluctuations has received little attention theoretically or empirically, and there has been no examination of how temporal fluctuations affects the evolution of host tolerance. In this study, we use a mathematical model to investigate the evolution of host tolerance in a temporally fluctuating environment. We show that investment in tolerance increases in more variable environments, giving qualitatively different evolutionary behaviours when compared to resistance. Once seasonality is introduced evolutionary branching though tolerance can occur and create diversity within the population, although potentially only temporarily. This branching behaviour arises due to the emergence of a negative feedback with the maximum infected density on a cycle, which is strongest when the infected population is large. This work reinforces the qualitative differences between tolerance and resistance evolution, but also provides theoretical evidence for the theory that heterogeneous environments promote host-parasite diversity, hence constant environment assumptions may omit important evolutionary outcomes.
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Affiliation(s)
- Charlotte Ferris
- School of Mathematics and Statistics, University of Sheffield, Sheffield, S3 7RH, UK.
| | - Alex Best
- School of Mathematics and Statistics, University of Sheffield, Sheffield, S3 7RH, UK
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14
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Bartlett LJ, Wilfert L, Boots M. A genotypic trade-off between constitutive resistance to viral infection and host growth rate. Evolution 2018; 72:2749-2757. [PMID: 30298913 PMCID: PMC6492093 DOI: 10.1111/evo.13623] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 10/05/2018] [Indexed: 02/07/2023]
Abstract
Genotypic trade‐offs are fundamental to the understanding of the evolution of life‐history traits. In particular, the evolution of optimal host defense and the maintenance of variation in defense against infectious disease is thought to be underpinned by such evolutionary trade‐offs. However, empirical demonstrations of these trade‐offs that satisfy the strict assumptions made by theoretical models are rare. Additionally, none of these trade‐offs have yet been shown to be robustly replicable using a variety of different experimental approaches to rule out confounding issues with particular experimental designs. Here, we use inbred isolines as a novel experimental approach to test whether a trade‐off between viral resistance and growth rate in Plodia interpunctella, previously demonstrated by multiple selection experiments, is robust and meets the strict criteria required to underpin theoretical work in this field. Critically, we demonstrate that this trade‐off is both genetic and constitutive. This finding helps support the large body of theory that relies on these assumptions, and makes this trade‐off for resistance unique in being replicated through multiple experimental approaches and definitively shown to be genetic and constitutive.
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Affiliation(s)
- Lewis J Bartlett
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, United Kingdom
| | - Lena Wilfert
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, United Kingdom
| | - Michael Boots
- Department of Integrative Biology, University of California, Berkeley, California, 94720
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