1
|
Fox QN, Farah KN, Shaw OS, Pollowitz M, Sánchez-Conde A, Goodson C, Penczykowski RM. Effects of microclimate on disease prevalence across an urbanization gradient. Ecology 2024:e4313. [PMID: 38708902 DOI: 10.1002/ecy.4313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 01/21/2024] [Accepted: 03/14/2024] [Indexed: 05/07/2024]
Abstract
Increased temperatures associated with urbanization (the "urban heat island" effect) have been shown to impact a wide range of traits across diverse taxa. At the same time, climatic conditions vary at fine spatial scales within habitats due to factors including shade from shrubs, trees, and built structures. Patches of shade may function as microclimate refugia that allow species to occur in habitats where high temperatures and/or exposure to ultraviolet radiation would otherwise be prohibitive. However, the importance of shaded microhabitats for interactions between species across urbanized landscapes remains poorly understood. Weedy plants and their foliar pathogens are a tractable system for studying how multiple scales of climatic variation influence infection prevalence. Powdery mildew pathogens are particularly well suited to this work, as these fungi can be visibly diagnosed on leaf surfaces. We studied the effects of shaded microclimates on rates of powdery mildew infection on Plantago host species in (1) "pandemic pivot" surveys in which undergraduate students recorded shade and infection status of thousands of plants along road verges in urban and suburban residential neighborhoods, (2) monthly surveys of plant populations in 22 parks along an urbanization gradient, and (3) a manipulative field experiment directly testing the effects of shade on the growth and transmission of powdery mildew. Together, our field survey results show strong positive effects of shade on mildew infection in wild Plantago populations across urban, suburban, and rural habitats. Our experiment suggests that this relationship is causal, where microclimate conditions associated with shade promote pathogen growth. Overall, infection prevalence increased with urbanization despite a negative association between urbanization and tree cover at the landscape scale. These findings highlight the importance of taking microclimate heterogeneity into account when establishing links between macroclimate or land use context and prevalence of disease.
Collapse
Affiliation(s)
- Quinn N Fox
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Keiko N Farah
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Olivia S Shaw
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Michelle Pollowitz
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | | | - Carrie Goodson
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | | |
Collapse
|
2
|
Abstract
Plant diseases are strongly influenced by host biodiversity, spatial structure, and abiotic conditions. All of these are undergoing rapid change, as the climate is warming, habitats are being lost, and nitrogen deposition is changing nutrient dynamics of ecosystems with ensuing consequences for biodiversity. Here, I review examples of plant-pathogen associations to demonstrate how our ability to understand, model and predict disease dynamics is becoming increasingly difficult, as both plant and pathogen populations and communities are undergoing extensive change. The extent of this change is influenced via both direct and combined effects of global change drivers, and especially the latter are still poorly understood. Change at one trophic level is expected to drive change also at the other, and hence feedback loops between plants and their pathogens are expected to drive changes in disease risk both through ecological as well as evolutionary mechanisms. Many of the examples discussed here demonstrate an increase in disease risk as a result of ongoing change, suggesting that unless we successfully mitigate global environmental change, plant disease is going to become an increasingly heavy burden on our societies with far-reaching consequences for food security and functioning of ecosystems.
Collapse
Affiliation(s)
- Anna-Liisa Laine
- Department of Evolutionary Biology and Environmental Studies, University of Zürich, 8057 Zürich, Switzerland; Research Centre for Ecological Change, Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, PO BOX 65 00014, University of Helsinki, Helsinki, Finland.
| |
Collapse
|
3
|
Eck JL, Barrès B, Soubeyrand S, Sirén J, Numminen E, Laine AL. Strain Diversity and Spatial Distribution Are Linked to Epidemic Dynamics in Host Populations. Am Nat 2022; 199:59-74. [DOI: 10.1086/717179] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
4
|
Potter JJ, Tan S, Penczykowski RM. Robotany: A portable, low‐cost platform for precise automated aerial imaging of field plots. Methods Ecol Evol 2021. [DOI: 10.1111/2041-210x.13688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- James J. Potter
- Department of Mechanical Engineering and Materials Science Washington University in St. Louis St. Louis Missouri USA
- Tyson Research Center Washington University in St. Louis Eureka Missouri USA
| | - Sylvia Tan
- Department of Mechanical Engineering and Materials Science Washington University in St. Louis St. Louis Missouri USA
- Department of Mechanical Engineering Northwestern University Evanston Illinois USA
| | - Rachel M. Penczykowski
- Department of Biology Washington University in St. Louis St. Louis Missouri USA
- Tyson Research Center Washington University in St. Louis Eureka Missouri USA
| |
Collapse
|
5
|
Turner WC, Kamath PL, van Heerden H, Huang YH, Barandongo ZR, Bruce SA, Kausrud K. The roles of environmental variation and parasite survival in virulence-transmission relationships. R Soc Open Sci 2021; 8:210088. [PMID: 34109041 PMCID: PMC8170194 DOI: 10.1098/rsos.210088] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Disease outbreaks are a consequence of interactions among the three components of a host-parasite system: the infectious agent, the host and the environment. While virulence and transmission are widely investigated, most studies of parasite life-history trade-offs are conducted with theoretical models or tractable experimental systems where transmission is standardized and the environment controlled. Yet, biotic and abiotic environmental factors can strongly affect disease dynamics, and ultimately, host-parasite coevolution. Here, we review research on how environmental context alters virulence-transmission relationships, focusing on the off-host portion of the parasite life cycle, and how variation in parasite survival affects the evolution of virulence and transmission. We review three inter-related 'approaches' that have dominated the study of the evolution of virulence and transmission for different host-parasite systems: (i) evolutionary trade-off theory, (ii) parasite local adaptation and (iii) parasite phylodynamics. These approaches consider the role of the environment in virulence and transmission evolution from different angles, which entail different advantages and potential biases. We suggest improvements to how to investigate virulence-transmission relationships, through conceptual and methodological developments and taking environmental context into consideration. By combining developments in life-history evolution, phylogenetics, adaptive dynamics and comparative genomics, we can improve our understanding of virulence-transmission relationships across a diversity of host-parasite systems that have eluded experimental study of parasite life history.
Collapse
Affiliation(s)
- Wendy C. Turner
- US Geological Survey, Wisconsin Cooperative Wildlife Research Unit, Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Pauline L. Kamath
- School of Food and Agriculture, University of Maine, Orono, ME 04469, USA
| | - Henriette van Heerden
- Faculty of Veterinary Science, Department of Veterinary Tropical Diseases, University of Pretoria, Onderstepoort, South Africa
| | - Yen-Hua Huang
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Zoe R. Barandongo
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Spencer A. Bruce
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY 12222, USA
| | - Kyrre Kausrud
- Section for Epidemiology, Norwegian Veterinary Institute, Ullevålsveien 68, 0454 Oslo, Norway
| |
Collapse
|
6
|
Penczykowski RM, Sieg RD. Plantago spp. as Models for Studying the Ecology and Evolution of Species Interactions across Environmental Gradients. Am Nat 2021; 198:158-176. [PMID: 34143715 DOI: 10.1086/714589] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractA central challenge in ecology and evolutionary biology is to understand how variation in abiotic and biotic factors combine to shape the distribution, abundance, and diversity of focal species. Environmental gradients, whether natural (e.g., latitude, elevation, ocean proximity) or anthropogenic (e.g., land-use intensity, urbanization), provide compelling settings for addressing this challenge. However, not all organisms are amenable to the observational and experimental approaches required for untangling the factors that structure species along gradients. Here we highlight herbaceous plants in the genus Plantago as models for studying the ecology and evolution of species interactions along abiotic gradients. Plantago lanceolata and P. major are native to Europe and Asia but distributed globally, and they are established models for studying population ecology and interactions with herbivores, pathogens, and soil microbes. Studying restricted range congeners in comparison with those cosmopolitan species can provide insight into abiotic and biotic determinants of range size and population structure. We highlight one such species, P. rugelii, which is endemic to eastern North America. We give an overview of the literature on these focal Plantago species and explain why they are logical candidates for studies of species interactions across environmental gradients. Finally, we emphasize collaborative and community science approaches that can facilitate such research and note the amenability of Plantago for authentic research projects in science education.
Collapse
|
7
|
Malta KK, Silva TP, Palazzi C, Neves VH, Carmo LAS, Cardoso SJ, Melo RCN. Changing our view of the Schistosoma granuloma to an ecological standpoint. Biol Rev Camb Philos Soc 2021; 96:1404-1420. [PMID: 33754464 DOI: 10.1111/brv.12708] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 02/26/2021] [Accepted: 03/01/2021] [Indexed: 12/27/2022]
Abstract
Schistosomiasis, a neglected parasitic tropical disease that has plagued humans for centuries, remains a major public health burden. A primary challenge to understanding schistosomiasis is deciphering the most remarkable pathological feature of this disease, the granuloma - a highly dynamic and self-organized structure formed by both host and parasite components. Granulomas are considered a remarkable example of how parasites evolved with their hosts to establish complex and intimate associations. However, much remains unclear regarding life within the granuloma, and strategies to restrain its development are still lacking. Here we explore current information on the hepatic Schistosoma mansoni granuloma in the light of Ecology and propose that this intricate structure acts as a real ecosystem. The schistosomal granuloma is formed by cells (biotic component), protein scaffolds, fibres, and chemical compounds (abiotic components) with inputs/outputs of energy and matter, as complex as in classical ecosystems. We review the distinct cell populations ('species') within the granuloma and examine how they integrate with each other and interact with their microenvironment to form a multifaceted cell community in different space-time frames. The colonization of the hepatic tissue to form granulomas is explained from the point of view of an ecological succession whereby a community is able to modify its physical environment, creating conditions and resources for ecosystem construction. Remarkably, the granuloma represents a dynamic evolutionary system that undergoes progressive changes in the 'species' that compose its community over time. In line with ecological concepts, we examine the granuloma not only as a place where a community of cells is settled (spatial niche or habitat) but also as a site in which the functional activities of these combined populations occur in an orchestrated way in response to microenvironmental gradients such as cytokines and egg antigens. Finally, we assert how the levels of organization of cellular components in a granuloma as conventionally defined by Cell Biology can fit perfectly into a hierarchical structure of biological systems as defined by Ecology. By rethinking the granuloma as an integrating and evolving ecosystem, we draw attention to the inner workings of this structure that are central to the understanding of schistosomiasis and could guide its future treatment.
Collapse
Affiliation(s)
- Kássia K Malta
- Laboratory of Cellular Biology, Department of Biology, Federal University of Juiz de Fora, Rua José Lourenço Kelmer, São Pedro, Juiz de Fora, MG, 36036-900, Brazil.,Graduate Program in Biodiversity, Federal University of Juiz de Fora, Rua José Lourenço Kelmer, São Pedro, Juiz de Fora, MG, 36036-900, Brazil
| | - Thiago P Silva
- Laboratory of Cellular Biology, Department of Biology, Federal University of Juiz de Fora, Rua José Lourenço Kelmer, São Pedro, Juiz de Fora, MG, 36036-900, Brazil.,Graduate Program in Biodiversity, Federal University of Juiz de Fora, Rua José Lourenço Kelmer, São Pedro, Juiz de Fora, MG, 36036-900, Brazil
| | - Cinthia Palazzi
- Laboratory of Cellular Biology, Department of Biology, Federal University of Juiz de Fora, Rua José Lourenço Kelmer, São Pedro, Juiz de Fora, MG, 36036-900, Brazil.,Graduate Program in Cell Biology, Federal University of Minas Gerais, Belo Horizonte, Av. Antônio Carlos, 6627, Pampulha, Belo Horizonte, MG, 31270-901, Brazil
| | - Vitor H Neves
- Laboratory of Cellular Biology, Department of Biology, Federal University of Juiz de Fora, Rua José Lourenço Kelmer, São Pedro, Juiz de Fora, MG, 36036-900, Brazil.,Graduate Program in Cell Biology, Federal University of Minas Gerais, Belo Horizonte, Av. Antônio Carlos, 6627, Pampulha, Belo Horizonte, MG, 31270-901, Brazil
| | - Lívia A S Carmo
- Laboratory of Cellular Biology, Department of Biology, Federal University of Juiz de Fora, Rua José Lourenço Kelmer, São Pedro, Juiz de Fora, MG, 36036-900, Brazil.,Department of Medicine, Federal University of Alagoas, Rodovia AL-115, Bom Sucesso, Arapiraca, AL, 57309-005, Brazil
| | - Simone J Cardoso
- Graduate Program in Biodiversity, Federal University of Juiz de Fora, Rua José Lourenço Kelmer, São Pedro, Juiz de Fora, MG, 36036-900, Brazil.,Laboratory of Plankton Ecology, Department of Zoology, Federal University of Juiz de Fora, Rua José Lourenço Kelmer, São Pedro, Juiz de Fora, MG, 36036-900, Brazil
| | - Rossana C N Melo
- Laboratory of Cellular Biology, Department of Biology, Federal University of Juiz de Fora, Rua José Lourenço Kelmer, São Pedro, Juiz de Fora, MG, 36036-900, Brazil.,Graduate Program in Biodiversity, Federal University of Juiz de Fora, Rua José Lourenço Kelmer, São Pedro, Juiz de Fora, MG, 36036-900, Brazil.,Graduate Program in Cell Biology, Federal University of Minas Gerais, Belo Horizonte, Av. Antônio Carlos, 6627, Pampulha, Belo Horizonte, MG, 31270-901, Brazil
| |
Collapse
|
8
|
Karvonen A, Räihä V, Klemme I, Ashrafi R, Hyvärinen P, Sundberg LR. Quantity and Quality of Aquaculture Enrichments Influence Disease Epidemics and Provide Ecological Alternatives to Antibiotics. Antibiotics (Basel) 2021; 10:antibiotics10030335. [PMID: 33810018 PMCID: PMC8004632 DOI: 10.3390/antibiotics10030335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 03/10/2021] [Accepted: 03/16/2021] [Indexed: 11/16/2022] Open
Abstract
Environmental heterogeneity is a central component influencing the virulence and epidemiology of infectious diseases. The number and distribution of susceptible hosts determines disease transmission opportunities, shifting the epidemiological threshold between the spread and fadeout of a disease. Similarly, the presence and diversity of other hosts, pathogens and environmental microbes, may inhibit or accelerate an epidemic. This has important applied implications in farming environments, where high numbers of susceptible hosts are maintained in conditions of minimal environmental heterogeneity. We investigated how the quantity and quality of aquaculture enrichments (few vs. many stones; clean stones vs. stones conditioned in lake water) influenced the severity of infection of a pathogenic bacterium, Flavobacterium columnare, in salmonid fishes. We found that the conditioning of the stones significantly increased host survival in rearing tanks with few stones. A similar effect of increased host survival was also observed with a higher number of unconditioned stones. These results suggest that a simple increase in the heterogeneity of aquaculture environment can significantly reduce the impact of diseases, most likely operating through a reduction in pathogen transmission (stone quantity) and the formation of beneficial microbial communities (stone quality). This supports enriched rearing as an ecological and economic way to prevent bacterial infections with the minimal use of antimicrobials.
Collapse
Affiliation(s)
- Anssi Karvonen
- Department of Biological and Environmental Science, University of Jyvaskyla, P.O. Box 35, 40014 Jyvaskyla, Finland; (V.R.); (I.K.); (R.A.); (L.-R.S.)
- Correspondence: ; Tel.: +358-40-8053882; Fax: +358-14-2601021
| | - Ville Räihä
- Department of Biological and Environmental Science, University of Jyvaskyla, P.O. Box 35, 40014 Jyvaskyla, Finland; (V.R.); (I.K.); (R.A.); (L.-R.S.)
| | - Ines Klemme
- Department of Biological and Environmental Science, University of Jyvaskyla, P.O. Box 35, 40014 Jyvaskyla, Finland; (V.R.); (I.K.); (R.A.); (L.-R.S.)
| | - Roghaieh Ashrafi
- Department of Biological and Environmental Science, University of Jyvaskyla, P.O. Box 35, 40014 Jyvaskyla, Finland; (V.R.); (I.K.); (R.A.); (L.-R.S.)
| | - Pekka Hyvärinen
- Natural Resources and Bioproduction, Natural Resources Institute Finland (Luke), Manamansalontie 90, 88300 Paltamo, Finland;
| | - Lotta-Riina Sundberg
- Department of Biological and Environmental Science, University of Jyvaskyla, P.O. Box 35, 40014 Jyvaskyla, Finland; (V.R.); (I.K.); (R.A.); (L.-R.S.)
- Nanoscience Center, University of Jyvaskyla, P.O. Box 35, 40014 Jyvaskyla, Finland
| |
Collapse
|
9
|
Papaïx J, Burdon JJ, Walker E, Barrett LG, Thrall PH. Metapopulation Structure Predicts Population Dynamics in the Cakile maritima- Alternaria brassicicola Host-Pathogen Interaction. Am Nat 2021; 197:E55-E71. [PMID: 33523787 DOI: 10.1086/712248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractIn symbiotic interactions, spatiotemporal variation in the distribution or population dynamics of one species represents spatial and temporal heterogeneity of the landscape for the other. Such interdependent demographic dynamics result in situations where the relative importance of biotic and abiotic factors in determining ecological processes is complicated to decipher. Using a detailed survey of three metapopulations of the succulent plant Cakile maritima and the necrotrophic fungus Alternaria brassicicola located along the southeastern Australian coast, we developed a series of statistical analyses-namely, synchrony analysis, patch occupancy dynamics, and a spatially explicit metapopulation model-to understand how habitat quality, weather conditions, dispersal, and spatial structure determine metapopulation dynamics. Climatic conditions are important drivers, likely explaining the high synchrony among populations. Host availability, landscape features facilitating dispersal, and habitat conditions also impact the occurrence and spread of disease. Overall, we show that the collection of extensive data on host and pathogen population dynamics, in combination with spatially explicit epidemiological modeling, makes it possible to accurately predict disease dynamics-even when there is extreme variability in host population dynamics. Finally, we discuss the importance of genetic information for predicting demographic dynamics in this pathosystem.
Collapse
|
10
|
Halliday FW, Penczykowski RM, Barrès B, Eck JL, Numminen E, Laine AL. Facilitative priority effects drive parasite assembly under coinfection. Nat Ecol Evol 2020; 4:1510-21. [PMID: 32868915 DOI: 10.1038/s41559-020-01289-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 07/22/2020] [Indexed: 12/14/2022]
Abstract
Host individuals are often coinfected with diverse parasite assemblages, resulting in complex interactions among parasites within hosts. Within hosts, priority effects occur when the infection sequence alters the outcome of interactions among parasites. Yet, the role of host immunity in this process remains poorly understood. We hypothesized that the host response to the first infection could generate priority effects among parasites, altering the assembly of later-arriving strains during epidemics. We tested this by infecting sentinel host genotypes of Plantago lanceolata with strains of the fungal parasite Podosphaera plantaginis and measuring susceptibility to subsequent infection during experimental and natural epidemics. In these experiments, prior infection by one strain often increased susceptibility to other strains, and these facilitative priority effects altered the structure of parasite assemblages, but this effect depended on host genotype, host population and parasite genotype. Thus, host genotype, spatial structure and priority effects among strains all independently altered parasite assembly. Using a fine-scale survey and sampling of infections on wild hosts in several populations, we then identified a signal of facilitative priority effects, which altered parasite assembly during natural epidemics. Together, these results provide evidence that within-host priority effects of early-arriving strains can drive parasite assembly, with implications for how strain diversity is spatially and temporally distributed during epidemics.
Collapse
|
11
|
Karasov TL, Shirsekar G, Schwab R, Weigel D. What natural variation can teach us about resistance durability. Curr Opin Plant Biol 2020; 56:89-98. [PMID: 32535454 DOI: 10.1016/j.pbi.2020.04.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 04/08/2020] [Accepted: 04/18/2020] [Indexed: 06/11/2023]
Abstract
Breeding a crop variety to be resistant to a pathogen usually takes years. This is problematic because pathogens, with short generation times and fluid genomes, adapt quickly to overcome resistance. The triumph of the pathogen is not inevitable, however, as there are numerous examples of durable resistance, particularly in wild plants. Which factors then contribute to such resistance stability over millennia? We review current knowledge of wild and agricultural pathosystems, detailing the importance of genetic, species and spatial heterogeneity in the prevention of pathogen outbreaks. We also highlight challenges associated with increasing resistance diversity in crops, both in light of pathogen (co-)evolution and breeding practices. Historically it has been difficult to incorporate heterogeneity into agriculture due to reduced efficiency in harvesting. Recent advances implementing computer vision and automation in agricultural production may improve our ability to harvest mixed genotype and mixed species plantings, thereby increasing resistance durability.
Collapse
Affiliation(s)
- Talia L Karasov
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Gautam Shirsekar
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Rebecca Schwab
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Detlef Weigel
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.
| |
Collapse
|
12
|
Laine AL, Barrès B, Numminen E, Siren JP. Variable opportunities for outcrossing result in hotspots of novel genetic variation in a pathogen metapopulation. eLife 2019; 8:47091. [PMID: 31210640 PMCID: PMC6667214 DOI: 10.7554/elife.47091] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 06/18/2019] [Indexed: 11/17/2022] Open
Abstract
Many pathogens possess the capacity for sex through outcrossing, despite being able to reproduce also asexually and/or via selfing. Given that sex is assumed to come at a cost, these mixed reproductive strategies typical of pathogens have remained puzzling. While the ecological and evolutionary benefits of outcrossing are theoretically well-supported, support for such benefits in pathogen populations are still scarce. Here, we analyze the epidemiology and genetic structure of natural populations of an obligate fungal pathogen, Podosphaera plantaginis. We find that the opportunities for outcrossing vary spatially. Populations supporting high levels of coinfection –a prerequisite of sex – result in hotspots of novel genetic diversity. Pathogen populations supporting coinfection also have a higher probability of surviving winter. Jointly our results show that outcrossing has direct epidemiological consequences as well as a major impact on pathogen population genetic diversity, thereby providing evidence of ecological and evolutionary benefits of outcrossing in pathogens. The existence of sex – broadly defined as the coming together of genes from different individuals – is one of the big evolutionary puzzles. Reproduction allows an organism to pass on its genes to future generations. However, while asexual and self-fertilizing individuals transmit all of their genes to their offspring, individuals that reproduce through sex transmit only half of their genome. This is considered the cost of sex. Many pathogens reproduce through sex, despite often also being able to reproduce asexually or by self-fertilization. Typically a pre-requisite of sex in pathogens is for at least two different strains to infect the same host. Aside from this limitation, little is known about when, where and why pathogens have sex. It has been tricky to study due to the microscopic size of pathogens and the difficulties of identifying different sexes. Moreover, sexual reproduction may be triggered by environmental cues that are difficult to mimic under controlled experimental conditions. Are there any benefits associated with pathogen sex? To find out, Laine et al. analyzed data collected over the course of four years from thousands of populations of a powdery mildew fungus that infected plants across the Åland islands. This revealed that the opportunities for pathogen sex vary in different locations. Areas where multiple strains of the fungus commonly infect the same plants result in hotspots of new genetic diversity. These mixed populations are also more likely to survive winter. This demonstrates the potential for pathogen sexual reproduction to provide an ecological benefit. Identifying areas and populations where pathogens have sex can help to identify when and where new strains are most likely to emerge. In the future, studies that use similar methods to Laine et al. could help to predict where infections and diseases are highly likely to arise.
Collapse
Affiliation(s)
- Anna-Liisa Laine
- Research Centre for Ecological Change, Organismal and Evolutionary Biology, University of Helsinki, Helsinki, Finland.,Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse, Switzerland
| | - Benoit Barrès
- Research Centre for Ecological Change, Organismal and Evolutionary Biology, University of Helsinki, Helsinki, Finland
| | - Elina Numminen
- Research Centre for Ecological Change, Organismal and Evolutionary Biology, University of Helsinki, Helsinki, Finland
| | - Jukka P Siren
- Research Centre for Ecological Change, Organismal and Evolutionary Biology, University of Helsinki, Helsinki, Finland.,Helsinki Institute for Information Technology, Department of Computer Science, Aalto University, Espoo, Finland
| |
Collapse
|