1
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Buss N, Hua J. Host exposure to a common pollutant can influence diversity-disease relationships. J Anim Ecol 2023; 92:2151-2162. [PMID: 37587564 DOI: 10.1111/1365-2656.13988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 05/15/2023] [Indexed: 08/18/2023]
Abstract
Hosts and parasites are embedded in communities where species richness and composition can influence disease outcomes (diversity-disease relationships). The direction and magnitude of diversity-disease relationships are influenced by variation in competence (ability to support and transmit infections) of hosts in a community. However, host susceptibility to parasites, which mediates host competence, is not static and is influenced by environmental factors, including pollutants. Despite the role that pollutants can play in augmenting host susceptibility, how pollutants influence diversity-disease dynamics is not well understood. Using an amphibian-trematode model, we tested how NaCl influences diversity-disease dynamics. We predicted that NaCl exposure can alter relative susceptibility of host species to trematodes, leading to cascading effects on the diversity-disease relationship. To test these predictions, we exposed hosts to benign or NaCl environments and generated communities that differed in number and composition of host species. We exposed these communities to trematodes and measured disease outcomes at the community (total infections across all hosts within a community) and species levels (average number of infections per host species within a community). Host species differed in their relative susceptibility to trematodes when exposed to NaCl. Consequently, at the community level (total infections across all hosts within a community), we only detected diversity-disease relationships (dilution effects) in communities where hosts were exposed to NaCl. At the species level, disease outcomes (average number of infections/species) and whether multi-species communities supported lower number of infections relative to single-species communities depended on community composition. Notably, however, as with overall community infection, diversity-disease relationships only emerged when hosts were exposed to NaCl. Synthesis. Pollutants are ubiquitous in nature and can influence disease dynamics across a number of host-parasite systems. Here, we show that NaCl exposure can alter the relative susceptibility of host species to parasites, influencing the relationship between biodiversity and disease at both community and species levels. Collectively, our study contributes to the limited knowledge surrounding environmental mediators of host susceptibility and their influence on diversity-disease dynamics.
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Affiliation(s)
- Nicholas Buss
- Department of Biological Sciences, Binghamton University (SUNY), Binghamton, New York, USA
| | - Jessica Hua
- Department of Biological Sciences, Binghamton University (SUNY), Binghamton, New York, USA
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin, USA
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2
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Atkinson MS, Savage AE. Widespread amphibian Perkinsea infections associated with Ranidae hosts, cooler months and Ranavirus co-infection. J Anim Ecol 2023; 92:1856-1868. [PMID: 37409362 DOI: 10.1111/1365-2656.13977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 05/26/2023] [Indexed: 07/07/2023]
Abstract
Amphibians suffer from large-scale population declines globally, and emerging infectious diseases contribute heavily to these declines. Amphibian Perkinsea (Pr) is a worldwide anuran pathogen associated with mass mortality events, yet little is known about its epidemiological patterns, especially in comparison to the body of literature on amphibian chytridiomycosis and ranavirosis. Here, we establish Pr infection patterns in natural anuran populations and identify important covariates including climate, host attributes and co-infection with Ranavirus (Rv). We used quantitative (q)PCR to determine the presence and intensity of Pr and Rv across 1234 individuals sampled throughout central Florida in 2017-2019. We then implemented random forest ensemble learning models to predict infection with both pathogens based on physiological and environmental characteristics. Perkinsea infected 32% of all sampled anurans, and Pr prevalence was significantly elevated in Ranidae frogs, cooler months, metamorphosed individuals and frogs co-infected with Rv, while Pr intensity was significantly higher in ranid frogs and individuals collected dead. Ranavirus prevalence was 17% overall and was significantly higher in Ranidae frogs, metamorphosed individuals, locations with higher average temperatures, and individuals co-infected with Pr. Perkinsea prevalence was significantly higher than Rv prevalence across months, regions, life stages and species. Among locations, Pr prevalence was negatively associated with crayfish prevalence and positively associated with relative abundance of microhylids, but Rv prevalence did not associate with any tested co-variates. Co-infections were significantly more common than single infections for both pathogens, and we propose that Pr infections may propel Rv infections because seasonal Rv infection peaks followed Pr infection peaks and random forest models found Pr intensity was a leading factor explaining Rv infections. Our study elucidates epidemiological patterns of Pr in Florida and suggests that Pr may be under-recognized as a cause of anuran declines, especially in the context of pathogen co-infection.
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Affiliation(s)
- Matthew S Atkinson
- Department of Biology, University of Central Florida, Orlando, Florida, USA
| | - Anna E Savage
- Department of Biology, University of Central Florida, Orlando, Florida, USA
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3
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Snyder PW, Ramsay CT, Harjoe CC, Khazan ES, Briggs CJ, Hoverman JT, Johnson PTJ, Preston D, Rohr JR, Blaustein AR. Experimental evidence that host species composition alters host-pathogen dynamics in a ranavirus-amphibian assemblage. Ecology 2023; 104:e3885. [PMID: 36217286 PMCID: PMC9898091 DOI: 10.1002/ecy.3885] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 08/12/2022] [Accepted: 08/19/2022] [Indexed: 02/06/2023]
Abstract
Losses in biodiversity can alter disease risk through changes in host species composition. Host species vary in pathogen susceptibility and competence, yet how changes in diversity alter host-pathogen dynamics remains unclear in many systems, particularly with respect to generalist pathogens. Amphibians are experiencing worldwide population declines linked to generalist pathogens, such as ranavirus, and thus represent an ideal group to investigate how host species composition affects disease risk. We conducted experiments in which amphibian larvae of three native species (Pacific tree frogs, Pseudacris regilla; Cascades frogs, Rana cascadae; and Western toads, Anaxyrus boreas) were exposed to ranavirus individually (in the laboratory) or as assemblages (in outdoor mesocosms). In a laboratory experiment, we observed low survival and high viral loads in P. regilla compared to the other species, suggesting that this species was highly susceptible to the pathogen. In the mesocosm experiment, we observed 41% A. boreas mortality when alone and 98% mortality when maintained with P. regilla and R. cascadae. Our results suggest that the presence of highly susceptible species can alter disease dynamics across multiple species, potentially increasing infection risk and mortality in co-occurring species.
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Affiliation(s)
- Paul W Snyder
- Integrative Biology, Oregon State University, Corvallis, Oregon, USA
| | - Chloe T Ramsay
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
| | - Carmen C Harjoe
- Integrative Biology, Oregon State University, Corvallis, Oregon, USA
| | - Emily S Khazan
- School of Natural Resources and Environment, University of Florida, Gainesville, Florida, USA
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Jason Todd Hoverman
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, Indiana, USA
| | - Pieter T J Johnson
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, USA
| | - Daniel Preston
- Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Jason R Rohr
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
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4
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Daversa D, Bosch J, Manica A, Garner TWJ, Fenton A. Host identity matters – up to a point: the community context of Batrachochytrium dendrobatidis transmission. Am Nat 2022; 200:584-597. [DOI: 10.1086/720638] [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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5
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Bienentreu JF, Schock DM, Greer AL, Lesbarrères D. Ranavirus Amplification in Low-Diversity Amphibian Communities. Front Vet Sci 2022; 9:755426. [PMID: 35224079 PMCID: PMC8863596 DOI: 10.3389/fvets.2022.755426] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Accepted: 01/03/2022] [Indexed: 11/13/2022] Open
Abstract
In an era where emerging infectious diseases are a serious threat to biodiversity, epidemiological patterns need to be identified, particularly the complex mechanisms driving the dynamics of multi-host pathogens in natural communities. Many amphibian species have faced unprecedented population declines associated with diseases. Yet, specific processes shaping host-pathogen relationships within and among communities for amphibian pathogens such as ranaviruses (RV) remain poorly understood. To address this gap, we conducted a comprehensive study of RV in low-diversity amphibian communities in north-western Canada to assess the effects of biotic factors (species identity, species richness, abundance) and abiotic factors (conductivity, pH) on the pathogen prevalence and viral loads. Across 2 years and 18 sites, with communities of up to three hosts (wood frog, Rana sylvatica; boreal chorus frog, Pseudacris maculata; Canadian toad, Anaxyrus hemiophrys), we observed that RV prevalence nearly doubled with each additional species in a community, suggesting an amplification effect in aquatic, as well as terrestrial life-history stages. Infection intensity among infected wood frogs and boreal chorus frogs also significantly increased with an increase in species richness. Interestingly, we did not observe any effects of host abundance or abiotic factors, highlighting the importance of including host identity and species richness when investigating multi-host pathogens. Ultimately, only such a comprehensive approach can improve our understanding of complex and often highly context-dependent host-pathogen interactions.
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Affiliation(s)
- Joe-Felix Bienentreu
- Department of Biology, Laurentian University, Sudbury, ON, Canada
- *Correspondence: Joe-Felix Bienentreu
| | - Danna M. Schock
- Sciences and Environmental Technology, Keyano College, Fort McMurray, AB, Canada
| | - Amy L. Greer
- Department of Population Medicine, University of Guelph, Guelph, ON, Canada
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6
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Espira LM, Brouwer AF, Han BA, Foufopoulos J, Eisenberg JNS. Dilution of Epidemic Potential of Environmentally Transmitted Infectious Diseases for Species with Partially Overlapping Habitats. Am Nat 2022; 199:E43-E56. [PMID: 35077275 PMCID: PMC9136953 DOI: 10.1086/717413] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/27/2023]
Abstract
AbstractSpecies diversity may play an important role in the modulation of pathogen transmission through the dilution effect. Infectious disease models can help elucidate mechanisms that may underlie this effect. While many modeling studies have assumed direct host-to-host transmission, many pathogens are transmitted through the environment. We present a mathematical modeling analysis exploring conditions under which we observe the dilution effect in systems with environmental transmission where host species interact through fully or partially overlapping habitats. We measure the strength of the dilution effect by the relative decrease in the basic reproduction number of two-species assemblages compared with that of a focal host species. We find that a dilution effect is most likely when the pathogen is environmentally persistent (frequency-dependent-like transmission). The magnitude of this effect is strongest when the species with the greater epidemic potential is relatively slow to pick up pathogens in the environment (density-dependent transmission) and the species with the lesser epidemic potential is efficient at picking up pathogens (frequency-dependent transmission). These findings suggest that measurable factors, including pathogen persistence and the host's relative efficiency of pathogen pickup, can guide predictions of when biodiversity might lead to a dilution effect and may thus give concrete direction to future ecological work.
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Affiliation(s)
- Leon M. Espira
- Department of Epidemiology, University of Michigan, Ann Arbor, MI 48109
| | - Andrew F. Brouwer
- Department of Epidemiology, University of Michigan, Ann Arbor, MI 48109
| | - Barbara A. Han
- Cary Institute of Ecosystem Studies, Millbrook, NY 12545
| | - Johannes Foufopoulos
- School for Environment and Sustainability, University of Michigan, Ann Arbor, MI 48109
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7
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Garrido M, Halle S, Flatau R, Cohen C, Navarro-Castilla Á, Barja I, Hawlena H. The dilution effect behind the scenes: testing the underlying assumptions of its mechanisms through quantifying the long-term dynamics and effects of a pathogen in multiple host species. Proc Biol Sci 2021; 288:20210773. [PMID: 34102894 PMCID: PMC8187991 DOI: 10.1098/rspb.2021.0773] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 05/12/2021] [Indexed: 01/01/2023] Open
Abstract
Disentangling the mechanisms that mediate the relationships between species diversity and disease risk has both theoretical and applied implications. We employed a model system of rodents and their Mycoplasma pathogens, in which an extreme negative diversity-disease relationship was demonstrated, to test the assumptions underlying three mechanisms that may explain this field pattern. Through quantifying the long-term dynamics and effects of the pathogen in its three host species, we estimated the between-host differences in pathogen spreading and transmission potentials, and host recovery potential and vulnerability to infection. The results suggest that one of the hosts is a pathogen amplifier and the other two hosts function as diluters. Considering the similarity in infection success and intensity among hosts, and the failure to detect any pathogen-induced damage, we could not validate the assumption underlying the hypotheses that diluters reduce the overall transmission or increase the mortality of infected hosts in the system. Instead, the results demonstrate that diluters clear the infection faster than amplifiers, supporting the possibility that the addition of diluters to the community may reduce the overall number of infected hosts through this mechanism. This study highlights the contribution of experimental studies that simultaneously explore different aspects of host-pathogen interactions in multiple hosts, in diversity-disease research.
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Affiliation(s)
- Mario Garrido
- Jacob Blaustein Center for Scientific Cooperation, Ben-Gurion University of the Negev, 849900 Midreshet Ben-Gurion, Israel
| | - Snir Halle
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 849900 Midreshet Ben-Gurion, Israel
| | - Ron Flatau
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 849900 Midreshet Ben-Gurion, Israel
| | - Carmit Cohen
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 849900 Midreshet Ben-Gurion, Israel
| | - Álvaro Navarro-Castilla
- Etho-Physiology Group. Unit of Zoology. Department of Biology. Faculty of Sciences, the Autonomous University of Madrid, Spain
| | - Isabel Barja
- Etho-Physiology Group. Unit of Zoology. Department of Biology. Faculty of Sciences, the Autonomous University of Madrid, Spain
- Center for Research on Biodiversity and Global Change (CIBC-UAM), the Autonomous University of Madrid, Spain
| | - Hadas Hawlena
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 849900 Midreshet Ben-Gurion, Israel
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8
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Burns TJ, Scheele BC, Brannelly LA, Clemann N, Gilbert D, Driscoll DA. Indirect terrestrial transmission of amphibian chytrid fungus from reservoir to susceptible host species leads to fatal chytridiomycosis. Anim Conserv 2020. [DOI: 10.1111/acv.12665] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Thomas J. Burns
- Centre for Integrative Ecology School of Life and Environmental Sciences Deakin University (Burwood Campus) Geelong Vic. Australia
| | - Ben C. Scheele
- Fenner School of Environment and Society Australian National University Canberra ACT Australia
| | - Laura A. Brannelly
- Melbourne Veterinary School Faculty of Veterinary and Agricultural Sciences University of Melbourne Werribee Vic. Australia
| | - Nick Clemann
- Department of Environment, Land, Water and Planning Arthur Rylah Institute for Environmental Research Heidelberg Vic. Australia
| | - Deon Gilbert
- Wildlife Conservation and Science. Zoos Victoria Parkville Vic. Australia
| | - Don A. Driscoll
- Centre for Integrative Ecology School of Life and Environmental Sciences Deakin University (Burwood Campus) Geelong Vic. Australia
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9
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Halliday FW, Rohr JR, Laine A. Biodiversity loss underlies the dilution effect of biodiversity. Ecol Lett 2020; 23:1611-1622. [PMID: 32808427 PMCID: PMC7693066 DOI: 10.1111/ele.13590] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 06/14/2020] [Accepted: 07/16/2020] [Indexed: 01/16/2023]
Abstract
The dilution effect predicts increasing biodiversity to reduce the risk of infection, but the generality of this effect remains unresolved. Because biodiversity loss generates predictable changes in host community competence, we hypothesised that biodiversity loss might drive the dilution effect. We tested this hypothesis by reanalysing four previously published meta-analyses that came to contradictory conclusions regarding generality of the dilution effect. In the context of biodiversity loss, our analyses revealed a unifying pattern: dilution effects were inconsistently observed for natural biodiversity gradients, but were commonly observed for biodiversity gradients generated by disturbances causing losses of biodiversity. Incorporating biodiversity loss into tests of generality of the dilution effect further indicated that scale-dependency may strengthen the dilution effect only when biodiversity gradients are driven by biodiversity loss. Together, these results help to resolve one of the most contentious issues in disease ecology: the generality of the dilution effect.
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Affiliation(s)
- Fletcher W. Halliday
- Department of Evolutionary Biology and Environmental StudiesUniversity of ZurichZurich8057Switzerland
| | - Jason R. Rohr
- Department of Biological SciencesEck Institute of Global HealthEnvironmental Change InitiativeUniversity of Notre DameNotre DameINUSA
| | - Anna‐Liisa Laine
- Department of Evolutionary Biology and Environmental StudiesUniversity of ZurichZurich8057Switzerland
- Organismal & Evolutionary Biology Research ProgramUniversity of HelsinkiPO Box 65HelsinkiFI‐00014Finland
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10
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Halliday FW, Heckman RW, Wilfahrt PA, Mitchell CE. Eutrophication, biodiversity loss, and species invasions modify the relationship between host and parasite richness during host community assembly. GLOBAL CHANGE BIOLOGY 2020; 26:4854-4867. [PMID: 32427383 DOI: 10.1111/gcb.15165] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 04/02/2020] [Accepted: 05/12/2020] [Indexed: 06/11/2023]
Abstract
Host and parasite richness are generally positively correlated, but the stability of this relationship in response to global change remains poorly understood. Rapidly changing biotic and abiotic conditions can alter host community assembly, which in turn, can alter parasite transmission. Consequently, if the relationship between host and parasite richness is sensitive to parasite transmission, then changes in host composition under various global change scenarios could strengthen or weaken the relationship between host and parasite richness. To test the hypothesis that host community assembly can alter the relationship between host and parasite richness in response to global change, we experimentally crossed host diversity (biodiversity loss) and resource supply to hosts (eutrophication), then allowed communities to assemble. As previously shown, initial host diversity and resource supply determined the trajectory of host community assembly, altering post-assembly host species richness, richness-independent host phylogenetic diversity, and colonization by exotic host species. Overall, host richness predicted parasite richness, and as predicted, this effect was moderated by exotic abundance-communities dominated by exotic species exhibited a stronger positive relationship between post-assembly host and parasite richness. Ultimately, these results suggest that, by modulating parasite transmission, community assembly can modify the relationship between host and parasite richness. These results thus provide a novel mechanism to explain how global environmental change can generate contingencies in a fundamental ecological relationship-the positive relationship between host and parasite richness.
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Affiliation(s)
- Fletcher W Halliday
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Robert W Heckman
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Peter A Wilfahrt
- Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, NC, USA
- Department of Disturbance Ecology, University of Bayreuth, Bayreuth, Germany
| | - Charles E Mitchell
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
- Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, NC, USA
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11
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Bienentreu JF, Lesbarrères D. Amphibian Disease Ecology: Are We Just Scratching the Surface? HERPETOLOGICA 2020. [DOI: 10.1655/0018-0831-76.2.153] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
| | - David Lesbarrères
- Department of Biology, Laurentian University, Sudbury, ON P3E 2C6, Canada
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12
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Ribeiro JW, Siqueira T, DiRenzo GV, Lambertini C, Lyra ML, Toledo LF, Haddad CFB, Becker CG. Assessing amphibian disease risk across tropical streams while accounting for imperfect pathogen detection. Oecologia 2020; 193:237-248. [DOI: 10.1007/s00442-020-04646-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Accepted: 04/07/2020] [Indexed: 12/23/2022]
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13
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Becker CG, Bletz MC, Greenspan SE, Rodriguez D, Lambertini C, Jenkinson TS, Guimarães PR, Assis APA, Geffers R, Jarek M, Toledo LF, Vences M, Haddad CFB. Low-load pathogen spillover predicts shifts in skin microbiome and survival of a terrestrial-breeding amphibian. Proc Biol Sci 2019; 286:20191114. [PMID: 31409249 DOI: 10.1098/rspb.2019.1114] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Wildlife disease dynamics are strongly influenced by the structure of host communities and their symbiotic microbiota. Conspicuous amphibian declines associated with the waterborne fungal pathogen Batrachochytrium dendrobatidis (Bd) have been observed in aquatic-breeding frogs globally. However, less attention has been given to cryptic terrestrial-breeding amphibians that have also been declining in tropical regions. By experimentally manipulating multiple tropical amphibian assemblages harbouring natural microbial communities, we tested whether Bd spillover from naturally infected aquatic-breeding frogs could lead to Bd amplification and mortality in our focal terrestrial-breeding host: the pumpkin toadlet Brachycephalus pitanga. We also tested whether the strength of spillover could vary depending on skin bacterial transmission within host assemblages. Terrestrial-breeding toadlets acquired lethal spillover infections from neighbouring aquatic hosts and experienced dramatic but generally non-protective shifts in skin bacterial composition primarily attributable to their Bd infections. By contrast, aquatic-breeding amphibians maintained mild Bd infections and higher survival, with shifts in bacterial microbiomes that were unrelated to Bd infections. Our results indicate that Bd spillover from even mildly infected aquatic-breeding hosts may lead to dysbiosis and mortality in terrestrial-breeding species, underscoring the need to further investigate recent population declines of terrestrial-breeding amphibians in the tropics.
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Affiliation(s)
- C Guilherme Becker
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35847, USA
| | - Molly C Bletz
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Sasha E Greenspan
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35847, USA
| | - David Rodriguez
- Department of Biology, Texas State University, San Marcos, TX 78666, USA
| | - Carolina Lambertini
- Department of Animal Biology, Universidade Estadual de Campinas, Campinas, SP 13083-865, Brazil
| | - Thomas S Jenkinson
- Department of Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, CA 94720, USA
| | - Paulo R Guimarães
- Departamento de Ecologia, Universidade de Sao Paulo, Sao Paulo, SP 05508-090, Brazil
| | - Ana Paula A Assis
- Departamento de Ecologia, Universidade de Sao Paulo, Sao Paulo, SP 05508-090, Brazil
| | - Robert Geffers
- Department of Genome Analytics, Helmholtz Centre for Infection Research, Braunschweig, LS 38124, Germany
| | - Michael Jarek
- Department of Genome Analytics, Helmholtz Centre for Infection Research, Braunschweig, LS 38124, Germany
| | - Luís Felipe Toledo
- Department of Animal Biology, Universidade Estadual de Campinas, Campinas, SP 13083-865, Brazil
| | - Miguel Vences
- Division of Evolutionary Biology, Zoological Institute, Braunschweig University of Technology, Braunschweig, LS 38106, Germany
| | - Célio F B Haddad
- Department of Zoology and Aquaculture Center (CAUNESP), Universidade Estadual Paulista, Rio Claro, SP 13506-900, Brazil
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14
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Kirk D, Shea D, Start D. Host traits and competitive ability jointly structure disease dynamics and community assembly. J Anim Ecol 2019; 88:1379-1391. [PMID: 31120552 DOI: 10.1111/1365-2656.13028] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 04/03/2019] [Indexed: 01/13/2023]
Abstract
Parasitism and competition are both ubiquitous interactions in ecological communities. The ability of host species to interact directly via competition and indirectly through shared parasites suggests that host traits related to competition and parasitism are likely important in structuring communities and disease dynamics. Specifically, those host traits affecting competition and those mediating parasitism are often correlated either because of trade-offs (in resource acquisition or resource allocation) or condition dependence, yet the consequences of these trait relationships for community and epidemiological dynamics are poorly understood. We conducted a literature review of parasite-related host traits-competitive ability relationships. We found that transmission-competitive ability relationships were most often reported, and that superior competitors exhibited elevated transmission relative to their less-competitive counterparts in nearly 80% of the cases. We also found a significant number of virulence-competitive ability and parasite shedding-competitive ability relationships. We investigated these links by altering the relationship between host competitive ability and three parasite-related traits (transmission, virulence and parasite shedding rates) in a simple model, incorporating competitive asymmetries in a multi-host community. We show that these relationships can lead to a range of different communities. For example, depending on the strength and direction of these distinct trait relationships, we observed communities with anywhere from high parasite prevalence to complete parasite extinction, and either one, two or the maximum of three host species coexisting. Our results suggest that parasite-competitive ability relationships may be common in nature, that further integration of these relationships can produce novel and unexpected community and disease dynamics, and that generalizations may allow for the prediction of how parasitism and competition jointly structure disease and diversity in natural communities.
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Affiliation(s)
- Devin Kirk
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
| | - Dylan Shea
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
| | - Denon Start
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
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15
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Martin LB, Addison B, Bean AGD, Buchanan KL, Crino OL, Eastwood JR, Flies AS, Hamede R, Hill GE, Klaassen M, Koch RE, Martens JM, Napolitano C, Narayan EJ, Peacock L, Peel AJ, Peters A, Raven N, Risely A, Roast MJ, Rollins LA, Ruiz-Aravena M, Selechnik D, Stokes HS, Ujvari B, Grogan LF. Extreme Competence: Keystone Hosts of Infections. Trends Ecol Evol 2019; 34:303-314. [PMID: 30704782 PMCID: PMC7114649 DOI: 10.1016/j.tree.2018.12.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 12/10/2018] [Accepted: 12/13/2018] [Indexed: 12/20/2022]
Abstract
Individual hosts differ extensively in their competence for parasites, but traditional research has discounted this variation, partly because modeling such heterogeneity is difficult. This discounting has diminished as tools have improved and recognition has grown that some hosts, the extremely competent, can have exceptional impacts on disease dynamics. Most prominent among these hosts are the superspreaders, but other forms of extreme competence (EC) exist and others await discovery; each with potentially strong but distinct implications for disease emergence and spread. Here, we propose a framework for the study and discovery of EC, suitable for different host-parasite systems, which we hope enhances our understanding of how parasites circulate and evolve in host communities.
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Affiliation(s)
- Lynn B Martin
- Global and Planetary Health, University of South Florida, Tampa, Florida 33620, USA.
| | - BriAnne Addison
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds, VIC 3216, Australia
| | - Andrew G D Bean
- CSIRO Health & Biosecurity at the Australian Animal Health Laboratory, Geelong, VIC 3220, Australia
| | - Katherine L Buchanan
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds, VIC 3216, Australia
| | - Ondi L Crino
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds, VIC 3216, Australia
| | - Justin R Eastwood
- School of Biological Sciences, Monash University, VIC 3800, Australia
| | - Andrew S Flies
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS 7008, Australia
| | - Rodrigo Hamede
- School of Natural Sciences, University of Tasmania, Hobart, TAS 7001, Australia
| | - Geoffrey E Hill
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA
| | - Marcel Klaassen
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds, VIC 3216, Australia
| | - Rebecca E Koch
- School of Biological Sciences, Monash University, VIC 3800, Australia
| | - Johanne M Martens
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds, VIC 3216, Australia
| | | | - Edward J Narayan
- School of Science and Health, Western Sydney University, Penrith, NSW 2751, Australia
| | - Lee Peacock
- School of Biological Sciences, Monash University, VIC 3800, Australia
| | - Alison J Peel
- Environmental Futures Research Institute, Griffith University, Nathan, QLD 4111, Australia
| | - Anne Peters
- School of Biological Sciences, Monash University, VIC 3800, Australia
| | - Nynke Raven
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds, VIC 3216, Australia
| | - Alice Risely
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds, VIC 3216, Australia
| | - Michael J Roast
- School of Biological Sciences, Monash University, VIC 3800, Australia
| | - Lee A Rollins
- School of Biological, Earth and Environmental Sciences, Evolution & Ecology Research Centre, University of New South Wales, Sydney, NSW 2052, Australia
| | - Manuel Ruiz-Aravena
- School of Natural Sciences, University of Tasmania, Hobart, TAS 7001, Australia
| | - Dan Selechnik
- School of Life and Environmental Sciences (SOLES), University of Sydney, Sydney, NSW 2006, Australia
| | - Helena S Stokes
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds, VIC 3216, Australia
| | - Beata Ujvari
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds, VIC 3216, Australia
| | - Laura F Grogan
- Environmental Futures Research Institute, Griffith University, Nathan, QLD 4111, Australia
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16
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Halliday FW, Heckman RW, Wilfahrt PA, Mitchell CE. Past is prologue: host community assembly and the risk of infectious disease over time. Ecol Lett 2018; 22:138-148. [PMID: 30403005 DOI: 10.1111/ele.13176] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 09/30/2018] [Accepted: 10/05/2018] [Indexed: 12/17/2022]
Abstract
Infectious disease risk is often influenced by host diversity, but the causes are unresolved. Changes in diversity are associated with changes in community structure, particularly during community assembly; therefore, by incorporating change over time, host community assembly may provide a framework to resolve causation. In turn, community assembly can be driven by many processes, including resource enrichment. To test the hypothesis that community assembly causally links host diversity to future disease, we experimentally manipulated host diversity and resource supply to hosts, then allowed communities to assemble for 2 years (surveyed 2012-2014). Initially, host diversity increased disease. Subsequently, host diversity did not directly alter disease. However, host diversity determined the trajectory of host community assembly, altering colonisation by exotic host species and richness-independent host phylogenetic diversity, which together reversed the initial increase in disease. Ultimately, incorporating the temporal dimension of community assembly revealed novel mechanisms linking host diversity to future disease.
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Affiliation(s)
- Fletcher W Halliday
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA.,Department of Integrative Biology, University of South Florida, Tampa, FL, 33620, USA
| | - Robert W Heckman
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Peter A Wilfahrt
- Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Charles E Mitchell
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA.,Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, NC, 27599, USA
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17
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Effects of Emerging Infectious Diseases on Amphibians: A Review of Experimental Studies. DIVERSITY-BASEL 2018. [DOI: 10.3390/d10030081] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Numerous factors are contributing to the loss of biodiversity. These include complex effects of multiple abiotic and biotic stressors that may drive population losses. These losses are especially illustrated by amphibians, whose populations are declining worldwide. The causes of amphibian population declines are multifaceted and context-dependent. One major factor affecting amphibian populations is emerging infectious disease. Several pathogens and their associated diseases are especially significant contributors to amphibian population declines. These include the fungi Batrachochytrium dendrobatidis and B. salamandrivorans, and ranaviruses. In this review, we assess the effects of these three pathogens on amphibian hosts as found through experimental studies. Such studies offer valuable insights to the causal factors underpinning broad patterns reported through observational studies. We summarize key findings from experimental studies in the laboratory, in mesocosms, and from the field. We also summarize experiments that explore the interactive effects of these pathogens with other contributors of amphibian population declines. Though well-designed experimental studies are critical for understanding the impacts of disease, inconsistencies in experimental methodologies limit our ability to form comparisons and conclusions. Studies of the three pathogens we focus on show that host susceptibility varies with such factors as species, host age, life history stage, population and biotic (e.g., presence of competitors, predators) and abiotic conditions (e.g., temperature, presence of contaminants), as well as the strain and dose of the pathogen, to which hosts are exposed. Our findings suggest the importance of implementing standard protocols and reporting for experimental studies of amphibian disease.
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18
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Mosher BA, Bailey LL, Muths E, Huyvaert KP. Host-pathogen metapopulation dynamics suggest high elevation refugia for boreal toads. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2018; 28:926-937. [PMID: 29430754 DOI: 10.1002/eap.1699] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 12/18/2017] [Accepted: 01/02/2018] [Indexed: 06/08/2023]
Abstract
Emerging infectious diseases are an increasingly common threat to wildlife. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is an emerging infectious disease that has been linked to amphibian declines around the world. Few studies exist that explore amphibian-Bd dynamics at the landscape scale, limiting our ability to identify which factors are associated with variation in population susceptibility and to develop effective in situ disease management. Declines of boreal toads (Anaxyrus boreas boreas) in the southern Rocky Mountains are largely attributed to chytridiomycosis but variation exists in local extinction of boreal toads across this metapopulation. Using a large-scale historic data set, we explored several potential factors influencing disease dynamics in the boreal toad-Bd system: geographic isolation of populations, amphibian community richness, elevational differences, and habitat permanence. We found evidence that boreal toad extinction risk was lowest at high elevations where temperatures may be suboptimal for Bd growth and where small boreal toad populations may be below the threshold needed for efficient pathogen transmission. In addition, boreal toads were more likely to recolonize high elevation sites after local extinction, again suggesting that high elevations may provide refuge from disease for boreal toads. We illustrate a modeling framework that will be useful to natural resource managers striving to make decisions in amphibian-Bd systems. Our data suggest that in the southern Rocky Mountains high elevation sites should be prioritized for conservation initiatives like reintroductions.
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Affiliation(s)
- Brittany A Mosher
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Larissa L Bailey
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Erin Muths
- U.S. Geological Survey, Fort Collins Science Center, 2150 Centre Avenue, Building C, Fort Collins, Colorado, 80526, USA
| | - Kathryn P Huyvaert
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
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19
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Halliday FW, Heckman RW, Wilfahrt PA, Mitchell CE. A multivariate test of disease risk reveals conditions leading to disease amplification. Proc Biol Sci 2018; 284:rspb.2017.1340. [PMID: 29046374 DOI: 10.1098/rspb.2017.1340] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 09/14/2017] [Indexed: 02/06/2023] Open
Abstract
Theory predicts that increasing biodiversity will dilute the risk of infectious diseases under certain conditions and will amplify disease risk under others. Yet, few empirical studies demonstrate amplification. This contrast may occur because few studies have considered the multivariate nature of disease risk, which includes richness and abundance of parasites with different transmission modes. By combining a multivariate statistical model developed for biodiversity-ecosystem-multifunctionality with an extensive field manipulation of host (plant) richness, composition and resource supply to hosts, we reveal that (i) host richness alone could not explain most changes in disease risk, and (ii) shifting host composition allowed disease amplification, depending on parasite transmission mode. Specifically, as predicted from theory, the effect of host diversity on parasite abundance differed for microbes (more density-dependent transmission) and insects (more frequency-dependent transmission). Host diversity did not influence microbial parasite abundance, but nearly doubled insect parasite abundance, and this amplification effect was attributable to variation in host composition. Parasite richness was reduced by resource addition, but only in species-rich host communities. Overall, this study demonstrates that multiple drivers, related to both host community and parasite characteristics, can influence disease risk. Furthermore, it provides a framework for evaluating multivariate disease risk in other systems.
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Affiliation(s)
- Fletcher W Halliday
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Robert W Heckman
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Peter A Wilfahrt
- Curriculum for the Environment and Ecology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Charles E Mitchell
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA.,Curriculum for the Environment and Ecology, University of North Carolina, Chapel Hill, NC 27599, USA
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20
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Hite JL, Bosch J, Fernández-Beaskoetxea S, Medina D, Hall SR. Joint effects of habitat, zooplankton, host stage structure and diversity on amphibian chytrid. Proc Biol Sci 2017; 283:rspb.2016.0832. [PMID: 27466456 DOI: 10.1098/rspb.2016.0832] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 07/05/2016] [Indexed: 11/12/2022] Open
Abstract
Why does the severity of parasite infection differ dramatically across habitats? This question remains challenging to answer because multiple correlated pathways drive disease. Here, we examined habitat-disease links through direct effects on parasites and indirect effects on parasite predators (zooplankton), host diversity and key life stages of hosts. We used a case study of amphibian hosts and the chytrid fungus, Batrachochytrium dendrobatidis, in a set of permanent and ephemeral alpine ponds. A field experiment showed that ultraviolet radiation (UVR) killed the free-living infectious stage of the parasite. Yet, permanent ponds with more UVR exposure had higher infection prevalence. Two habitat-related indirect effects worked together to counteract parasite losses from UVR: (i) UVR reduced the density of parasite predators and (ii) permanent sites fostered multi-season host larvae that fuelled parasite production. Host diversity was unlinked to hydroperiod or UVR but counteracted parasite gains; sites with higher diversity of host species had lower prevalence of infection. Thus, while habitat structure explained considerable variation in infection prevalence through two indirect pathways, it could not account for everything. This study demonstrates the importance of creating mechanistic, food web-based links between multiple habitat dimensions and disease.
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Affiliation(s)
- Jessica L Hite
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Jaime Bosch
- Museo Nacional de Ciencias Naturales, CSIC, José Gutiérrez Abascal 2, 28006 Madrid, Spain Centro de Investigación, Seguimiento y Evaluación, Parque Nacional de la Sierra de Guadarrama, Cta. M-604, Km. 27.6, 28740 Rascafría, Spain
| | | | - Daniel Medina
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA
| | - Spencer R Hall
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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21
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Lips KR. Overview of chytrid emergence and impacts on amphibians. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0465. [PMID: 28080989 DOI: 10.1098/rstb.2015.0465] [Citation(s) in RCA: 135] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/2016] [Indexed: 11/12/2022] Open
Abstract
Chytridiomycosis is an emerging infectious disease of amphibians that affects over 700 species on all continents where amphibians occur. The amphibian-chytridiomycosis system is complex, and the response of any amphibian species to chytrid depends on many aspects of the ecology and evolutionary history of the amphibian, the genotype and phenotype of the fungus, and how the biological and physical environment can mediate that interaction. Impacts of chytridiomycosis on amphibians are varied; some species have been driven extinct, populations of others have declined severely, whereas still others have not obviously declined. Understanding patterns and mechanisms of amphibian responses to chytrids is critical for conservation and management. Robust estimates of population numbers are needed to identify species at risk, prioritize taxa for conservation actions, design management strategies for managing populations and species, and to develop effective measures to reduce impacts of chytrids on amphibians.This article is part of the themed issue 'Tackling emerging fungal threats to animal health, food security and ecosystem resilience'.
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Affiliation(s)
- Karen R Lips
- Department of Biology, University of Maryland, College Park, MD 20742, USA
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