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Trumbo DR, Hardy BM, Crockett HJ, Muths E, Forester BR, Cheek RG, Zimmerman SJ, Corey-Rivas S, Bailey LL, Funk WC. Conservation genomics of an endangered montane amphibian reveals low population structure, low genomic diversity and selection pressure from disease. Mol Ecol 2023; 32:6777-6795. [PMID: 37864490 DOI: 10.1111/mec.17175] [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: 03/31/2023] [Revised: 10/07/2023] [Accepted: 10/11/2023] [Indexed: 10/23/2023]
Abstract
Wildlife diseases are a major global threat to biodiversity. Boreal toads (Anaxyrus [Bufo] boreas) are a state-endangered species in the southern Rocky Mountains of Colorado and New Mexico, and a species of concern in Wyoming, largely due to lethal skin infections caused by the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd). We performed conservation and landscape genomic analyses using single nucleotide polymorphisms from double-digest, restriction site-associated DNA sequencing in combination with the development of the first boreal toad (and first North American toad) reference genome to investigate population structure, genomic diversity, landscape connectivity and adaptive divergence. Genomic diversity (π = 0.00034-0.00040) and effective population sizes (Ne = 8.9-38.4) were low, likely due to post-Pleistocene founder effects and Bd-related population crashes over the last three decades. Population structure was also low, likely due to formerly high connectivity among a higher density of geographically proximate populations. Boreal toad gene flow was facilitated by low precipitation, cold minimum temperatures, less tree canopy, low heat load and less urbanization. We found >8X more putatively adaptive loci related to Bd intensity than to all other environmental factors combined, and evidence for genes under selection related to immune response, heart development and regulation and skin function. These data suggest boreal toads in habitats with Bd have experienced stronger selection pressure from disease than from other, broad-scale environmental variations. These findings can be used by managers to conserve and recover the species through actions including reintroduction and supplementation of populations that have declined due to Bd.
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Affiliation(s)
- D R Trumbo
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
| | - B M Hardy
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
- Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, Colorado, USA
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
| | - H J Crockett
- Colorado Parks and Wildlife, Fort Collins, Colorado, USA
| | - E Muths
- U.S. Geological Survey, Fort Collins Science Center, Fort Collins, Colorado, USA
| | - B R Forester
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
| | - R G Cheek
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
| | - S J Zimmerman
- U.S. Geological Survey, Fort Collins Science Center, Fort Collins, Colorado, USA
| | - S Corey-Rivas
- Department of Biology, New Mexico Highlands University, Las Vegas, New Mexico, USA
| | - L L Bailey
- Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, Colorado, USA
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
| | - W C Funk
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, 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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Torres-Sánchez M, Longo AV. Linking pathogen-microbiome-host interactions to explain amphibian population dynamics. Mol Ecol 2022; 31:5784-5794. [PMID: 36130047 DOI: 10.1111/mec.16701] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 09/13/2022] [Accepted: 09/16/2022] [Indexed: 01/13/2023]
Abstract
Symbiotic interactions can determine the evolutionary trajectories of host species, influencing genetic variation through selection and changes in demography. In the context of strong selective pressures such as those imposed by infectious diseases, symbionts providing defences could contribute to increase host fitness upon pathogen emergence. Here, we generated genome-wide data of an amphibian species to find evidence of evolutionary pressures driven by two skin symbionts: a batrachochytrid fungal pathogen and an antifungal bacterium. Using demographic modelling, we found evidence of decreased effective population size, probably due to pathogen infections. Additionally, we investigated host genetic associations with infection status, antifungal bacterium abundance and overall microbiome diversity using structural equation models. We uncovered relatively lower nucleotide diversity in infected frogs and potential heterozygote advantage to recruit the candidate beneficial symbiont and fight infections. Our models indicate that environmental conditions have indirect effects on symbiont abundance through both host body traits and microbiome diversity. Likewise, we uncovered a potential offsetting effect among host heterozygosity-fitness correlations, plausibly pointing to different ecological and evolutionary processes among the three species due to dynamic interactions. Our findings revealed that evolutionary pressures not only arise from the pathogen but also from the candidate beneficial symbiont, and both interactions shape the genetics of the host. Our results advance knowledge about multipartite symbiotic relationships and provide a framework to model ecological and evolutionary dynamics in wild populations. Finally, our study approach can be applied to inform conservation actions such as bioaugmentation strategies for other imperilled amphibians affected by infectious diseases.
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Affiliation(s)
| | - Ana V Longo
- Department of Biology, University of Florida, Gainesville, Florida, USA
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4
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Smith D, O'Brien D, Hall J, Sergeant C, Brookes LM, Harrison XA, Garner TWJ, Jehle R. Challenging a host-pathogen paradigm: Susceptibility to chytridiomycosis is decoupled from genetic erosion. J Evol Biol 2022; 35:589-598. [PMID: 35167143 PMCID: PMC9306973 DOI: 10.1111/jeb.13987] [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: 09/01/2021] [Accepted: 02/07/2022] [Indexed: 11/26/2022]
Abstract
The putatively positive association between host genetic diversity and the ability to defend against pathogens has long attracted the attention of evolutionary biologists. Chytridiomycosis, a disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), has emerged in recent decades as a cause of dramatic declines and extinctions across the amphibian clade. Bd susceptibility can vary widely across populations of the same species, but the relationship between standing genetic diversity and susceptibility has remained notably underexplored so far. Here, we focus on a putatively Bd‐naive system of two mainland and two island populations of the common toad (Bufo bufo) at the edge of the species’ range and use controlled infection experiments and dd‐RAD sequencing of >10 000 SNPs across 95 individuals to characterize the role of host population identity, genetic variation and individual body mass in mediating host response to the pathogen. We found strong genetic differentiation between populations and marked variation in their susceptibility to Bd. This variation was not, however, governed by isolation‐mediated genetic erosion, and individual heterozygosity was even found to be negatively correlated with survival. Individual survival during infection experiments was strongly positively related to body mass, which itself was unrelated to population of origin or heterozygosity. Our findings underscore the general importance of context‐dependency when assessing the role of host genetic variation for the ability of defence against pathogens.
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Affiliation(s)
- Donal Smith
- School of Science, Engineering and Environment, University of Salford, M5 4WT, Salford, UK.,Institute of Zoology, Zoological Society of London, Regent's Park, London, NW1 4RY, UK
| | - David O'Brien
- Highland Amphibian and Reptile Project, Woodlands, Brae of Kinkell, Dingwall, IV7 8HZ, UK
| | - Jeanette Hall
- Highland Amphibian and Reptile Project, Woodlands, Brae of Kinkell, Dingwall, IV7 8HZ, UK
| | - Chris Sergeant
- Institute of Zoology, Zoological Society of London, Regent's Park, London, NW1 4RY, UK
| | - Lola M Brookes
- Institute of Zoology, Zoological Society of London, Regent's Park, London, NW1 4RY, UK.,MRC Centre for Global Infectious Disease Analysis, Imperial College School of Public Health, Floor 11, Sir Michael Uren Building, 80 Wood Lane, London, W12 0BZ, UK.,Royal Veterinary College, Hawkshead Lane, North Mymms, Herts, AL9 7TA, UK
| | - Xavier A Harrison
- Institute of Zoology, Zoological Society of London, Regent's Park, London, NW1 4RY, UK.,Centre for Ecology and Conservation, University of Exeter, UK
| | - Trenton W J Garner
- Institute of Zoology, Zoological Society of London, Regent's Park, London, NW1 4RY, UK
| | - Robert Jehle
- School of Science, Engineering and Environment, University of Salford, M5 4WT, Salford, UK
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5
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Trujillo AL, Hoffman EA, Becker CG, Savage AE. Spatiotemporal adaptive evolution of an MHC immune gene in a frog-fungus disease system. Heredity (Edinb) 2021; 126:640-655. [PMID: 33510466 PMCID: PMC8115231 DOI: 10.1038/s41437-020-00402-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Revised: 12/29/2020] [Accepted: 12/31/2020] [Indexed: 01/30/2023] Open
Abstract
Genetic diversity of major histocompatibility complex (MHC) genes is linked to reduced pathogen susceptibility in amphibians, but few studies also examine broad spatial and temporal patterns of MHC and neutral genetic diversity. Here, we characterized range-wide MHC diversity in the Northern leopard frog, Rana pipiens, a species found throughout North America that is experiencing disease-related declines. We used previously sequenced neutral markers (mitochondrial DNA and microsatellites), sequenced an expressed MHC class IIß gene fragment, and measured infection prevalence and intensity of the global fungal pathogen Batrachochytrium dendrobatidis (Bd) across 14 populations. Four populations were sampled across two decades, enabling temporal comparisons of selection and demography. We recovered 37 unique MHC alleles, including 17 that were shared across populations. Phylogenetic and population genetic patterns between MHC and neutral markers were incongruent, and five MHC codon positions associated with peptide binding were under positive selection. MHC heterozygosity, but not neutral marker heterozygosity, was a significant factor explaining spatial patterns of Bd prevalence, whereas only environmental variables predicted Bd intensity. MHC allelic richness (AR) decreased significantly over time but microsatellite-based AR did not, highlighting a loss of functional immunogenetic diversity that may be associated with Bd selective pressures. MHC supertype 4 was significantly associated with an elevated risk of Bd infection, whereas one supertype 2 allele was associated with a nearly significant reduced risk of Bd. Taken together, these results provide evidence that positive selection contributes to MHC class IIß evolution in R. pipiens and suggest that functional MHC differences across populations may contribute to disease adaptation.
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Affiliation(s)
- Alexa L. Trujillo
- grid.170430.10000 0001 2159 2859Department of Biology, University of Central Florida, Orlando, FL USA
| | - Eric A. Hoffman
- grid.170430.10000 0001 2159 2859Department of Biology, University of Central Florida, Orlando, FL USA
| | - C. Guilherme Becker
- grid.411015.00000 0001 0727 7545Department of Biological Sciences, University of Alabama, Tuscaloosa, AL USA
| | - Anna E. Savage
- grid.170430.10000 0001 2159 2859Department of Biology, University of Central Florida, Orlando, FL USA
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6
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Goff CB, Walls SC, Rodriguez D, Gabor CR. Changes in physiology and microbial diversity in larval ornate chorus frogs are associated with habitat quality. CONSERVATION PHYSIOLOGY 2020; 8:coaa047. [PMID: 32577287 PMCID: PMC7294888 DOI: 10.1093/conphys/coaa047] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 04/29/2020] [Accepted: 05/08/2020] [Indexed: 06/11/2023]
Abstract
Environmental change associated with anthropogenic disturbance can lower habitat quality, especially for sensitive species such as many amphibians. Variation in environmental quality may affect an organism's physiological health and, ultimately, survival and fitness. Using multiple health measures can aid in identifying populations at increased risk of declines. Our objective was to measure environmental variables at multiple spatial scales and their effect on three indicators of health in ornate chorus frog (Pseudacris ornata) tadpoles to identify potential correlates of population declines. To accomplish this, we measured a glucocorticoid hormone (corticosterone; CORT) profile associated with the stress response, as well as the skin mucosal immune function (combined function of skin secretions and skin bacterial community) and bacterial communities of tadpoles from multiple ponds. We found that water quality characteristics associated with environmental variation, including higher water temperature, conductivity and total dissolved solids, as well as percent developed land nearby, were associated with elevated CORT release rates. However, mucosal immune function, although highly variable, was not significantly associated with water quality or environmental factors. Finally, we examined skin bacterial diversity as it aids in immunity and is affected by environmental variation. We found that skin bacterial diversity differed between ponds and was affected by land cover type, canopy cover and pond proximity. Our results indicate that both local water quality and land cover characteristics are important determinants of population health for ornate chorus frogs. Moreover, using these proactive measures of health over time may aid in early identification of at-risk populations that could prevent further declines and aid in management decisions.
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Affiliation(s)
- Cory B Goff
- Department of Biology, Texas State University, 601 University Dr.
San Marcos, TX 78666, USA
- Department of Biology and Chemistry, Liberty University, 1971
University Blvd. Lynchburg, VA 24515, USA
| | - Susan C Walls
- Wetland and Aquatic Research Center, U.S. Geological Survey, 7920
NW 71st St. Gainesville, FL 32653, USA
| | - David Rodriguez
- Department of Biology, Texas State University, 601 University Dr.
San Marcos, TX 78666, USA
| | - Caitlin R Gabor
- Department of Biology, Texas State University, 601 University Dr.
San Marcos, TX 78666, USA
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7
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Pabijan M, Palomar G, Antunes B, Antoł W, Zieliński P, Babik W. Evolutionary principles guiding amphibian conservation. Evol Appl 2020; 13:857-878. [PMID: 32431739 PMCID: PMC7232768 DOI: 10.1111/eva.12940] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 02/05/2020] [Accepted: 02/18/2020] [Indexed: 12/18/2022] Open
Abstract
The Anthropocene has witnessed catastrophic amphibian declines across the globe. A multitude of new, primarily human-induced drivers of decline may lead to extinction, but can also push species onto novel evolutionary trajectories. If these are recognized by amphibian biologists, they can be engaged in conservation actions. Here, we summarize how principles stemming from evolutionary concepts have been applied for conservation purposes, and address emerging ideas at the vanguard of amphibian conservation science. In particular, we examine the consequences of increased drift and inbreeding in small populations and their implications for practical conservation. We then review studies of connectivity between populations at the landscape level, which have emphasized the limiting influence of anthropogenic structures and degraded habitat on genetic cohesion. The rapid pace of environmental changes leads to the central question of whether amphibian populations can cope either by adapting to new conditions or by shifting their ranges. We gloomily conclude that extinction seems far more likely than adaptation or range shifts for most species. That said, conservation strategies employing evolutionary principles, such as selective breeding, introduction of adaptive variants through translocations, ecosystem interventions aimed at decreasing phenotype-environment mismatch, or genetic engineering, may effectively counter amphibian decline in some areas or for some species. The spread of invasive species and infectious diseases has often had disastrous consequences, but has also provided some premier examples of rapid evolution with conservation implications. Much can be done in terms of setting aside valuable amphibian habitat that should encompass both natural and agricultural areas, as well as designing protected areas to maximize the phylogenetic and functional diversity of the amphibian community. We conclude that an explicit consideration and application of evolutionary principles, although certainly not a silver bullet, should increase effectiveness of amphibian conservation in both the short and long term.
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Affiliation(s)
- Maciej Pabijan
- Institute of Zoology and Biomedical ResearchFaculty of BiologyJagiellonian UniversityKrakówPoland
| | - Gemma Palomar
- Institute of Environmental SciencesFaculty of BiologyJagiellonian UniversityKrakówPoland
| | - Bernardo Antunes
- Institute of Environmental SciencesFaculty of BiologyJagiellonian UniversityKrakówPoland
| | - Weronika Antoł
- Institute of Environmental SciencesFaculty of BiologyJagiellonian UniversityKrakówPoland
| | - Piotr Zieliński
- Institute of Environmental SciencesFaculty of BiologyJagiellonian UniversityKrakówPoland
| | - Wiesław Babik
- Institute of Environmental SciencesFaculty of BiologyJagiellonian UniversityKrakówPoland
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8
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Rivera B, Cook K, Andrews K, Atkinson MS, Savage AE. Pathogen Dynamics in an Invasive Frog Compared to Native Species. ECOHEALTH 2019; 16:222-234. [PMID: 31332577 DOI: 10.1007/s10393-019-01432-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 04/10/2019] [Accepted: 05/09/2019] [Indexed: 06/10/2023]
Abstract
Emerging infectious diseases threaten the survival of wildlife populations and species around the world. In particular, amphibians are experiencing population declines and species extinctions primarily in response to two pathogens, the fungus Batrachochytrium dendrobatidis (Bd) and the iridovirus Ranavirus (Rv). Here, we use field surveys and quantitative (q)PCR to compare infection intensity and prevalence of Bd and Rv across species and seasons on Jekyll Island, a barrier island off the coast of Georgia, USA. We collected oral and skin swabs for 1 year from four anuran species and three families, including two native hylids (Hyla cinerea and Hyla squirella), a native ranid (Rana sphenocephala), and the invasive rain frog Eleutherodactylus planirostris. Bd infection dynamics did not vary significantly over sampling months, but Rv prevalence and intensity were significantly higher in fall 2014 compared to spring 2015. Additionally, Rv prevalence and intensity were significantly higher in E. planirostris than in the other three species. Our study highlights the potential role of invasive amphibians as drivers of disease dynamics and demonstrates the importance of pathogen surveillance across multiple time periods and species to accurately capture the infectious disease landscape.
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Affiliation(s)
- Brenda Rivera
- Department of Biology, University of Central Florida, 4110 Libra Dr, Orlando, FL, 32816, USA
| | - Katrina Cook
- Wyoming Natural Diversity Database, University of Wyoming, 1000 E. University Ave, Laramie, WY, 82071, USA
| | - Kimberly Andrews
- Odum School of Ecology, University of Georgia, UGA Marine Extension, Brunswick, GA, 31520, USA
| | - Matthew S Atkinson
- Department of Biology, University of Central Florida, 4110 Libra Dr, Orlando, FL, 32816, USA
| | - Anna E Savage
- Department of Biology, University of Central Florida, 4110 Libra Dr, Orlando, FL, 32816, USA.
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9
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Functional variation at an expressed MHC class IIβ locus associates with Ranavirus infection intensity in larval anuran populations. Immunogenetics 2019; 71:335-346. [PMID: 30761419 DOI: 10.1007/s00251-019-01104-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2018] [Accepted: 01/07/2019] [Indexed: 12/31/2022]
Abstract
Infectious diseases are causing catastrophic losses to global biodiversity. Iridoviruses in the genus Ranavirus are among the leading causes of amphibian disease-related mortality. Polymorphisms in major histocompatibility complex (MHC) genes are significantly associated with variation in amphibian pathogen susceptibility. MHC genes encode two classes of polymorphic cell-surface molecules that can recognize and bind to diverse pathogen peptides. While MHC class I genes are the classic mediators of viral-acquired immunity, larval amphibians do not express them. Consequently, MHC class II gene diversity may be an important predictor of Ranavirus susceptibility in larval amphibians, the life stage most susceptible to Ranavirus. We surveyed natural populations of larval wood frogs (Rana sylvatica), which are highly susceptible to Ranavirus, across 17 ponds and 2 years in Maryland, USA. We sequenced the peptide-binding region of an expressed MHC class IIβ locus and assessed allelic and genetic diversity. We converted alleles to functional supertypes and determined if supertypes or alleles influenced host responses to Ranavirus. Among 381 sampled individuals, 26% were infected with Ranavirus. We recovered 20 unique MHC class IIβ alleles that fell into two deeply diverged clades and seven supertypes. MHC genotypes were associated with Ranavirus infection intensity, but not prevalence. Specifically, MHC heterozygotes and supertype ST1/ST7 had significantly lower Ranavirus infection intensity compared to homozygotes and other supertypes. We conclude that MHC class IIβ functional genetic variation is an important component of Ranavirus susceptibility. Identifying immunogenetic signatures linked to variation in disease susceptibility can inform mitigation strategies for combatting global amphibian declines.
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10
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Karwacki EE, Atkinson MS, Ossiboff RJ, Savage AE. Novel quantitative PCR assay specific for the emerging Perkinsea amphibian pathogen reveals seasonal infection dynamics. DISEASES OF AQUATIC ORGANISMS 2018; 129:85-98. [PMID: 29972369 DOI: 10.3354/dao03239] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Amphibians are suffering from large-scale population declines worldwide, and infectious diseases are a central driving force. Most pathogen-mediated declines are attributed to 2 pathogens, the fungus Batrachochytrium dendrobatidis and iridoviruses in the genus Ranavirus. However, another emerging pathogen within Perkinsea is associated with mass mortality events in anurans throughout the southeastern USA. Molecular resources for detecting amphibian Perkinsea have been limited to general protistan primers that amplify a range of organisms, not all of which are disease agents. Moreover, the only quantitative method available involves histopathology, which is labor intensive, requires destructive sampling, and lacks sensitivity. Here, we developed a novel quantitative (q)PCR assay that is sensitive and specific for amphibian Perkinsea, providing a resource for rapid and reliable pathogen diagnosis. We used histopathology to confirm that qPCR burdens track the severity of Perkinsea infections across multiple anuran tissues. We also sampled 3 natural amphibian communities in Florida, USA, to assess the prevalence and intensity of amphibian Perkinsea infections across species, seasons, tissues, and life stages. Anurans from 2 of 3 sampling locations were infected, totaling 25.1% of all individuals. Infection prevalence varied significantly among locations, seasons, species, and life stages. Infection intensity was significantly higher in larval tissues than adult tissues, and was significantly different across locations, seasons, and species. Understanding relationships between amphibian Perkinsea infection, other pathogens, and biotic and abiotic cofactors will allow us to assess what drives population declines, improving our ability to develop conservation strategies for susceptible species to reduce global amphibian biodiversity loss.
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Affiliation(s)
- Emily E Karwacki
- University of Central Florida, Department of Biology, 4110 Libra Dr., Orlando, Florida 32816, USA
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11
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Horner AA, Hoffman EA, Tye MR, Hether TD, Savage AE. Correction: Cryptic chytridiomycosis linked to climate and genetic variation in amphibian populations of the southeastern United States. PLoS One 2017; 12:e0186066. [PMID: 28973040 PMCID: PMC5626507 DOI: 10.1371/journal.pone.0186066] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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