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Ambystoma Tigrinum

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Andrew Storfer – One of the best experts on this subject based on the ideXlab platform.

  • Combined Effects of Atrazine and Chlorpyrifos on Susceptibility of the Tiger Salamander to Ambystoma Tigrinum Virus
    EcoHealth, 2009
    Co-Authors: Jacob L. Kerby, Andrew Storfer
    Abstract:

    Several hypotheses have been examined as potential causes of global amphibian declines, including emerging infectious diseases and environmental contaminants. Although these factors are typically studied separately, animals are generally exposed to both stressors simultaneously. We examined the effects of the herbicide atrazine and the insecticide chlorpyrifos on the susceptibility of tiger salamander larvae, Ambystoma Tigrinum, to a viral pathogen, Ambystoma Tigrinum virus (ATV). Environmentally relevant concentrations of atrazine (0, 20, 200 μg/L) and chlorpyrifos (0, 2, 20, 200 μg/L) were used along with ATV in a fully factorial experimental design whereby individually housed, 4-week-old larvae were exposed for 2 weeks. Atrazine alone was not lethal to larvae, and chlorpyrifos alone was lethal only at the highest concentration. When combined with ATV, chlorpyrifos increased susceptibility to viral infection and resulted in increased larval mortality. A significant interactive effect between atrazine and ATV was detected. Atrazine treatments slightly decreased survival in virus-exposed treatments, yet slightly increased survival in the virus-free treatments. These findings corroborate earlier research on the impacts of atrazine, in particular, on disease susceptibility, but exhibit greater effects (i.e., reduced survival) when younger larvae were examined. This study is the first of its kind to demonstrate decreases in amphibian survival with the combination of pesticide and a viral disease. Further examination of these multiple stressors can provide key insights into potential significance of environmental cofactors, such as pesticides, in disease dynamics.

  • Geographically variable selection in Ambystoma Tigrinum virus (Iridoviridae) throughout the western USA
    Journal of evolutionary biology, 2008
    Co-Authors: Benjamin J. Ridenhour, Andrew Storfer
    Abstract:

    We investigated spatially variable selection in Ambystoma Tigrinum virus (ATV) which causes frequent and geographically widespread epizootics of the tiger salamander, Ambystoma Tigrinum. To test for evidence of selection, we sequenced several coding and noncoding regions from virus strains isolated from epizootics throughout western North America. Three of the sequenced regions contained homologues for genes putatively involved in host immune evasion and virulence: eIF-2a, caspase activation and recruitment domain (CARD) and b-OH-steroid oxidoreductase. Selection analysis showed evidence of very strong purifying selection on eIF-2a, purifying selection within certain viral clades on CARD and positive selection on b-OH-steroid oxidoreductase within certain clades. Analysis using MULTIDIVTIME and Tajima’s relative rate tests indicate accelerated rates of evolution within clades associated with anthropogenic movement. These clades also demonstrate greater spatial variability in selection, suggesting a lack of local adaptation (i.e. locally adapted populations should exhibit little to no selection because of absent or reduced variation in fitness once a fitness optimum is reached). Increased transfer of non-native viral strains to nao¨ve salamander populations, in conjunction with local maladaptation as a result of local selection pressures, may explain the spread and emergence of ATV epizootics in A. Tigrinum in western North America.

  • transcriptional response of mexican axolotls to Ambystoma Tigrinum virus atv infection
    BMC Genomics, 2008
    Co-Authors: Jennifer D Cotter, Andrew Storfer, Robert B Page, Christopher K Beachy, Randal S Voss
    Abstract:

    Background Very little is known about the immunological responses of amphibians to pathogens that are causing global population declines. We used a custom microarray gene chip to characterize gene expression responses of axolotls (Ambystoma mexicanum) to an emerging viral pathogen, Ambystoma Tigrinum virus (ATV).

James P Collins – One of the best experts on this subject based on the ideXlab platform.

  • spatial and temporal patterns of Ambystoma Tigrinum virus atv prevalence in tiger salamanders Ambystoma Tigrinum nebulosum
    Diseases of Aquatic Organisms, 2009
    Co-Authors: Amy L. Greer, Jesse L. Brunner, James P Collins
    Abstract:

    Amphibian ranaviruses have been documented as causes of mass mortality in amphib- ian populations throughout the world. The temporal and spatial dynamics of ranavirus infections when epidemics are not apparent remains unclear. To address this question, we collected tissue sam- ples from 2003 to 2006 in 4 geographically separated tiger salamander Ambystoma Tigrinum nebulo- sum host populations on the Kaibab Plateau in northern Arizona. We tested for Ambystoma Tigrinum virus (ATV), a lethal ranavirus of tiger salamanders, calculated ATV prevalence for each sampling date, and examined temporal and spatial patterns by quantifying the annual level of ATV synchrony among populations using the intraclass correlation coefficient. Salamander populations were com- monly infected with ATV. We observed no morbidity or mortality in these populations even as ATV prevalence values varied from 0 to 57%. Infection prevalence across the landscape was more similar within a given year than between years. There was no statistically significant spatial pattern in preva- lence across the landscape. Our findings highlight the need to explore new hypotheses regarding the population level impact of these pathogens on amphibian communities.

  • Transmission dynamics of the amphibian ranavirus Ambystoma Tigrinum virus.
    Diseases of aquatic organisms, 2007
    Co-Authors: Jesse L. Brunner, Danna M. Schock, James P Collins
    Abstract:

    Transmission is central to pathogen fitness and strongly influences the impact of pathogens on host populations. Particularly important to transmission dynamics is the distinction between direct transmission requiring close physical contact (e.g. bumping, fighting, or coughing) and indirect transmission from environmental sources such as contaminated substrates. We present data from 4 experiments addressing the form, routes, and timing of transmission of Ambystoma Tigrinum virus (ATV) among tiger salamanders Ambystoma Tigrinum nebulosum. Our data suggest that ATV is efficiently transmitted by direct interactions between live animals (bumping, biting and cannibalism) as well as by necrophagy and indirectly via water and fomites. Determining which form of transmission is most important in nature is essential for understanding transmission at the population level. Our experiments also revealed an important temporal aspect of infectiousness: larval salamanders become infectious soon after exposure to ATV and their propensity to infect others increases with time. These results begin to clarify the mechanisms and dynamics of ATV transmission and lead to key questions that need to be addressed in future research.

  • Life-History Responses to Pathogens in Tiger Salamander (Ambystoma Tigrinum) Larvae
    Journal of Herpetology, 2005
    Co-Authors: Matthew J. Parris, James P Collins, Andrew Storfer, Elizabeth W. Davidson
    Abstract:

    We tested whether the presence of an iridovirus (Ambystoma Tigrinum virus; ATV) could alter patterns of larval life histories in Arizona Tiger Salamanders (Ambystoma Tigrinum nebulosum). Viral epidemics cause extreme mortality in natural populations and, thus, impose a strong selective force. We tested how exposure to ATV during larval development influences survival, growth, and frequency of cannibalism by manipulating the presence of ATV in replicated experimental tanks. ATV significantly reduced survival and larval growth. Propensity to become cannibalistic was not related to ATV exposure, suggesting that salamanders cannot facultatively respond to the presence of diseased conspecifics by reducing cannibalism. Our results demonstrate that viral pathogens may have both a direct and indirect effect on A. Tigrinum fit- ness by reducing survival and growth rate.

Elizabeth A. Hadly – One of the best experts on this subject based on the ideXlab platform.

  • Developmental dynamics of Ambystoma Tigrinum in a changing landscape
    BMC ecology, 2010
    Co-Authors: Sarah K. Mcmenamin, Elizabeth A. Hadly
    Abstract:

    Background Loss of pond habitat is catastrophic to aquatic larval amphibians, but even reduction in the amount of time a breeding site holds water (hydroperiod) can influence amphibian development and limit reproductive success. Using the landscape variation of a glacial valley in the Greater Yellowstone Ecosystem as the context for a natural experiment, we examined variation in growth pattern and life history of the salamander Ambystoma Tigrinum melanostictum and determined how these developmental characteristics varied with hydroperiod over several summers.

  • Temporal response of the tiger salamander (Ambystoma Tigrinum) to 3,000 years of climatic variation
    BMC Ecology, 2005
    Co-Authors: Judsen E Bruzgul, Webb Long, Elizabeth A. Hadly
    Abstract:

    Background Amphibians are sensitive indicators of environmental conditions and show measurable responses, such as changes in phenology, abundance and range limits to local changes in precipitation and temperature regimes. Amphibians offer unique opportunities to study the important ecological and evolutionary implications of responses in life history characteristics to climatic change. We analyzed a late-Holocene fossil record of the Tiger Salamander ( Ambystoma Tigrinum ) for evidence of population-level changes in body size and paedomorphosis to climatic change over the last 3000 years. Results We found a significant difference in body size index between paedomorphic and metamorphic individuals during the time interval dominated by the Medieval Warm Period. There is a consistent ratio of paedomorphic to metamorphic specimens through the entire 3000 years, demonstrating that not all life history characteristics of the population were significantly altered by changes in climate on this timescale. Conclusion The fossil record of Ambystoma Tigrinum we used spans an ecologically relevant timescale appropriate for understanding population and community response to projected climatic change. The population-level responses we documented are concordant with expectations based on modern environmental studies, and yield insight into population-level patterns across hundreds of generations, especially the independence of different life history characteristics. These conclusions lead us to offer general predictions about the future response of this species based on likely scenarios of climatic warming in the Rocky Mountain region.

  • Temporal response of the tiger salamander (Ambystoma Tigrinum) to 3,000 years of climatic variation.
    BMC ecology, 2005
    Co-Authors: Judsen E Bruzgul, Webb Long, Elizabeth A. Hadly
    Abstract:

    Background Amphibians are sensitive indicators of environmental conditions and show measurable responses, such as changes in phenology, abundance and range limits to local changes in precipitation and temperature regimes. Amphibians offer unique opportunities to study the important ecological and evolutionary implications of responses in life history characteristics to climatic change. We analyzed a late-Holocene fossil record of the Tiger Salamander (Ambystoma Tigrinum) for evidence of population-level changes in body size and paedomorphosis to climatic change over the last 3000 years.

James Collins – One of the best experts on this subject based on the ideXlab platform.

  • Ancestry of An Isolated Subspecies of Salamander, Ambystoma Tigrinum stebbinsi Lowe: the Evolutionary Significance of Hybridization
    Molecular phylogenetics and evolution, 1995
    Co-Authors: T. R. Jones, Eric J. Routman, David J. Begun, James Collins
    Abstract:

    Abstract Most phylogenetic systematists assume speciation results in dichotomously branching phylogenies. Hybridization that gives rise to a new Lineage can produce character homoplasy that might obscure a species′ true history. We report the results of a restriction-enzyme analysis of mitochondrial DNA (mtDNA) variation in three tiger salamander subspecies (Ambystoma Tigrinum mavortium, Ambystoma Tigrinum nebulosum, and Ambystoma Tigrinum stebbinsi) and compare the results to studies of morphological and allozymic variation in these taxa. Allozymically, A. t. mavortium and A. t. nebulosum share most of their genomes (although each has several unique alleles), yet color pattern and mtDNA haplotypes are distinct. Color pattern and allozyme data suggest that A. t. stebbinsi shares a common ancestor with A. t. mavortium, while the A. t. stebbinsi mtDNA haplotype is derived from an A. t. nebulosum haplotype. Thus, our data suggest that A. t. stebbinsi originated through hybridization between A. t. mavortium and A. t. nebulosum. That hybridization can produce recognizably distinct evolutionary entities has long been recognized for plants, but the evolutionary significance of hybridization in animals should be examined more closely. Conservation agencies must recognize that hybrids and hybrid tars are not necessarily evolutionary “mistakes,” and they might have significant importance in the production of natural biodiversity.

  • The role of prey in controlling expression of a trophic polymorphism in Ambystoma Tigrinum nebulosum
    Functional Ecology, 1994
    Co-Authors: M. L G Loeb, James Collins, Timothy J. Maret
    Abstract:

    1. With only a few exceptions, the potential contribution of heterospecific prey to the evolution of cannibalism and accompanying morphologies in amphibians and other taxa is unknown. In this study we tested the role of invertebrate and vertebrate prey in controlling variation in frequencies of a non-cannibal and an environmentally cued cannibal morph among populations of the Arizona tiger salamander, Ambystoma Tigrinum nebulosum. 2. In parts of its range, A. t. nebulosum is syntopic with larvae of the chorus frog, Pseudacris triseriata. Our field measurements revealed a significant positive correlation between the frequency of cannibal morphs in larval tiger salamanders and density of chorus frog tadpoles. Cannibal frequency did not correlate significantly with larval salamander density, although frequency of cannibals varies positively with conspecific density in the laboratory

David J. Begun – One of the best experts on this subject based on the ideXlab platform.

  • Ancestry of An Isolated Subspecies of Salamander, Ambystoma Tigrinum stebbinsi Lowe: the Evolutionary Significance of Hybridization
    Molecular phylogenetics and evolution, 1995
    Co-Authors: T. R. Jones, Eric J. Routman, David J. Begun, James Collins
    Abstract:

    Abstract Most phylogenetic systematists assume speciation results in dichotomously branching phylogenies. Hybridization that gives rise to a new Lineage can produce character homoplasy that might obscure a species′ true history. We report the results of a restriction-enzyme analysis of mitochondrial DNA (mtDNA) variation in three tiger salamander subspecies (Ambystoma Tigrinum mavortium, Ambystoma Tigrinum nebulosum, and Ambystoma Tigrinum stebbinsi) and compare the results to studies of morphological and allozymic variation in these taxa. Allozymically, A. t. mavortium and A. t. nebulosum share most of their genomes (although each has several unique alleles), yet color pattern and mtDNA haplotypes are distinct. Color pattern and allozyme data suggest that A. t. stebbinsi shares a common ancestor with A. t. mavortium, while the A. t. stebbinsi mtDNA haplotype is derived from an A. t. nebulosum haplotype. Thus, our data suggest that A. t. stebbinsi originated through hybridization between A. t. mavortium and A. t. nebulosum. That hybridization can produce recognizably distinct evolutionary entities has long been recognized for plants, but the evolutionary significance of hybridization in animals should be examined more closely. Conservation agencies must recognize that hybrids and hybrid tars are not necessarily evolutionary “mistakes,” and they might have significant importance in the production of natural biodiversity.

  • Biochemical Plasticity in the Arizona Tiger Salamander (Ambystoma Tigrinum nebulosum)
    The Journal of heredity, 1992
    Co-Authors: David J. Begun, James P Collins
    Abstract:

    The Arizona tiger salamander, Ambystoma Tigrinum nebulosum, is a developmentally polymorphic species. Some individuals become sexually mature while retaining some larval traits (paedomorphs), while other individuals mature as metamorphosed salamanders. In this study, relative enzyme activities of the products of two duplicate loci in each of three enzyme systems (aconitase, malate dehydrogenase, and isocitrate dehydrogenase) were measured in paedomorphs and in paedomorphs forced to metamorphose by treatment with thyroxine. We found that thyroxine and laboratory conditions affect enzyme activities of four of the six enzymes examined and that activities of products of duplicate loci are altered to different degrees.