211 research outputs found
The effects of pesticide interactions malathion and glyphosate with an emerging viral disease in tiger salamanders (Ambystoma tigrinum)
No full textHonors College, Washington State UniversityDressel, Christina and Storfer, Andrew and Kerby Jacob The effects of pesticide interactions malathion and glyphosate with an emerging viral disease in tiger salamanders (Ambystoma tigrinum), Washington State University Honors College thesis, Spring 2007, 31 p
Basics of Study Design: Sampling Landscape Heterogeneity and Genetic Variation for Landscape Genetic Studies
No full textThis chapter reviews the basics of study design and suggests guidelines for optimal sampling strategies in landscape genetics. It first provides an overview of study design terminology and discusses general study design considerations that lead to strong scientific inferences. The chapter then highlights the specific design challenges encountered in landscape genetic studies and summarizes current sampling effects on landscape genetic conclusions. Based on this summary, the chapter provides study design recommendations for various landscape genetic research questions and outlines future research needs on study design effects in landscape genetics. The chapter highlights that both genetic variation and landscape heterogeneity need to be sampled in such a way that their statistical comparison allows meaningful conclusions about landscape-genetic relationships. Many factors and their interactions need to be considered for optimal sampling design in landscape genetics, so that results from a particular sampling study cannot simply be applied to all other instances
Inbreeding and strong population subdivision in an endangered salamander
No full textStudies of genetic population structure and genetic diversity are often critical components of endangered species conservation and management plans. Genetic studies are thus particularly important for amphibians, which are in global decline. We studied genetic variation and population structure among 276 individuals from approximately half of the known localities of the endangered Sonora tiger salamander, Ambystoma mavortium stebbinsi, using ten microsatellite loci. Allelic diversity was generally low (2.7 alleles per locus per population) and overall observed heterozygosity (0.191) was significantly lower than expected (0.332). Most populations showed significant departures from Hardy–Weinberg equilibrium, which are likely due to inbreeding. In addition, evidence of recent bottlenecks was suggested by shifted allele frequency distributions in 5 of 16 populations, and ratios of allele number to allele size range (M) values lower than
critical values in all populations. A high degree of genetic subdivision (h = 0.133) was found over all populations,
and nearly all pairwise population combinations were genetically subdivided. Thus, gene flow is limited even over small distances, perhaps because high desert grassland throughout the study area limits the efficacy of inter-pond
movement of salamanders. Further, population sizes and gene flow of Sonora tiger salamanders are likely compromised by several contemporary ecological threats, including: frequent die-offs due to an infectious virus, introductions of non-native species, and continuing cattle grazing. Overall, these genetic data support the endangered status of the Sonora tiger salamander and suggest the subspecies exists in small, inbred populations.Peer reviewedfinal article publishedInbreedingGenetic structureMicrosatellitesSalamanderAmbystoma tigrinu
Speciation, phylogeography, and gene flow in giant salamanders (Dicamptodon)
No full textThesis (Ph.D.), Zoology, Washington State Universit
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Spatial variation in selection and multivariate estimates of local adaptation in a salamander-virus system
No full textIt is expected that pathogens should be locally adapted to their hosts because of higher evolutionary and reproductive rates and shorter generation times. We chose four Ambystoma tigrinum virus (ATV) strains and their sympatric salamander hosts (Ambystoma tigrinum) to test for the presence of local adaptation in a fully crossed infection experiment. Infectivity has been the sole measure of local adaptation in most studies though it does not measure pathogen fitness in its complexity. Our study incorporated four measures of pathogen fitness including infectivity, within host growth, virulence, and transmission. We combined two analysis methods to identify local adaptation: "local vs. foreign" and "home vs. away" as both discern local adaptation in unique ways. As host- pathogen interactions vary across space, different patterns of selection can lead to trait divergence and local adaptation. We chose viral strains from different selection regimes based on putative pathogenesis genes to assess the affect the strength of selection had on local adaptation. We predicted that strains under weak selection would be locally adapted or ahead of their sympatric hosts, while those under strong selection would be locally maladapted or "lagging" behind their sympatric hosts. Infectivity alone was a misleading determinant of pathogen local adaptation. Nearly all ATV strains appeared locally adapted based on infectivity while other measures of pathogen fitness suggested local maladaptation. When coupled, the two analysis methods gave a clearer picture of the interaction than when used independently. Using these combined analysis methods, we found that the strength of selection appears to affect local adaptation in the predicted manner. The viral strain under weak selection and that under intermediate selection appeared to be locally adapted to their sympatric hosts. The strain under strong selection appeared to be locally maladapted to its sympatric host, which is indicative of the pathogen experiencing a lag as the host is temporarily ahead. Our data capture a specific moment in time of the interaction between ATV strains and their sympatric hosts, so the observed range of states of local adaptation may be an expected outcome
The Effect of Pesticide Interactions Malathion and Glyphosate with an Emerging Viral Disease in Tiger Salamanders
No full textIn this study, we examine the effects of both a viral disease and two commonly used pesticides. The insecticide malathion and the popular herbicide glyphosate were crossed in a factorial design with Ambystoma tigrinum virus (ATV) and the synergistic affects on tiger salamanders were investigated. The response variables examined include mass, snout vent length (SVL), infection level, and mortality. This is the first study of its kind to examine the interactions of an insecticide and an herbicide with disease. With a continual increase in the use of pesticides around the world (oftentimes applied very close to riparian communities), and because emerging diseases are resulting in devastating effects on amphibian populations, studies ofthis nature could provide vital insight on epizootics by uncovering factors that contribute to disease emergence
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Investigating telomere length as a susceptibility marker for Tasmanian Devil facial tumor disease
No full textTasmanian devils have suffered dramatic population declines due to the recently emerged contagious cancer, devil facial tumor disease (DFTD). The purpose of this study was to compare telomere lengths of devils throughout Tasmania, including individuals infected with DFTD versus healthy animals. Telomeres are DNA-protein complexes found at the ends of all linear chromosomes and are essential for maintaining genome stability. While telomere dynamics within wild species are not fully understood, recent studies have found interesting links between telomere length and organismal performance in the wild. Specifically, short telomere length is shown to be associated with reduced survival in wild birds. Further, telomere length was found to be indicative of infection status in birds and badgers infected with malaria and tuberculosis, respectively. Findings from these and other studies suggest that possessing long telomeres is beneficial in the face of stressful conditions. Here, we tested the prediction that susceptibility to DFTD is negatively correlated with telomere length in devils. Our findings suggest telomere length is associated with DFTD resistance in two ways. First, devils from the West Pencil Pine population have significantly longer telomeres. This population had the slowest initial increase in prevalence as DFTD has moved nearly across the entire island of Tasmania. Second, using extensive recapture data, we found that individuals with long telomeres first show signs of DFTD at a later age than those with shorter telomeres. This research provides a rare study of telomere length variation and its association with disease in a wildlife population
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