The challenge of observing interactions between plant pathogens, their hosts, and environmental h... more The challenge of observing interactions between plant pathogens, their hosts, and environmental heterogeneity across multiple spatial scales commonly limits our ability to understand and manage wildland forest epidemics. Using the forest pathogen Phytopthora ramorum as a case study, we established 20 multiscale field sites to analyze how host-pathogen-environment relationships vary across spatial scales of observation in a wildland pathosystem. We developed statistical models of disease intensity across five nested levels of spatial aggregation, from an individual host through four broader spatial extents of observation. Analyses were conducted from two spatial perspectives: a focal view, where disease intensity at one scale was examined as a function of broader-scale landscape conditions , and an aggregate view, where disease intensity and landscape conditions was observed at the same scale of spatial aggregation. For each perspective, separate models were developed to compare direct field measurements of host density versus less expensive remotely sensed estimates of host habitat as predictors of disease in landscape-scale studies. From both perspectives, models using direct measurements of host density performed better than models using remotely sensed estimates of host habitat across all four spatial extents. We found no significant difference in model performance at the individual level. From the focal view, the performance of host density models declined with increasing spatial extent, whereas the performance of host habitat models improved with spatial extent. These results illustrate how the scale of observation – both spatial extent and measurement detail – can influence conclusions drawn from epidemiological models of wildland pathosystems.
Landscape epidemiology of species diversity effects on disease risk in a multihost plant pathogen... more Landscape epidemiology of species diversity effects on disease risk in a multihost plant pathogen invasion. Sarah E. Haas, Geography and Earth Sciences, University of North Carolina at Charlotte, Charlotte, NC, Mevin B. Hooten ...
Background/Question/Methods The dynamic and inherently spatial nature of epidemiological processe... more Background/Question/Methods The dynamic and inherently spatial nature of epidemiological processes presents unique challenges to managing the spread of emerging infectious diseases in natural communities. Long-term ecological studies that combine data across multiple scales of host-pathogen-environment interactions are needed to identity the principal drivers of wildland epidemics and their generality across pathosystems. However, this is not a trivial task given the logistical challenges of conducting longitudinal field surveys of host populations with measurements of corresponding biotic and abiotic conditions across broad geographical regions and over meaningful time scales. As such, we still have a limited understanding of the factors governing the distribution, abundance and impacts of emerging wildland pathogens. We designed a long-term study to capture spatial-temporal heterogeneity of wildland disease dynamics across multiple levels of host-pathogen-environment interactions ...
Landscape epidemiology of species diversity effects on disease risk in a multihost plant pathogen... more Landscape epidemiology of species diversity effects on disease risk in a multihost plant pathogen invasion. Sarah E. Haas, Geography and Earth Sciences, University of North Carolina at Charlotte, Charlotte, NC, Mevin B. Hooten ...
Populations of brown-headed nuthatches (Sitta pusilla) are declining throughout the species range... more Populations of brown-headed nuthatches (Sitta pusilla) are declining throughout the species range. Here we characterize twelve polymorphic microsatellite loci for this species. Analysis of 32 presumably unrelated individuals from a single population revealed an average of 14.9 alleles per locus (range 4–25), an average observed heterozygosity of 0.74 (range 0.52–0.94) and an average polymorphic information content of 0.80 (range 0.57–0.95).
Despite a century of research into the factors that generate and maintain biodiversity, we know r... more Despite a century of research into the factors that generate and maintain biodiversity, we know remarkably little about the drivers of parasite diversity. To identify the mechanisms governing parasite diversity, we combined surveys of 8100 amphibian hosts with an outdoor experiment that tested theory developed for free-living species. Our analyses revealed that parasite diversity increased consistently with host diversity due to habitat (i.e. host) heterogeneity, with secondary contributions from parasite colonisation and host abundance. Results of the experiment, in which host diversity was manipulated while parasite colonisation and host abundance were fixed, further reinforced this conclusion. Finally, the coefficient of host diversity on parasite diversity increased with spatial grain, which was driven by differences in their species–area curves: while host richness quickly saturated, parasite richness continued to increase with neighbourhood size. These results offer mechanistic insights into drivers of parasite diversity and provide a hierarchical framework for multi-scale disease research.
The challenge of observing interactions between plant pathogens, their hosts, and environmental h... more The challenge of observing interactions between plant pathogens, their hosts, and environmental heterogeneity across multiple spatial scales commonly limits our ability to understand and manage wildland forest epidemics. Using the forest pathogen Phytopthora ramorum as a case study, we established 20 multiscale field sites to analyze how host-pathogen-environment relationships vary across spatial scales of observation in a wildland pathosystem. We developed statistical models of disease intensity across five nested levels of spatial aggregation, from an individual host through four broader spatial extents of observation. Analyses were conducted from two spatial perspectives: a focal view, where disease intensity at one scale was examined as a function of broader-scale landscape conditions , and an aggregate view, where disease intensity and landscape conditions was observed at the same scale of spatial aggregation. For each perspective, separate models were developed to compare direct field measurements of host density versus less expensive remotely sensed estimates of host habitat as predictors of disease in landscape-scale studies. From both perspectives, models using direct measurements of host density performed better than models using remotely sensed estimates of host habitat across all four spatial extents. We found no significant difference in model performance at the individual level. From the focal view, the performance of host density models declined with increasing spatial extent, whereas the performance of host habitat models improved with spatial extent. These results illustrate how the scale of observation – both spatial extent and measurement detail – can influence conclusions drawn from epidemiological models of wildland pathosystems.
Landscape epidemiology of species diversity effects on disease risk in a multihost plant pathogen... more Landscape epidemiology of species diversity effects on disease risk in a multihost plant pathogen invasion. Sarah E. Haas, Geography and Earth Sciences, University of North Carolina at Charlotte, Charlotte, NC, Mevin B. Hooten ...
Background/Question/Methods The dynamic and inherently spatial nature of epidemiological processe... more Background/Question/Methods The dynamic and inherently spatial nature of epidemiological processes presents unique challenges to managing the spread of emerging infectious diseases in natural communities. Long-term ecological studies that combine data across multiple scales of host-pathogen-environment interactions are needed to identity the principal drivers of wildland epidemics and their generality across pathosystems. However, this is not a trivial task given the logistical challenges of conducting longitudinal field surveys of host populations with measurements of corresponding biotic and abiotic conditions across broad geographical regions and over meaningful time scales. As such, we still have a limited understanding of the factors governing the distribution, abundance and impacts of emerging wildland pathogens. We designed a long-term study to capture spatial-temporal heterogeneity of wildland disease dynamics across multiple levels of host-pathogen-environment interactions ...
Landscape epidemiology of species diversity effects on disease risk in a multihost plant pathogen... more Landscape epidemiology of species diversity effects on disease risk in a multihost plant pathogen invasion. Sarah E. Haas, Geography and Earth Sciences, University of North Carolina at Charlotte, Charlotte, NC, Mevin B. Hooten ...
Populations of brown-headed nuthatches (Sitta pusilla) are declining throughout the species range... more Populations of brown-headed nuthatches (Sitta pusilla) are declining throughout the species range. Here we characterize twelve polymorphic microsatellite loci for this species. Analysis of 32 presumably unrelated individuals from a single population revealed an average of 14.9 alleles per locus (range 4–25), an average observed heterozygosity of 0.74 (range 0.52–0.94) and an average polymorphic information content of 0.80 (range 0.57–0.95).
Despite a century of research into the factors that generate and maintain biodiversity, we know r... more Despite a century of research into the factors that generate and maintain biodiversity, we know remarkably little about the drivers of parasite diversity. To identify the mechanisms governing parasite diversity, we combined surveys of 8100 amphibian hosts with an outdoor experiment that tested theory developed for free-living species. Our analyses revealed that parasite diversity increased consistently with host diversity due to habitat (i.e. host) heterogeneity, with secondary contributions from parasite colonisation and host abundance. Results of the experiment, in which host diversity was manipulated while parasite colonisation and host abundance were fixed, further reinforced this conclusion. Finally, the coefficient of host diversity on parasite diversity increased with spatial grain, which was driven by differences in their species–area curves: while host richness quickly saturated, parasite richness continued to increase with neighbourhood size. These results offer mechanistic insights into drivers of parasite diversity and provide a hierarchical framework for multi-scale disease research.
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