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Are novel or locally adapted pathogens more devastating and why?: Resolving opposing hypotheses
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  • Erin Sauer,
  • Matthew Venesky,
  • Taegan McMahon,
  • Jeremy M. Cohen,
  • Scott Bessler,
  • Laura Brannelly,
  • Forest Brem,
  • Neal Halstead,
  • Oliver Hyman,
  • Pieter Johnson,
  • Corinne Richards-Zawacki,
  • Samantha Rumschlag,
  • Brittany Sears,
  • Jason Rohr
Erin Sauer
University of Arkansas Fayetteville
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Matthew Venesky
Allegheny College
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Taegan McMahon
Connecticut College
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Jeremy M. Cohen
Yale University
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Scott Bessler
University of South Florida
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Laura Brannelly
The University of Melbourne
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Forest Brem
Memphis State University
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Neal Halstead
Wildlands Conservation
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Oliver Hyman
James Madison University
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Pieter Johnson
University of Colorado at Boulder
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Corinne Richards-Zawacki
University of Pittsburgh
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Samantha Rumschlag
US Environmental Protection Agency
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Brittany Sears
University of South Florida
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Jason Rohr
University of Notre Dame

Corresponding Author:jrohr2@nd.edu

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Abstract

There is a rich literature highlighting that pathogens are generally better adapted to infect local than novel hosts, and a separate seemingly contradictory literature indicating that novel pathogens pose the greatest threat to biodiversity and public health. Here, using Batrachochytrium dendrobatidis, the fungus associated with worldwide amphibian declines, we test the hypothesis that there is enough variance in novel host-pathogen outcomes to pose substantial risk of pathogen introductions despite local adaptation being common. Our continental-scale, common garden experiment and global-scale meta-analysis demonstrate that local amphibian-fungal interactions result in higher pathogen prevalence, pathogen growth, and host mortality, but novel interactions led to strikingly variable consequences with the greatest risk occurring when susceptible hosts and virulent strains interacted. Thus, while most pathogen introductions are benign, enough variance exists in novel host-pathogen outcomes that moving organisms around the planet greatly increases the chance of pathogen introductions causing profound harm.