ORCID Profile
0000-0002-7997-5390
Current Organisation
University of Colorado at Boulder
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Publisher: Authorea, Inc.
Date: 13-06-2023
DOI: 10.22541/AU.168666867.70785552/V1
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 bio ersity and public health. Here, using Batrachochytrium dendrobatidis , the fungus associated with worldwide hibian 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 hibian-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.
Publisher: Springer Science and Business Media LLC
Date: 25-07-2017
DOI: 10.1038/S41467-018-06157-6
Abstract: Changing climate will impact species’ ranges only when environmental variability directly impacts the demography of local populations. However, measurement of demographic responses to climate change has largely been limited to single species and locations. Here we show that hibian communities are responsive to climatic variability, using ,000 time-series observations for 81 species across 86 North American study areas. The effect of climate on local colonization and persistence probabilities varies among eco-regions and depends on local climate, species life-histories, and taxonomic classification. We found that local species richness is most sensitive to changes in water availability during breeding and changes in winter conditions. Based on the relationships we measure, recent changes in climate cannot explain why local species richness of North American hibians has rapidly declined. However, changing climate does explain why some populations are declining faster than others. Our results provide important insights into how hibians respond to climate and a general framework for measuring climate impacts on species richness.
Publisher: Wiley
Date: 13-02-2015
Publisher: Wiley
Date: 07-09-2017
DOI: 10.1002/LNO.10676
Publisher: Wiley
Date: 04-2006
Publisher: Wiley
Date: 22-11-2018
DOI: 10.1111/BRV.12480
Abstract: In the 12 years since Dudgeon et al. (2006) reviewed major pressures on freshwater ecosystems, the bio ersity crisis in the world's lakes, reservoirs, rivers, streams and wetlands has deepened. While lakes, reservoirs and rivers cover only 2.3% of the Earth's surface, these ecosystems host at least 9.5% of the Earth's described animal species. Furthermore, using the World Wide Fund for Nature's Living Planet Index, freshwater population declines (83% between 1970 and 2014) continue to outpace contemporaneous declines in marine or terrestrial systems. The Anthropocene has brought multiple new and varied threats that disproportionately impact freshwater systems. We document 12 emerging threats to freshwater bio ersity that are either entirely new since 2006 or have since intensified: (i) changing climates (ii) e-commerce and invasions (iii) infectious diseases (iv) harmful algal blooms (v) expanding hydropower (vi) emerging contaminants (vii) engineered nanomaterials (viii) microplastic pollution (ix) light and noise (x) freshwater salinisation (xi) declining calcium and (xii) cumulative stressors. Effects are evidenced for hibians, fishes, invertebrates, microbes, plants, turtles and waterbirds, with potential for ecosystem-level changes through bottom-up and top-down processes. In our highly uncertain future, the net effects of these threats raise serious concerns for freshwater ecosystems. However, we also highlight opportunities for conservation gains as a result of novel management tools (e.g. environmental flows, environmental DNA) and specific conservation-oriented actions (e.g. dam removal, habitat protection policies, managed relocation of species) that have been met with varying levels of success. Moving forward, we advocate hybrid approaches that manage fresh waters as crucial ecosystems for human life support as well as essential hotspots of bio ersity and ecological function. Efforts to reverse global trends in freshwater degradation now depend on bridging an immense gap between the aspirations of conservation biologists and the accelerating rate of species endangerment.
Publisher: Proceedings of the National Academy of Sciences
Date: 17-12-2012
Abstract: Batrachochytrium dendrobatidis , a pathogenic chytrid fungus implicated in worldwide hibian declines, is considered an hibian specialist. Identification of non hibian hosts could help explain the virulence, heterogeneous distribution, variable rates of spread, and persistence of B. dendrobatidis in freshwater ecosystems even after hibian extirpations. Here, we test whether mosquitofish ( Gambusia holbrooki) and crayfish ( Procambarus spp. and Orconectes virilis ), which are syntopic with many hibian species, are possible hosts for B. dendrobatidis . Field surveys in Louisiana and Colorado revealed that zoosporangia occur within crayfish gastrointestinal tracts, that B. dendrobatidis prevalence in crayfish was up to 29%, and that crayfish presence in Colorado wetlands was a positive predictor of B. dendrobatidis infections in cooccurring hibians. In experiments, crayfish, but not mosquitofish, became infected with B. dendrobatidis , maintained the infection for at least 12 wk, and transmitted B. dendrobatidis to hibians. Exposure to water that previously held B. dendrobatidis also caused significant crayfish mortality and gill recession. These results indicate that there are non hibian hosts for B. dendrobatidis and suggest that B. dendrobatidis releases a chemical that can cause host pathology, even in the absence of infection. Managing these biological reservoirs for B. dendrobatidis and identifying this chemical might provide new hope for imperiled hibians.
Publisher: Wiley
Date: 25-01-2021
DOI: 10.1111/ELE.13681
Abstract: When facing an emerging infectious disease of conservation concern, we often have little information on the nature of the host‐parasite interaction to inform management decisions. However, it is becoming increasingly clear that the life‐history strategies of host species can be predictive of in idual‐ and population‐level responses to infectious disease, even without detailed knowledge on the specifics of the host‐parasite interaction. Here, we argue that a deeper integration of life‐history theory into disease ecology is timely and necessary to improve our capacity to understand, predict and mitigate the impact of endemic and emerging infectious diseases in wild populations. Using wild vertebrates as an ex le, we show that host life‐history characteristics influence host responses to parasitism at different levels of organisation, from in iduals to communities. We also highlight knowledge gaps and future directions for the study of life‐history and host responses to parasitism. We conclude by illustrating how this theoretical insight can inform the monitoring and control of infectious diseases in wildlife.
Publisher: Springer Science and Business Media LLC
Date: 24-02-2016
No related grants have been discovered for PIETER JOHNSON.