VREDENBURG LAB
Research
Research in the Vredenburg lab focuses broadly on ecology, evolution and conservation. Most projects focus on amphibians, but we also study avian behavior and ecology. We incorporate elements of population, community, and behavioral ecology to investigate hypotheses that can explain vertebrate species loss such as the impacts of emerging infectious disease, introduced predators, and habitat destruction. Our approach is to use a combination of field and lab-based experiments as well as comparative methods.
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Major Research Topics
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Ecology of emerging infectious fungal and viral diseases in amphibians
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How does host skin microbiome (symbiotic bacteria) affect disease?​
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How does pathogen invasion history affect current disease dynamics?
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How does host behavior affect pathogen transmission?
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How do wildfires affect disease dynamics?
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Ecology and evolution of stable multi-species flocks of birds (with Dr. Martinez)
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Conservation of Amphibians: AmphibiaWeb
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Mountain ecosystems:
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How do humans impact aquatic and terrestrial montane systems?
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See Belmont Forum Research Project: P3 - People, pollution and pathogens
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Ecology of emerging infectious diseases in amphibians
Chytridiomycosis, a disease caused by the chytrid fungal pathogens Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans, is causing massive epidemics in amphibians around the world. Why? Amphibians are considered one of the most successful lineages of terrestrial vertebrates, and have a long history of survival (>360 million years); yet, today they are the most imperiled of all land vertebrates with over 40% being threatened with extinction.
A southern mountain yellow-legged frog dying from chytridiomycosis in the Sierra Nevada mountains, Kings Canyon National Park, California USA (Photo: V. Vredenburg). These frogs were once the most abundant vertebrates in the high elevation Sierra Nevada. The species is now endangered after suffering from decades of non-native fish introductions (Vredenburg 2004) and the invasion by the fungal pathogen, Batrachochytrium dendrobatidis (Bd). We documented mass die-offs of tens of thousands of frogs (Vredenburg et al. 2010, see publications).
Why study disease in wildlife?
Emerging infectious diseases are not only a threat to wildlife but to humans as well (e.g. Ebola, SARS, AIDS). Our best hope in controlling diseases for the benefits of humans, and our planet, is to understand the underlying ecological processes that govern them. We study chytridiomycosis because it is devastating amphibians on a scale never seen before. With over 500 species affected, and potentially 200 species driven to extinction, chytridiomycosis is the most significant disease recorded in vertebrates.
Our research includes aspects of phylogeography, genetics, breeding behavior, growth, and movement dynamics of amphibians. We incorporate these data in a variety of ways (e.g. stage structured disease models) to predict the spread of the pathogen in the wild and its effect on host species. We have documented the catastrophic impact of chytridiomycosis in natural populations. To better understand the dynamics of the disease, we are investigating the transmission of the fungal pathogen between and within the life stages of the host. Like many other emergent diseases, little is known about the origin of the pathogens (B. dendrobatidis and B. salamandrivorans) that cause the disease. There is considerable debate whether these are novel pathogens or newly virulent strains. One thing is clear, the resulting health of the hosts can vary dramatically depending on many factors. Our research takes place mostly in field settings, but also in the lab and in natural history museums. Currently we are tracking the spread of the pathogens globally using natural history collections that contain amphibian specimens collected over the last century and a half. The outcome of our current research will help shape recovery efforts for threatened species, will help inform models for this disease, and will also help with our general understanding of how diseases work in general. Below we provide some details on the two pathogens that cause chytridiomycosis and on the studies we are currently undertaking to better understand the skin microbiome of amphibians: the symbiotic species of bacteria and other microbes that live on the skin of amphibians.
Microbiome
The skin of amphibians harbors hundreds to thousands of species of bacteria, fungi and other microbes. The relationship between these species and the host amphibian is only now being studied. Recent work has shown that the skin bacteria may benefit the host by producing anti-fungal compounds that may shield the host from fungal pathogen invasion and disease.
Batrachochytrium dendrobatidis (Bd)
This is fungal pathogen that has caused populations and entire species of amphibians to collapse in epizootics (epidemics in wildlife). This pathogen was discovered ~20 years after many populations began mysteriously dying off in Western North America, Central, and South America, and Australia.
Batrachochytrium salamandrivorans (Bsal)
This fungal pathogen was discovered causing epizootics in salamanders native to Europe only recently. This pathogen is believe to have been introduced to Europe through the live pet trade in salamanders transported from Asia. Bsal has luckily not been found in North America, a biodiversity hotspot for the world's amphibians.