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Faculty Research Spotlight

David Rodriguez, Department of Biology

Rodriguez Lab Investigates Fungi Infecting Reptiles and Amphibians


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“Using our Ecuador program as a framework, we will implement an expanded educational program for students at Texas State University that supports impactful international research experiences, especially for underrepresented minorities in ecology and evolutionary biology.”

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Dr. David Rodriguez

The negative effects of fungal disease on humans, plants, and wildlife have increased over the last few decades, yet host-pathogen interactions remain poorly understood. One reason is that biodiversity of both hosts and fungi is critically understudied, especially among wildlife. To detect which hosts are responsible for transmitting newly introduced fungal pathogens, genetic diversity needs to be measured at population-scale across invaded landscapes.

In the 1970s, scientists began noticing stark declines of amphibian populations in different parts of the world. While habitat change and pollution are well-known factors leading to local extinction of indicator species such as frogs, major declines were occurring even in remote and pristine habitats. In 1993, a new fungus was detected in diseased frogs from Australia, which was formally described in 1999 as Batrachochytrium dendrobatidis. It became known as the amphibian-killing fungus or the amphibian chytrid fungus. This species belongs to an ancient group of fungi that are characterized by having spores that can actively swim through the water; generally, they are not harmful and live on decaying material. However, B. dendrobatidis was unique in its ability to infect vertebrates, and increased surveys of amphibians around the world revealed it was globally distributed. Invasive fungal chytrids can cause chytridiomycosis, a potentially fatal disease, in susceptible amphibians. Early signs of the disease include excessive skin sloughing and lesions on the skin, while advanced signs include lethargy, splayed legs, and eventually death owing to the loss of osmoregulatory capacity of the very permeable amphibian skin.

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Many studies have associated outbreaks of chytridiomycosis with high-elevation, cool climate regions; however, expanded global sampling by my team and other researchers is beginning to reveal the importance of lowland hosts in the transmission of B. dendrobatidis across the landscape. Additionally, global sampling and DNA sequencing of isolates suggest an “out of Asia” origin and have revealed additional diversity among strains of B. dendrobatidis, which is currently composed of four genetically distinct lineages. However, there is a lack of sampling in Pacific coastal forests and the Amazon, especially along the equator where known invasions and amphibian declines have occurred. This lack is critical because Equatorial tropical rain forests are likely the most biodiverse terrestrial ecosystems in the world.

For tropical amphibians, the threat of disease, coupled with habitat loss, requires rapid measurements of host diversity at the population scale to unravel complex disease dynamics. By leveraging emerging portable technology to measure genetic diversity, our research will gather data for both hosts and pathogens to test hypotheses regarding the specificity of their interactions, determine which hosts drive spread or act as reservoirs, and contribute to amphibian conservation.

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A nascent but fruitful approach to addressing the need for rapid (real-time) host and pathogen diversity assessments is leveraging portable emerging technologies such as nanopore sequencing. DNA sequencing and pathogen detection has traditionally required a full molecular laboratory to process samples and generate data using bulky, expensive equipment inaccessible to many scientists in Latin America. However, the recent miniaturization and increased portability of genetic equipment now make it possible to conduct real-time measurement and analysis of genetic variation in the field. We have implemented these portable technologies as a teaching tool in our Education Abroad – Ecuador program.

Using our Ecuador program as a framework, we will implement an expanded educational program for students at Texas State University that supports impactful international research experiences, especially for underrepresented minorities in ecology and evolutionary biology. This project will integrate postdoctoral researchers into student training and develop coding courses for undergraduates.

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In Ecuador, parabiologists (citizen scientists with no formal education) have been instrumental in driving positive and long-lasting community engagement and facilitating our research. Therefore, we will partner with Third Millennium Alliance (a non-profit, non-governmental organization) to recruit and train parabiologists from Ecuadorian communities. The project will drive cultural and academic exchanges and serve to train Ecuadorian students in emerging genetic technologies through ongoing international research facilitated by these collaborative activities with other faculty at Texas State University, Texas A&M–Corpus Christi, and Universidad San Francisco de Quito.

Collection of preliminary data and instrumentation support for this project has been provided by the Verena and Kenneth J. Wilson Latin America Research Program, the Research Enhancement Program, and the International Research Accelerator program. These preliminary data and our Education Abroad – Ecuador program have served as the foundation for a pending National Science Foundation CAREER proposal that will support this integrative research over the next five years.