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Open Access Publications from the University of California

Scholarly Works (7 results)

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UCLA Electronic Theses and Dissertations (2016)

Batrachochytrium dendrobatidis (Bd), a fungal pathogen that causes chytridiomycosis in amphibians, has infected >500 species and caused declines and extinctions in >200 species. Recently, a second deadly fungal pathogen that also causes chytridiomycosis, Batrachochytrium salamandrivorans (Bsal) was discovered. The presence of these lethal pathogens in international trade threatens amphibian diversity. In this dissertation, I use a novel modeling approach to predict disease risk from Bd and/or Bsal to amphibian populations in North America and Asia by incorporating pathogen habitat suitability, host availability, the potential presence of an invasive carrier species, and pathogen invasion history. First I identify Bsal threat to North American salamanders to be greatest in the Southeast US, the West Coast, and highlands of Mexico. I then investigate the compounded risk of Bd and Bsal in North America and find highest relative risk in those same areas and in the Sierra Nevada Mountains and the northern Rocky Mountains. However, when I incorporate the historical context of Bd into the model by treating the eastern US as the native range of Bd, I find invasive Bd risk to be highest in the mountain ranges of the western US and Mexico, which could influence how amphibians in these areas respond to Bsal. I also uncover a pattern that suggests the translocation of the American bullfrog (Rana catesbeiana) to western North America may have facilitated Bd spread. Last, I investigate the threat of Bd in Asia and find that mountain forests in China, Southeast Asia, and the Pacific Islands have the highest relative Bd risk, and the potential presence of R. catesbeiana and amphibian richness may have a strong influence on Bd risk. I also predict that climate change may lead to a 3-23% decrease in total area of Bd risk in Asia by 2070. These findings provide helpful guidance for conservation planning and management by further highlighting the role of R. catesbeiana in Bd spread and identifying areas at highest risk to prioritize for surveillance, monitoring, and species susceptibility studies needed to enhance our understanding of the pathogen invasion history, disease dynamics, and potential interactions of Bd and Bsal.

    Cover page: Assessing the threat of two deadly fungal pathogens (Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans) to amphibian biodiversity and the impacts of human-mediated movement of an invasive carrier species and climate change
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2015)
    A newly described pathogen poses a major threat to salamanders via trade
      Cover page: Averting a North American biodiversity crisis
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2018)
      Batrachochytrium dendrobatidis (Bd), a causal agent of the amphibian fungal skin disease chytridiomycosis, has been implicated in the decline and extinction of over 200 species worldwide since the 1970s. Despite almost two decades of research, the history of Bd and its global spread is not well understood. However, the spread of the Global Panzootic Lineage of Bd (Bd-GPL), the lineage associated with amphibian die-offs, has been linked with the American bullfrog (Rana [Aqurana] catesbeiana) and global trade. Interestingly, R. catesbeiana is native to the eastern U.S., where no Bd-related declines have been observed despite Bd's presence since the late 1800s. In contrast Bd has been found to have emerged in California and Mexico in the 1960s and 1970s, after which epizootics (i.e., epidemics in wildlife) ensued. We hypothesize that Bd-GPL spread from the eastern U.S. with the introduction of R. catesbeiana into the western US, resulting in epizootics and declines of native host species. Using museum records, we investigated the historical relationship between R. catesbeiana and Bd invasion in the western US and found that R. catesbeiana arrived in the same year or prior to Bd in most western watersheds that had data for both species, suggesting that Bd-GPL may have originated in the eastern US and R. catesbeiana may have facilitated Bd invasion in the western US. To predict areas with greatest suitability for Bd, we created a suitability model by integrating habitat suitability and host availability. When we incorporated invasion history with high Bd suitability, we found that watersheds with non-native R. catesbeiana in the mountain ranges of the West Coast have the highest disease risk. These findings shed light on the invasion history and disease dynamics of Bd in North America. Targeted historical surveys using archived specimens in natural history collections and present-day field surveys along with more localized, community-level studies, monitoring, and surveillance are needed to further test this hypothesis and grow our understanding of the disease ecology and host-pathogen dynamics of Bd.
        Cover page: Introduced bullfrog facilitates pathogen invasion in the western United States
        • Article
        • Peer Reviewed
        UC Santa Barbara Previously Published Works (2017)
          • Article
          • Peer Reviewed
          UC Berkeley Previously Published Works (2022)
          Amphibians are a clade of over 8,400 species that provide unique research opportunities and challenges. With amphibians undergoing severe global declines, we posit that assessing our current understanding of amphibians is imperative. Focusing on the past five years (2016-2020), we examine trends in amphibian research, data, and systematics. New species of amphibians continue to be described at a pace of â 150 per year. Phylogenomic studies are increasing, fueling a growing consensus in the amphibian tree of life. Over 3,000 species of amphibians are now represented by expert-curated accounts or data in AmphibiaWeb, AmphibiaChina, BIOWEB, or the Amphibian Disease Portal. Nevertheless, many species lack basic natural history data (e.g., diet records, morphological measurements, call recordings) and major gaps exist for entire amphibian clades. Genomic resources appear on the cusp of a rapid expansion, but large, repetitive amphibian genomes still pose significant challenges. Conservation continues to be a major focus for amphibian research, and threats cataloged on AmphibiaWeb for 1,261 species highlight the need to address land use change and disease using adaptive management strategies. To further promote amphibian research and conservation, we underscore the importance of database integration and suggest that other understudied or imperiled clades would benefit from similar assessments of existing data.
            Cover page: State of the Amphibia 2020: A Review of Five Years of Amphibian Research and Existing ResourcesCreative Commons 'BY-NC-ND' version 4.0 license
            • Article
            • Peer Reviewed
            UC Berkeley Previously Published Works (2019)
            Biodiversity loss is one major outcome of human-mediated ecosystem disturbance. One way that humans have triggered wildlife declines is by transporting disease-causing agents to remote areas of the world. Amphibians have been hit particularly hard by disease due in part to a globally distributed pathogenic chytrid fungus (Batrachochytrium dendrobatidis [Bd]). Prior research has revealed important insights into the biology and distribution of Bd; however, there are still many outstanding questions in this system. Although we know that there are multiple divergent lineages of Bd that differ in pathogenicity, we know little about how these lineages are distributed around the world and where lineages may be coming into contact. Here, we implement a custom genotyping method for a global set of Bd samples. This method is optimized to amplify and sequence degraded DNA from noninvasive skin swab samples. We describe a divergent lineage of Bd, which we call BdASIA3, that appears to be widespread in Southeast Asia. This lineage co-occurs with the global panzootic lineage (BdGPL) in multiple localities. Additionally, we shed light on the global distribution of BdGPL and highlight the expanded range of another lineage, BdCAPE. Finally, we argue that more monitoring needs to take place where Bd lineages are coming into contact and where we know little about Bd lineage diversity. Monitoring need not use expensive or difficult field techniques but can use archived swab samples to further explore the history-and predict the future impacts-of this devastating pathogen.
              Cover page: Cryptic diversity of a widespread global pathogen reveals expanded threats to amphibian conservation
              • Article
              • Peer Reviewed
              UC Davis Previously Published Works (2018)
              Many efforts to improve science teaching in higher education focus on a few faculty members at an institution at a time, with limited published evidence on attempts to engage faculty across entire departments. We created a long-term, department-wide collaborative professional development program, Biology Faculty Explorations in Scientific Teaching (Biology FEST). Across 3 years of Biology FEST, 89% of the department's faculty completed a weeklong scientific teaching institute, and 83% of eligible instructors participated in additional semester-long follow-up programs. A semester after institute completion, the majority of Biology FEST alumni reported adding active learning to their courses. These instructor self-reports were corroborated by audio analysis of classroom noise and surveys of students in biology courses on the frequency of active-learning techniques used in classes taught by Biology FEST alumni and nonalumni. Three years after Biology FEST launched, faculty participants overwhelmingly reported that their teaching was positively affected. Unexpectedly, most respondents also believed that they had improved relationships with departmental colleagues and felt a greater sense of belonging to the department. Overall, our results indicate that biology department-wide collaborative efforts to develop scientific teaching skills can indeed attract large numbers of faculty, spark widespread change in teaching practices, and improve departmental relations.
                Cover page: Collectively Improving Our Teaching: Attempting Biology Department–wide Professional Development in Scientific Teaching
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