Reframing wildlife disease management problems with decision analysis.

Contemporary wildlife disease management is complex because managers need to respond to a wide range of stakeholders, multiple uncertainties, and difficult trade-offs that characterize the interconnected challenges of today. Despite general acknowledgment of these complexities, managing wildlife disease tends to be framed as a scientific problem, in which the major challenge is lack of knowledge. The complex and multifactorial process of decision-making is collapsed into a scientific endeavor to reduce uncertainty. As a result, contemporary decision-making may be oversimplified, rely on simple heuristics, and fail to account for the broader legal, social, and economic context in which the decisions are made. Concurrently, scientific research on wildlife disease may be distant from this decision context, resulting in information that may not be directly relevant to the pertinent management questions. We propose reframing wildlife disease management challenges as decision problems and addressing them with decision analytical tools to divide the complex problems into more cognitively manageable elements. In particular, structured decision-making has the potential to improve the quality, rigor, and transparency of decisions about wildlife disease in a variety of systems. Examples of management of severe acute respiratory syndrome coronavirus 2, white-nose syndrome, avian influenza, and chytridiomycosis illustrate the most common impediments to decision-making, including competing objectives, risks, prediction uncertainty, and limited resources.

Replanteamiento del manejo de problemas por enfermedades de fauna mediante el análisis de decisiones Resumen El manejo actual de las enfermedades de la fauna es complejo debido a que los gestores necesitan responder a una amplia gama de actores, varias incertidumbres y compensaciones difíciles que caracterizan los retos interconectados del día de hoy. A pesar de que en general se reconocen estas complejidades, el manejo de las enfermedades tiende a plantearse como un problema científico en el que el principal obstáculo es la falta de conocimiento. El proceso complejo y multifactorial de la toma decisiones está colapsado dentro de un esfuerzo científico para reducir la incertidumbre. Como resultado de esto, las decisiones contemporáneas pueden estar simplificadas en exceso, depender de métodos heurísticos simples y no considerar el contexto legal, social y económico más amplio en el que se toman las decisiones. De manera paralela, las investigaciones científicas sobre las enfermedades de la fauna pueden estar lejos de este contexto de decisiones, lo que deriva en información que puede no ser directamente relevante para las preguntas pertinentes de manejo. Proponemos replantear los obstáculos para el manejo de enfermedades de fauna como problemas de decisión y abordarlos con herramientas analíticas de decisión para dividir los problemas complejos en elementos más manejables de manera cognitiva. En particular, las decisiones estructuradas tienen el potencial de mejorar la calidad, el rigor y la transparencia de las decisiones sobre las enfermedades de la fauna en una variedad de sistemas. Ejemplos como el manejo del coronavirus del síndrome de respiración agudo tipo 2, el síndrome de nariz blanca, la influenza aviar y la quitridiomicosis ilustran los impedimentos más comunes para la toma de decisiones, incluyendo los objetivos en competencia, riesgos, incertidumbre en las predicciones y recursos limitados.

One Health Approach to Globalizing, Accelerating, and Focusing Amphibian and Reptile Disease Research-Reflections and Opinions from the First Global Amphibian and Reptile Disease Conference.

The world's reptiles and amphibians are experiencing dramatic and ongoing losses in biodiversity, changes that can have substantial effects on ecosystems and human health. In 2022, the first Global Amphibian and Reptile Disease Conference was held, using One Health as a guiding principle. The conference showcased knowledge on numerous reptile and amphibian pathogens from several standpoints, including epidemiology, host immune defenses, wild population effects, and mitigation. The conference also provided field experts the opportunity to discuss and identify the most urgent herpetofaunal disease research directions necessary to address current and future threats to reptile and amphibian biodiversity.

Winter is coming-Temperature affects immune defenses and susceptibility to Batrachochytrium salamandrivorans.

Environmental temperature is a key factor driving various biological processes, including immune defenses and host-pathogen interactions. Here, we evaluated the effects of environmental temperature on the pathogenicity of the emerging fungal pathogen, Batrachochytrium salamandrivorans (Bsal), using controlled laboratory experiments, and measured components of host immune defense to identify regulating mechanisms. We found that adult and juvenile Notophthalmus viridescens died faster due to Bsal chytridiomycosis at 14°C than at 6 and 22°C. Pathogen replication rates, total available proteins on the skin, and microbiome composition likely drove these relationships. Temperature-dependent skin microbiome composition in our laboratory experiments matched seasonal trends in wild N. viridescens, adding validity to these results. We also found that hydrophobic peptide production after two months post-exposure to Bsal was reduced in infected animals compared to controls, perhaps due to peptide release earlier in infection or impaired granular gland function in diseased animals. Using our temperature-dependent susceptibility results, we performed a geographic analysis that revealed N. viridescens populations in the northeastern United States and southeastern Canada are at greatest risk for Bsal invasion, which shifted risk north compared to previous assessments. Our results indicate that environmental temperature will play a key role in the epidemiology of Bsal and provide evidence that temperature manipulations may be a viable disease management strategy.

Inhibitory Bacterial Diversity and Mucosome Function Differentiate Susceptibility of Appalachian Salamanders to Chytrid Fungal Infection.

Mucosal defenses are crucial in animals for protection against pathogens and predators. Host defense peptides (antimicrobial peptides, AMPs) as well as skin-associated microbes are key components of mucosal immunity, particularly in amphibians. We integrate microbiology, molecular biology, network-thinking, and proteomics to understand how host and microbially derived products on amphibian skin (referred to as the mucosome) serve as pathogen defenses. We studied defense mechanisms against chytrid pathogens, Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal), in four salamander species with different Batrachochytrium susceptibilities. Bd infection was quantified using qPCR, mucosome function (i.e., ability to kill Bd or Bsal zoospores in vitro), skin bacterial communities using 16S rRNA gene amplicon sequencing, and the role of Bd-inhibitory bacteria in microbial networks across all species. We explored the presence of candidate-AMPs in eastern newts and red-backed salamanders. Eastern newts had the highest Bd prevalence and mucosome function, while red-back salamanders had the lowest Bd prevalence and mucosome function, and two-lined salamanders and seal salamanders were intermediates. Salamanders with highest Bd infection intensity showed greater mucosome function. Bd infection prevalence significantly decreased as putative Bd-inhibitory bacterial richness and relative abundance increased on hosts. In co-occurrence networks, some putative Bd-inhibitory bacteria were found as hub-taxa, with red-backs having the highest proportion of protective hubs and positive associations related to putative Bd-inhibitory hub bacteria. We found more AMP candidates on salamanders with lower Bd susceptibility. These findings suggest that salamanders possess distinct innate mechanisms that affect chytrid fungi. IMPORTANCE How host mucosal defenses interact, and influence disease outcome is critical in understanding host defenses against pathogens. A more detailed understanding is needed of the interactions between the host and the functioning of its mucosal defenses in pathogen defense. This study investigates the variability of chytrid susceptibility in salamanders and the innate defenses each species possesses to mediate pathogens, thus advancing the knowledge toward a deeper understanding of the microbial ecology of skin-associated bacteria and contributing to the development of bioaugmentation strategies to mediate pathogen infection and disease. This study improves the understanding of complex immune defense mechanisms in salamanders and highlights the potential role of the mucosome to reduce the probability of Bd disease development and that putative protective bacteria may reduce likelihood of Bd infecting skin.

Cryptic diversity of a widespread global pathogen reveals expanded threats to amphibian conservation.

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.

No impact of a short-term climatic "El Niño" fluctuation on gut microbial diversity in populations of the Galápagos marine iguana (Amblyrhynchus cristatus).

Gut microorganisms are crucial for many biological functions playing a pivotal role in the host's well-being. We studied gut bacterial community structure of marine iguana populations across the Galápagos archipelago. Marine iguanas depend heavily on their specialized gut microbiome for the digestion of dietary algae, a resource whose growth was strongly reduced by severe "El Niño"-related climatic fluctuations in 2015/2016. As a consequence, marine iguana populations showed signs of starvation as expressed by a poor body condition. Body condition indices (BCI) varied between island populations indicating that food resources (i.e., algae) are affected differently across the archipelago during 'El Niño' events. Though this event impacted food availability for marine iguanas, we found that reductions in body condition due to "El Niño"-related starvation did not result in differences in bacterial gut community structure. Species richness of gut microorganisms was instead correlated with levels of neutral genetic diversity in the distinct host populations. Our data suggest that marine iguana populations with a higher level of gene diversity and allelic richness may harbor a more diverse gut microbiome than those populations with lower genetic diversity. Since low values of these diversity parameters usually correlate with small census and effective population sizes, we use our results to propose a novel hypothesis according to which small and genetically less diverse host populations might be characterized by less diverse microbiomes. Whether such genetically depauperate populations may experience additional threats from reduced dietary flexibility due to a limited intestinal microbiome is currently unclear and calls for further investigation.

Mentorship, equity, and research productivity: lessons from a pandemic.

The coronavirus pandemic is more fully exposing ubiquitous economic and social inequities that pervade conservation science. In this time of prolonged stress on members of the research community, primary investigators or project leaders (PLs) have a unique opportunity to adapt their programs to jointly create more equitable and productive research environments for their teams. Institutional guidance for PLs pursuing field and laboratory work centers on the physical safety of individuals while in the lab or field, but largely ignores the vast differences in how team members may be experiencing the pandemic. Strains on mental, physical, and emotional health; racial trauma; familial responsibilities; and compulsory productivity resources, such as high-speed internet, quiet work spaces, and support are unequally distributed across team members. The goal of this paper is to summarize the shifting dynamics of leadership and mentorship during the coronavirus pandemic and highlight opportunities for increasing equity in conservation research at the scale of the project team. Here, we (1) describe how the pandemic differentially manifests inequity on project teams, particularly for groups that have been structurally excluded from conservation science, (2) consider equitable career advancement during the coronavirus pandemic, and (3) offer suggestions for PLs to provide mentorship that prioritizes equity and wellbeing during and beyond the pandemic. We aim to support PLs who have power and flexibility in how they manage research, teaching, mentoring, consulting, outreach, and extension activities so that individual team members' needs are met with compassion and attention to equity.

Extraction-free detection of amphibian pathogens from water baths.

Detecting and quantifying pathogens with quick, cost-efficient and sensitive methods is needed across disease systems for addressing pertinent epidemiological questions. Typical methods rely on extracting DNA from collected samples. Here we develop and test an extraction-free method from water bath samples that is both sensitive and efficient for 2 major amphibian pathogens-Batrachochytrium dendrobatidis and B. salamandrivorans. We tested mock samples with known pathogen quantities as well as comparatively assessed detection from skin swabs and water baths from field sampled amphibians. Quantitative PCR (qPCR) directly on lyophilized water baths was able to reliably detect low loads of 10 and 1 zoospores for both pathogens, and detection rates were greater than those of swabs from field samples. Further concentration of samples did not improve detection, and collection container type did not influence pathogen load estimates. This method of lyophilization (i.e. freeze-drying) followed by direct qPCR offers an effective and efficient tool from detecting amphibian pathogens, which is crucial for surveillance efforts and estimating shedding rates for robust epidemiological understanding of transmission dynamics. Furthermore, water bath samples have multiple functions and can be used to evaluate mucosal function against pathogens and characterize mucosal components. The multifunctionality of water bath samples and reduced monetary costs and time expenditures make this method an optimal tool for amphibian disease research and may also prove to be useful in other wildlife disease systems.

Responsible biosecurity and risk mitigation for laboratory research on emerging pathogens of amphibians.

The increasing study of emerging wildlife pathogens and a lack of policy or legislation regulating their translocation and use has heightened concerns about laboratory escape, species spillover, and subsequent epizootics among animal populations. Responsible self-regulation by research laboratories, in conjunction with institutional-level safeguards, has an important role in mitigating pathogen transmission and spillover, as well as potential interspecies pathogenesis. A model system in disease ecology that highlights these concerns and related amelioration efforts is research focused on amphibian emerging infectious diseases. Whereas laboratory escape of amphibian pathogens has not been reported and may be rare compared with introduction events from trade or human globalization, the threat that novel disease outbreaks with mass mortality effects pose to wild populations warrants thorough biosecurity measures to ensure containment and prevent spillover. Here, we present a case study of the laboratory biosecurity concerns for the emerging amphibian fungal pathogen Batrachochytrium salamandrivorans. We conclude that proactive biosecurity strategies are needed to integrate researcher and institutional oversight of aquatic wildlife pathogens generally, and we call for increased national and international policy and legislative enforcement. Furthermore, taking professional responsibility beyond current regulations is needed as development of legal guidance can be slow at national and international levels. We outline the need for annual laboratory risk assessments, comprehensive training for all laboratory personnel, and appropriate safeguards specific to pathogens under study. These strategies are critical for upholding the integrity and credibility of the scientific community and maintaining public support for research on wildlife diseases.

Isolation and maintenance of Batrachochytrium salamandrivorans cultures.

Discovered in 2013, the chytrid fungus Batrachochytrium salamandrivorans (Bsal) is an emerging amphibian pathogen that causes ulcerative skin lesions and multifocal erosion. A closely related pathogen, B. dendrobatidis (Bd), has devastated amphibian populations worldwide, suggesting that Bsal poses a significant threat to global salamander biodiversity. To expedite research into this emerging threat, we seek to standardize protocols across the field so that results of laboratory studies are reproducible and comparable. We have collated data and experience from multiple labs to standardize culturing practices of Bsal. Here we outline common culture practices including a medium for standardized Bsal growth, standard culturing protocols, and a method for isolating Bsal from infected tissue.

Low-load pathogen spillover predicts shifts in skin microbiome and survival of a terrestrial-breeding amphibian.

Wildlife disease dynamics are strongly influenced by the structure of host communities and their symbiotic microbiota. Conspicuous amphibian declines associated with the waterborne fungal pathogen Batrachochytrium dendrobatidis (Bd) have been observed in aquatic-breeding frogs globally. However, less attention has been given to cryptic terrestrial-breeding amphibians that have also been declining in tropical regions. By experimentally manipulating multiple tropical amphibian assemblages harbouring natural microbial communities, we tested whether Bd spillover from naturally infected aquatic-breeding frogs could lead to Bd amplification and mortality in our focal terrestrial-breeding host: the pumpkin toadlet Brachycephalus pitanga. We also tested whether the strength of spillover could vary depending on skin bacterial transmission within host assemblages. Terrestrial-breeding toadlets acquired lethal spillover infections from neighbouring aquatic hosts and experienced dramatic but generally non-protective shifts in skin bacterial composition primarily attributable to their Bd infections. By contrast, aquatic-breeding amphibians maintained mild Bd infections and higher survival, with shifts in bacterial microbiomes that were unrelated to Bd infections. Our results indicate that Bd spillover from even mildly infected aquatic-breeding hosts may lead to dysbiosis and mortality in terrestrial-breeding species, underscoring the need to further investigate recent population declines of terrestrial-breeding amphibians in the tropics.

Arthropod-bacteria interactions influence assembly of aquatic host microbiome and pathogen defense.

The host-associated microbiome is vital to host immunity and pathogen defense. In aquatic ecosystems, organisms may interact with environmental bacteria to influence the pool of potential symbionts, but the effects of these interactions on host microbiome assembly and pathogen resistance are unresolved. We used replicated bromeliad microecosystems to test for indirect effects of arthropod-bacteria interactions on host microbiome assembly and pathogen burden, using tadpoles and the fungal amphibian pathogen Batrachochytrium dendrobatidis as a model host-pathogen system. Arthropods influenced host microbiome assembly by altering the pool of environmental bacteria, with arthropod-bacteria interactions specifically reducing host colonization by transient bacteria and promoting antimicrobial components of aquatic bacterial communities. Arthropods also reduced fungal zoospores in the environment, but fungal infection burdens in tadpoles corresponded most closely with arthropod-mediated patterns in microbiome assembly. This result indicates that the cascading effects of arthropods on the maintenance of a protective host microbiome may be more strongly linked to host health than negative effects of arthropods on pools of pathogenic zoospores. Our work reveals tight links between healthy ecosystem dynamics and the functioning of host microbiomes, suggesting that ecosystem disturbances such as loss of arthropods may have downstream effects on host-associated microbial pathogen defenses and host fitness.

Disruption of skin microbiota contributes to salamander disease.

Escalating occurrences of emerging infectious diseases underscore the importance of understanding microbiome-pathogen interactions. The amphibian cutaneous microbiome is widely studied for its potential to mitigate disease-mediated amphibian declines. Other microbial interactions in this system, however, have been largely neglected in the context of disease outbreaks. European fire salamanders have suffered dramatic population crashes as a result of the newly emerged Batrachochytrium salamandrivorans (Bsal). In this paper, we investigate microbial interactions on multiple fronts within this system. We show that wild, healthy fire salamanders maintain complex skin microbiotas containing Bsal-inhibitory members, but these community are present at a remarkably low abundance. Through experimentation, we show that increasing bacterial densities of Bsal-inhibiting bacteria via daily addition slowed disease progression in fire salamanders. Additionally, we find that experimental-Bsal infection elicited subtle changes in the skin microbiome, with selected opportunistic bacteria increasing in relative abundance resulting in septicemic events that coincide with extensive destruction of the epidermis. These results suggest that fire salamander skin, in natural settings, maintains bacterial communities at numbers too low to confer sufficient protection against Bsal, and, in fact, the native skin microbiota can constitute a source of opportunistic bacterial pathogens that contribute to pathogenesis. By shedding light on the complex interaction between the microbiome and a lethal pathogen, these data put the interplay between skin microbiomes and a wildlife disease into a new perspective.

The Intestinal Microbiota of Tadpoles Differs from Those of Syntopic Aquatic Invertebrates.

Bacterial communities associated to eukaryotes play important roles in the physiology, development, and health of their hosts. Here, we examine the intestinal microbiota in tadpoles and aquatic invertebrates (insects and gastropods) to better understand the degree of specialization in the tadpole microbiotas. Samples were collected at the same time in one pond, and the V4 region of the bacterial 16S rRNA gene was sequenced with Illumina amplicon sequencing. We found that bacterial richness and diversity were highest in two studied snail individuals, intermediate in tadpoles, and lowest in the four groups of aquatic insects. All groups had substantial numbers of exclusive bacterial operational taxonomic units (OTUs) in their guts, but also shared a high proportion of OTUs, probably corresponding to transient environmental bacteria. Significant differences were found for all pairwise comparisons of tadpoles and snails with the major groups of insects, but not among insect groups or between snails and tadpoles. The similarity between tadpoles and snails may be related to similar feeding mode as both snails and tadpoles scratch biofilms and algae from surfaces; however, this requires confirmation due to low sample sizes. Overall, the gut microbiota differences found among syntopic aquatic animals are likely shaped by both food preferences and host identity.

Prodigiosin, Violacein, and Volatile Organic Compounds Produced by Widespread Cutaneous Bacteria of Amphibians Can Inhibit Two Batrachochytrium Fungal Pathogens.

Symbiotic bacteria can produce secondary metabolites and volatile compounds that contribute to amphibian skin defense. Some of these symbionts have been used as probiotics to treat or prevent the emerging disease chytridiomycosis. We examined 20 amphibian cutaneous bacteria for the production of prodigiosin or violacein, brightly colored defense compounds that pigment the bacteria and have characteristic spectroscopic properties making them readily detectable, and evaluated the antifungal activity of these compounds. We detected violacein from all six isolates of Janthinobacterium lividum on frogs from the USA, Switzerland, and on captive frogs originally from Panama. We detected prodigiosin from five isolates of Serratia plymuthica or S. marcescens, but not from four isolates of S. fonticola or S. liquefaciens. All J. lividum isolates produced violacein when visibly purple, while prodigiosin was only detected on visibly red Serratia isolates. When applied to cultures of chytrid fungi Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal), prodigiosin caused significant growth inhibition, with minimal inhibitory concentrations (MIC) of 10 and 50 µM, respectively. Violacein showed a MIC of 15 µM against both fungi and was slightly more active against Bsal than Bd at lower concentrations. Although neither violacein nor prodigiosin showed aerosol activity and is not considered a volatile organic compound (VOC), J. lividum and several Serratia isolates did produce antifungal VOCs. White Serratia isolates with undetectable prodigiosin levels could still inhibit Bd growth indicating additional antifungal compounds in their chemical arsenals. Similarly, J. lividum can produce antifungal compounds such as indole-3-carboxaldehyde in addition to violacein, and isolates are not always purple, or turn purple under certain growth conditions. When Serratia isolates were grown in the presence of cell-free supernatant (CFS) from the fungi, CFS from Bd inhibited growth of the prodigiosin-producing isolates, perhaps indicative of an evolutionary arms race; Bsal CFS did not inhibit bacterial growth. In contrast, growth of one J. lividum isolate was facilitated by CFS from both fungi. Isolates that grow and continue to produce antifungal compounds in the presence of pathogens may represent promising probiotics for amphibians infected or at risk of chytridiomycosis. In a global analysis, 89% of tested Serratia isolates and 82% of J. lividum isolates were capable of inhibiting Bd and these have been reported from anurans and caudates from five continents, indicating their widespread distribution and potential for host benefit.

Temporal changes in cutaneous bacterial communities of terrestrial- and aquatic-phase newts (Amphibia).

Animal-associated bacterial communities play essential roles for their host's ecology, physiology and health. Temporal dynamics of these communities are poorly understood, but might be of high relevance for amphibians with a well-expressed biphasic biology of adults where the structure of their skin changes drastically between the aquatic and terrestrial phases. Here, we investigated the temporal dynamics of cutaneous bacterial communities of Lissotriton boscai and Triturus marmoratus by monthly sampling populations from a pond and surrounding terrestrial habitats near A Coruña, Spain. These communities were characterized by 16S rRNA gene amplicons from DNA isolated from skin swabs. Newt bacterial communities displayed variation at three levels: between larvae and aquatic adults, between adult life phases (terrestrial versus aquatic), and temporally within life phases. The skin bacterial communities tended to differ to a lesser extent temporally and between larvae and adults, and more strongly between life phases. Larvae had a higher proportion of reads associated with antifungal taxa compared with adults, while no differences were found among adult life phases. Terrestrial specimens exhibited the highest community diversity. The regular transitions of adult newts between aquatic and terrestrial environments might contribute to the diversity of their skin microbiota and could increase disease resistance.

Cutaneous Bacterial Communities of a Poisonous Salamander: a Perspective from Life Stages, Body Parts and Environmental Conditions.

Amphibian skin provides a habitat for bacterial communities in its mucus. Understanding the structure and function of this "mucosome" in the European fire salamander (Salamandra salamandra) is critical in the context of novel emerging pathogenic diseases. We compare the cutaneous bacterial communities of this species using amplicon-based sequencing of the 16S rRNA V4 region. Across 290 samples, over 4000 OTUs were identified, four of them consistently present in all samples. Larvae and post-metamorphs exhibited distinct cutaneous microbial communities. In adults, the parotoid gland surface had a community structure different from the head, dorsum, flanks and ventral side. Larvae from streams had higher phylogenetic diversity than those found in ponds. Their bacterial community structure also differed; species of Burkholderiaceae, Comamonadaceae, Methylophilaceae and Sphingomonadaceae were more abundant in pond larvae, possibly related to differences in factors like desiccation and decomposition rate in this environment. The observed differences in the cutaneous bacterial community among stages, body parts and habitats of fire salamanders suggest that both host and external factors shape these microbiota. We hypothesize that the variation in cutaneous bacterial communities might contribute to variation in pathogen susceptibility among individual salamanders.

Expanding Distribution of Lethal Amphibian Fungus Batrachochytrium salamandrivorans in Europe.

Emerging fungal diseases can drive amphibian species to local extinction. During 2010-2016, we examined 1,921 urodeles in 3 European countries. Presence of the chytrid fungus Batrachochytrium salamandrivorans at new locations and in urodeles of different species expands the known geographic and host range of the fungus and underpins its imminent threat to biodiversity.

Gut bacterial communities across tadpole ecomorphs in two diverse tropical anuran faunas.

Animal-associated microbial communities can play major roles in the physiology, development, ecology, and evolution of their hosts, but the study of their diversity has yet focused on a limited number of host species. In this study, we used high-throughput sequencing of partial sequences of the bacterial 16S rRNA gene to assess the diversity of the gut-inhabiting bacterial communities of 212 specimens of tropical anuran amphibians from Brazil and Madagascar. The core gut-associated bacterial communities among tadpoles from two different continents strongly overlapped, with eight highly represented operational taxonomic units (OTUs) in common. In contrast, the core communities of adults and tadpoles from Brazil were less similar with only one shared OTU. This suggests a community turnover at metamorphosis. Bacterial diversity was higher in tadpoles compared to adults. Distinct differences in composition and diversity occurred among gut bacterial communities of conspecific tadpoles from different water bodies and after experimental fasting for 8 days, demonstrating the influence of both environmental factors and food on the community structure. Communities from syntopic tadpoles clustered by host species both in Madagascar and Brazil, and the Malagasy tadpoles also had species-specific isotope signatures. We recommend future studies to analyze the turnover of anuran gut bacterial communities at metamorphosis, compare the tadpole core communities with those of other aquatic organisms, and assess the possible function of the gut microbiota as a reservoir for protective bacteria on the amphibian skin.