Freshwater salinization is an anthropogenic pollution issue that is receiving exponentially greater attention as we appreciate the global nature of the problem and the widespread lethal and sublethal impacts. A growing body of research is discovering that some freshwater taxa can evolve increased salt tolerance over generations, but such evolved tolerance often has tradeoffs in performance and fitness. We examined whether tadpoles collected from nine wood frog populations (Rana sylvatica), which have been exposed to generations of different elevated salt concentrations, differ in their susceptibility to common amphibian pathogens. When exposed to echinostomes, all tadpoles became infected, but there was no mortality and the populations had similar pathogen loads. When exposed to ranavirus (FV3), there were large population differences in survival, with populations from saltier ponds exhibiting lower survival. However, among the survivors, populations from saltier ponds had lower viral loads, suggesting higher resistance. Collectively, these results suggest that historic salt exposures in ponds can be associated with differences in susceptibility to some pathogens, although much more work needs to be conducted on additional populations, host species, and pathogen species.

Terrestrial leaf litter can release chemical compounds into the water, creating a solution called "leachate" that can have direct and indirect impacts on freshwater organisms. In this study, we investigated the direct effects of leaf litter leachates from six plant species on the fungal pathogen, Batrachochytrium dendrobatidis (Bd) in vitro, and their effects on tadpole infection in vivo, when tadpoles were reared in leachates before Bd exposure. In our in vitro experiment, all six types of leachates reduced the concentration of Bd zoosporangia, and there were mixed effects of leachate type on the concentration of Bd zoospores. Purple loosestrife leachate had the greatest effect on Bd in the in vitro experiment suggesting that this plant species may produce chemicals that are directly detrimental to Bd. The negative effects of leachates on Bd in vitro increased with leachate concentration. In our in vivo tadpole experiments, leachates had no measurable impact on the tadpole host survival, size, development, or infection with Bd. Our results indicate that leaf litter leachate can have direct negative effects on Bd, but these effects may not translate to large changes in infection in tadpoles. However, future studies are necessary to determine the comprehensive impact of leachates on aquatic amphibians and their pathogens in natural populations. These results highlight the importance of understanding terrestrial inputs into freshwater systems.

Per- and poly-fluoroalkyl substances (PFAS) present a significant challenge for human, wildlife, and environmental health due to their persistence and bioaccumulative tendencies. Despite growing public concern, information on PFAS in many plants and animals is relatively limited. This information gap includes species harvested for human consumption and traditional Indigenous foods. As PFAS contamination may pose disproportionate risks to Indigenous food sovereignty and lifeways, understanding the potential presence of these contaminants in traditional foods is crucially important. Seeking to address the information gap, this Tribally driven study analyzed PFAS in two species of aquatic plants; Manoomin (Zizania palustris) and Psincinca (Sagittaria latifolia). Found across the Great Lakes region, these plants have both ecological importance and cultural significance for Indigenous peoples. In Psincinca, no PFAS were detected above the minimum level of detection (LOD). In Manoomin, four PFAS (perfluoro(2-ethoxyethane) sulfonic acid (PFEESA), perfluorohexane sulfonic acid (PFHxS), perfluorooctane sulfonic acid (PFOS), perfluoro-n-pentanoic acid (PFPeA) were detected in varied plant tissues (roots, stalks, and seeds). All PFAS were detected at levels below 2 ng/g that are unlikely to pose a risk for human consumption at this time. This study is the first to investigate PFAS bioaccumulation in Manoomin or Psincinca and quantifies PFAS in surrounding environmental matrices (sediment and surface water). These findings highlight potential exposure pathways for harvesters and can help to inform Tribal food sovereignty initiatives. This study establishes a foundation for future research exploring the impacts of PFAS on the health of Manoomin, Psincinca, and the overall condition of aquatic ecosystems.

Microplastic (MP) pollution poses a growing threat to freshwater ecosystems, yet its effects on ecological interactions, such as host-parasite or host-microbiota dynamics, are poorly understood. Using leopard frog (Lithobates pipiens) tadpoles and their interactions with a common trematode parasite as a model, this study experimentally manipulated MP fiber size (short: ∼0.24 mm; long: ∼1.5 mm) and concentration (10 or 40 μg L⁻¹) to assess effects on tadpole survival, growth, development, behavior, gut microbiota, and parasite susceptibility. High MP concentrations significantly reduced tadpole survival, with long fibers causing greater mortality. Sublethal exposures inhibited development at both concentrations, while 40 μg L⁻¹ also reduced mass and length. Shorter fibers were more frequently ingested, coinciding with altered host behavior and elevated infection intensities, suggesting impaired parasite avoidance. MP exposure caused modest shifts in gut microbiota. In contrast, tadpole gut microbiota was minimally altered by the parasite and MP-parasite treatments. Our findings revealed that MP fiber morphology and concentration interact to shape amphibian health and susceptibility to parasitic infection. These results underscore the importance of incorporating ecological interactions into risk assessments of MP and highlight how environmentally-relevant fiber sizes can disrupt key ecological interactions in freshwater systems.

Monitoring biomarkers of physiological stress (e.g., oxidative stress) in sensitive wildlife populations can allow conservationists to identify, quantify, and make predictions about the impacts of global change. However, interpretation of stress responses can be complicated by multiple interacting factors (e.g., individual development, evolved physiological tolerance to stressors) which alter biomarker expression. To better understand the relative influences of these factors, we used wood frog (Rana sylvatica) populations with known variation in ontogenetic and contaminant tolerance traits. We examined how both individual ontogenetic traits and population-level tolerance traits influence oxidative stress responses under baseline and sodium chloride (NaCl)-contaminated environmental conditions. We exposed tadpoles from six noninteracting populations with known variation in ontogeny, pesticide tolerance, and NaCl tolerance to either baseline or NaCl-contaminated conditions and evaluated five biomarkers of oxidative stress. We found that individual body mass was a significant predictor of two oxidative stress biomarkers (catalase and glutathione reductase) in baseline conditions only, such that greater mass predicted lower enzyme activity. Separately, population pesticide tolerance was a significant predictor of one oxidative stress biomarker (glutathione peroxidase) in NaCl-contaminated conditions only, such that higher pesticide tolerance predicted higher enzyme activity. Our results demonstrate that both individual traits (mass) and population history (selection for pesticide tolerance) can explain some variation in oxidative stress biomarkers. However, these associations are largely dependent on the environmental conditions experienced. Our findings demonstrate that individual development and population history influence stress responses. This underscores the need for future applications of oxidative stress biomarkers to consider both historical and contemporary environmental contexts to improve their use as indicators of change.

Per- and poly-fluoroalkyl substances (PFAS) pose significant health and environmental risks due to their persistence and potential for bioaccumulation. Using a new analytical method, we quantified PFAS in maple sap and syrup from Indigenous lands in the Ceded Territories, a largely under-surveyed area. Our investigation focuses on maple products due to their cultural significance to Ojibwe communities, and economic importance as harvestable resources. We detected two PFAS (PFBA and PFPeA) in maple sap, and ten PFAS (8:2 FTSA, N-EtFOSE, N-MeFOSE, PFBA, PFBS, PFDoA, PFHxA, PFOA, PFPeA, and PFTeDA) in maple syrup at low concentrations that do not presently pose an immediate health risk for human consumption in this area. This study is the first to detect PFAS in both maple sap and syrup, demonstrating the efficacy of an adapted analytical method with low detection limits (> 1 ng/L) for a broad range of PFAS compounds. This method represents a novel application of established techniques to test previously unstudied matrices. Indigenous herbalists encourage paying close attention to plants, as they offer valuable insight into environmental well-being, including the presence of contamination. Given that maple sap and syrup reflect environmental contamination from various sources including rainwater, groundwater, porous water, and soil, we propose that maple trees can be used as a biomonitoring system for PFAS across a forested area. This tribally driven approach can help assess ecosystem health and evaluate potential human health risk associated with PFAS contamination in maple products.

Diseases are emerging at unprecedented rates, prompting global efforts to understand factors shaping disease outcomes. Microbes associated with hosts and the environment influence disease by secreting antipathogenic metabolites, hindering pathogen success. However, antibiotic contamination and costs associated with microbial responses to antibiotics may reduce antipathogenic efficacy. We investigated how antibiotic tolerance influences the antipathogenic properties of metabolites produced by Pseudomonas aeruginosa using in vitro and in vivo experiments. We found that metabolites from antibiotic-non-tolerant P. aeruginosa strains retained their antipathogenic properties and inhibited the growth of Batrachochytrium dendrobatidis (Bd), an amphibian fungal pathogen responsible for amphibian declines worldwide. In contrast, metabolites from P. aeruginosa strains that developed antibiotic tolerance promoted Bd growth and exacerbated infection severity. These patterns were consistent in vitro and in vivo. We also ran toxicological and small molecule analyses of microbial metabolites, and findings suggest the divergent experimental outcomes may stem from differences in metabolite toxicity and profiles between strains. These findings underscore the hidden consequences of interactions between microbial responses to environmental changes and pathogens on infectious disease dynamics and highlight the need to integrate environmental change and eco-evolutionary perspectives into disease research.

Animal coloration serves a variety of visually related functions in nature (e.g. mate choice, aposematism and camouflage) but the pigments in integumentary tissues such as skin, scales and feathers may also serve functions unrelated to the visual environment (e.g. temperature regulation, detoxification and pollutant protection). Our understanding of the significance of the non-visual functions of animal integumentary pigments, as well as how they interact with the visually related functions to shape animal visual systems, remains limited. Furthermore, due to their important roles in shaping species interactions and mediating interactions in the environment, animal colour traits are likely to be impacted by global change (e.g. increased temperatures, altered habitat quality and quantity, increased environmental stochasticity, pollutants and novel species assemblages). Considering the effects of global change on both visual and non-visual functions is important for understanding whether the selection is acting directly on the pigment or on coloration. Since changing the trait distributions can then lead to changes in visual systems, we advocate for studies to consider all potential functions of integumentary pigments, both visual and non-visual functions and their interaction. Towards this goal, we first highlight common functions of pigments with a focus on non-visual functions across animal systems. Then we synthesize our current understanding of how global change can impact pigmentation and discuss factors that can modify the interactions between climate change and pigment function. Lastly, we discuss how changes in colour traits can impact visual systems and provide an example using amphibians and their responses to climate change as a model.Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog.image

Human impacts on ecological communities are pervasive and species must either move or adapt to changing environmental conditions. For environments polluted by contaminants, researchers have found hundreds of target pest species evolving increased tolerance, but we have substantially fewer cases of evolved tolerance in non-target species. When species do evolve increased tolerance, inducible tolerance can provide immediate protection and favor the evolution of increased tolerance over generations via genetic assimilation. Using a model larval amphibian (wood frogs, Rana sylvatica), we examined the tolerance of 15 populations from western Pennsylvania and eastern New York (USA), when first exposed to no pesticide or sublethal concentrations and subsequently exposed to lethal concentrations of three common insecticides (carbaryl, chlorpyrifos, and diazinon). We found high variation in naïve tolerance among the populations for all three insecticides. We also discovered that nearly half of the populations exhibited inducible tolerance, though the degree of inducible tolerance (magnitude of tolerance plasticity; MoTP) varied. We observed a cross-tolerance pattern of the populations between chlorpyrifos and diazinon, but no pattern of similar MoTP among the pesticides. With populations combined from two regions, increased tolerance was not associated with proximity to agricultural fields, but there were correlations between proximity to agriculture and MoTP. Collectively, these results suggests that amphibian populations possess a wide range of naïve tolerance to common pesticides, with many also being able to rapidly induce increased tolerance. Future research should examine inducible tolerance in a wide variety of other taxa and contaminants to determine the ubiquity of these responses to anthropogenic factors.

Engaging youth in early and sustained conservation education has important implications for promoting positive attitudes and behaviors in those who will become the future of conservation and management. Toward this goal, visual narratives (comic books, graphic novels) are an increasingly popular method used by conservation scientists to educate young people due to their approachable use of art and narrative storytelling. However, no studies have directly assessed how visual narratives compare with more traditional forms of conservation education for youth. We asked, how does education about biodiversity through visual narrative affect student perceptions and knowledge of science content relative to a traditional resource, and is there a novelty effect when using visual narrative versus traditional resources? To assess our questions, we utilized a semistructured approach to develop a biodiversity education program. Specifically, we developed an original graphic novel (visual narrative treatment) and a slideshow presentation (traditional treatment) with the same content to educate children about wetland biodiversity. We recruited, trained, and randomized 26 third-grade teachers to deliver either the visual narrative or traditional resource in their classrooms. Students completed pretest, posttest, and follow-up surveys assessing their perceptions of science and knowledge of the lesson content. Students in the visual narrative treatment held more positive perceptions of science (by 3.79%, p  = 0.001), whereas students in the traditional treatment performed better on content quizzes (by 7.97%, p  = 0.002). We found evidence for a novelty bias when using the visual narrative but not the traditional resource. These findings point to the importance of understanding the target audience and clearly defining educational goals. Overall, our results contribute to broader understanding of the relative benefits and limitations of conservation education through nontraditional means and of practices for successfully delivering effective, accessible, and rewarding conservation education to educators and youth.

Artificial light at night (ALAN) is a global pollutant of rising concern. While alterations to natural day-night cycles caused by ALAN can affect a variety of traits, the broader fitness and ecological implications of these ALAN-induced shifts remain unclear. This study evaluated the interactive effects of ALAN and background color on traits that have important implications for predator-prey interactions and fitness: crypsis, background adaptation efficacy, and growth. Using three amphibian species as our models, we discovered that: (1) Exposure to ALAN reduced the ability for some species to match their backgrounds (background adaptation efficacy), (2) Crypsis and background adaptation efficacy were enhanced when tadpoles were exposed to dark backgrounds only, emphasizing the importance of environmental context when evaluating the effects of ALAN, (3) ALAN and background color have a combined effect on a common metric of fitness (growth), and (4) Effects of ALAN were not generalizable across amphibian species, supporting calls for more studies that utilize a diversity of species. Notably, to our knowledge, we found the first evidence that ALAN can diminish background adaptation efficacy in an amphibian species (American toad tadpoles). Collectively, our study joins others in highlighting the complex effects of ALAN on wildlife and underscores the challenges of generalizing ALAN's effect across species, emphasizing the need for a greater diversity of species and approaches used in ALAN research.

Ecotoxicological studies using single test populations may miss the inherent variation of natural systems and limit our understanding of how contaminants affect focal species. Though population-level variation in pesticide tolerance is commonly observed in host taxa, few studies have assessed population-level differences in the tolerance of parasites to different contaminants. We investigated population-level variation in insecticide tolerance of three Echinostoma trivolvis life stages (egg, miracidium, and cercaria) to three insecticides (carbaryl, chlorpyrifos, and diazinon). We tested two relevant metrics of insecticide tolerance-baseline and induced-across up to eight different parasite populations per life stage. Across all life stages, the insecticide treatments tended to reduce survival, but the magnitude of their effects often varied significantly among populations. Surprisingly, we found that exposure to chlorpyrifos increased the hatching success of echinostome eggs relative to the control treatment in three of six tested populations. We also found that cercariae shed from snails previously exposed to a sublethal concentration of chlorpyrifos had a significantly lower mortality rate when subsequently exposed to a lethal concentration of chlorpyrifos relative to individuals from snails that were not previously exposed; this suggests inducible tolerance in cercariae. We found no evidence that insecticide tolerance is correlated across parasite life stages within a population. Together the findings of our study demonstrate that single-population toxicity assays may greatly over- or underestimate the effects of pesticides on the survival of free-living parasite stages, insecticide tolerance levels may not be predictable from one parasite life stage to the next, and insecticides can have both expected and counterintuitive effects on non-target taxa.

Art is a common approach for communicating and educating about science, yet it remains unclear the extent to which science art can benefit varied audiences in varied contexts. To examine this gap, we developed an art exhibit based on the findings of two publications in disease ecology. In study 1, we asked visitors with varying formal science, technology, engineering, and math (STEM) education backgrounds to complete a survey about their interest in science research before and after viewing the exhibit. In study 2, we recruited upper-level ecology undergraduate students to receive one of three treatments: engage with the art exhibit, read the abstracts of the papers, or do neither. Students completed a comprehension quiz immediately after their learning treatment and again 2 weeks later to evaluate retention. Following the exhibit, visitors who did not report a career or major in STEM showed a greater increase in research interest than visitors who did report a career or major in STEM. For the ecology undergraduate students, comprehension quiz scores were higher for students in the abstract group than the art exhibit group, while both groups scored higher than the control group. Retention of information did not significantly differ between the three groups. Overall, these findings suggest that science art exhibits are an effective method for increasing the accessibility of science to broader audiences and that audience identifiers (e.g., level of formal education in STEM) play an important role in audience experience of science communication and science education initiatives.

Hosts and parasites are embedded in communities where species richness and composition can influence disease outcomes (diversity-disease relationships). The direction and magnitude of diversity-disease relationships are influenced by variation in competence (ability to support and transmit infections) of hosts in a community. However, host susceptibility to parasites, which mediates host competence, is not static and is influenced by environmental factors, including pollutants. Despite the role that pollutants can play in augmenting host susceptibility, how pollutants influence diversity-disease dynamics is not well understood. Using an amphibian-trematode model, we tested how NaCl influences diversity-disease dynamics. We predicted that NaCl exposure can alter relative susceptibility of host species to trematodes, leading to cascading effects on the diversity-disease relationship. To test these predictions, we exposed hosts to benign or NaCl environments and generated communities that differed in number and composition of host species. We exposed these communities to trematodes and measured disease outcomes at the community (total infections across all hosts within a community) and species levels (average number of infections per host species within a community). Host species differed in their relative susceptibility to trematodes when exposed to NaCl. Consequently, at the community level (total infections across all hosts within a community), we only detected diversity-disease relationships (dilution effects) in communities where hosts were exposed to NaCl. At the species level, disease outcomes (average number of infections/species) and whether multi-species communities supported lower number of infections relative to single-species communities depended on community composition. Notably, however, as with overall community infection, diversity-disease relationships only emerged when hosts were exposed to NaCl. Synthesis. Pollutants are ubiquitous in nature and can influence disease dynamics across a number of host-parasite systems. Here, we show that NaCl exposure can alter the relative susceptibility of host species to parasites, influencing the relationship between biodiversity and disease at both community and species levels. Collectively, our study contributes to the limited knowledge surrounding environmental mediators of host susceptibility and their influence on diversity-disease dynamics.

This review summarizes the role of environmental factors on amphibian microbiotas at the organismal, population, community, ecosystem, and biosphere levels. At the organismal-level, tissue source, disease status, and experimental manipulations were the strongest predictors of variation in amphibian microbiotas. At the population-level, habitat quality, disease status, and ancestry were commonly documented as drivers of microbiota turnover. At the community-level, studies focused on how species’ niche influence microbiota structure and function. At the ecosystem-level, abiotic and biotic reservoirs were important contributors to microbiota structure. At the biosphere-level, databases, sample banks, and seminatural experiments were commonly used to describe microbiota assembly mechanisms among temperate and tropical amphibians. Collectively, our review demonstrates that environmental factors can influence microbiotas through diverse mechanisms at all biological scales. Importantly, while environmental mechanisms occurring at each of the different scales can interact to shape microbiotas, the past 10 years of research have mostly been characterized by targeted approaches at individual scales. Looking forward, efforts considering how environmental factors at multiple organizational levels interact to shape microbiota diversity and function are paramount. Generating opportunities for meaningful cross-disciplinary interactions and supporting infrastructure for research that spans biological scales are imperative to addressing this gap.