The behavioral and neurobiological response to sound stress in salmon.

INTRODUCTION: Noise associated with human activities in aquatic environments can affect the physiology and behavior of aquatic species which may have consequences at the population and ecosystem levels. Low frequency sound is particularly stressful for fish, since it is an important factor in predator-prey interactions. Even though behavioral and physiological studies have been conducted to assess the effects of sound on fish species, neurobiological studies are still lacking. METHODS: In this study we exposed farmed salmon to low frequency sound for 5 minutes a day for 30 trials and conducted behavioral observations and tissue sampling before sound exposure (timepoint zero; T0) and after 1 (T1), 10 (T2), 20 (T3) and 30 (T4) exposures, to assess markers of stress. These included plasma cortisol, neuronal activity, monoaminergic signaling, and gene expression in 4 areas of the forebrain. RESULTS: We found that sound exposure induced an activation of the stress response by eliciting an initial startle behavioral response, together with increased plasma cortisol levels and a decrease in neuronal activity in the hypothalamic tubercular nuclei (TN). At T3 and T4 salmon showed a degree of habituation in their behavioral and cortisol response. However, at T4, salmon showed signs of chronic stress with increased serotonergic activity levels in the dorsolateral and dorsomedial pallium, the preoptic area, and the TN, as well as an inhibition of growth and reproduction transcripts in the TN. CONCLUSIONS: Together, our results suggest that prolonged exposure to sound results in chronic stress that leads to neurological changes which suggest a reduction of life fitness traits.

Achieving conservation and restoration outcomes through ecologically beneficial aquaculture.

A range of conservation and restoration tools are needed to safeguard the structure and function of aquatic ecosystems. Aquaculture, the culturing of aquatic organisms, often contributes to the numerous stressors that aquatic ecosystems face, yet some aquaculture activities can also deliver ecological benefits. We reviewed the literature on aquaculture activities that may contribute to conservation and restoration outcomes, either by enhancing the persistence or recovery of one or more target species or by moving aquatic ecosystems toward a target state. We identified 12 ecologically beneficial outcomes achievable via aquaculture: species recovery, habitat restoration, habitat rehabilitation, habitat protection, bioremediation, assisted evolution, climate change mitigation, wild harvest replacement, coastal defense, removal of overabundant species, biological control, and ex situ conservation. This list may be expanded as new applications are discovered. Positive intentions do not guarantee positive ecological outcomes, so it is critical that potentially ecologically beneficial aquaculture activities be evaluated via clear and measurable indicators of success to reduce potential abuse by greenwashing. Unanimity on outcomes, indicators, and related terminology will bring the field of aquaculture-environment interactions into line with consensus standards in conservation and restoration ecology. Broad consensus will also aid the development of future certification schemes for ecologically beneficial aquaculture.

Se necesita una gama de herramientas de conservación y restauración para salvaguardar la estructura y función de los ecosistemas acuáticos. La acuacultura (el cultivo de organismos acuáticos) generalmente contribuye a los numerosos estresantes que soportan los ecosistemas acuáticos, aunque algunas actividades de la acuacultura también pueden proporcionar beneficios ecológicos. Revisamos la literatura sobre las actividades de acuacultura que pueden contribuir a los resultados de conservación y restauración, ya sea al incrementar la persistencia o recuperación de una o más especies objetivo o al llevar a los ecosistemas acuáticos hacia un estado objetivo. Identificamos doce resultados con beneficios ecológicos que pueden lograrse con la acuacultura: recuperación de la especie, recuperación del hábitat, restauración del hábitat, rehabilitación del hábitat, protección del hábitat, bioreparación, evolución asistida, mitigación del cambio climático, sustitución de la captura silvestre, defensa costera, eliminación de las especies sobreabundantes, control biológico y conservación ex situ. Esta lista puede expandirse conforme se descubren nuevas aplicaciones. Las intenciones positivas no garantizan resultados ecológicos positivos, así que es importante que se evalúen las actividades de acuacultura con un posible beneficio ecológico por medio de indicadores del éxito claros y medibles para reducir el abuso potencial por ecoblanqueo o greenwashing. La unanimidad en los resultados, indicadores y terminología relacionada armonizará las interacciones entre la acuacultura y el ambiente con los estándares de la conservación y la ecología de la restauración. Un consenso generalizado también ayudará con el desarrollo de futuros esquemas de certificación para la acuacultura con beneficios ecológicos. Obtención de resultados de conservación y restauración a través de la acuacultura con beneficios ecológicos.

Reductions in Children's Blood Lead Levels from a Drinking-Water Intervention in Madagascar, Sub-Saharan Africa.

One in three children globally is estimated to have blood lead levels (BLL) at or above the BLL reference value of 5 µg/dL with increased burden falling on low- and middle-income countries (LMIC). Within developed countries, aqueous lead is the predominant exposure route. However, aqueous lead exposure is rarely examined in the LMIC, leaving a gap in the literature that ignores a potentially significant route of exposure. Furthermore, limited lead-based remediation efforts around consumer products have been examined. This study investigates the importance of lead exposure from the water supply through a case study in Toamasina, Madagascar. The project measured aqueous lead and BLL of children pre- and postremediation efforts (i.e., removal of leaded pump components in hand pumps) to verify the impact of aqueous lead exposure within this community. Removal of the leaded pump components (i.e., piston and foot valves) and replacement with nonleaded components decreased aqueous lead levels below the World Health Organization provisional guideline of 10 µg/L in all but 4% of pumps tested. Measured BLL concentrations indicated a statistically significant decrease in BLL from pre- to postremediation. Furthermore, the remediation resulted in a decrease in BLL for 87% of children with the greatest changes in BLL observed for children with the highest preremediation concentrations. These findings point to a need for greater consideration of lead in drinking and cooking waters as an important exposure route in LMIC.

AgroEcoList 1.0: A checklist to improve reporting standards in ecological research in agriculture.

Many publications lack sufficient background information (e.g. location) to be interpreted, replicated, or reused for synthesis. This impedes scientific progress and the application of science to practice. Reporting guidelines (e.g. checklists) improve reporting standards. They have been widely taken up in the medical sciences, but not in ecological and agricultural research. Here, we use a community-centred approach to develop a reporting checklist (AgroEcoList 1.0) through surveys and workshops with 23 experts and the wider agroecological community. To put AgroEcoList in context, we also assessed the agroecological community's perception of reporting standards in agroecology. A total of 345 researchers, reviewers, and editors, responded to our survey. Although only 32% of respondents had prior knowledge of reporting guidelines, 76% of those that had said guidelines improved reporting standards. Overall, respondents agreed on the need of AgroEcolist 1.0; only 24% of respondents had used reporting guidelines before, but 78% indicated they would use AgroEcoList 1.0. We updated AgroecoList 1.0 based on respondents' feedback and user-testing. AgroecoList 1.0 consists of 42 variables in seven groups: experimental/sampling set-up, study site, soil, livestock management, crop and grassland management, outputs, and finances. It is presented here, and is also available on github (https://github.com/AgroecoList/Agroecolist). AgroEcoList 1.0 can serve as a guide for authors, reviewers, and editors to improve reporting standards in agricultural ecology. Our community-centred approach is a replicable method that could be adapted to develop reporting checklists in other fields. Reporting guidelines such as AgroEcoList can improve reporting standards and therefore the application of research to practice, and we recommend that they are adopted more widely in agriculture and ecology.

Applying genetic technologies to combat infectious diseases in aquaculture.

Disease and parasitism cause major welfare, environmental and economic concerns for global aquaculture. In this review, we examine the status and potential of technologies that exploit genetic variation in host resistance to tackle this problem. We argue that there is an urgent need to improve understanding of the genetic mechanisms involved, leading to the development of tools that can be applied to boost host resistance and reduce the disease burden. We draw on two pressing global disease problems as case studies-sea lice infestations in salmonids and white spot syndrome in shrimp. We review how the latest genetic technologies can be capitalised upon to determine the mechanisms underlying inter- and intra-species variation in pathogen/parasite resistance, and how the derived knowledge could be applied to boost disease resistance using selective breeding, gene editing and/or with targeted feed treatments and vaccines. Gene editing brings novel opportunities, but also implementation and dissemination challenges, and necessitates new protocols to integrate the technology into aquaculture breeding programmes. There is also an ongoing need to minimise risks of disease agents evolving to overcome genetic improvements to host resistance, and insights from epidemiological and evolutionary models of pathogen infestation in wild and cultured host populations are explored. Ethical issues around the different approaches for achieving genetic resistance are discussed. Application of genetic technologies and approaches has potential to improve fundamental knowledge of mechanisms affecting genetic resistance and provide effective pathways for implementation that could lead to more resistant aquaculture stocks, transforming global aquaculture.

Provenance of rhizobial symbionts is similar for invasive and noninvasive acacias introduced to California.

Plant-soil interactions can be important drivers of biological invasions. In particular, the symbiotic relationship between legumes and nitrogen-fixing soil bacteria (i.e. rhizobia) may be influential in invasion success. Legumes, including Australian acacias, have been introduced into novel ranges around the world. Our goal was to examine the acacia-rhizobia symbiosis to determine whether cointroduction of non-native mutualists plays a role in invasiveness of introduced legumes. To determine whether acacias were introduced abroad concurrently with native symbionts, we selected four species introduced to California (two invasive and two noninvasive in the region) and identified rhizobial strains associating with each species in their native and novel ranges. We amplified three genes to examine phylogenetic placement (16S rRNA) and provenance (nifD and nodC) of rhizobia associating with acacias in California and Australia. We found that all Acacia species, regardless of invasive status, are associating with rhizobia of Australian origin in their introduced ranges, indicating that concurrent acacia-rhizobia introductions have occurred for all species tested. Our results suggest that cointroduction of rhizobial symbionts may be involved in the establishment of non-native acacias in their introduced ranges, but do not contribute to the differential invasiveness of Acacia species introduced abroad.

Childhood blood lead levels and environmental risk factors in Madagascar.

One-third of children globally have blood lead levels (BLLs) exceeding the (former) US CDC reference value of 5 µg/dL; this value may be as high as one-half for children in low- and middle-income countries (LMICs). Lead exposure occurs through a variety of routes (e.g., water, dust, air), and in LMICs specifically, informal economies (e.g., battery recycling) can drive lead exposures due, in part, to absent regulation. Previous work by our team identified a ubiquitous source of lead (Pb), in the form of Pb-containing components used in manually operated pumps, in Toamasina, Madagascar. Characterization of BLLs of children exposed to this drinking water, and identification of additional exposure routes were needed. BLLs were measured for 362 children (aged 6 months to 6 years) in parallel with surveying to assess 14 risk factors related to demographics/socioeconomics, diet, use of pitcher pumps, and parental occupations. BLL data were also compared against a recent meta-review of BLLs for LMICs. Median childhood BLL (7.1 µg/dL) was consistent with those of other Sub-Saharan African LMICs (6.8 µg/dL) and generally higher than LMICs in other continents. Risk factors significantly associated (p < 0.05, univariate logistic regression) with elevated BLL (at ≥ 5 µg/dL) included male gender, living near a railway or major roadway (owing potentially to legacy lead pollution), having lower-cost flooring, daily consumption of foods (beans, vegetables, rice) commonly cooked in recycled aluminum pots (a previously identified lead source for this community), and a maternal occupation (laundry-person) associated with lower socioeconomic status (SES). Findings were similar at the ≥ 10 µg/dL BLL status. Our methods and findings may be appropriate in identifying and reducing lead exposures for children in other urbanizing cities, particularly in Sub-Saharan Africa, where lead exposure routes are complex and varied owing to informal economics and substantial legacy pollution.

Comparison of non-subjective relative fungal biomass measurements to quantify the Leptosphaeria maculans-Brassica napus interaction.

BACKGROUND: Blackleg disease, caused by the fungal pathogen Leptosphaeria maculans, is a serious threat to canola (Brassica napus) production worldwide. Quantitative resistance to this disease is a highly desirable trait but is difficult to precisely phenotype. Visual scores can be subjective and are prone to assessor bias. Methods to assess variation in quantitative resistance more accurately were developed based on quantifying in planta fungal biomass, including the Wheat Germ Agglutinin Chitin Assay (WAC), qPCR and ddPCR assays. RESULTS: Disease assays were conducted by inoculating a range of canola cultivars with L. maculans isolates in glasshouse experiments and assessing fungal biomass in cotyledons, petioles and stem tissue harvested at different timepoints post-inoculation. PCR and WAC assay results were well correlated, repeatable across experiments and host tissues, and able to differentiate fungal biomass in different host-isolate treatments. In addition, the ddPCR assay was shown to differentiate between L. maculans isolates. CONCLUSIONS: The ddPCR assay is more sensitive in detecting pathogens and more adaptable to high-throughput methods by using robotic systems than the WAC assay. Overall, these methods proved accurate and non-subjective, providing alternatives to visual assessments to quantify the L. maculans-B. napus interaction in all plant tissues throughout the progression of the disease in seedlings and mature plants and have potential for fine-scale blackleg resistance phenotyping in canola.

Gene drive strategies of pest control in agricultural systems: Challenges and opportunities.

Recent advances in gene-editing technologies have opened new avenues for genetic pest control strategies, in particular around the use of gene drives to suppress or modify pest populations. Significant uncertainty, however, surrounds the applicability of these strategies to novel target species, their efficacy in natural populations and their eventual safety and acceptability as control methods. In this article, we identify issues associated with the potential use of gene drives in agricultural systems, to control pests and diseases that impose a significant cost to agriculture around the world. We first review the need for innovative approaches and provide an overview of the most relevant biological and ecological traits of agricultural pests that could impact the outcome of gene drive approaches. We then describe the specific challenges associated with using gene drives in agricultural systems, as well as the opportunities that these environments may offer, focusing in particular on the advantages of high-threshold gene drives. Overall, we aim to provide a comprehensive view of the potential opportunities and the remaining uncertainties around the use of gene drives in agricultural systems.

Midstream Players Determine Population-Level Behavior Change: Social Marketing Research to Increase Demand for Lead-Free Components in Pitcher Pumps in Madagascar.

Lead (Pb) exposure through water contamination is an important issue at the intersection of public health and water, sanitation, and hygiene (WASH). Behavior-change programs designed to address this pressing problem rarely take a behavioral-science-informed approach, nor do they consider the role of intermediate players who often influence and support behavior change. Social marketing segments the population and focuses on the consumer/user throughout program development and implementation. To illustrate the social marketing process, this cross-sectional, qualitative design study investigates the use of Pb in the construction and maintenance of household pitcher pumps for potable water in Madagascar. A sample of 18 technicians were interviewed on their current practices, motivators, barriers, and communication channels for knowledge exchange. The results reveal the importance of peers, those considered experts or "market mavens", and the need for information on the dangers of Pb as an outdated practice for any future intervention. This study advances the notion of a design shift within engineering WASH projects, whereby social/behavioral approaches are used to consider the needs, concerns, and current behaviors of the consumer. We also advocate for engaging intermediate players who often influence behavior change in the rollout of an engineering innovation.

Anti-Inflammatory and Anti-Platelet Properties of Lipid Bioactives from Apple Cider By-Products.

The valorization of food industry by-products as sources of bioactive compounds is at the forefront of research in functional foods and nutraceuticals. This study focuses on bioactives of apple cider by-products (ACBPs) with putative cardio-protective properties. Total lipids (TLs) were extracted from ACBPs of apple varieties that are low (ACBP1), medium (ACBP2), and high (ACBP3) in tannins and were further separated into polar lipids (PLs) and neutral lipids (NLs). The functionality of these lipid extracts and of their HPLC-derived lipid fractions/PL subclasses were assessed in vitro against human platelet aggregation induced by the thrombotic and inflammatory platelet agonists platelet-activating factor (PAF) and adenosine diphosphate (ADP). The fatty acid profile of PLs and their most bioactive lipid fractions were evaluated by GC-MS analysis. The PL extracts exhibited higher specificity against the PAF-induced platelet aggregation compared to their anti-ADP effects, while TL and NL showed lower bioactivities in all ACBPs. HPLC analysis unveiled that the most bioactive PL from all ACBPs were those in PL fraction 3 containing phosphatidylcholines (PCs). PLs from all ACBPs and their PC bioactives were rich in polyunsaturated fatty acids (PUFAs) and especially in the essential omega-6 (n-6) linoleic acid (LA) and omega-3 (n-3) alpha linolenic acid (ALA), with favorably low values of the n-6/n-3 PUFA ratio, thus providing a rationale for their higher anti-inflammatory bioactivities. Within this study, highly bioactive PL compounds with strong anti-inflammatory and anti-platelet properties were identified in ACBPs, which can be potentially utilized for producing cardio-protective functional foods and/or nutraceuticals.

Health and Economic Consequences of Lead Exposure Associated with Products and Services Provided by the Informal Economy.

In low- and middle-income countries (LMICs), the presence of an informal economy can lead to human exposure to toxic metals such as lead (Pb). This paper demonstrates the local health and economic benefits of modifying practices within the informal economic sector in Madagascar. Specifically, leaded components in 504 locally manufactured household water pumps were replaced with unleaded components. Prior to the intervention, 32% of the household systems exhibited lead concentrations above the World Health Organization (WHO) provisional drinking water guideline of 10 µg/L, but after the intervention, fewer than 3% of the systems were in exceedance. The reduction of lead concentration is modeled to reduce the fraction of children with elevated BLLs (>5 µg/dL) from 34 to 13%. The reduction in BLLs is estimated to provide an average economic benefit of US$11 800 per child based on predicted increases in lifetime productivity. This corresponds to a total benefit of US$8.7 million for the 730 children aged 1-5 associated with the pumps, representing a return on investment of greater than 1000-to-1. Results demonstrate how the formation of partnerships between public, private, and civil society entities, as suggested by UN Sustainable Development Goal 17, can realize important local economic and health benefits in LMICs.

Models of Plant Resistance Deployment.

Owing to their evolutionary potential, plant pathogens are able to rapidly adapt to genetically controlled plant resistance, often resulting in resistance breakdown and major epidemics in agricultural crops. Various deployment strategies have been proposed to improve resistance management. Globally, these rely on careful selection of resistance sources and their combination at various spatiotemporal scales (e.g., via gene pyramiding, crop rotations and mixtures, landscape mosaics). However, testing and optimizing these strategies using controlled experiments at large spatiotemporal scales are logistically challenging. Mathematical models provide an alternative investigative tool, and many have been developed to explore resistance deployment strategies under various contexts. This review analyzes 69 modeling studies in light of specific model structures (e.g., demographic or demogenetic, spatial or not), underlying assumptions (e.g., whether preadapted pathogens are present before resistance deployment), and evaluation criteria (e.g., resistance durability, disease control, cost-effectiveness). It highlights major research findings and discusses challenges for future modeling efforts.

Maintenance of variation in virulence and reproduction in populations of an agricultural plant pathogen.

Genetic diversity within pathogen populations is critically important for predicting pathogen evolution, disease outcomes and prevalence. However, we lack a good understanding of the processes maintaining genetic variation and constraints on pathogen life-history evolution. Here, we analysed interactions between 12 wheat host genotypes and 145 strains of Zymoseptoria tritici from five global populations to investigate the evolution and maintenance of variation in pathogen virulence and reproduction. We found a strong positive correlation between virulence (amount of leaf necrosis) and reproduction (pycnidia density within lesions), with substantial variation in both traits maintained within populations. On average, highly virulent isolates exhibited higher reproduction, which might increase transmission potential in agricultural fields planted to homogeneous hosts at a high density. We further showed that pathogen strains with a narrow host range (i.e. specialists) for reproduction were on average less virulent, and those with a broader host range (i.e. generalists) were on average less fecund on a given specific host. These costs associated with adaptation to different host genotypes might constrain the emergence of generalists by disrupting the directional evolution of virulence and fecundity. We conclude that selection favouring pathogen strains that are virulent across diverse hosts, coupled with selection that maximizes fecundity on specific hosts, may explain the maintenance of these pathogenicity traits within and among populations.

Mixed infections alter transmission potential in a fungal plant pathogen.

Infections by more than one strain of a pathogen predominate under natural conditions. Mixed infections can have significant, though often unpredictable, consequences for overall virulence, pathogen transmission and evolution. However, effects of mixed infection on disease development in plants often remain unclear and the critical factors that determine the outcome of mixed infections remain unknown. The fungus Zymoseptoria tritici forms genetically diverse infections in wheat fields. Here, for a range of pathogen traits, we experimentally decompose the infection process to determine how the outcomes and consequences of mixed infections are mechanistically realized. Different strains of Z. tritici grow in close proximity and compete in the wheat apoplast, resulting in reductions in growth of individual strains and in pathogen reproduction. We observed different outcomes of competition at different stages of the infection. Overall, more virulent strains had higher competitive ability during host colonization, and less virulent strains had higher transmission potential. We showed that within-host competition can have a major effect on infection dynamics and pathogen population structure in a pathogen and host genotype-specific manner. Consequently, mixed infections likely have a major effect on the development of septoria tritici blotch epidemics and the evolution of virulence in Z. tritici.

Metapopulation Structure Predicts Population Dynamics in the Cakile maritima-Alternaria brassicicola Host-Pathogen Interaction.

AbstractIn symbiotic interactions, spatiotemporal variation in the distribution or population dynamics of one species represents spatial and temporal heterogeneity of the landscape for the other. Such interdependent demographic dynamics result in situations where the relative importance of biotic and abiotic factors in determining ecological processes is complicated to decipher. Using a detailed survey of three metapopulations of the succulent plant Cakile maritima and the necrotrophic fungus Alternaria brassicicola located along the southeastern Australian coast, we developed a series of statistical analyses-namely, synchrony analysis, patch occupancy dynamics, and a spatially explicit metapopulation model-to understand how habitat quality, weather conditions, dispersal, and spatial structure determine metapopulation dynamics. Climatic conditions are important drivers, likely explaining the high synchrony among populations. Host availability, landscape features facilitating dispersal, and habitat conditions also impact the occurrence and spread of disease. Overall, we show that the collection of extensive data on host and pathogen population dynamics, in combination with spatially explicit epidemiological modeling, makes it possible to accurately predict disease dynamics-even when there is extreme variability in host population dynamics. Finally, we discuss the importance of genetic information for predicting demographic dynamics in this pathosystem.

Resistance to natural and synthetic gene drive systems.

Scientists are rapidly developing synthetic gene drive elements intended for release into natural populations. These are intended to control or eradicate disease vectors and pests, or to spread useful traits through wild populations for disease control or conservation purposes. However, a crucial problem for gene drives is the evolution of resistance against them, preventing their spread. Understanding the mechanisms by which populations might evolve resistance is essential for engineering effective gene drive systems. This review summarizes our current knowledge of drive resistance in both natural and synthetic gene drives. We explore how insights from naturally occurring and synthetic drive systems can be integrated to improve the design of gene drives, better predict the outcome of releases and understand genomic conflict in general.

Native predator limits the capacity of an invasive seastar to exploit a food-rich habitat.

Biodiverse ecosystems are sometimes inherently resistant to invasion, but environmental change can facilitate invasion by disturbing natural communities and providing resources that are underutilised by native species. In such cases, sufficiently abundant native predators may help to limit invasive population growth. We studied native and invasive seastars feeding under two mussel aquaculture sites in south-east Australia, to determine whether food-rich farm habitats are likely to be reproductive hotspots for the invasive seastar (Asterias amurensis) and whether the larger native seastar (Coscinasterias muricata) reduces the value of the farms for the invader. We found that invaders were not significantly more abundant inside the farms, despite individuals residing within the farms having higher body condition metrics and reproductive investment than those outside. By contrast, the native seastar was 25 × more abundant inside the two farms than outside. We observed several intraguild predation events and an absence of small invaders at the farms despite reports of high larval recruitment to these environments, consistent with some level of biotic control by the native predator. A laboratory choice experiment showed that invaders were strongly attracted to mussels except when the native predator was present. Together, these findings indicate that a combination of predation and predator evasion may play a role in reducing the value of food-rich anthropogenic habitats for this invasive species.

Genetic analysis reveals long-standing population differentiation and high diversity in the rust pathogen Melampsora lini.

A priority for research on infectious disease is to understand how epidemiological and evolutionary processes interact to influence pathogen population dynamics and disease outcomes. However, little is understood about how population adaptation changes across time, how sexual vs. asexual reproduction contribute to the spread of pathogens in wild populations and how diversity measured with neutral and selectively important markers correlates across years. Here, we report results from a long-term study of epidemiological and genetic dynamics within several natural populations of the Linum marginale-Melampsora lini plant-pathogen interaction. Using pathogen isolates collected from three populations of wild flax (L. marginale) spanning 16 annual epidemics, we probe links between pathogen population dynamics, phenotypic variation for infectivity and genomic polymorphism. Pathogen genotyping was performed using 1567 genome-wide SNP loci and sequence data from two infectivity loci (AvrP123, AvrP4). Pathogen isolates were phenotyped for infectivity using a differential set. Patterns of epidemic development were assessed by conducting surveys of infection prevalence in one population (Kiandra) annually. Bayesian clustering analyses revealed host population and ecotype as key predictors of pathogen genetic structure. Despite strong fluctuations in pathogen population size and severe annual bottlenecks, analysis of molecular variance revealed that pathogen population differentiation was relatively stable over time. Annually, varying levels of clonal spread (0-44.8%) contributed to epidemics. However, within populations, temporal genetic composition was dynamic with rapid turnover of pathogen genotypes, despite the dominance of only four infectivity phenotypes across the entire study period. Furthermore, in the presence of strong fluctuations in population size and migration, spatial selection may maintain pathogen populations that, despite being phenotypically stable, are genetically highly dynamic.