Top-predator recovery abates geomorphic decline of a coastal ecosystem.

The recovery of top predators is thought to have cascading effects on vegetated ecosystems and their geomorphology1,2, but the evidence for this remains correlational and intensely debated3,4. Here we combine observational and experimental data to reveal that recolonization of sea otters in a US estuary generates a trophic cascade that facilitates coastal wetland plant biomass and suppresses the erosion of marsh edges-a process that otherwise leads to the severe loss of habitats and ecosystem services5,6. Monitoring of the Elkhorn Slough estuary over several decades suggested top-down control in the system, because the erosion of salt marsh edges has generally slowed with increasing sea otter abundance, despite the consistently increasing physical stress in the system (that is, nutrient loading, sea-level rise and tidal scour7-9). Predator-exclusion experiments in five marsh creeks revealed that sea otters suppress the abundance of burrowing crabs, a top-down effect that cascades to both increase marsh edge strength and reduce marsh erosion. Multi-creek surveys comparing marsh creeks pre- and post-sea otter colonization confirmed the presence of an interaction between the keystone sea otter, burrowing crabs and marsh creeks, demonstrating the spatial generality of predator control of ecosystem edge processes: densities of burrowing crabs and edge erosion have declined markedly in creeks that have high levels of sea otter recolonization. These results show that trophic downgrading could be a strong but underappreciated contributor to the loss of coastal wetlands, and suggest that restoring top predators can help to re-establish geomorphic stability.

Fiber chromatographic enabled process intensification increases monoclonal antibody product yield.

The most straightforward method to increase monoclonal antibody (mAb) product yield is to complete the purification process in less steps. Here, three different fiber chromatographic devices were implemented using a holistic approach to intensify the mAb purification process and increase yield. Fiber protein A (proA) chromatography was first investigated, but traditional depth filtration was not sufficient in reducing the contaminant load as the fiber proA device prematurely fouled. Further experimentation revealed that chromatin aggregates were the most likely reason for the fiber fouling. To reduce levels of chromatin aggregates, a chromatographic clarification device (CCD) was incorporated into the process, resulting in single-stage clarification of harvested cell culture fluid and reduction of DNA levels. The CCD clarified pool was then successfully processed through the fiber proA device, fully realizing the productivity gains that the fiber technology offers. After the proA and viral inactivation neutralization (VIN) hold step, the purification process was further intensified using a novel single-use fiber-based polishing anion exchange (AEX) material that is capable of binding both soluble and insoluble contaminants. The three-stage fiber chromatographic purification process was compared to a legacy five-step process of dual-stage depth filtration, bead-based proA chromatography, post-VIN depth filtration, and bead-based AEX chromatography. The overall yield from the five-step process was 60%, while the fiber chromatographic-enabled intensified process had an overall yield of 70%. The impurity clearance of DNA and host cell protein (HCP) for both processes were within the regulatory specification (<100 ppm HCP, <1 ppb DNA). For the harvest of a 2000 L cell culture, the intensified process is expected to increase productivity by 2.5-fold at clarification, 50-fold at the proA step, and 1.6-fold in polishing. Relative to the legacy process, the intensified process would reduce buffer use by 1088 L and decrease overall process product mass intensity by 12.6%.

Impact on species' online attention when named after celebrities.

Celebrities can generate substantial attention and influence public interest in species. Using a large-scale examination of publicly available data, we assessed whether species across 6 taxonomic groups received more page views on Wikipedia when the species was named after a celebrity than when it was not. We conducted our analysis for 4 increasingly strict thresholds of how many average daily Wikipedia page views a celebrity had (1, 10, 100, or 1000 views). Overall, we found a high probability (0.96-0.98) that species named after celebrities had more page views than their closest relatives that were not named after celebrities, irrespective of the celebrity threshold. The multiplicative effect on species' page views was larger but more uncertain as celebrity page-view thresholds increased. The range for thresholds of 1 to 1000 was 1.08 (95% credible interval [CI] 1.00-1.18) to 1.76 (95% CI 0.96-2.80), respectively. The hierarchical estimates for the taxa tended to be positive. The strongest effects were for invertebrates, followed by amphibians, reptiles, fish, and mammals, whereas the weakest effect was for birds at lower page-view thresholds. Our results suggest that naming species after celebrities could be particularly significant for those belonging to taxonomic groups that are generally less popular than others (e.g., invertebrates). Celebrities may further influence the effectiveness of this marketing strategy, depending on their likability and connection to the species named after them. Eponyms may serve as a reminder of the disproportionate power dynamics between populations and some namesakes' untenable actions. However, they also provide an opportunity to recognize remarkable individuals and promote equity, inclusivity, and diversity in taxonomic practice. We encourage taxonomists to examine whether naming threatened species after celebrities could affect conservation support, especially for species that are otherwise typically overlooked by the public.

Impacto sobre la atención virtual de una especie si lleva el nombre de una celebridad Resumen Las celebridades pueden generar atención considerable e influir sobre el interés público por las especies. Usamos un análisis a gran escala de datos con disponibilidad pública para evaluar si las especies de seis grupos taxonómicos recibían más visitas en Wikipedia cuando el nombre de la especie provenía del de una celebridad que cuando no. Realizamos nuestro análisis en cuatro umbrales cada vez más estrictos de cuántas visitas diarias en promedio tenía la página de Wikipedia de una celebridad (1, 10, 100 or 1000 visitas). En general, descubrimos una probabilidad alta (0.96­0.98) de que las especies con nombres de celebridades tuvieran más visitas que sus parientes más cercanos que no tenían un nombre así, sin importar el umbral de la celebridad. El efecto multiplicativo sobre las visitas a la página de la especie fue mayor pero más incierto si incrementaba el umbral de visitas de la celebridad. El rango para los umbrales de 1 a 1000 fue de 1.08 (95% intervalo creíble [IC] 1.00­1.18) a 1.76 (95% IC 0.96­2.80) respectivamente. Los estimados jerárquicos para los taxones tuvieron una tendencia positiva. Los efectos más fuertes se presentaron en los invertebrados, seguidos de los anfibios, reptiles, peces y mamíferos, mientras que el efecto más débil fue para las aves en los umbrales de menor número de visitas. Nuestros resultados sugieren que nombrar a una especie con el nombre de una celebridad podría ser particularmente importante para aquellas que pertenecen a grupos taxonómicos que generalmente suelen ser menos populares que otros (invertebrados). Las celebridades podrían influir todavía más en la efectividad de esta estrategia de marketing, dependiendo de su popularidad y la conexión con la especie que lleva su nombre. Los epónimos pueden funcionar como recordatorios de las dinámicas disparejas de poder entre las poblaciones y las acciones indefendibles de algunos homónimos. Sin embargo, los epónimos también proporcionan la oportunidad para reconocer individuos destacados y promover la equidad, inclusividad y diversidad en la práctica taxonómica. Alentamos a que los taxónomos analicen si nombrar a una especie amenazada con el nombre de una celebridad podría afectar el apoyo a su conservación, especialmente para las especies que de otra manera suelen ser ignoradas por el público.

Character displacement drives trait divergence in a continental fauna.

Coexisting (sympatric) pairs of closely related species are often characterized by exaggerated trait differences. This widespread pattern is consistent with adaptation for reduced similarity due to costly interactions (i.e., "character displacement")-a classic hypothesis in evolutionary theory. But it is equally consistent with a community assembly bias in which lineages with greater trait differences are more likely to establish overlapping ranges in the first place (i.e., "species sorting"), as well as with null expectations of trait divergence through time. Few comparative analyses have explicitly modeled these alternatives, and it remains unclear whether trait divergence is a general prerequisite for sympatry or a consequence of interactions between sympatric species. Here, we develop statistical models that allow us to distinguish the signature of these processes based on patterns of trait divergence in closely related lineage pairs. We compare support for each model using a dataset of bill shape differences in 207 pairs of New World terrestrial birds representing 30 avian families. We find that character displacement models are overwhelmingly supported over species sorting and null expectations, indicating that exaggerated bill shape differences in sympatric pairs result from enhanced divergent selection in sympatry. We additionally detect a latitudinal gradient in character displacement, which appears strongest in the tropics. Our analysis implicates costly species interactions as powerful drivers of trait divergence in a major vertebrate fauna. These results help substantiate a long-standing but equivocally supported linchpin of evolutionary theory.

Expressive vocabulary word categories of children who are deaf and hard-of-hearing.

This study investigated the acquisition of early expressive vocabulary among young children who are deaf and hard-of-hearing (DHH; n = 68) using auditory technology (hearing aids and cochlear implants). Parents completed a standardized vocabulary checklist, which allowed analyses of (i) the size of their child's spoken vocabulary; (ii) composition of the expressive lexicon (e.g., parts of speech such as nouns and verbs; semantic categories such as routines and body parts); and (iii) demographic and audiologic factors (e.g., chronologic age, degree of hearing access) potentially associated with these metrics. Young children who are DHH and use auditory technology acquired fewer spoken words than peers with typical hearing (TH) matched for chronologic age but more spoken words than peers with TH matched for listening experience. Action verbs-not nouns-significantly increased the odds of a child who is DHH achieving a vocabulary quotient within the normative range. These findings support the exploration of early expressive vocabulary size and composition-especially the number of active verbs-to guide clinical management and decision-making for young children who are DHH.

The Role of the Gut Microbiome in Cancer: A Review, With Special Focus on Colorectal Neoplasia and Clostridioides difficile.

The gut microbiome has coevolved with humans to aid in physiologic functions and prevent disease. An increasing prevalence of gut dysbiosis in modern society exists and has strong linkages to multiple disease processes common in the developed world. Mechanisms for microbiome-human interactions that impact host homeostasis include bacterial metabolite/toxin production, biofilm formation with mucous layer infiltration, and host immune system modulation. Most of this crosstalk occurs at the epithelial layer of the gut, and as such the role of these interactions in the induction of colorectal cancer-a highly prevalent disease globally and one undergoing significant epidemiologic shifts-is under increasing scrutiny. Although multiple individual gut bacteria have been hypothesized as possible driver organisms in the oncogenic process, no bacterium has been definitively identified as a causal agent of colorectal cancer, suggesting that host lifestyle factors, microbiome community interactions, and the mucosal and/or systemic immune response may play a critical role in the process. Recent evidence has emerged implicating the ubiquitous human pathogen Clostridioides difficile as a possible promoter of colorectal cancer through chronic toxin-mediated cellular changes. Although much remains to be defined regarding the natural history of infections caused by this pathogen and its potential for oncogenesis, it provides a strong model for the role of both individual bacteria and of the gut microbial community as a whole in the development of colorectal cancer.

Ecology and the Origin of Nonephemeral Species.

AbstractResearch over the past three decades has shown that ecology-based extrinsic reproductive barriers can rapidly arise to generate incipient species-but such barriers can also rapidly dissolve when environments change, resulting in incipient species collapse. Understanding the evolution of unconditional, "intrinsic" reproductive barriers is therefore important for understanding the longer-term buildup of biodiversity. In this article, we consider ecology's role in the evolution of intrinsic reproductive isolation. We suggest that this topic has fallen into a gap between disciplines: while evolutionary ecologists have traditionally focused on the rapid evolution of extrinsic isolation between co-occurring ecotypes, speciation geneticists studying intrinsic isolation in other taxa have devoted little attention to the ecological context in which it evolves. We argue that for evolutionary ecology to close this gap, the field will have to expand its focus beyond rapid adaptation and its traditional model systems. Synthesizing data from several subfields, we present circumstantial evidence for and against different forms of ecological adaptation as promoters of intrinsic isolation and discuss alternative forces that may be significant. We conclude by outlining complementary approaches that can better address the role of ecology in the evolution of nonephemeral reproductive barriers and, by extension, less ephemeral species.

Microphone array analysis for simultaneous condition detection, localization, and classification in a pipe.

An acoustic method for simultaneous condition detection, localization, and classification in air-filled pipes is proposed. The contribution of this work is threefold: (1) a microphone array is used to extend the usable acoustic frequency range to estimate the reflection coefficient from blockages and lateral connections; (2) a robust regularization method of sparse representation based on a wavelet basis function is adapted to reduce the background noise in acoustical data; and (3) the wavelet components are used to localize and classify the condition of the pipe. The microphone array and sparse representation method enhance the acoustical signal reflected from blockages and lateral connections and suppress unwanted higher-order modes. Based on the sparse representation results, higher-level wavelet functions representing the impulse response are used to localize the position of the sensor corresponding to a blockage or lateral connection with higher spatial resolution. It is shown that the wavelet components can be used to train and to test a support vector machine (SVM) classifier for the condition identification more accurately than with a time domain SVM classifier. This work paves the way for the development of simultaneous condition classification and localization methods to be deployed on autonomous robots working in buried pipes.

Web-based psychoacoustics of binaural hearing: Two validation experiments.

Web-based testing is an appealing option for expanding psychoacoustics research outside laboratory environments due to its simple logistics. For example, research participants partake in listening tasks using their own computer and audio hardware and can participate in a comfortable environment of their choice at their own pace. However, it is unknown how deviations from conventional in-lab testing affect data quality, particularly in binaural hearing tasks that traditionally require highly precise audio presentation. Here, we used an online platform to replicate two published in-lab experiments: lateralization to interaural time and level differences (ITD and ILD, experiment I) and dichotic and contralateral unmasking of speech (experiment II) in normal-hearing (NH) young adults. Lateralization data collected online were strikingly similar to in-lab results. Likewise, the amount of unmasking measured online and in-lab differed by less than 1 dB, although online participants demonstrated higher speech reception thresholds overall than those tested in-lab by up to ∼7 dB. Results from online participants who completed a hearing screening versus those who self-reported NH did not differ significantly. We conclude that web-based psychoacoustics testing is a viable option for assessing binaural hearing abilities among young NH adults and discuss important considerations for online study design.

Chronic aseptic meningitis caused by enterovirus in a humorally immunosuppressed adult patient presenting with sensorineural hearing loss: a case report.

BACKGROUND: Enterovirus has been described as a cause of aseptic meningitis in humorally immunosuppressed patients. CASE PRESENTATION: A 67-year-old female with a history of mantle cell lymphoma on rituximab therapy presented with subacute hepatitis, myalgias, and sensorineural hearing loss several months after an initial febrile illness. She was diagnosed with enterovirus infection by CSF PCR as a unifying etiology of her presentation, representing an unusual presentation of disease. DISCUSSION AND CONCLUSIONS: This patient's unique presentation and clinical course presents important implications in the care of similarly immunosuppressed patients with cryptic complaints.

Asymmetric temporal envelope sensitivity: Within- and across-ear envelope comparisons in listeners with bilateral cochlear implants.

For listeners with bilateral cochlear implants (BiCIs), patient-specific differences in the interface between cochlear implant (CI) electrodes and the auditory nerve can lead to degraded temporal envelope information, compromising the ability to distinguish between targets of interest and background noise. It is unclear how comparisons of degraded temporal envelope information across spectral channels (i.e., electrodes) affect the ability to detect differences in the temporal envelope, specifically amplitude modulation (AM) rate. In this study, two pulse trains were presented simultaneously via pairs of electrodes in different places of stimulation, within and/or across ears, with identical or differing AM rates. Results from 11 adults with BiCIs indicated that sensitivity to differences in AM rate was greatest when stimuli were paired between different places of stimulation in the same ear. Sensitivity from pairs of electrodes was predicted by the poorer electrode in the pair or the difference in fidelity between both electrodes in the pair. These findings suggest that electrodes yielding poorer temporal fidelity act as a bottleneck to comparisons of temporal information across frequency and ears, limiting access to the cues used to segregate sounds, which has important implications for device programming and optimizing patient outcomes with CIs.

Geographic contact drives increased reproductive isolation in two cryptic Empidonax flycatchers.

Geographic contact between sister lineages often occurs near the final stages of speciation, but its role in speciation's completion remains debated. Reproductive isolation may be essentially complete prior to secondary contact. Alternatively, costly interactions between partially reproductively isolated species - such as maladaptive hybridization or competition for resources - may select for divergence, increasing reproductive isolation and driving speciation toward completion. Here, we use coalescent demographic modelling and whole-genome data sets to show that a period of contact and elevated hybridization between sympatric eastern North American populations of two cryptic bird species preceded a major increase in reproductive isolation between these populations within the last 10,000 years. In contrast, substantial introgression continues to the present in a western contact zone where geographic overlap is much narrower and probably of more recent origin. In the sympatric eastern region where reproductive isolation has increased, it is not accompanied by character displacement in key morphometric traits, plumage coloration, or ecological traits. While the precise trait and underlying mechanism driving increased reproductive isolation remains unknown, we discuss several possibilities and outline avenues for future research. Overall, our results highlight how demographic models can reveal the geographic context in which reproductive isolation was completed, and demonstrate how contact can accelerate the final stages of speciation.

Are we ready to track climate-driven shifts in marine species across international boundaries? - A global survey of scientific bottom trawl data.

Marine biota are redistributing at a rapid pace in response to climate change and shifting seascapes. While changes in fish populations and community structure threaten the sustainability of fisheries, our capacity to adapt by tracking and projecting marine species remains a challenge due to data discontinuities in biological observations, lack of data availability, and mismatch between data and real species distributions. To assess the extent of this challenge, we review the global status and accessibility of ongoing scientific bottom trawl surveys. In total, we gathered metadata for 283,925 samples from 95 surveys conducted regularly from 2001 to 2019. We identified that 59% of the metadata collected are not publicly available, highlighting that the availability of data is the most important challenge to assess species redistributions under global climate change. Given that the primary purpose of surveys is to provide independent data to inform stock assessment of commercially important populations, we further highlight that single surveys do not cover the full range of the main commercial demersal fish species. An average of 18 surveys is needed to cover at least 50% of species ranges, demonstrating the importance of combining multiple surveys to evaluate species range shifts. We assess the potential for combining surveys to track transboundary species redistributions and show that differences in sampling schemes and inconsistency in sampling can be overcome with spatio-temporal modeling to follow species density redistributions. In light of our global assessment, we establish a framework for improving the management and conservation of transboundary and migrating marine demersal species. We provide directions to improve data availability and encourage countries to share survey data, to assess species vulnerabilities, and to support management adaptation in a time of climate-driven ocean changes.

Quantifying the impact of COVID-19 control measures using a Bayesian model of physical distancing.

Extensive non-pharmaceutical and physical distancing measures are currently the primary interventions against coronavirus disease 2019 (COVID-19) worldwide. It is therefore urgent to estimate the impact such measures are having. We introduce a Bayesian epidemiological model in which a proportion of individuals are willing and able to participate in distancing, with the timing of distancing measures informed by survey data on attitudes to distancing and COVID-19. We fit our model to reported COVID-19 cases in British Columbia (BC), Canada, and five other jurisdictions, using an observation model that accounts for both underestimation and the delay between symptom onset and reporting. We estimated the impact that physical distancing (social distancing) has had on the contact rate and examined the projected impact of relaxing distancing measures. We found that, as of April 11 2020, distancing had a strong impact in BC, consistent with declines in reported cases and in hospitalization and intensive care unit numbers; individuals practising physical distancing experienced approximately 0.22 (0.11-0.34 90% CI [credible interval]) of their normal contact rate. The threshold above which prevalence was expected to grow was 0.55. We define the "contact ratio" to be the ratio of the estimated contact rate to the threshold rate at which cases are expected to grow; we estimated this contact ratio to be 0.40 (0.19-0.60) in BC. We developed an R package 'covidseir' to make our model available, and used it to quantify the impact of distancing in five additional jurisdictions. As of May 7, 2020, we estimated that New Zealand was well below its threshold value (contact ratio of 0.22 [0.11-0.34]), New York (0.60 [0.43-0.74]), Washington (0.84 [0.79-0.90]) and Florida (0.86 [0.76-0.96]) were progressively closer to theirs yet still below, but California (1.15 [1.07-1.23]) was above its threshold overall, with cases still rising. Accordingly, we found that BC, New Zealand, and New York may have had more room to relax distancing measures than the other jurisdictions, though this would need to be done cautiously and with total case volumes in mind. Our projections indicate that intermittent distancing measures-if sufficiently strong and robustly followed-could control COVID-19 transmission. This approach provides a useful tool for jurisdictions to monitor and assess current levels of distancing relative to their threshold, which will continue to be essential through subsequent waves of this pandemic.

Dynamics of intracellular stress-induced tRNA trafficking.

Stress is known to induce retrograde tRNA translocation from the cytoplasm to the nucleus but translocation kinetics and tRNA-spatial distribution have not been characterized previously. We microinject fluorescently-labeled tRNA into living cells and use confocal microscopy to image tRNA spatial distribution in single cells at various levels of starvation and to determine translocation rate constants. Retrograde tRNA translocation occurs reversibly, within minutes after nutrition depletion of the extracellular medium. Such nutritional starvation leads to down-regulation of tRNA nuclear import and nearly complete curtailment of its nuclear export. Nuclear tRNA accumulation is suppressed in cells treated with the translation inhibitor puromycin, but is enhanced in cells treated with the microtubule inhibitor nocodazole. tRNA in the cytoplasm exhibits distinct spatial distribution inconsistent with diffusion, implying that such distribution is actively maintained. We propose that tRNA biological complexes and/or cytoplasmic electric fields are the likely regulators of cytoplasmic tRNA spatial distribution.

Rewards interact with explicit knowledge to enhance skilled motor performance.

From typing on a keyboard to playing the piano, many everyday skills require the ability to quickly and accurately perform sequential movements. It is well known that the availability of rewards leads to increases in motivational vigor whereby people enhance both the speed and force of their movements. However, in the context of motor skills, it is unclear whether rewards also lead to more effective motor planning and action selection. Here, we trained human participants to perform four separate sequences in a skilled motor sequencing task. Two of these sequences were trained explicitly and performed with precues that allow for the planning of movements, while the other two were trained implicitly. Immediately following the introduction of performance-contingent monetary incentives, participants improved their performance on all sequences consistent with enhancements in motivational vigor. However, there was a much larger performance boost for explicitly trained sequences. We replicated these results in a second, preregistered experiment with an independent sample. We conclude from these experiments that rewards enhance both the planning of movements as well as motivational vigor.NEW & NOTEWORTHY Offering people rewards and incentives typically improves their performance on skilled motor tasks. However, the mechanisms by which motivation impacts motor skills remains unclear. In two experiments, we show that motivation impacts motor sequencing skills in two separate ways. First, the prospect of reward speeds up the execution of all actions. Second, rewards provide an additional boost to motor planning when explicit skill knowledge can be used to prepare movements in advance.

A Comparative Test for Divergent Adaptation: Inferring Speciation Drivers from Functional Trait Divergence.

AbstractEcological differentiation between lineages is widely considered to be an important driver of speciation, but support for this hypothesis is mainly derived from the detailed study of a select set of model species pairs. Mounting evidence from nonmodel taxa, meanwhile, suggests that speciation often occurs with minimal differentiation in ecology or ecomorphology, calling into question the true contribution of divergent adaptation to species richness in nature. To better understand divergent ecological adaptation and its role in speciation generally, researchers require a comparative approach that can distinguish its signature from alternative processes, such as drift and parallel selection, in data sets containing many species pairs. Here we introduce new statistical models of divergent adaptation in the continuous traits of paired lineages. In these models, ecomorphological characters diverge as two lineages adapt toward alternative phenotypic optima following their departure from a common ancestor. The absolute distance between optima measures the extent of divergent selection and provides a basis for interpretation. We encode the models in the new R package diverge and extend them to allow the distance between optima to vary across continuous and categorical variables. We test model performance using simulation and demonstrate model application using published data sets of trait divergence in birds and mammals. Our framework provides the first explicit test for signatures of divergent selection in trait divergence data sets, and it will enable empiricists from a wide range of fields to better understand the dynamics of divergent adaptation and its prevalence in nature beyond just our best-studied model systems.

Sensorimotor maps can be dynamically calibrated using an adaptive-filter model of the cerebellum.

Substantial experimental evidence suggests the cerebellum is involved in calibrating sensorimotor maps. Consistent with this involvement is the well-known, but little understood, massive cerebellar projection to maps in the superior colliculus. Map calibration would be a significant new role for the cerebellum given the ubiquity of map representations in the brain, but how it could perform such a task is unclear. Here we investigated a dynamic method for map calibration, based on electrophysiological recordings from the superior colliculus, that used a standard adaptive-filter cerebellar model. The method proved effective for complex distortions of both unimodal and bimodal maps, and also for predictive map-based tracking of moving targets. These results provide the first computational evidence for a novel role for the cerebellum in dynamic sensorimotor map calibration, of potential importance for coordinate alignment during ongoing motor control, and for map calibration in future biomimetic systems. This computational evidence also provides testable experimental predictions concerning the role of the connections between cerebellum and superior colliculus in previously observed dynamic coordinate transformations.

Black-swan events in animal populations.

Black swans are improbable events that nonetheless occur-often with profound consequences. Such events drive important transitions in social systems (e.g., banking collapses) and physical systems (e.g., earthquakes), and yet it remains unclear the extent to which ecological population numbers buffer or suffer from such extremes. Here, we estimate the prevalence and direction of black-swan events (heavy-tailed process noise) in 609 animal populations after accounting for population dynamics (productivity, density dependence, and typical stochasticity). We find strong evidence for black-swan events in [Formula: see text]4% of populations. These events occur most frequently for birds (7%), mammals (5%), and insects (3%) and are not explained by any life-history covariates but tend to be driven by external perturbations such as climate, severe winters, predators, parasites, or the combined effect of multiple factors. Black-swan events manifest primarily as population die-offs and crashes (86%) rather than unexpected increases, and ignoring heavy-tailed process noise leads to an underestimate in the magnitude of population crashes. We suggest modelers consider heavy-tailed, downward-skewed probability distributions, such as the skewed Student [Formula: see text] used here, when making forecasts of population abundance. Our results demonstrate the importance of both modeling heavy-tailed downward events in populations, and developing conservation strategies that are robust to ecological surprises.

Benefits and risks of diversification for individual fishers.

Individuals relying on natural resource extraction for their livelihood face high income variability driven by a mix of environmental, biological, management, and economic factors. Key to managing these industries is identifying how regulatory actions and individual behavior affect income variability, financial risk, and, by extension, the economic stability and the sustainable use of natural resources. In commercial fisheries, communities and vessels fishing a greater diversity of species have less revenue variability than those fishing fewer species. However, it is unclear whether these benefits extend to the actions of individual fishers and how year-to-year changes in diversification affect revenue and revenue variability. Here, we evaluate two axes by which fishers in Alaska can diversify fishing activities. We show that, despite increasing specialization over the last 30 years, fishing a set of permits with higher species diversity reduces individual revenue variability, and fishing an additional permit is associated with higher revenue and lower variability. However, increasing species diversity within the constraints of existing permits has a fishery-dependent effect on revenue and is usually (87% probability) associated with increased revenue uncertainty the following year. Our results demonstrate that the most effective option for individuals to decrease revenue variability is to participate in additional or more diverse fisheries. However, this option is expensive, often limited by regulations such as catch share programs, and consequently unavailable to many individuals. With increasing climatic variability, it will be particularly important that individuals relying on natural resources for their livelihood have effective strategies to reduce financial risk.