Pandemic Action Plan: Phase 3-Lessons Learned from Implementation. "What Did We Learn?"

The COVID-19 pandemic created critical challenges for hospitals and health care providers. Suddenly clinics were forced to close; elective procedures were delayed; scheduled visits were canceled; emergency rooms were overcrowded; hospital beds, equipment, and personal protective equipment (PPE) were in short supply; and staff were faced with rapidly changing circumstances, care protocols, trauma, and personal risk. To better address challenges of the ongoing COVID-19 pandemic and prepare for future pandemics, the National Telemedicine Technology Assessment Resource Center (TTAC) was asked to develop a Pandemic Response Action Plan that would allow its users to address critical issues with available telemedicine and related technologies. The project was constructed in 3 phases. Phase 1-Develop a Pandemic Response Action Plan and a Pandemic Response Action Plan Policy and Regulatory Summary, which identifies the regulatory challenges as well as policy recommendations. Phase 2-Publish the Action Plan and the Policy and Regulatory Summary. Phase 3-Look at health care providers who used the approaches, tools, and technology in the Pandemic Action Plan and document the results. This document represents Phase 3. This document is Phase 3. In this report we look back at health care providers who used the approaches in the Phase 1 Pandemic Response Action Plan as published in Phase 2. In this document we report on the challenges and results of implementing parts of the Pandemic Action Plan. It records the findings, conclusions, and recommendations resulting from the experience of health care providers and the professional experiences of the team and their organizations in implementing parts or all of the plan. Methods: The same multidisciplinary team that constructed Phase 1 and Phase 2 were engaged to develop this Phase 3 report. The members of the team represent leadership expertise and key stakeholders in health care delivery during a pandemic (administration, infection control, physicians, nurses, public health, contingency planning, disaster response, and information technology) as well as a facilitator. For Phase 3, the group used structured brainstorming to define the findings, issues, and results of their own organizations' digital health response to the pandemic. In addition, eight health care providers (hospitals) identified by the Telemedicine Resource Centers' (TRCs) organizations, who used the Pandemic response Plan (created in Phases 1 and 2), were interviewed. All interviews were conducted by the same facilitator with leaders (CEO, and leaders of the telemedicine programs) in each of the eight programs, using a standard questionnaire created by the team. Current literature references are included in this report to illustrate when findings are known to have broader applicability. Conclusions: The impact of the COVID-19 Pandemic was severe and identified multiple critical challenges and weaknesses. Applying the approaches, tools, and technology outlined in the Pandemic Response Action Plan proved to be effective in addressing critical provider challenges. However, implementing these tools during a crisis was difficult unless the organization had experience with the tools and necessary workflows in advance. Implementing these tools as part of standard workflows and everyday operations increased the capabilities and resilience of these organizations in the provision of care during this and for future pandemics.

Diversity of mitochondrial DNA in 3 species of great whales before and after modern whaling.

The 20th century commercial whaling industry severely reduced populations of great whales throughout the Southern Hemisphere. The effect of this exploitation on genetic diversity and population structure remains largely undescribed. Here, we compare pre- and post-whaling diversity of mitochondrial DNA (mtDNA) control region sequences for 3 great whales in the South Atlantic, such as the blue, humpback, and fin whale. Pre-whaling diversity is described from mtDNA extracted from bones collected near abandoned whaling stations, primarily from the South Atlantic island of South Georgia. These bones are known to represent the first stage of 20th century whaling and thus pre-whaling diversity of these populations. Post-whaling diversity is described from previously published studies reporting large-scale sampling of living whales in the Southern Hemisphere. Despite relatively high levels of surviving genetic diversity in the post-whaling populations, we found evidence of a probable loss of mtDNA lineages in all 3 species. This is evidenced by the detection of a large number of haplotypes found in the pre-whaling samples that are not present in the post-whaling samples. A rarefaction analysis further supports a loss of haplotypes in the South Atlantic humpback and Antarctic blue whale populations. The bones from former whaling stations in the South Atlantic represent a remarkable molecular archive for further investigation of the decline and ongoing recovery in the great whales of the Southern Hemisphere.

Red-list status and extinction risk of the world's whales, dolphins, and porpoises.

To understand the scope and scale of the loss of biodiversity, tools are required that can be applied in a standardized manner to all species globally, spanning realms from land to the open ocean. We used data from the International Union for the Conservation of Nature Red List to provide a synthesis of the conservation status and extinction risk of cetaceans. One in 4 cetacean species (26% of 92 species) was threatened with extinction (i.e., critically endangered, endangered, or vulnerable) and 11% were near threatened. Ten percent of cetacean species were data deficient, and we predicted that 2-3 of these species may also be threatened. The proportion of threatened cetaceans has increased: 15% in 1991, 19% in 2008, and 26% in 2021. The assessed conservation status of 20% of species has worsened from 2008 to 2021, and only 3 moved into categories of lesser threat. Cetacean species with small geographic ranges were more likely to be listed as threatened than those with large ranges, and those that occur in freshwater (100% of species) and coastal (60% of species) habitats were under the greatest threat. Analysis of odontocete species distributions revealed a global hotspot of threatened small cetaceans in Southeast Asia, in an area encompassing the Coral Triangle and extending through nearshore waters of the Bay of Bengal, northern Australia, and Papua New Guinea and into the coastal waters of China. Improved management of fisheries to limit overfishing and reduce bycatch is urgently needed to avoid extinctions or further declines, especially in coastal areas of Asia, Africa, and South America.

Estado en la lista roja y riesgo de extinción de las ballenas, delfines y marsopas del mundo Resumen Para comprender el alcance y la escala de la pérdida de biodiversidad, se necesitan herramientas que puedan aplicarse de forma estandarizada a todas las especies a nivel mundial y que abarquen todos los ámbitos desde la tierra hasta el océano. Utilizamos datos de la Lista Roja de la Unión Internacional para la Conservación de la Naturaleza para proporcionar una síntesis del estado de conservación y el riesgo de extinción de los cetáceos. Una de cada 4 especies de cetáceos (26% de 92 especies) se encuentra amenazada (es decir, en peligro crítico, en peligro o vulnerable) y el 11% de las especies está clasificado como casi amenazada. El 10% de las especies de cetáceos carecía de datos, por lo que predijimos que 2-3 de estas especies también podrían estar amenazadas. La proporción de cetáceos amenazados ha aumentado: 15% en 1991, 19% en 2008 y 26% en 2021. El estado de conservación evaluado del 20% de las especies ha empeorado de 2008 a 2021, pues sólo 3 pasaron a categorías de menor amenaza. Las especies de cetáceos con áreas de distribución geográficas pequeñas tenían más probabilidades de ser catalogadas como amenazadas que aquellas con áreas de distribución extensas, y aquellas que ocurren en hábitats de agua dulce (100% de las especies) y costeros (60% de las especies) eran las que se encontraban bajo mayor amenaza. La superposición de los mapas de distribución de las especies reveló la existencia de puntos calientes de pequeños cetáceos amenazados en el sudeste asiático y en una zona que abarca el Triángulo de Coral y se extiende por las aguas cercanas a la costa de la Bahía de Bengala, el norte de Australia, Papúa Nueva Guinea y las aguas costeras de China. Urge mejorar la gestión de las pesquerías para limitar la sobrepesca y reducir la captura accesoria con el fin de evitar extinciones o mayores descensos, especialmente en las zonas costeras de Asia, África y Sudamérica.

A Review of Wearable Multi-Wavelength Photoplethysmography.

Optical pulse detection 'photoplethysmography' (PPG) provides a means of low cost and unobtrusive physiological monitoring that is popular in many wearable devices. However, the accuracy, robustness and generalizability of single-wavelength PPG sensing are sensitive to biological characteristics as well as sensor configuration and placement; this is significant given the increasing adoption of single-wavelength wrist-worn PPG devices in clinical studies and healthcare. Since different wavelengths interact with the skin to varying degrees, researchers have explored the use of multi-wavelength PPG to improve sensing accuracy, robustness and generalizability. This paper contributes a novel and comprehensive state-of-the-art review of wearable multi-wavelength PPG sensing, encompassing motion artifact reduction and estimation of physiological parameters. The paper also encompasses theoretical details about multi-wavelength PPG sensing and the effects of biological characteristics. The review findings highlight the promising developments in motion artifact reduction using multi-wavelength approaches, the effects of skin temperature on PPG sensing, the need for improved diversity in PPG sensing studies and the lack of studies that investigate the combined effects of factors. Recommendations are made for the standardization and completeness of reporting in terms of study design, sensing technology and participant characteristics.

DeepPulse: An Uncertainty-aware Deep Neural Network for Heart Rate Estimations from Wrist-worn Photoplethysmography.

Wearable Photoplethysmography (PPG) has gained prominence as a low cost, unobtrusive and continuous method for physiological monitoring. The quality of the collected PPG signals is affected by several sources of interference, predominantly due to physical motion. Many methods for estimating heart rate (HR) from PPG signals have been proposed with Deep Neural Networks (DNNs) gaining popularity in recent years. However, the "black-box" and complex nature of DNNs has caused a lack of trust in the predicted values. This paper contributes DeepPulse, an uncertainty-aware DNN method for estimating HR from PPG and accelerometer signals, with aims of increasing trust of the predicted HR values. To the best of the authors' knowledge no PPG HR estimation method has considered aleatoric and epistemic uncertainty metrics. The results show DeepPulse is the most accurate method for DNNs with smaller network sizes. Finally, recommendations are given to reduce epistemic uncertainty, validate uncertainty estimates, improve the accuracy of DeepPulse as well as reduce the model size for resource-constrained edge devices.

Promoting nurse-led behaviour change interventions to prevent cardiovascular disease in disadvantaged communities: A scoping review.

Cardiovascular diseases (CVD) are the leading cause of death worldwide and they disproportionally affect people living in disadvantaged communities. Nurse-led behaviour change interventions have shown great promise in preventing CVD. However, knowledge regarding the impact and nature of such interventions in disadvantaged communities is limited. This review aimed to address this knowledge gap. A six-stage scoping review framework developed by Arksey and O'Malley, with revisions by Levac et al., was used. The search process was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses-Extension for Scoping Reviews (PRISMA-ScR). Three electronic databases were searched (PUBMED/MEDLINE, CINAHL Plus, and Cochrane CENTRAL), and included studies were analysed using Braun and Clarke's 'Thematic Analysis' approach. Initial searches yielded 952 papers and 30 studies were included in the review following duplicate, title/abstract, and full-text screening. The included studies indicate that nurse-led behaviour change primary prevention interventions in disadvantaged areas are largely effective; albeit the considerable variety of intervention approaches, study populations and outcome measures used to date make it difficult to ascertain this. Other identified key areas in the promotion of nurse-led behaviour change included tailoring interventions to specific populations, providing adequate training for nurses, overcoming patient access difficulties and encouraging patient engagement. Overall, the findings indicate that nurse-led behaviour change interventions for high-risk CVD patients in disadvantaged areas show much promise, although there is considerable variety in the interventions employed and studied to date. Further research is needed to examine the unique barriers and facilitators of interventions for specific disadvantaged groups.

Carcinogenic air pollution along the United States' southern border: Neighborhood inequities in risk.

Air pollution poses serious and socially inequitable risks to public health. Social disparities are marked along the US-Mexico border, yet prior research has not assessed inequities in air pollution exposure across the entire US-side of the border region. We apply an intersectional approach to examine contextually relevant sociodemographic variables, including (1) Hispanic/Latinx ethnicity by race and (2) nativity (US vs. Foreign) by citizenship, and cancer risks attributable to air pollution exposures. We pair data from the 2012-2016 American Community Survey with 2014 National Air Toxics Assessment estimates of carcinogenic risks from all sources of hazardous air pollutants at the census tract level (n = 1448) and use a series of generalized estimating equations to assess inequities in risk. Increased concentrations of renter-occupants, Hispanics, mid-to-high socioeconomic status households, and foreign-born citizens were associated with elevated risks. Hispanic ethnicity intersected with non-White racial identification to amplify risks. In contrast, increased concentrations of non-Hispanic Black people and foreign-born non-citizens were not associated with disparate risks. To ameliorate environmental health inequities in this context, research and policy actions must be tailored to the US-Mexico border and consider intersectional positions within the Hispanic population.

Pandemic Telemedicine Technology Response Plan and Technology Assessment Phase 2: Pandemic Action Plan Key Issues and Technology Solutions for Health Care Delivery Organizations in a Pandemic.

Introduction: The Covid-19 pandemic created critical challenges for hospitals and healthcare providers. Suddenly clinics were forced to close; scheduled visits were cancelled; emergency rooms were overcrowded; hospital beds, equipment and personal protective equipment (PPE) was in short supply; and staff were faced with rapidly changing circumstances, care protocols, trauma and personal risk. In order to better address the ongoing the Covid-19 pandemic and prepare for future pandemics, the National Telemedicine Technology Assessment resource Center (TTAC) was asked to develop an Pandemic Response Action Plan that would allow its user to address critical issues with available telemedicine and related technologies. The project was constructed into three phases: Phase 1. Develop a Pandemic Response Action Plan (this document) and a Policy document which identifies the regulatory challenges in the Pandemic Response as well as policy recommendations (published separately). Phase 2. Publish the plan and policy documents. Phase 3 Look at healthcare providers who used the approaches, tools and technology in the Pandemic Action Plan and document the results (to be published separately). TTAC will also assess selected technology and publish results as part of their normal course of services. Materials and Methods: A multi-disciplinary team was created representing leadership expertise and key stakeholders in healthcare delivery during a pandemic (administration, infection control, physicians, nurses, public health, contingency planning, disaster response, information technology) as well as a facilitator. The group used structured brainstorming, current literature and iterative review to identify the most critical challenges facing healthcare providers during the current Covid 19 pandemic. The team then used structured brainstorming, professional experience and current literature to take a deeper look into these impacts, identify applicable solutions and develop a plan to address the critical challenges using telemedicine and related technologies. Result: A Pandemic Action Response Plan that describes the critical challenges and then identifies approaches, tools and technology to address them as well as identifying samples of the technology. Conclusions: The impact of the Covid 19 Pandemic was severe and identified multiple critical challenges and weaknesses in most healthcare providers. Applying the approaches, tools and technology in this Pandemic Action Plan will help providers address these challenges and increase the capabilities and resilience of their organizations in the provision of care during this and future pandemics.

Pandemic Action Plan Policy and Regulatory Summary Telehealth Policy and Regulatory Considerations During a Pandemic.

Reports, studies, and surveys have demonstrated telehealth provides opportunities to make health care more efficient, better coordinated, convenient, and affordable. Telehealth can also help address health income and access disparities in underserved communities by removing location and transportation barriers, unproductive time away from work, childcare expenses, and so on. Despite evidence showing high-quality outcomes, satisfaction, and success rates (e.g., 95% patient satisfaction rate and 84% success rate in which patients were able to completely resolve their medical concerns during a telehealth visit), nationwide adoption of telehealth has been quite low due to policy and regulatory barriers, constraints, and complexities.

Runs of homozygosity in killer whale genomes provide a global record of demographic histories.

Runs of homozygosity (ROH) occur when offspring inherit haplotypes that are identical by descent from each parent. Length distributions of ROH are informative about population history; specifically, the probability of inbreeding mediated by mating system and/or population demography. Here, we investigated whether variation in killer whale (Orcinus orca) demographic history is reflected in genome-wide heterozygosity and ROH length distributions, using a global data set of 26 genomes representative of geographic and ecotypic variation in this species, and two F1 admixed individuals with Pacific-Atlantic parentage. We first reconstructed demographic history for each population as changes in effective population size through time using the pairwise sequential Markovian coalescent (PSMC) method. We found a subset of populations declined in effective population size during the Late Pleistocene, while others had more stable demography. Genomes inferred to have undergone ancestral declines in effective population size, were autozygous at hundreds of short ROH (<1 Mb), reflecting high background relatedness due to coalescence of haplotypes deep within the pedigree. In contrast, longer and therefore younger ROH (>1.5 Mb) were found in low latitude populations, and populations of known conservation concern. These include a Scottish killer whale, for which 37.8% of the autosomes were comprised of ROH >1.5 Mb in length. The fate of this population, in which only two adult males have been sighted in the past five years, and zero fecundity over the last two decades, may be inextricably linked to its demographic history and consequential inbreeding depression.

Multigenerational immigrant trajectories and children's unequal exposure to fine particulate matter in the US.

Fine particulate matter is a serious health threat and exposures are particularly damaging for children. The environmental justice (EJ) literature shows that racial/ethnic minority communities experience disproportionate exposure to particulate pollution in the US. While important, those EJ studies tend to neglect people's complex identities, including their nativity and their families' generational histories of residence in the US. Yet there is growing interest in the intersection of immigrant populations and EJ. Our use of individual-level data enables examination of immigrant generational status by race/ethnicity, which provides insights on the intergenerational persistence of environmental injustice. We pair data on 12,570 US third graders (from 2013 to 2014) collected through the Early Childhood Longitudinal Survey with PM2.5 concentrations for the census tracts of their home and school locations. We apply generalized estimating equations to test for intergenerational disparities in exposure and to examine how those disparities vary between racial/ethnic groups. Independent of race/ethnicity, first- and second-generation children have greater PM2.5 exposure than 2.5- and third-generation children. However, generational status disparities in exposures vary based on race/ethnicity. First-generation White children face greater exposure than White children of later generational statuses, with inequalities attenuating by the second generation. In contrast, Hispanic/Latinx children experience no significant drop in exposure until the third generation. Among Asian and Black children, generational status was not a significant determinant of exposure. Results quantify the intergenerational persistence of environmental injustices for persons of color while showing the amelioration of inequalities for Whites after just one generation is born in the US, reflecting another facet of White privilege in the US.

Quantifying Missingness in Wearable Heart Rate Recordings.

Wrist-worn photoplethysmography (PPG) heart rate monitoring devices are increasingly used in clinical applications despite the potential for data missingness and inaccuracy. This paper provides an analysis of the intermittency of experimental wearable data recordings. Devices recorded heart rate with gaps of 5 or more minutes 41.6% of the time and 15 or more minutes 3.8% of the time.

Deep Neural Network Architecture Search for Wearable Heart Rate Estimations.

Extracting accurate heart rate estimations from wrist-worn photoplethysmography (PPG) devices is challenging due to the signal containing artifacts from several sources. Deep Learning approaches have shown very promising results outperforming classical methods with improvements of 21% and 31% on two state-of-the-art datasets. This paper provides an analysis of several data-driven methods for creating deep neural network architectures with hopes of further improvements.

British Association of Critical Care Nurses: Evidence-based consensus paper for oral care within adult critical care units.

BACKGROUND: Patients who are critically ill are at increased risk of hospital acquired pneumonia and ventilator associated pneumonia. Effective evidence based oral care may reduce the incidence of such iatrogenic infection. AIM: To provide an evidence-based British Association of Critical Care Nurses endorsed consensus paper for best practice relating to implementing oral care, with the intention of promoting patient comfort and reducing hospital acquired pneumonia and ventilator associated pneumonia in critically ill patients. DESIGN: A nominal group technique was adopted. A consensus committee of adult critical care nursing experts from the United Kingdom met in 2018 to evaluate and review the literature relating to oral care, its application in reducing pneumonia in critically ill adults and to make recommendations for practice. An elected national board member for the British Association of Critical Care Nurses chaired the round table discussion. METHODS: The committee focused on 5 aspects of oral care practice relating to critically ill adult patients. The evidence was evaluated for each practice within the context of reducing pneumonia in the mechanically ventilated patient or pneumonia in the non-ventilated patient. The five practices included the frequency for oral care; tools for oral care; oral care technique; solutions used and oral care in the non-ventilated patient who is critically ill and is at risk of aspiration. The group searched the best available evidence and evaluated this using the Grading of Recommendations Assessment, Development, and Evaluation system to assess the quality of evidence from high to very low, and to formulate recommendations as strong, moderate, weak, or best practice consensus statement when applicable. RESULTS: The consensus group generated recommendations, delineating an approach to best practice for oral care in critically ill adult patients. Recommendations included guidance for frequency and procedure for oral assessment, toothbrushing, and moisturising the mouth. Evidence on the use of chlorhexidine is not consistent and caution is advised with its routine use. CONCLUSION: Oral care is an important part of the care of critically ill patients, both ventilated and non-ventilated. An effective oral care programme reduces the incidence of pneumonia and promotes patient comfort. RELEVANCE TO CLINICAL PRACTICE: Effective oral care is integral to safe patient care in critical care.

Association between continuity and access in primary care: a retrospective cohort study.

BACKGROUND: Continuity of care is a tenet of primary care. Our objective was to explore the relation between a change in access to a primary care physician and continuity of care. METHODS: We conducted a retrospective cohort study among physicians in a primary care network in southwest Alberta who measured access consistently between 2009 and 2016. We used time to the third next available appointment as a measure of access to physicians. We calculated the provider and clinic continuity, discontinuity and emergency department use based on the physicians' own panels. Physicians who improved, worsened or maintained their level of access within a given year were assessed in multilevel models to determine the association with continuity of care at the physician and clinic levels and the emergency department. RESULTS: We analyzed data from 190 primary care physicians. Physicians with improved access increased provider continuity by 6.8% per year, reduced discontinuity by 2.1% per year, and decreased emergency department encounters by 78 visits per 1000 patients per year compared to physicians with stable access. Physicians with worsening access had a 6.2% decrease in provider continuity and an increased number of emergency department encounters (64 visits per 1000 panelled patients per year) compared to physicians with stable access. INTERPRETATION: Changes in access to primary care can affect whether patients seek care from their own physician, from another clinic or at the emergency department. Improving access by reducing the delay in obtaining an appointment with one's primary care physician may be one mechanism to improve continuity of care.

Phylogenomics of the genus Tursiops and closely related Delphininae reveals extensive reticulation among lineages and provides inference about eco-evolutionary drivers.

Phylogeographic inference has provided extensive insight into the relative roles of geographical isolation and ecological processes during evolutionary radiations. However, the importance of cross-lineage admixture in facilitating adaptive radiations is increasingly being recognised, and suggested as a main cause of phylogenetic uncertainty. In this study, we used a double digest RADseq protocol to provide a high resolution (~4 Million bp) nuclear phylogeny of the Delphininae. Phylogenetic resolution of this group has been especially intractable, likely because it has experienced a recent species radiation. We carried out cross-lineage reticulation analyses, and tested for several sources of potential bias in determining phylogenies from genome sampling data. We assessed the divergence time and historical demography of T. truncatus and T. aduncus by sequencing the T. aduncus genome and comparing it with the T. truncatus reference genome. Our results suggest monophyly for the genus Tursiops, with the recently proposed T. australis species falling within the T. aduncus lineage. We also show the presence of extensive cross-lineage gene flow between pelagic and European coastal ecotypes of T. truncatus, as well as in the early stages of diversification between spotted (Stenella frontalis; Stenella attenuata), spinner (Stenella longirostris), striped (Stenella coeruleoalba), common (Delphinus delphis), and Fraser's (Lagenodelphis hosei) dolphins. Our study suggests that cross-lineage gene flow in this group has been more extensive and complex than previously thought. In the context of biogeography and local habitat dependence, these results improve our understanding of the evolutionary processes determining the history of this lineage.

Genomics of Population Differentiation in Humpback Dolphins, Sousa spp. in the Indo-Pacific Ocean.

Speciation is a fundamental process in evolution and crucial to the formation of biodiversity. It is a continuous and complex process, which can involve multiple interacting barriers leading to heterogeneous genomic landscapes with various peaks of divergence among populations. In this study, we used a population genomics approach to gain insights on the speciation process and to understand the population structure within the genus Sousa across its distribution in the Indo-Pacific region. We found 5 distinct clusters, corresponding to S. plumbea along the eastern African coast and the Arabian Sea, the Bangladesh population, S. chinensis off Thailand and S. sahulensis off Australian waters. We suggest that the high level of differentiation found, even across geographically close areas, is likely determined by different oceanographic features such as sea surface temperature and primary productivity.

Investigation of wearable health tracker version updates.

BACKGROUND: Wearable fitness trackers are increasingly used in healthcare applications; however, the frequent updating of these devices is at odds with traditional medical device practices. OBJECTIVE: Our objective was to explore the nature and frequency of wearable tracker updates recorded in device changelogs, to reveal the chronology of updates and to estimate the intervals where algorithm updates could impact device validations. METHOD: Updates for devices meeting selection criteria (that included their use in clinical trials) were independently labelled by four researchers according to simple function and specificity schema. RESULTS: Device manufacturers have diverse approaches to update reporting and changelog practice. Visual representations of device changelogs reveal the nature and chronology of device iterations. 13% of update items were unspecified and 32% possibly affected validations with as few as 5 days between updates that may affect validation. CONCLUSION: Manufacturers could aid researchers and health professionals by providing more informative device update changelogs.

Killer whale genomes reveal a complex history of recurrent admixture and vicariance.

Reconstruction of the demographic and evolutionary history of populations assuming a consensus tree-like relationship can mask more complex scenarios, which are prevalent in nature. An emerging genomic toolset, which has been most comprehensively harnessed in the reconstruction of human evolutionary history, enables molecular ecologists to elucidate complex population histories. Killer whales have limited extrinsic barriers to dispersal and have radiated globally, and are therefore a good candidate model for the application of such tools. Here, we analyse a global data set of killer whale genomes in a rare attempt to elucidate global population structure in a nonhuman species. We identify a pattern of genetic homogenisation at lower latitudes and the greatest differentiation at high latitudes, even between currently sympatric lineages. The processes underlying the major axis of structure include high drift at the edge of species' range, likely associated with founder effects and allelic surfing during postglacial range expansion. Divergence between Antarctic and non-Antarctic lineages is further driven by ancestry segments with up to four-fold older coalescence time than the genome-wide average; relicts of a previous vicariance during an earlier glacial cycle. Our study further underpins that episodic gene flow is ubiquitous in natural populations, and can occur across great distances and after substantial periods of isolation between populations. Thus, understanding the evolutionary history of a species requires comprehensive geographic sampling and genome-wide data to sample the variation in ancestry within individuals.