RESUMEN
BACKGROUND: Serial neurological examinations (NEs) are routinely recommended in the intensive care unit (ICU) within the first 24 hours following a traumatic brain injury (TBI). There are currently no widely accepted guidelines for the frequency of NEs. Disruptions to the sleep-wake cycles increase the delirium rate. We aimed to evaluate whether there is a correlation between prolonged hourly (Q1)-NE and development of delirium and to determine if this practice reduces the likelihood of missing the detection of a process requiring emergent intervention. METHODS: A retrospective analysis of patients with mild/moderate TBI, admitted to the ICU with serial NEs, was performed. Cohorts were stratified by the duration of exposure to Q1-NE, into prolonged (≥24 hours) and nonprolonged (<24 hours). Our primary outcomes of interest were delirium, evaluated using the Confusion Assessment Method; radiological progression from baseline images; neurological deterioration (focal neurological deficit, abnormal pupillary examination, or Glasgow Coma Scale score decrease >2); and neurosurgical procedures. RESULTS: A total of 522 patients were included. No significant differences were found in demographics. Patients in the prolonged Q1-NE group (26.1%) had higher Injury Severity Score with similar head Abbreviated Injury Score, significantly higher delirium rate (59% vs. 35%, p < 0.001), and a longer hospital/ICU length of stay when compared with the nonprolonged Q1-NE group. No neurosurgical interventions were found to be performed emergently as a result of findings on NEs. Multivariate analysis demonstrated that prolonged Q1-NE was the only independent risk factor associated with a 2.5-fold increase in delirium rate. The number needed to harm for prolonged Q1-NE was 4. CONCLUSION: Geriatric patients with mild/moderate TBI exposed to Q1-NE for periods longer than 24 hours had nearly a threefold increase in ICU delirium rate. One of five patients exposed to prolonged Q1-NE is harmed by the development of delirium. No patients were found to directly benefit as a result of more frequent NEs. LEVEL OF EVIDENCE: Prognostic and Epidemiological; Level IV.
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Lesiones Traumáticas del Encéfalo , Delirio , Escala de Coma de Glasgow , Unidades de Cuidados Intensivos , Examen Neurológico , Humanos , Delirio/diagnóstico , Delirio/etiología , Delirio/epidemiología , Masculino , Lesiones Traumáticas del Encéfalo/complicaciones , Lesiones Traumáticas del Encéfalo/diagnóstico , Femenino , Estudios Retrospectivos , Anciano , Examen Neurológico/métodos , Unidades de Cuidados Intensivos/estadística & datos numéricos , Factores de Tiempo , Anciano de 80 o más Años , Persona de Mediana Edad , Factores de RiesgoRESUMEN
Neutrophils exacerbate pulmonary ischemia-reperfusion injury (IRI) resulting in poor short and long-term outcomes for lung transplant recipients. Glycolysis powers neutrophil activation, but it remains unclear if neutrophil-specific targeting of this pathway will inhibit IRI. Lipid nanoparticles containing the glycolysis flux inhibitor 2-deoxyglucose (2-DG) were conjugated to neutrophil-specific Ly6G antibodies (NP-Ly6G[2-DG]). Intravenously administered NP-Ly6G(2-DG) to mice exhibited high specificity for circulating neutrophils. NP-Ly6G(2-DG)-treated neutrophils were unable to adapt to hypoglycemic conditions of the lung airspace environment as evident by the loss of demand-induced glycolysis, reductions in glycogen and ATP content, and an increased vulnerability to apoptosis. NP-Ly6G(2-DG) treatment inhibited pulmonary IRI following hilar occlusion and orthotopic lung transplantation. IRI protection was associated with less airspace neutrophil extracellular trap generation, reduced intragraft neutrophilia, and enhanced alveolar macrophage efferocytotic clearance of neutrophils. Collectively, our data show that pharmacologically targeting glycolysis in neutrophils inhibits their activation and survival leading to reduced pulmonary IRI.
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Glucólisis , Trasplante de Pulmón , Ratones Endogámicos C57BL , Nanopartículas , Neutrófilos , Daño por Reperfusión , Animales , Daño por Reperfusión/prevención & control , Daño por Reperfusión/metabolismo , Ratones , Glucólisis/efectos de los fármacos , Neutrófilos/metabolismo , Neutrófilos/efectos de los fármacos , Nanopartículas/química , Masculino , Trasplante de Pulmón/efectos adversos , Desoxiglucosa/farmacología , Apoptosis/efectos de los fármacos , Pulmón/patología , Pulmón/metabolismo , Pulmón/efectos de los fármacosRESUMEN
Effective population size estimates are critical information needed for evolutionary predictions and conservation decisions. This is particularly true for species with social factors that restrict access to breeding or experience repeated fluctuations in population size across generations. We investigated the genomic estimates of effective population size along with diversity, subdivision, and inbreeding from 162,109 minimally filtered and 81,595 statistically neutral and unlinked SNPs genotyped in 437 grey wolf samples from North America collected between 1986 and 2021. We found genetic structure across North America, represented by three distinct demographic histories of western, central, and eastern regions of the continent. Further, grey wolves in the northern Rocky Mountains have lower genomic diversity than wolves of the western Great Lakes and have declined over time. Effective population size estimates revealed the historical signatures of continental efforts of predator extermination, despite a quarter century of recovery efforts. We are the first to provide molecular estimates of effective population size across distinct grey wolf populations in North America, which ranged between Ne ~ 275 and 3050 since early 1980s. We provide data that inform managers regarding the status and importance of effective population size estimates for grey wolf conservation, which are on average 5.2-9.3% of census estimates for this species. We show that while grey wolves fall above minimum effective population sizes needed to avoid extinction due to inbreeding depression in the short term, they are below sizes predicted to be necessary to avoid long-term risk of extinction.
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Lobos , Animales , Lobos/genética , Genética de Población , Genómica , Densidad de Población , América del NorteRESUMEN
Background: Ludwig's angina (LA) is a diffuse cellulitis of the submandibular space and adjacent tissues. During the coronavirus disease 2019 (COVID-19) pandemic, odontogenic treatments were often delayed because of the implementation of safety measures to avoid the spread of the virus. We hypothesized that delayed odontogenic treatments associated with the onset of the COVID-19 pandemic would be associated with an increase in the incidence of LA and worse outcomes related to these infections. Patients and Methods: Patients from June 2018 to June 2022 with computed tomography images suggestive of LA and confirmed by ear, nose, throat (ENT) consult were included. We abstracted demographics, outcomes, clinical management, and microbiology. Patients were stratified into pre-COVID and COVID-onset. Our primary outcome, incidence of LA, was defined as: (new LA cases) ÷ (ED evaluations of oral or dental infections × 1.5 years). Results: In the pre-COVID group, we identified 32 of 1,301 patients with LA for an incidence of 0.02 per year. The COVID-onset group consisted of 41 of 641 patients, with an incidence of 0.04 per year. In the COVID-onset group, progression to necrotizing fasciitis was more likely (0% vs. 15%; p < 0.024), and they returned to the operating room for repeated debridement (3% vs. 22%; p < 0.020). Likewise, hospital length of stay, intensive care unit (ICU) length of stay, and ventilator days were higher (4.3 ± 3.5 vs. 9.5 ± 11.3; 1.1 ± 1.2 vs. 9.5 ± 7.1; 0.3 ± 1 vs. 3.6 ± 7.1; p < 0.001). Conclusions: Although the prognosis for dental infections diagnosed early is generally favorable, we observed a notable increase in the incidence of LA after the onset of the COVID-19 pandemic. Moreover, complications stemming from these infections became more severe in the COVID-onset era. Specifically, the likelihood of necrotizing fasciitis showed a substantial increase, accompanied by an increased risk of respiratory failure and mediastinitis.
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COVID-19 , Fascitis Necrotizante , Angina de Ludwig , Humanos , Angina de Ludwig/epidemiología , Angina de Ludwig/terapia , Angina de Ludwig/complicaciones , Pandemias , Incidencia , COVID-19/epidemiologíaRESUMEN
The gray wolf (Canis lupus) population on the Iberian Peninsula was the largest in western and central Europe during most of the 20th century, with its size apparently never under a few hundred individuals. After partial legal protection in the 1970s in Spain, the northwest Iberian population increased to about 300-350 packs and then stabilized. In contrast to many current European wolf populations, which have been connected through gene flow, the Iberian wolf population has been isolated for decades. Here we measured changes on genomic diversity and inbreeding through the last decades in a geographic context. We find that the level of genomic diversity in Iberian wolves is low compared to other Eurasian wolf populations. Despite population expansion in the last 50 years, some modern wolves had very high inbreeding, especially in the recently recolonized and historical edge areas. These individuals contrast with others with low inbreeding within the same population. The high variance in inbreeding despite population expansion seems associated with small-scale fragmentation of the range that is revealed by the genetic similarity between modern and historical samples from close localities despite being separated by decades, remaining differentiated from other individuals that are just over 100 km away, a small distance for a species with great dispersal capacity inhabiting a continuous range. This illustrates that, despite its demographically stable condition, the population would probably benefit from favoring connectivity within the population as well as genetic exchange with other European wolf populations to avoid excessive fragmentation and local inbreeding depression.
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Sacrificio de Animales , Carnívoros , Ganado , Conducta Predatoria , Animales , Conservación de los Recursos Naturales , Ecosistema , Unión Europea , LobosRESUMEN
Oceanic islands are characterized by conditions that favour diversification into endemic lineages that can be very different from their mainland counterparts. This can be the result of fast phenotypic divergence due to drift or the result of slower adaptation to local conditions. This uniqueness can obscure their evolutionary history. Here we used morphological, stable isotope, genetic and genomic data to characterize common quails (Coturnix coturnix) in the Azores archipelago and assess the divergence from neighbouring common quail populations. Historical documents suggested that these quails could have a recent origin associated with the arrival of humans in the last centuries. Our results show that Azorean quails constitute a well-differentiated lineage with small size and dark throat pigmentation that has lost the migratory ability and that diverged from mainland quail lineages more than 0.8 mya, contrary to the notion of a recent human-mediated arrival. Even though some Azorean quails carry an inversion that affects 115 Mbp of chromosome 1 and that has been associated with the loss of the migratory behaviour in other common quail populations, half of the analysed individuals do not have that inversion and still do not migrate. The long coexistence and evolution in isolation in the Azores of two chromosomal variants (with and without the inversion) is best explained by balancing selection. Thus, a unique and long evolutionary history led to the island endemic that we know today, C. c. conturbans.
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OBJECTIVES: Deep venous thrombosis (DVT) causes significant morbidity and mortality after trauma. Recently, we have shown that blood flow patterns at vein valves induce oscillatory stress genes, which maintain an anticoagulant endothelial phenotype that inhibits spontaneous clotting at vein valves and sinuses, is lost in the presence of DVT in human pathological samples, and is dependent on expression of the transcription factor FOXC2. We describe an assay, modifying our mouse multiple injury system, which shows evidence of clinically relevant microthrombosis and hypercoagulability applicable to the study of spontaneous DVT in trauma without requiring direct vascular injury or ligation. Finally, we investigated whether these model findings are relevant to a human model of critical illness by examining gene expression changes by quantitative polymerase chain reaction and immunofluorescence in veins collected from critically ill. METHODS: C57/Bl6 mice were subjected to a modified mouse multiple injury model with liver crush injury, crush and pseudofracture of a single lower extremity, and 15% total blood volume hemorrhage. Serum was assayed for d-dimer at 2, 6, 24, and 48 hours after injury by enzyme-linked immunosorbent assay. For the thrombin clotting assay, veins of the leg were exposed, 100 µL of 1 mM rhodamine (6 g) was injected retro-orbitally, and 450 µg/mL thrombin was then applied to the surface of the vein with examination of real-time clot formation via in vivo immunofluorescence microscopy. Images were then examined for percentage area of clot coverage of visible mouse saphenous and common femoral vein. Vein valve specific knockout of FOXC2 was induced with tamoxifen treatment in PROX1 Ert2Cre FOXC2 fl/fl mice as previously described. Animals were then subjected to a modified mouse multiple injury model with liver crush injury, crush and pseudofracture of a single lower extremity, and 15% total blood volume hemorrhage. Twenty-four hours after injury, we examined the valve phenotype in naive versus multiple injury animals, with and without loss of the FOXC2 gene from the vein valve (FOXC2 del ) via the thrombin assay. Images were then examined for proximity of clot formation to the valve present at the junction of the mouse saphenous, tibial, and superficial femoral vein and presence of spontaneous microthrombi present in the veins before exposure to thrombin. Human vein samples were obtained from excess tissue preserved after harvest for elective cardiac surgery and from organ donors after organ procurement. Sections were submitted for paraffin embedding and then assayed by immunofluorescence for PROX1, FOXC2, thrombomodulin, endothelial protein C receptor, and von Willebrand's factor. All animal studies were reviewed and approved by the Institutional Animal Care and Use Committee, and all human studies reviewed and approved by the institutional review board. RESULTS: After mouse multiple injuries, enzyme-linked immunosorbent assay for d-dimer showed evidence of products of fibrin breakdown consistent with formation of clot related to injury, fibrinolysis, and/or microthrombosis. The thrombin clotting assay demonstrated higher percentage area of vein covered with clot when exposed to thrombin in the multiple injury animals compared with uninjured (45% vs. 27% p = 0.0002) consistent with a phenotype of hypercoagulable state after trauma in our model system. Unmanipulated FoxC2 knockout mice manifest increased clotting at the vein valve as compared with unmanipulated wild type animals. After multiple injuries, wild type mice manifest increase clotting at the vein after thrombin exposure ( p = 0.0033), and equivalent to that of valvular knockout of FoxC2 (FoxC2del), recapitulating the phenotype seen in FoxC2 knockout animals. The combination of multiple injuries and FoxC2 knockout resulted in spontaneous microthrombi in 50% of the animals, a phenotype not observed with either multiple injuries or FoxC2 deficiency alone (χ 2 , p = 0.017). Finally, human vein samples demonstrated the protective vein valve phenotype of increased FOXC2 and PROX1 and showed decreased expression in the critically ill organ donor population by immunofluorescence imaging in organ donor samples. CONCLUSION: We have established a novel model of posttrauma hypercoagulation that does not require direct restriction of venous flow or direct injury to the vessel endothelium to assay for hypercoagulability and can generate spontaneous microthrombosis when combined with valve-specific FOXC2 knockout. We find that multiple injuries induce a procoagulant phenotype that recapitulates the valvular hypercoagulability seen in FOXC2 knockout and, in critically ill human specimens, find evidence for loss of oscillatory shear stress-induced gene expression of FOXC2 and PROX1 in the valvular endothelium consistent with potential loss of DVT-protective valvular phenotype.
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Lesiones por Aplastamiento , Traumatismo Múltiple , Trombofilia , Trombosis , Animales , Humanos , Ratones , Enfermedad Crítica , Células Endoteliales , Vena Femoral , Fibrinolíticos , Trombina/farmacología , Trombofilia/etiología , Trombosis/etiología , Factores de TranscripciónRESUMEN
Several surgically relevant conditions are directly or indirectly influenced by the human microbiome. Different microbiomes may be found within, or along, specific organs and intra-organ variation is common. Such variations include those found along the course of the gastrointestinal tract as well as those on different regions of the skin. A variety of physiologic stressors and care interventions may derange the native microbiome. A deranged microbiome is termed a dysbiome and is characterized by decreased diversity and an increase in the proportion of potentially pathogenic organisms; the elaboration of virulence factors coupled with clinical consequences defines a pathobiome. Specific conditions such as Clostridium difficile colitis, inflammatory bowel disease, obesity, and diabetes mellitus are tightly linked to a dysbiome or pathobiome. Additionally, massive transfusion after injury appears to derange the gastrointestinal microbiome as well. This review explores what is known about these surgically relevant clinical conditions to chart how non-surgical interventions may support surgical undertakings or potentially reduce the need for operation.
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Microbioma Gastrointestinal , Enfermedades Inflamatorias del Intestino , Microbiota , Humanos , PielRESUMEN
The recognition that a resident community of microbes contributes substantially to human health and disease is one of the emerging great discoveries in modern medicine. This collection of bacteria, archaea, fungi, viruses, and eukaryotes are referred to as microbiota, which together with the individual tissues they inhabit is defined as our individual microbiome. Recent advances in modern DNA sequencing technologies permit the identification, description, and characterization of these microbial communities as well as their variations within and between individuals and groups. This complex understanding of the human microbiome is supported by a rapidly expanding field of inquiry and offers the potential to significantly impact the treatment of a wide variety of disease states. This review explores the recent findings associated with the various components of the human microbiome, and the geodiversity of microbial communities between different tissue types, individuals, and clinical conditions.
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Microbiota , Virus , Humanos , Bacterias , Microbiota/genética , HongosRESUMEN
The horse is central to many Indigenous cultures across the American Southwest and the Great Plains. However, when and how horses were first integrated into Indigenous lifeways remain contentious, with extant models derived largely from colonial records. We conducted an interdisciplinary study of an assemblage of historic archaeological horse remains, integrating genomic, isotopic, radiocarbon, and paleopathological evidence. Archaeological and modern North American horses show strong Iberian genetic affinities, with later influx from British sources, but no Viking proximity. Horses rapidly spread from the south into the northern Rockies and central plains by the first half of the 17th century CE, likely through Indigenous exchange networks. They were deeply integrated into Indigenous societies before the arrival of 18th-century European observers, as reflected in herd management, ceremonial practices, and culture.
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Animales Domésticos , Domesticación , Caballos , Animales , Humanos , Arqueología , Estados UnidosRESUMEN
Background: Victims of assault (VOA) often present with fractures of the mandible and maxilla. They represent a complex challenge because of possible compromise of the airway, and infection-related complications because of potential involvement of the oral cavity. We hypothesized that open mandible and maxillary fractures in VOA are associated with a higher rate of infection compared with non-VOA patients with open facial fractures. Patients and Methods: Patients admitted to our level 1 trauma center from 2005 to 2020 with a diagnosis of open mandible and maxillary fractures were included. Demographics, mechanisms of injury, fracture location, cultures, infectious complications, antibiotic treatments, and clinical outcomes were abstracted. Patients were stratified by their mechanism of injury into VOA or non-VOA and were compared using χ2 and Student t-test using SPSS (IBM Corp, Armonk, NY). Results: We identified 316 patients with open mandible and maxillary fractures. There were 198 patients categorized as being VOA, and 118 as non-VOA. Nineteen of 316 patients were diagnosed with infection related to the fracture (3.8% abscesses, 1.9% cellulitis, and 1.9% osteomyelitis). Although the Injury Severity Score (ISS) was higher in non-VOA patients (5.8 ± 2.6 vs. 4.9 ± 1.8; p < 0.013), most of the infections were in the VOA cohort (17/19; 89.5%; p < 0.013). Conclusions: Open fractures of the mandible and maxilla in VOA are associated with a greater risk of infection compared with non-victims of assault. The relation between VOA and poor SDH has been studied recently; clinicians should be aware of this association and implement special considerations and appropriate follow-up visits to decrease the rate of infection in this currently expanding population.
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Fracturas Abiertas , Fracturas Mandibulares , Fracturas Maxilares , Humanos , Fracturas Maxilares/complicaciones , Fracturas Mandibulares/complicaciones , Fracturas Mandibulares/epidemiología , Fracturas Mandibulares/terapia , Antibacterianos/uso terapéutico , Fracturas Abiertas/complicaciones , Mandíbula , Estudios RetrospectivosRESUMEN
Bergmann's and Allen's rules were defined to describe macroecological patterns across latitudinal gradients. Bergmann observed a positive association between body size and latitude for endothermic species while Allen described shorter appendages as latitude increases. Almost two centuries later, there is still ongoing discussion about these patterns. Temperature, the common variable in these two rules, varies predictably across both latitude and elevation. Although these rules have been assessed extensively in mammals across latitude, particularly in regions with strong seasonality, studies on tropical montane mammals are scarce. We here test for these patterns and assess the variation of several other locomotory, diet-associated, body condition, and thermoregulatory traits across elevation in the Mountain Treeshrew (Tupaia montana) on tropical mountains in Borneo. Based on morphological measurements from both the field and scientific collections, we found a complex pattern: Bergmann's rule was not supported in our tropical mountain system, since skull length, body size, and weight decreased from the lowest elevations (<1000 m) to middle elevations (2000-2500 m), and then increased from middle elevations to highest elevations. Allen's rule was supported for relative tail length, which decreased with elevation, but not for ear and hindfoot length, with the former remaining constant and the latter increasing with elevation. This evidence together with changes in presumed diet-related traits (rostrum length, zygomatic breadth and upper tooth row length) along elevation suggest that selective pressures other than temperature, are playing a more important role shaping the morphological variation across the distribution of the Mountain Treeshrew. Diet, food acquisition, predation pressure, and/or intra- and inter-specific competition, are some of the potential factors driving the phenotypic variation of this study system. The lack of variation in body condition might suggest local adaptation of this species across its elevational range, perhaps due to generalist foraging strategies. Finally, a highly significant temporal effect was detected in several traits but not in others, representing the first phenotypic variation temporal trends described on treeshrews.
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Variación Biológica Poblacional , Tupaia , Animales , Tamaño Corporal , Montana , TemperaturaRESUMEN
The global COVID-19 pandemic has claimed the lives of more than 750,000 US citizens. Dysregulation of the immune system underlies the pathogenesis of COVID-19, with inflammation mediated tissue injury to the lung in the setting of suppressed systemic immune function. To define the molecular mechanisms of immune dysfunction in COVID-19 we utilized a systems immunology approach centered on the circulating leukocyte phosphoproteome measured by mass cytometry. We find that although COVID-19 is associated with wholesale activation of a broad set of signaling pathways across myeloid and lymphoid cell populations, STAT3 phosphorylation predominated in both monocytes and T cells. STAT3 phosphorylation was tightly correlated with circulating IL-6 levels and high levels of phospho-STAT3 was associated with decreased markers of myeloid cell maturation/activation and decreased ex-vivo T cell IFN-γ production, demonstrating that during COVID-19 dysregulated cellular activation is associated with suppression of immune effector cell function. Collectively, these data reconcile the systemic inflammatory response and functional immunosuppression induced by COVID-19 and suggest STAT3 signaling may be the central pathophysiologic mechanism driving immune dysfunction in COVID-19.
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COVID-19 , Humanos , Monocitos/metabolismo , Pandemias , Factor de Transcripción STAT3/metabolismo , Transducción de Señal , Linfocitos TRESUMEN
Gray wolves (Canis lupus) in the Iberian Peninsula declined substantially in both range and population size in the last few centuries due to human persecution and habitat fragmentation. However, unlike many other western European populations, gray wolves never went extinct in Iberia. Since the minimum number was recorded around 1970, their numbers have significantly increased and then stabilized in recent decades. We analyzed mitochondrial genomes from 54 historical specimens of Iberian wolves from across their historical range using ancient DNA methods. We compared historical and current mitochondrial diversity in Iberian wolves at the 5' end of the control region (n = 17 and 27) and the whole mitochondrial genome excluding the control region (n = 19 and 29). Despite an increase in population size since the 1970s, genetic diversity declined. We identified 10 whole mitochondrial DNA haplotypes in 19 historical specimens, whereas only six of them were observed in 29 modern Iberian wolves. Moreover, a haplotype that was restricted to the southern part of the distribution has gone extinct. Our results illustrate a lag between demographic and genetic diversity changes, and show that after severe population declines, genetic diversity can continue to be lost in stable or even expanding populations. This suggests that such populations may be of conservation concern even after their demographic trajectory has been reversed.
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Lobos , Humanos , Animales , Lobos/genética , Genética de Población , Crecimiento Demográfico , Europa (Continente) , Variación Genética/genéticaRESUMEN
The presence of population-specific phenotypes often reflects local adaptation or barriers to gene flow. The co-occurrence of phenotypic polymorphisms that are restricted within the range of a highly mobile species is more difficult to explain. An example of such polymorphisms is in the common quail Coturnix coturnix, a small migratory bird that moves widely during the breeding season in search of new mating opportunities, following ephemeral habitats,1,2 and whose females may lay successive clutches at different locations while migrating.3 In spite of this vagility, previous studies reported a higher frequency of heavier males with darker throat coloration in the southwest of the distribution (I. Jiménez-Blasco et al., 2015, Int. Union Game Biol., conference). We used population genomics and cytogenetics to explore the basis of this polymorphism and discovered a large inversion in the genome of the common quail. This inversion extends 115 Mbp in length and encompasses more than 7,000 genes (about 12% of the genome), producing two very different forms. Birds with the inversion are larger, have darker throat coloration and rounder wings, are inferred to have poorer flight efficiency, and are geographically restricted despite the high mobility of the species. Stable isotope analyses confirmed that birds carrying the inversion have shorter migratory distances or do not migrate. However, we found no evidence of pre- or post-zygotic isolation, indicating the two forms commonly interbreed and that the polymorphism remains locally restricted because of the effect on behavior. This illustrates a genomic mechanism underlying maintenance of geographically structured polymorphisms despite interbreeding with a lineage with high mobility.