Energetic physiology mediates individual optimization of breeding phenology in a migratory Arctic Seabird

The influence of variation in individual state on key reproductive decisions impacting fitness is well appreciated in evolutionary ecology. Rowe et al. (1994) developed a condition-dependent individual optimization model predicting that three key factors impact the ability of migratory female birds to individually optimize breeding phenology tomaximize fitness in seasonal environments: arrival condition, arrival date, and ability to gain in condition on the breeding grounds. While empirical studies have confirmed that greater arrival body mass and earlier arrival dates result in earlier laying, no study has assessed whether individual variation in energetic management of condition gain effects this key fitness-related decision. Using an 8-year data set from over 350 prebreeding female Arctic common eiders (Somateria mollissima), we tested this component of the model by examining whether individual variation in two physiological traits influencing energetic management (plasma triglycerides: physiological fattening rate; baseline corticosterone: energetic demand) predicted individual variation in breeding phenology after controlling for arrival date and body mass. As predicted by the optimization model, individuals with higher fattening rates and lower energetic demand had the earliest breeding phenology (shortest delays between arrival and laying; earliest laying dates). Our results are the first to empirically determine that individual flexibility in prebreeding energetic management influences key fitness-related reproductive decisions, suggesting that individuals have the capacity to optimally manage reproductive investment

Stable isotopes can be used to infer the overwintering locations of prebreeding marine birds in the Canadian Arctic

Although assessments of winter carryover effects on fitness-related breeding parameters are vital for determining the links between environmental variation and fitness, direct methods of determining overwintering distributions (e.g., electronic tracking) can be expensive, limiting the number of individuals studied. Alternatively, stable isotope analysis in specific tissues can be used as an indirect means of determining individual overwintering areas of residency. Although increasingly used to infer the overwintering distributions of terrestrial birds, stable isotopes have been used less often to infer overwintering areas of marine birds. Using Arctic-breeding common eiders, we test the effectiveness of an integrated stable isotope approach (13-carbon, 15-nitrogen, and 2-hydrogen) to infer overwintering locations. Knowing the overwinter destinations of eiders from tracking studies at our study colony at East Bay Island, Nunavut, we sampled claw and blood tissues at two known overwintering locations, Nuuk, Greenland, and Newfoundland, Canada. These two locations yielded distinct tissue-specific isotopic profiles. We then compared the isotope profiles of tissues collected from eiders upon their arrival at our breeding colony, and used a k-means cluster analysis approach to match arriving eiders to an overwintering group. Samples from the claws of eiders were most effective for determining overwinter origin, due to this tissue\u27s slow growth rate relative to the 40-day turnover rate of blood. Despite taking an integrative approach using multiple isotopes, k-means cluster analysis was most effective when using 13-carbon alone to assign eiders to an overwintering group. Our research demonstrates that it is possible to use stable isotope analysis to assign an overwintering location to a marine bird. There are few examples of the effective use of this technique on a marine bird at this scale; we provide a framework for applying this technique to detect changes in the migration phenology of birds\u27 responses to rapid changes in the Arctic

No selection on immunological markers in response to a highly virulent pathogen in an Arctic breeding bird

In natural populations, epidemics provide opportunities to look for intense natural selection on genes coding for life history and immune or other physiological traits. If the populations being considered are of management or conservation concern, then identifying the traits under selection (or 'markers') might provide insights into possible intervention strategies during epidemics. We assessed potential for selection on multiple immune and life history traits of Arctic breeding common eiders (Somateria mollissima) during annual avian cholera outbreaks (summers of 2006, 2007 & 2008). We measured prelaying body condition, immune traits, and subsequent reproductive investment (i.e., clutch size) and survival of female common eiders and whether they were infected with Pasteurella multocida, the causative agent of avian cholera. We found no clear and consistent evidence of directional selection on immune traits; however, infected birds had higher levels of haptoglobin than uninfected birds. Also, females that laid larger clutches had slightly lower immune responses during the prelaying period reflecting possible downregulation of the immune system to support higher costs of reproduction. This supports a recent study indicating that birds investing in larger clutches were more likely to die from avian cholera and points to a possible management option to maximize female survival during outbreaks

Polymorphism in a lincRNA Associates with a Doubled Risk of Pneumococcal Bacteremia in Kenyan Children.

Bacteremia (bacterial bloodstream infection) is a major cause of illness and death in sub-Saharan Africa but little is known about the role of human genetics in susceptibility. We conducted a genome-wide association study of bacteremia susceptibility in more than 5,000 Kenyan children as part of the Wellcome Trust Case Control Consortium 2 (WTCCC2). Both the blood-culture-proven bacteremia case subjects and healthy infants as controls were recruited from Kilifi, on the east coast of Kenya. Streptococcus pneumoniae is the most common cause of bacteremia in Kilifi and was thus the focus of this study. We identified an association between polymorphisms in a long intergenic non-coding RNA (lincRNA) gene (AC011288.2) and pneumococcal bacteremia and replicated the results in the same population (p combined = 1.69 × 10(-9); OR = 2.47, 95% CI = 1.84-3.31). The susceptibility allele is African specific, derived rather than ancestral, and occurs at low frequency (2.7% in control subjects and 6.4% in case subjects). Our further studies showed AC011288.2 expression only in neutrophils, a cell type that is known to play a major role in pneumococcal clearance. Identification of this novel association will further focus research on the role of lincRNAs in human infectious disease.Wellcome Trust (Grant ID: 084716/Z/08/Z)This is the final version of the article. It first appeared from Cell Press/Elsevier via http://dx.doi.org/10.1016/j.ajhg.2016.03.02

Genetic mechanisms of critical illness in COVID-19.

Host-mediated lung inflammation is present1, and drives mortality2, in the critical illness caused by coronavirus disease 2019 (COVID-19). Host genetic variants associated with critical illness may identify mechanistic targets for therapeutic development3. Here we report the results of the GenOMICC (Genetics Of Mortality In Critical Care) genome-wide association study in 2,244 critically ill patients with COVID-19 from 208 UK intensive care units. We have identified and replicated the following new genome-wide significant associations: on chromosome 12q24.13 (rs10735079, P = 1.65 × 10-8) in a gene cluster that encodes antiviral restriction enzyme activators (OAS1, OAS2 and OAS3); on chromosome 19p13.2 (rs74956615, P = 2.3 × 10-8) near the gene that encodes tyrosine kinase 2 (TYK2); on chromosome 19p13.3 (rs2109069, P = 3.98 ×  10-12) within the gene that encodes dipeptidyl peptidase 9 (DPP9); and on chromosome 21q22.1 (rs2236757, P = 4.99 × 10-8) in the interferon receptor gene IFNAR2. We identified potential targets for repurposing of licensed medications: using Mendelian randomization, we found evidence that low expression of IFNAR2, or high expression of TYK2, are associated with life-threatening disease; and transcriptome-wide association in lung tissue revealed that high expression of the monocyte-macrophage chemotactic receptor CCR2 is associated with severe COVID-19. Our results identify robust genetic signals relating to key host antiviral defence mechanisms and mediators of inflammatory organ damage in COVID-19. Both mechanisms may be amenable to targeted treatment with existing drugs. However, large-scale randomized clinical trials will be essential before any change to clinical practice

Improved reference genome of Aedes aegypti informs arbovirus vector control

Female Aedes aegypti mosquitoes infect more than 400 million people each year with dangerous viral pathogens including dengue, yellow fever, Zika and chikungunya. Progress in understanding the biology of mosquitoes and developing the tools to fight them has been slowed by the lack of a high-quality genome assembly. Here we combine diverse technologies to produce the markedly improved, fully re-annotated AaegL5 genome assembly, and demonstrate how it accelerates mosquito science. We anchored physical and cytogenetic maps, doubled the number of known chemosensory ionotropic receptors that guide mosquitoes to human hosts and egg-laying sites, provided further insight into the size and composition of the sex-determining M locus, and revealed copy-number variation among glutathione S-transferase genes that are important for insecticide resistance. Using high-resolution quantitative trait locus and population genomic analyses, we mapped new candidates for dengue vector competence and insecticide resistance. AaegL5 will catalyse new biological insights and intervention strategies to fight this deadly disease vector

Snow buntings sing individually distinctive songs and show inter-annual variation in song structure

Birds use song to communicate with conspecifics, and song can influence both intra-sexual competition and inter-sexual mate choice. Some birds produce repertoires consisting of hundreds of songs while others produce a single song type. For species with a single-song repertoire, there are varying levels of inter-individual variation which can be the result of environmental, genetic, and physiological factors. Male Snow Buntings (Plectrophenax nivalis) typically produce a single song type, and while syllable sharing occurs between individuals, many researchers have anecdotally noted the individuality of each male\u27s song. To investigate this long-held assertion, we performed a detailed bioacoustic analysis of male Snow Buntings recorded in the Canadian Arctic. We use canonical discriminant analysis to provide quantitative evidence confirming that male Snow Buntings sing individually distinctive songs. Furthermore, we present the first evidence that some Snow Buntings exhibit inter-annual variation in song structure; while songs remain consistent within each year, two males changed their song type between years. Inter-individual variation in song content can have important behavioral implications, because it facilitates individual recognition and can affect individual fitness

The Oxidative Cost of Acoustic Signals: Examining Steroid Versus Aerobic Activity Hypotheses in a Wild Bird

Vertebrate vocalizations are widespread secondary sexual signals used for mate attraction and territory defence, and variation in signal quality is often condition dependent and impacts reproductive outcomes. Although vocal signal performance is known to reflect various aspects of male quality, few studies have examined the underlying mechanisms mediating its costs and hence its honesty. Using a population of Arctic-breeding snow buntings (Plectrophenax nivalis), we compared the \u27Oxidation Handicap Hypothesis\u27, which predicts that testosterone-induced increases in oxidative stress provide a direct mechanistic basis for ensuring the honesty of many secondary sexual signals, to the \u27Aerobic Activity Hypothesis, which predicts that it is the aerobic activity involved with signal production (i.e. vocal performance or defending a large territory) and not testosterone directly that links signal quality and oxidative stress. Males singing at faster rates had higher levels of both reactive oxygen metabolites and non-enzymatic antioxidant capacity in the plasma (i.e. without an increase in overall oxidative stress), enabling certain males to produce high-quality signals while also mitigating the costs of an associated increase in oxidative stress. However, these results were completely independent of plasma testosterone levels, supporting the role of aerobic performance in directly affecting oxidative stress. Although song performance was not linked to reproductive parameters in our data set, our research is the first to test these competing hypotheses in a behavioural trait and results suggest that oxidative stress may be an underlying physiological cost preventing low-quality individuals from producing high-quality signals. © 2015 Blackwell Verlag GmbH

The Oxidative Cost of Acoustic Signals: Examining Steroid Versus Aerobic Activity Hypotheses in a Wild Bird

Vertebrate vocalizations are widespread secondary sexual signals used for mate attraction and territory defence, and variation in signal quality is often condition dependent and impacts reproductive outcomes. Although vocal signal performance is known to reflect various aspects of male quality, few studies have examined the underlying mechanisms mediating its costs and hence its honesty. Using a population of Arctic-breeding snow buntings (Plectrophenax nivalis), we compared the \u27Oxidation Handicap Hypothesis\u27, which predicts that testosterone-induced increases in oxidative stress provide a direct mechanistic basis for ensuring the honesty of many secondary sexual signals, to the \u27Aerobic Activity Hypothesis, which predicts that it is the aerobic activity involved with signal production (i.e. vocal performance or defending a large territory) and not testosterone directly that links signal quality and oxidative stress. Males singing at faster rates had higher levels of both reactive oxygen metabolites and non-enzymatic antioxidant capacity in the plasma (i.e. without an increase in overall oxidative stress), enabling certain males to produce high-quality signals while also mitigating the costs of an associated increase in oxidative stress. However, these results were completely independent of plasma testosterone levels, supporting the role of aerobic performance in directly affecting oxidative stress. Although song performance was not linked to reproductive parameters in our data set, our research is the first to test these competing hypotheses in a behavioural trait and results suggest that oxidative stress may be an underlying physiological cost preventing low-quality individuals from producing high-quality signals. © 2015 Blackwell Verlag GmbH