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The ubiquitous and global ecological footprint arising from the rapidly increasing rates of plastic production, use, and release into the environment is an important modern environmental issue. Of increasing concern are the risks associated with at least 16,000 chemicals present in plastics, some of which are known to be toxic, and which may leach out both during use and once exposed to environmental conditions, leading to environmental and human exposure. In response, the United Nations member states agreed to establish an international legally binding instrument on plastic pollution, the global plastics treaty. The resolution acknowledges that the treaty should prevent plastic pollution and its related impacts, that effective prevention requires consideration of the transboundary nature of plastic production, use and pollution, and that the full life cycle of plastics must be addressed. As a group of scientific experts and members of the Scientists' Coalition for an Effective Plastics Treaty, we concur that there are six essential "pillars" necessary to truly reduce plastic pollution and allow for chemical detoxification across the full life cycle of plastics. These include a plastic chemical reduction and simplification, safe and sustainable design of plastic chemicals, incentives for change, holistic approaches for alternatives, just transition and equitable interventions, and centering human rights. There is a critical need for scientifically informed and globally harmonized information, transparency, and traceability criteria to protect the environment and public health. The right to a clean, healthy, and sustainable environment must be upheld, and thus it is crucial that scientists, industry, and policy makers work in concert to create a future free from hazardous plastic contamination., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Susanne M Brander reports financial support was provided by National Science Foundation. Andy Booth reports financial support was provided by The Research Council of Norway. Andy Booth reports financial support was provided by European Commission. Annika Jahnke reports financial support was provided by Heimholtz Association. Dorte Hertz reports financial support was provided by The Research Council of Norway. Amila Abeynayaka reports financial support was provided by European Union Horizon Europe Research and Innovation. Susanne Brander reports a relationship with Southern California Coastal Water Research Project that includes: consulting or advisory. Brander previously consulted for the Environmental Defense fund and is on advisory boards or groups for the Plastic Pollution Coalition, as well as the Department of Toxic Substances Control (California) and the San Francisco Estuary Institute. Martin Wagner is an unremunerated member of the Scientific Advisory Board of the Food Packaging Forum Foundation and received travel support for attending annual board meetings. Marina Fernandez is a member of the Endocrine Society's delegation at the Intergovernmental Negotiating Committee (INC) to develop an international legally binding instrument on plastic pollution. All authors are members of the Scientists Coalition for an Effective Plastics Treaty, and Susanne Brander, Martin Wagner, Marina Fernandez, Trisia Farrelly, Kristian Syberg, Amila Abeynayaka, and Bethanie Carney Alroth are Scientists Coalition Steering Committee Members. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2024. Published by Elsevier B.V. All rights reserved.)

Mercury (Hg) concentrations and their associated toxicological effects in terrestrial ecosystems of the Gulf of Mexico are largely unknown. Compounding this uncertainty, a large input of organic matter from the 2010 Deepwater Horizon oil spill may have altered Hg cycling and bioaccumulation dynamics. To test this idea, we quantified blood concentrations of total mercury (THg) in Seaside Sparrows (Ammospiza maritima) and Marsh Rice Rats (Oryzomys palustris) in marshes west and east of the Mississippi River in 2015 and 2016. We also tested for a difference in THg concentrations between oiled and non-oiled sites. To address the potential confounding effect of diet variation on Hg transfer, we used stable nitrogen (δ 15 N) and carbon (δ 13 C) isotope values as proxies of trophic position and the source of primary production, respectively. Our results revealed that five to six years after the spill, THg concentrations were not higher in sites oiled by the spill compared to non-oiled sites. In both species, THg was higher at sites east of the Mississippi River compared to control and oiled sites, located west. In Seaside Sparrows but not in Marsh Rice Rats, THg increased with δ 15 N values, suggesting Hg trophic biomagnification. Overall, even in sites with the most elevated THg, concentrations were generally low. In Seaside Sparrows, THg concentrations were also lower than previously reported in this and other closely related passerines, with only 7% of tested birds exceeding the lowest observed effect concentration associated with toxic effects across bird species (0.2 µg/g ww). The factors associated with geographic heterogeneity in Hg exposure remain uncertain. Clarification could inform risk assessment and future restoration and management actions in a region facing vast anthropogenic changes., (© 2024. The Author(s).)

The immunogenetics of wildlife populations influence the epidemiology and evolutionary dynamic of the host-pathogen system. Profiling immune gene diversity present in wildlife may be especially important for those species that, while not at risk of disease or extinction themselves, are host to diseases that are a threat to humans, other wildlife, or livestock. Hantaviruses (genus: Orthohantavirus) are globally distributed zoonotic RNA viruses with pathogenic strains carried by a diverse group of rodent hosts. The marsh rice rat (Oryzomys palustris) is the reservoir host of Orthohantavirus bayoui, a hantavirus that causes fatal cases of hantavirus cardiopulmonary syndrome in humans. We performed a genome wide association study (GWAS) using the rice rat "immunome" (i.e., all exons related to the immune response) to identify genetic variants associated with infection status in wild-caught rice rats naturally infected with their endemic strain of hantavirus. First, we created an annotated reference genome using 10× Chromium Linked Reads sequencing technology. This reference genome was used to create custom baits which were then used to target enrich prepared rice rat libraries (n = 128) and isolate their immunomes prior to sequencing. Top SNPs in the association test were present in four genes (Socs5, Eprs, Mrc1, and Il1f8) which have not been previously implicated in hantavirus infections. However, these genes correspond with other loci or pathways with established importance in hantavirus susceptibility or infection tolerance in reservoir hosts: the JAK/STAT, MHC, and NFκB. These results serve as informative markers for future exploration and highlight the importance of immune pathways that repeatedly emerge across hantavirus systems. Our work aids in creating cross-species comparisons for better understanding mechanisms of genetic susceptibility and host-pathogen coevolution in hantavirus systems., Competing Interests: Declaration of Competing Interest None., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Insights into the evolution of non-model organisms are limited by the lack of reference genomes of high accuracy, completeness, and contiguity. Here, we present a chromosome-level, karyotype-validated reference genome and pangenome for the barn swallow (Hirundo rustica). We complement these resources with a reference-free multialignment of the reference genome with other bird genomes and with the most comprehensive catalog of genetic markers for the barn swallow. We identify potentially conserved and accelerated genes using the multialignment and estimate genome-wide linkage disequilibrium using the catalog. We use the pangenome to infer core and accessory genes and to detect variants using it as a reference. Overall, these resources will foster population genomics studies in the barn swallow, enable detection of candidate genes in comparative genomics studies, and help reduce bias toward a single reference genome., Competing Interests: Declaration of interests D.S. and K.W. are full-time employees at Pacific Biosciences, a company commercializing single-molecule sequencing technologies., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

The barn swallow (Hirundo rustica) poses a number of fascinating scientific questions, including the taxonomic status of postulated subspecies. Here, we obtained and assessed the sequence variation of 411 complete mitogenomes, mainly from the European H. r. rustica, but other subspecies as well. In almost every case, we observed subspecies-specific haplogroups, which we employed together with estimated radiation times to postulate a model for the geographical and temporal worldwide spread of the species. The female barn swallow carrying the Hirundo rustica ancestral mitogenome left Africa (or its vicinity) around 280 thousand years ago (kya), and her descendants expanded first into Eurasia and then, at least 51 kya, into the Americas, from where a relatively recent (<20 kya) back migration to Asia took place. The exception to the haplogroup subspecies specificity is represented by the sedentary Levantine H. r. transitiva that extensively shares haplogroup A with the migratory European H. r. rustica and, to a lesser extent, haplogroup B with the Egyptian H. r. savignii. Our data indicate that rustica and transitiva most likely derive from a sedentary Levantine population source that split at the end of the Younger Dryas (YD) (11.7 kya). Since then, however, transitiva received genetic inputs from and admixed with both the closely related rustica and the adjacent savignii. Demographic analyses confirm this species' strong link with climate fluctuations and human activities making it an excellent indicator for monitoring and assessing the impact of current global changes on wildlife., (© The Author(s) 2022. Published by Oxford University Press on behalf of Society for Molecular Biology and Evolution.)

The objective of this paper is to present the results of discussions at a workshop held as part of the International Congress of Radiation Research (Environmental Health stream) in Manchester UK, 2019. The main objective of the workshop was to provide a platform for radioecologists to engage with radiobiologists to address major questions around developing an Ecosystem approach in radioecology and radiation protection of the environment. The aim was to establish a critical framework to guide research that would permit integration of a pan-ecosystem approach into radiation protection guidelines and regulation for the environment. The conclusions were that the interaction between radioecologists and radiobiologists is useful in particular in addressing field versus laboratory issues where there are issues and challenges in designing good field experiments and a need to cross validate field data against laboratory data and vice versa. Other main conclusions were that there is a need to appreciate wider issues in ecology to design good approaches for an ecosystems approach in radioecology and that with the capture of 'Big Data', novel tools such as machine learning can now be applied to help with the complex issues involved in developing an ecosystem approach.

In 2010, the Deepwater Horizon oil spill released an estimated 4.9 million barrels of oil into the Gulf of Mexico, damaging coastal ecosystems. Seaside Sparrows (Ammospiza maritima)-a year-round resident of Gulf Coast salt marshes-were exposed to oil, as shown by published isotopic and molecular analyses, but fitness consequences have not been clarified. We monitored nests around two bays in Plaquemines Parish, Louisiana, USA from 2012-2017 to assess possible impacts on the nesting biology of Seaside Sparrows. A majority of nests failed (76% of known-fate nests, N = 252 nests, 3521 exposure-days) during our study, and predation was the main cause of nest failure (~91% of failed nests). Logistic exposure analysis revealed that daily nest survival rate: (1) was greater at nests with denser vegetation at nest height, (2) was higher in the more sheltered bay we studied, (3) decreased over the course of the breeding season in each year, and (4) was not correlated with either sediment polycyclic aromatic hydrocarbon concentrations or estimated predator abundance during the years for which we had those data. Although the Deepwater Horizon spill impacted other aspects of Seaside Sparrow ecology, we found no definitive effect of initial oiling or oiled sediment on nest survival during 2012-2017. Because predation was the overwhelming cause of nest failure in our study, additional work on these communities is needed to fully understand demographic and ecological impacts of storms, oil spills, other pollutants, and sea-level rise on Seaside Sparrows and their predators., Competing Interests: The authors have declared that no competing interests exist.

Bioindicator species are commonly used as proxies to help identify the ecological effects of oil spills and other stressors. However, the utility of taxa as bioindicators is dependent on understanding their trophic niche and life history characteristics, as these factors mediate their ecological responses. Seaside sparrows ( Ammospiza maritima) and marsh rice rats ( Oryzomys palustris ) are two ubiquitous terrestrial vertebrates that are thought to be bioindicators of oil spills in saltmarsh ecosystems. To improve the utility of these omnivorous taxa as bioindicators, we used carbon and nitrogen stable isotope analysis to quantify their trophic niches at saltmarshes in coastal Louisiana with differing oiling histories. We found that rats generally had lower trophic positions and incorporated more aquatic prey relative to seaside sparrows. The range of resources used (i.e.,trophic niche width) varied based on oiling history. Seaside sparrows had wider trophic niches than marsh rice rats at unoiled sites, but not at oiled sites. Trophic niche widths of conspecifics were less consistent at oiled sites, although marsh rice rats at oiled sites had wider trophic niches than rats at unoiled sites. These results suggest that past oiling histories may have imparted subtle, yet differing effects on the foraging ecology of these two co-occurring species. However, the temporal lag between initial oiling and our study makes identifying the ultimate drivers of differences between oiled and unoiled sites challenging. Even so, our findings provide a baseline quantification of the trophic niches of sympatric seaside sparrows and marsh rice rats that will aid in the use of these species as indicators of oiling and other environmental stressors in saltmarsh ecosystems., Competing Interests: The authors declare there are no competing interests., (©2021 Moyo et al.)

In the Fall of 2016 a workshop was held which brought together over 50 scientists from the ecological and radiological fields to discuss feasibility and challenges of reintegrating ecosystem science into radioecology. There is a growing desire to incorporate attributes of ecosystem science into radiological risk assessment and radioecological research more generally, fueled by recent advances in quantification of emergent ecosystem attributes and the desire to accurately reflect impacts of radiological stressors upon ecosystem function. This paper is a synthesis of the discussions and consensus of the workshop participant's responses to three primary questions, which were: 1) How can ecosystem science support radiological risk assessment? 2) What ecosystem level endpoints potentially could be used for radiological risk assessment? and 3) What inference strategies and associated methods would be most appropriate to assess the effects of radionuclides on ecosystem structure and function? The consensus of the participants was that ecosystem science can and should support radiological risk assessment through the incorporation of quantitative metrics that reflect ecosystem functions which are sensitive to radiological contaminants. The participants also agreed that many such endpoints exit or are thought to exit and while many are used in ecological risk assessment currently, additional data need to be collected that link the causal mechanisms of radiological exposure to these endpoints. Finally, the participants agreed that radiological risk assessments must be designed and informed by rigorous statistical frameworks capable of revealing the causal inference tying radiological exposure to the endpoints selected for measurement., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In marine species, the transcriptomic response to Deepwater Horizon (DWH) oil implicated many biochemical pathways, with corresponding adverse outcomes on organ development and physiological performance. Terrestrial organisms differ in their mechanisms of exposure to polycyclic aromatic hydrocarbons (PAHs) and their physiological challenges, and may reveal either distinct effects of oil on biochemical pathways or the generality of the responses to oil shown in marine species. Using a cross-species hybridization microarray approach, we investigated the transcriptomic response in the liver of Seaside Sparrows (Ammospiza maritima) exposed to DWH oil compared with birds from a control site. Our analysis identified 295 genes differentially expressed between birds exposed to oil and controls. Gene ontology (GO) and canonical pathway analysis suggested that the identified genes were involved in a coordinated response that promoted hepatocellular proliferation and liver regeneration while inhibiting apoptosis, necrosis, and liver steatosis. Exposure to oil also altered the expression of genes regulating energy homeostasis, including carbohydrate metabolism and gluconeogenesis, and the biosynthesis, transport and metabolism of lipids. These results provide a molecular mechanism for the long-standing observation of hepatic hypertrophy and altered lipid biosynthesis and transport in birds exposed to crude oil. Several of the activated pathways and pathological outcomes shown here overlap with the ones altered in fish species upon exposure to oil. Overall, our study shows that the path of oil contamination from the marine system into salt marshes can lead to similar responses in terrestrial birds to those described in marine organisms, suggesting similar adverse outcomes and shared machinery for detoxification., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: The barn swallow (Hirundo rustica) is a migratory bird that has been the focus of a large number of ecological, behavioral, and genetic studies. To facilitate further population genetics and genomic studies, we present a reference genome assembly for the European subspecies (H. r. rustica)., Findings: As part of the Genome10K effort on generating high-quality vertebrate genomes (Vertebrate Genomes Project), we have assembled a highly contiguous genome assembly using single molecule real-time (SMRT) DNA sequencing and several Bionano optical map technologies. We compared and integrated optical maps derived from both the Nick, Label, Repair, and Stain technology and from the Direct Label and Stain (DLS) technology. As proposed by Bionano, DLS more than doubled the scaffold N50 with respect to the nickase. The dual enzyme hybrid scaffold led to a further marginal increase in scaffold N50 and an overall increase of confidence in the scaffolds. After removal of haplotigs, the final assembly is approximately 1.21 Gbp in size, with a scaffold N50 value of more than 25.95 Mbp., Conclusions: This high-quality genome assembly represents a valuable resource for future studies of population genetics and genomics in the barn swallow and for studies concerning the evolution of avian genomes. It also represents one of the very first genomes assembled by combining SMRT long-read sequencing with the new Bionano DLS technology for scaffolding. The quality of this assembly demonstrates the potential of this methodology to substantially increase the contiguity of genome assemblies.

In Chernobyl, chronic exposure to radioactive contaminants has a variety of deleterious effects on exposed organisms, including genetic damage and mutation accumulation. However, the potential for such effects to be transmitted to the next generation is poorly understood. We captured lesser marsh grasshoppers (Chorthippus albomarginatus) in the Chernobyl Exclusion Zone from sites varying in levels of environmental radiation by more than three orders of magnitude. We then raised their offspring in a common garden experiment in order to assess the effects of parental exposure to radiation on offspring development and DNA damage. Offspring that reached maturity at a younger age had higher levels of DNA damage. Contrary to our hypothesis, parental exposure to radioactive contamination did not affect DNA damage in their offspring possibly because of intervening adaptation or parental compensatory mechanisms. Our results suggest a trade-off between developmental rate and resistance to DNA damage, whereby offspring developing at faster rates do so at the cost of damaging their DNA. This result is consistent with and extends findings in other species, suggesting that faster growth rates cause increased oxidative damage and stress. We propose that growth rates are subject to stabilizing selection balancing the benefits of fast development and the competing need of buffering its damaging effects to macromolecules and tissues.

This paper reports the output of a consensus symposium organized by the International Union of Radioecology in November 2015. The symposium gathered an academically diverse group of 30 scientists to consider the still debated ecological impact of radiation on populations and ecosystems. Stimulated by the Chernobyl and Fukushima disasters' accidental contamination of the environment, there is increasing interest in developing environmental radiation protection frameworks. Scientific research conducted in a variety of laboratory and field settings has improved our knowledge of the effects of ionizing radiation on the environment. However, the results from such studies sometimes appear contradictory and there is disagreement about the implications for risk assessment. The Symposium discussions therefore focused on issues that might lead to different interpretations of the results, such as laboratory versus field approaches, organism versus population and ecosystemic inference strategies, dose estimation approaches and their significance under chronic exposure conditions. The participating scientists, from across the spectrum of disciplines and research areas, extending also beyond the traditional radioecology community, successfully developed a constructive spirit directed at understanding discrepancies. From the discussions, the group has derived seven consensus statements related to environmental protection against radiation, which are supplemented with some recommendations. Each of these statements is contextualized and discussed in view of contributing to the orientation and integration of future research, the results of which should yield better consensus on the ecological impact of radiation and consolidate suitable approaches for efficient radiological protection of the environment., (Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.)

One mechanism proposed as a link between exposure to ionizing radiation and detrimental effects on organisms is oxidative damage. To test this hypothesis, we surveyed the scientific literature on the effects of chronic low-dose ionizing radiation (LDIR) on antioxidant responses and oxidative damage. We found 40 publications and 212 effect sizes for antioxidant responses and 288 effect sizes for effects of oxidative damage. We performed a meta-analysis of signed and unsigned effect sizes. We found large unsigned effects for both categories (0.918 for oxidative damage; 0.973 for antioxidant response). Mean signed effect size weighted by sample size was 0.276 for oxidative damage and -0.350 for antioxidant defenses, with significant heterogeneity among effects for both categories, implying that ionizing radiation caused small to intermediate increases in oxidative damage and small to intermediate decreases in antioxidant defenses. Our estimates are robust, as shown by very high fail-safe numbers. Species, biological matrix (tissue, blood, sperm) and age predicted the magnitude of effects for oxidative damage as well as antioxidant response. Meta-regression models showed that effect sizes for oxidative damage varied among species and age classes, while effect sizes for antioxidant responses varied among species and biological matrices. Our results are consistent with the description of mechanisms underlying pathological effects of chronic exposure to LDIR. Our results also highlight the importance of resistance to oxidative stress as one possible mechanism associated with variation in species responses to LDIR-contaminated areas., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A number of studies have assessed or modeled the distribution of the radionuclides released by the accident at the Fukushima-Daiichi Nuclear Power Plant (FDNPP). Few studies however have investigated its consequences for the local biota. We tested whether exposure of barn swallow (Hirundo rustica) nestlings to low dose ionizing radiation increased genetic damage to their peripheral erythrocytes. We estimated external radiation exposure by using thermoluminescent dosimeters, and by measuring radioactivity of the nest material. We then assessed DNA damage by means of the neutral comet assay. In addition, we conducted standard point-count censuses of barn swallows across environmental radiation levels, and estimated their abundance and local age ratio. Radioactivity of nest samples was in the range 479-143,349 Bq kg(-1), while external exposure varied between 0.15 and 4.9 mGy. Exposure to radioactive contamination did not correlate with higher genetic damage in nestlings. However, at higher levels of radioactive contamination the number of barn swallows declined and the fraction of juveniles decreased, indicating lower survival and lower reproduction and/or fledging rate. Thus, genetic damage to nestlings does not explain the decline of barn swallows in contaminated areas, and a proximate mechanism for the demographic effects documented here remains to be clarified.

Reproduction is a demanding activity, since organisms must produce and, in some cases, protect and provision their progeny. Hence, a central tenet of life-history theory predicts that parents have to trade parental care against body maintenance. One physiological cost thought to be particularly important as a modulator of such trade-offs is oxidative stress. However, evidence in favour of the hypothesis of an oxidative cost of reproduction is contradictory. In this study, we manipulated the brood size of wild barn swallows Hirundo rustica soon after hatching of their nestlings to test whether an increase in nestling rearing effort translates into an increased oxidative damage and a decreased antioxidant protection at the end of the nestling rearing period. We found that, while plasma oxidative damage was unaffected by brood size enlargement, females rearing enlarged broods showed a decrease in plasma non-enzymatic antioxidants during the nestling rearing period. This was not the case among females rearing reduced broods and among males assigned to either treatment. Moreover, individuals with higher plasma oxidative damage soon after the brood size manipulation had lower plasma non-enzymatic antioxidants at the end of the nestling rearing period, suggesting that non-enzymatic antioxidants were depleted to buffer the negative effects of high oxidative damage. Our findings point to antioxidant depletion as a potential mechanism mediating the cost of reproduction among female birds.

Background: Following the Chernobyl nuclear power plant accident, large amounts of radionuclides were emitted and spread in the environment. Animals living in such contaminated areas are predicted to suffer fitness costs including reductions in the quality and quantity of gametes., Methodology/principal Findings: We studied whether aspermy and sperm quality were affected by radioactive contamination by examining ejaculates from wild caught birds breeding in areas varying in background radiation level by more than three orders of magnitude around Chernobyl, Ukraine. The frequency of males with aspermy increased logarithmically with radiation level. While 18.4% of males from contaminated areas had no sperm that was only the case for 3.0% of males from uncontaminated control areas. Furthermore, there were negative relationships between sperm quality as reflected by reduced sperm velocity and motility, respectively, and radiation., Conclusions/significance: Our results suggest that radioactive contamination around Chernobyl affects sperm production and quality. We are the first to report an interspecific difference in sperm quality in relation to radioactive contamination.

The effects of radioactive contamination on the phenotype of free-living organisms are poorly understood, mainly because of the difficulty of capturing the large numbers of individual specimens that are required to quantify rare events such as albinism and tumour formation. We hypothesized that the frequency of abnormalities like albinism and the frequency of radiation-induced diseases like cancer would increase with the level of background radiation, that the two markers of radiation would be positively correlated, and that the reduction in abundance of animals would be greater in species with a higher frequency of albinism and tumour formation, if these markers reliably reflected poor viability. Here we analyzed the frequency of albinistic feathers and tumours in a sample of 1669 birds captured during 2010-2012 at eight sites around Chernobyl that varied in level of background radiation from 0.02 to more than 200μSv/h. We recorded 111 cases of partial albinism and 25 cases of tumour formation. Nominal logistic models were used to partition the variance into components due to species and background radiation. Radiation was a strong predictor of the two markers in birds, with a small, but significant effect of species for albinism. The slope of the relationship between abundance and radiation in different bird species was significantly inversely correlated with the frequency of albinism and tumours, as was to be expected if a common underlying cause (i.e. radiation) affects both variables. These findings are consistent with the hypothesis that background radiation is a cause of albinism and tumours, that albinism and tumours are biomarkers of radiation exposure, and that high frequencies of albinism and tumours were present despite the low viability of birds with these conditions., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Females of several vertebrate species selectively mate with males on the basis of the major histocompatibility complex (MHC) genes. As androgen-mediated maternal effects have long-lasting consequences for the adult phenotype, both mating and reproductive success may depend on the combined effect of MHC genotype and exposure to androgens during early ontogeny. We studied how MHC-based mate choice in ring-necked pheasants (Phasianus colchicus) was influenced by an experimental in ovo testosterone (T) increase. There was no conclusive evidence of in ovo T treatment differentially affecting mate choice in relation to MHC genotype. However, females avoided mating with males with a wholly different MHC genotype compared with males sharing at least one MHC allele. Females also tended to avoid mating with MHC-identical males, though not significantly so. These findings suggest that female pheasants preferred males with intermediate MHC dissimilarity. Male MHC heterozygosity or diversity did not predict the expression of ornaments or male dominance rank. Thus, MHC-based mating preferences in the ring-necked pheasant do not seem to be mediated by ornaments' expression and may have evolved mainly to reduce the costs of high heterozygosity at MHC loci for the progeny, such as increased risk of autoimmune diseases or disruption of coadapted gene pools., (© 2012 The Authors. Journal of Evolutionary Biology © 2012 European Society For Evolutionary Biology.)

Mutagenic and epigenetic effects of environmental stressors and their transgenerational consequences are of interest to evolutionary biologists because they can amplify natural genetic variation. We studied the effect of parental exposure to radioactive contamination on offspring development in lesser marsh grasshopper Chorthippus albomarginatus. We used a geometric morphometric approach to measure fluctuating asymmetry (FA), wing shape and wing size. We measured time to sexual maturity to check whether parental exposure to radiation influenced offspring developmental trajectory and tested effects of radiation on hatching success and parental fecundity. Wings were larger in early maturing individuals born to parents from high radiation sites compared to early maturing individuals from low radiation sites. As time to sexual maturity increased, wing size decreased but more sharply in individuals from high radiation sites. Radiation exposure did not significantly affect FA or shape in wings nor did it significantly affect hatching success and fecundity. Overall, parental radiation exposure can adversely affect offspring development and fitness depending on developmental trajectories although the cause of this effect remains unclear. We suggest more direct measures of fitness and the inclusion of replication in future studies to help further our understanding of the relationship between developmental instability, fitness and environmental stress., (© 2012 The Authors. Journal of Evolutionary Biology © 2012 European Society For Evolutionary Biology.)

Background: Radiation has negative effects on survival of animals including humans, although the generality of this claim is poorly documented under low-dose field conditions. Because females may suffer disproportionately from the effects of radiation on survival due to differences in sex roles during reproduction, radiation-induced mortality may result in male-skewed adult sex ratios., Methodology/principal Finding: We estimated the effects of low-dose radiation on adult survival rates in birds by determining age ratios of adults captured in mist nets during the breeding season in relation to background radiation levels around Chernobyl and in nearby uncontaminated control areas. Age ratios were skewed towards yearlings, especially in the most contaminated areas, implying that adult survival rates were reduced in contaminated areas, and that populations in such areas could only be maintained through immigration from nearby uncontaminated areas. Differential mortality in females resulted in a strongly male-skewed sex ratio in the most contaminated areas. In addition, males sang disproportionately commonly in the most contaminated areas where the sex ratio was male skewed presumably because males had difficulty finding and acquiring mates when females were rare. The results were not caused by permanent emigration by females from the most contaminated areas because none of the recaptured birds had changed breeding site, and the proportion of individuals with morphological abnormalities did not differ significantly between the sexes for areas with normal and higher levels of contamination., Conclusions/significance: These findings are consistent with the hypothesis that the adult survival rate of female birds is particularly susceptible to the effects of low-dose radiation, resulting in male skewed sex ratios at high levels of radiation. Such skewed age ratios towards yearlings in contaminated areas are consistent with the hypothesis that an area exceeding 30,000 km(2) in Chernobyl's surroundings constitutes an ecological trap that causes dramatic excess mortality.

Sperm are highly susceptible to reactive oxygen species (ROS) that can damage sperm DNA and structure, resulting in reduced fertilizing capacity. Exposure to radioactive contamination can also impair sperm swimming behavior and fertilizing ability, both through a reduction of sperm DNA integrity and via an increased generation of reactive oxygen species (ROS). However, the relationship between individual oxidative status and sperm swimming behavior has never been investigated in any wild population of animals exposed to radioactive contamination. We studied the motility of sperm collected from barn swallows, Hirundo rustica, breeding under different levels of radioactive contamination following the Chernobyl accident in 1986, in relation to individual oxidative status. We tested the hypothesis that the degree of impairment of sperm swimming behavior by radioactive contamination depended on plasma antioxidant capacity, the level of reactive oxygen metabolites (ROMs) and oxidative stress (sensu Costantini et al. 2006), a better oxidative status being associated with higher sperm motility. Sperm behavior parameters were subjected to principal component (PC) analysis, which extracted four PCs explaining 86% of the variance in sperm motility. PC2, representing sperm with high track velocity and ample lateral head displacement, was significantly predicted by the interaction between radiation level and either oxidative damage or oxidative stress. Contrary to our predictions, the highest values of PC2 were associated with relatively high radiation levels, particularly for high levels of either ROMs or oxidative stress. In addition, there was a tendency for values of PC3 (representing the percent of motile sperm) and PC4 (representing slow sperm with high beat cross frequency) to depend on the interaction between radiation level and total plasma antioxidant protection. Our results confirm the importance of oxidative status in determining the genetic and physiological outcome of exposure to radioactive contamination, complementing previous studies relating sperm abnormality to circulating levels of specific antioxidants. Our results also complement previous evidence that oxidative damage of sperm was negatively related to sperm motility, thus indicating a possible trade-off in quenching pro-oxidant compounds in the plasma and the seminal fluid., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Background: Normal and pathological processes entail the production of oxidative substances that can damage biological molecules and harm physiological functions. Organisms have evolved complex mechanisms of antioxidant defense, and any imbalance between oxidative challenge and antioxidant protection can depress fitness components and accelerate senescence. While the role of oxidative stress in pathogenesis and aging has been studied intensively in humans and model animal species under laboratory conditions, there is a dearth of knowledge on its role in shaping life-histories of animals under natural selection regimes. Yet, given the pervasive nature and likely fitness consequences of oxidative damage, it can be expected that the need to secure efficient antioxidant protection is powerful in molding the evolutionary ecology of animals. Here, we test whether overall antioxidant defense varies with age and predicts long-term survival, using a wild population of a migratory passerine bird, the barn swallow (Hirundo rustica), as a model., Methodology/principal Findings: Plasma antioxidant capacity (AOC) of breeding individuals was measured using standard protocols and annual survival was monitored over five years (2006-2010) on a large sample of selection episodes. AOC did not covary with age in longitudinal analyses after discounting the effect of selection. AOC positively predicted annual survival independently of sex. Individuals were highly consistent in their relative levels of AOC, implying the existence of additive genetic variance and/or environmental (including early maternal) components consistently acting through their lives., Conclusions: Using longitudinal data we showed that high levels of antioxidant protection positively predict long-term survival in a wild animal population. Present results are therefore novel in disclosing a role for antioxidant protection in determining survival under natural conditions, strongly demanding for more longitudinal eco-physiological studies of life-histories in relation to oxidative stress in wild populations.

Success in competition for limiting parental resources depends on the interplay between parental decisions over allocation of care and offspring traits. Birth order, individual sex and sex of competing siblings are major candidates as determinants of success in sib-sib competition, but experimental studies focusing on the combined effect of these factors on parent-offspring communication and within-brood competitive dynamics are rare. Here, we assessed individual food intake and body mass gain during feeding trials in barn swallow chicks differing for seniority and sex, and compared the intensity of their acoustic and postural solicitation (begging) displays. Begging intensity and success in competition depended on seniority in combination with individual sex and sex of the opponent. Junior chicks begged more than seniors, independently of satiation level (which was also experimentally manipulated), and obtained greater access to food. Females were generally weaker competitors than males. Individual sex and sex of the opponent also affected duration of begging bouts. Present results thus show that competition with siblings can make the rearing environment variably harsh for developing chicks, depending on individual sex, sex of competing broodmates and age ranking within the nest. They also suggest that parental decisions on the allocation of care and response of kin to signalling siblings may further contribute to the outcome of sibling competition.

Background: Animals living in areas contaminated by radioactive material from Chernobyl suffer from increased oxidative stress and low levels of antioxidants. Therefore, normal development of the nervous system is jeopardized as reflected by high frequencies of developmental errors, reduced brain size and impaired cognitive abilities in humans. Alternatively, associations between psychological effects and radiation have been attributed to post-traumatic stress in humans., Methodology/principal Finding: Here we used an extensive sample of 550 birds belonging to 48 species to test the prediction that even in the absence of post-traumatic stress, there is a negative association between relative brain size and level of background radiation. We found a negative association between brain size as reflected by external head volume and level of background radiation, independent of structural body size and body mass. The observed reduction in brain size in relation to background radiation amounted to 5% across the range of almost a factor 5,000 in radiation level. Species differed significantly in reduction in brain size with increasing background radiation, and brain size was the only morphological character that showed a negative relationship with radiation. Brain size was significantly smaller in yearlings than in older individuals., Conclusions/significance: Low dose radiation can have significant effects on normal brain development as reflected by brain size and therefore potentially cognitive ability. The fact that brain size was smaller in yearlings than in older individuals implies that there was significant directional selection on brain size with individuals with larger brains experiencing a viability advantage.

Evidence is accumulating that sex steroids in the eggs, besides affecting progeny phenotype and behavior in the short term, also have enduring effects until adulthood, when they may translate into differences in reproductive strategies and success. Maternal steroids transfer may therefore affect both agonistic behavior and mate choice decisions, either through the promotion of body size and condition or through a priming effect on the neuroendocrine system. However, owing to the prevalence of a short-term perspective, relevance of maternal transfer of sex steroids to sexual selection processes has been seldom studied. Here we investigate the effects of an experimental increase in egg testosterone on male dominance and copulation success in the ring-necked pheasant, Phasianus colchicus, a polygynous galliform with multiple male ornamental traits, in captivity. We found that females from testosterone (T) injected eggs copulated less than control females. Males from T-injected eggs obtained more copulations than control males, specifically with control females. The effect of male 'ordinary' and secondary sexual traits on either dominance or copulation frequency did not depend on early exposure to T, nor did T treatment affect male dominance. Present results demonstrate that variation in the early hormonal environment set up by mothers affects sexual behavior of the offspring, which might translate into fitness differences., (Copyright © 2010 Elsevier Inc. All rights reserved.)

We investigated levels of DNA damage in blood cells of barn swallows (Hirundo rustica) inhabiting the Chernobyl region to evaluate whether chronic exposure to low-level radioactive contamination continues to induce genetic damage in free-living populations of animals. Blood samples were obtained from barn swallows collected at sites with different background levels of radiation, including a relatively uncontaminated area. The extent of DNA damage was evaluated using the alkaline (pH=12.1) comet assay, a robust and sensitive electrophoresis-based technique widely employed in research ranging from biomonitoring to clinical studies. We found that levels of DNA damage, as indexed by the extent of DNA migration, were increased in barn swallows living in areas surrounding Chernobyl when compared to swallows sampled at low-level sites. The results we obtained are consistent with previous findings on this same species, which showed that swallows breeding in areas heavily contaminated with radionuclides have increased mutation rates, higher oxidative stress and incidence of morphological aberrations and tumors. Overall, these results indicate that chronic exposure to radioactive contaminants, even 20years after the accident at the Chernobyl nuclear power plant, continues to induce DNA damage in cells of free-living animals.

The Chernobyl nuclear accident produced the largest unintended release of radionuclides in history, with dramatic consequences for humans and other organisms. Exposure to ionizing radiation is known to reduce circulating and stored levels of specific antioxidants in birds and humans, thus potentially increasing oxidative stress. However, overall effects of radioactive exposure on oxidative status have never been investigated in any free ranging vertebrate. We measured plasma antioxidant capacity and concentration of reactive oxygen metabolites in adult barn swallows (Hirundo rustica) from colonies with variable background radiation levels in the Chernobyl region in Ukraine and Belarus. We predicted that antioxidants would decrease while reactive oxygen metabolites would increase with exposure to increasing levels of radiation at the breeding sites. Consistent with this expectation, radiation level positively predicted plasma concentration of reactive oxygen metabolites, whereas no significant covariation was found with non-enzymatic plasma antioxidant capacity. An index of oxidative stress was also larger in barn swallows exposed to high contamination levels. Thus, radioactive contamination appeared to be responsible for the increased generation of reactive oxygen metabolites and the imbalance between reactive oxygen metabolites and non-enzymatic plasma antioxidant capacity., (2009 Elsevier Inc. All rights reserved.)

Phenological responses to climate change vary among taxa and across trophic levels. This can lead to a mismatch between the life cycles of ecologically interrelated populations (e.g. predators and prey), with negative consequences for population dynamics of some of the interacting species. Here we provide, to our knowledge, the first evidence that climate change might disrupt the association between the life cycles of the common cuckoo (Cuculus canorus), a migratory brood parasitic bird, and its hosts. We investigated changes in timing of spring arrival of the cuckoo and its hosts throughout Europe over six decades, and found that short-distance, but not long-distance, migratory hosts have advanced their arrival more than the cuckoo. Hence, cuckoos may keep track of phenological changes of long-distance, but not short-distance migrant hosts, with potential consequences for breeding of both cuckoo and hosts. The mismatch to some of the important hosts may contribute to the decline of cuckoo populations and explain some of the observed local changes in parasitism rates of migratory hosts.

In avian species, maternal provisioning to the eggs is predicted to be more valuable for the offspring under adverse environmental conditions and intense sibling competition. However, studies manipulating both the amount of maternal pre-hatching resources and the harshness of post-hatching environment have seldom been performed to date. In this experimental study of Barn Swallow (Hirundo rustica) nestlings, we tested the consequences of a reduction in the albumen content of the eggs for fitness-related offspring traits, while performing an unbalanced partial cross-fostering soon after hatching, either increasing or decreasing brood size by one nestling. By molecular sexing of the chicks, we additionally tested for sex-specific sensitivity of individual nestlings to experimental treatments and to sex ratio variation in nestmates. We predicted that chicks hatching from albumen-deprived eggs should suffer more than control chicks from the harsher rearing conditions of enlarged broods. However, although albumen removal depressed chick body mass, chicks hatching from control eggs did not fare better than those hatching from eggs with reduced albumen content in enlarged vs. reduced broods. Albumen removal had sex-specific effects on immunity, with males, but not females, hatching from eggs with reduced albumen content showing a lower T-cell-mediated immune response than controls, suggesting that the two sexes were differentially susceptible to resource deprivation during early ontogeny. In addition, both immune response and chick body mass at age 7 days, when maximum growth rate is attained, declined with an increasing proportion of male nestmates. The effect of brood size manipulation on chick body mass at age 12 days, when peak body mass is attained, was also found to depend on brood sex composition, in that an increase in the proportion of male nestmates depressed offspring body mass in reduced broods, while the reverse was true in enlarged broods. On the whole, these findings suggest that sex differences may exist in environmental sensitivity and patterns of resource allocation among different body functions, and that brood size variation and sex composition may affect offspring fitness-related traits.

Abstract Carotenoids perform important biological actions in animal tissues, including contributing antioxidant protection. However, the function of transmission of maternal carotenoids to bird eggs is still largely unknown. We made a yolk biopsy of yellow-legged gull (Larus michahellis) eggs and found that the concentration of lutein declined with laying date and across the laying order and increased with egg mass. The concentration of all the main carotenoids (lutein, zeaxanthin, and dehydrolutein) pooled also declined with date and increased with egg mass. We also performed a partial reciprocal cross-fostering of eggs between clutches and investigated the covariation between morphology, T cell-mediated immunity, and plasma carotenoid concentrations of the chicks and carotenoid concentrations in their original eggs. Absolute plasma carotenoid concentrations did not covary with those in the yolk, whereas a positive covariation was found for relative concentrations. Yolk and absolute plasma carotenoid concentrations positively predicted chick body mass and size but not the intensity of the cell-mediated immune response. Thus, yolk carotenoid concentrations may affect chick carotenoid profile and growth, possibly mediating early maternal effects. However, rearing conditions also contributed to determining relative concentrations of circulating carotenoids. Since yolk or plasma antioxidant capacity did not correlate with carotenoid concentrations, future studies of maternal effects mediated by antioxidants should integrate information on carotenoids with information on other components of the antioxidant systems.

Maternal effects mediated by egg quality are important sources of offspring phenotypic variation and can influence the course of evolutionary processes. Mothers allocate to the eggs diverse antioxidants that protect the embryo from oxidative stress. In the yellow-legged gull (Larus michahellis), yolk antioxidant capacity varied markedly among clutches and declined considerably with egg laying date. Analysis of bioptic yolk samples from clutches that were subsequently partially cross-fostered revealed a positive effect of yolk antioxidant capacity on embryonic development and chick growth, but not on immunity and begging behaviour, while controlling for parentage and common environment effects. Chick plasma antioxidant capacity varied according to rearing environment, after statistically partitioning out maternal influences mediated by egg quality. Thus, the results of this study indicate that egg antioxidants are important mediators of maternal effects also in wild bird populations, especially during the critical early post-hatching phase.

In humans, most of the mammals and one bird species studied so far, the relative length of individual digits is sexually dimorphic. Most studies of humans have been concerned with the ratio between second (2D) and fourth digits (4D), whereas some studies of humans and other mammals have also investigated other digit ratios. Inter- and intra-sexual variation in 2D:4D may depend on differential exposure to androgens during embryonic life, and the genetic mechanisms linking 2D:4D to androgens may be mediated by Hox genes. Because Hox genes are conserved in vertebrates, similar patterns of variation in digit ratios might be expected across vertebrate classes. The observation of correlations between digit ratios and physiological, psychological and performance traits in humans has generated interest in exploring the possibility that digit ratios are a marker of embryonic exposure to androgens, which have diverse consequences on several phenotypic traits. However, the hypothesis that digit ratios depend on androgen effects during development has never been tested experimentally. In this study, we increased testosterone concentration in ring-necked pheasant eggs and measured length ratios between the second, third and fourth digits of both feet in fully grown offspring. Females from testosterone-injected eggs had larger 2D:3D in the left foot, whereas this was not the case in males. The other digit ratios were unaffected by hormone treatment in both sexes. However, digit ratios showed no sexual dimorphism among controls. Thus, present results are consistent with the hypothesis that variation in testosterone levels during development affects digit ratios.