A chromosome-level reference genome and pangenome for barn swallow population genomics.

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.

The Mitogenome Relationships and Phylogeography of Barn Swallows (Hirundo rustica).

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.

Telomere shortening is associated with corticosterone stress response in adult barn swallows.

When vertebrates face stressful events, the hypothalamic-pituitary-adrenal (HPA) axis is activated, generating a rapid increase in circulating glucocorticoid (GC) stress hormones followed by a return to baseline levels. However, repeated activation of HPA axis may lead to increase in oxidative stress. One target of oxidative stress is telomeres, nucleoprotein complexes at the end of chromosomes that shorten at each cell division.

The genome sequence of the European nightjar, (Linnaeus, 1758).

We present a genome assembly from an individual female (the European nightjar; Chordata; Aves; Caprimulgiformes; Caprimulgidae). The genome sequence is 1,178 megabases in span. The majority of the assembly (99.

Prenatal yolk corticosterone exposure promotes skeletal growth and induces oxidative imbalance in yellow-legged gull embryos.

Maternally derived hormones induce variation in offspring phenotype, with consequences that can carry over into post-natal life and even into adulthood. In birds, maternal egg corticosterone (CORT) is known to exert contrasting effects on offspring morphology, physiology and behaviour after hatching. However, information on the effects of CORT exposure on pre-hatching embryonic development is limited.

Prenatal exposure to triclosan induced brain telomere shortening in a wild bird species.

Exposure to the antimicrobial agent Triclosan (TCS) induces oxidative stress in diverse organisms, including birds. However, whether TCS-induced oxidative stress effectively translates into detrimental effects is still unclear. The present study examined whether prenatal TCS exposure induces oxidative stress and telomere shortening in the brain and the liver of near-term embryos of the yellow-legged gull (Larus michahellis).

Trace elements fingerprint of feathers differs between breeding and non-breeding areas in an Afro-Palearctic migratory bird, the barn swallow (Hirundo rustica).

Trace elements are widespread contaminants that can potentially threaten ecosystems and human health. Considering their distribution and toxicity, monitoring their presence in animals represents a priority in environmental risk assessment. Migratory birds have been suggested to be useful biomonitors for trace elements because they can provide information on contaminants even from remote areas that they may exploit during their life cycle.

Perinatal variation and covariation of oxidative status and telomere length in yellow-legged gull chicks.

The perinatal period is critical to survival and performance of many organisms. In birds, rapid postnatal growth and sudden exposure to aerial oxygen around hatching markedly affect the chick redox status, with potentially negative consequences on physiology mediated by oxidative stress. In addition, telomere length (TL) undergoes reduction during birds' early life, partly depending on oxidative status.

Predation risk affects egg mass but not egg steroid hormone concentrations in yellow-legged gulls.

Predators have both direct, consumptive effects on their prey and non-lethal effects on physiology and behavior, including reproductive decisions, with cascading effects on prey ecology and evolution. Here, we experimentally tested such non-lethal effects of exposure to increased predation risk on clutch size, egg mass, and the concentration of yolk steroid hormones in the yellow-legged gull . We simulated increased predation risk by displaying stuffed predators (adult fox , and adult buzzard ) to breeding adults before egg laying.

Egg Testosterone Differentially Affects Telomere Length in Somatic Tissues of Yellow-Legged Gull Embryos.

Maternal decisions on egg composition have major consequences for offspring. Maternal egg androgens have diverse, often contrasting, effects depending on offspring trait and life stage, suggesting that mothers face trade-offs in egg hormone transfer. However, the effect of egg androgens on embryonic telomere length, which is a major trait potentially affecting performance, has been never investigated.

Cloacal microbiomes and ecology of individual barn swallows.

Microbiomes can be considered as 'second genomes' for the host, and can deeply affect its physiology, behaviour and fitness. We investigated the cloacal microbiomes (CMs) of adult and nestling barn swallows (Hirundo rustica), a small insectivorous migratory passerine bird, in order to assess whether CM structure was related to major ecological traits of individuals. Illumina sequencing of the V5-V6 hypervariable regions of the bacterial 16S rRNA gene showed that barn swallow CMs were dominated by Proteobacteria, Firmicutes, Actinobacteria, Tenericutes and Bacteroidetes.

Inter-generational resemblance of methylation levels at circadian genes and associations with phenology in the barn swallow.

Regulation of gene expression can occur via epigenetic effects as mediated by DNA methylation. The potential for epigenetic effects to be transmitted across generations, thus modulating phenotypic variation and affecting ecological and evolutionary processes, is increasingly appreciated. However, the study of variation in epigenomes and inter-generational transmission of epigenetic alterations in wild populations is at its very infancy.

Embryotoxic effects of in-ovo triclosan injection to the yellow-legged gull.

Triclosan (TCS) is an antimicrobial agent used in diverse personal care products that is considered as an emerging contaminant of both aquatic and terrestrial ecosystems. Although TCS aquatic ecotoxicity is well known, information on the presence and effects on terrestrial organisms is still scarce. This study was aimed at exploring the embryotoxicity of TCS to the yellow-legged gull (Larus michahellis) induced by the in-ovo injection of 150 ng TCS/g egg weight.

Yolk vitamin E positively affects prenatal growth but not oxidative status in yellow-legged gull embryos.

Parental effects occur whenever the phenotype of parents or the environment that they experience influences the phenotype and fitness of their offspring. In birds, parental effects are often mediated by the size and biochemical quality of the eggs in terms of maternally transferred components. Exogenous antioxidants are key egg components that accomplish crucial physiological functions during early life.

Physiological increase of yolk testosterone level does not affect oxidative status and telomere length in gull hatchlings.

Conditions experienced during early-life can cause the onset of oxidative stress, resulting in pervasive effects on diverse life-history traits, including lifespan. In birds, maternally-transferred egg substances may exert positive or negative influence over the offspring phenotype. Among these, testosterone can upregulate the bioavailability of certain antioxidants but simultaneously promotes the production of pro-oxidants, leading to an oxidative stress situation, which is one of the main forces causing telomere attrition However, no study has investigated the role of this androgen on telomere dynamics in birds and little is known about the effects of yolk testosterone on oxidative status in early-life of these species.

Independent and combined effects of egg pro- and anti-oxidants on gull chick phenotype.

Oviparous mothers transfer to their eggs components that have both independent and combined effects on offspring phenotype. The functional interaction between egg components, such as antioxidants and hormones, suggests that a change in the concentration of one component will have effects on offspring traits that depend on the concentration of other interacting components. However, the combined effects of variation in different egg components are virtually unknown.

Effect of yolk corticosterone on begging in the yellow-legged gull.

Behavioral lateralization is widespread across vertebrates. The development of lateralization is affected by both genetic and environmental factors. In birds, maternal substances in the egg can affect offspring lateralization via activational and/or organizational effects.

Wing morphology, winter ecology, and fecundity selection: evidence for sex-dependence in barn swallows (Hirundo rustica).

Variation in wing morphology results from the combination of diverse selection pressures. Wing feather morphology within species varies with sex and ontogenetic effects, and also with ecological factors. Yet, the direction of causation for the wing morphology-ecology association remains to be elucidated.

Lifetime reproductive success, selection on lifespan, and multiple sexual ornaments in male European barn swallows.

Natural and sexual selection arise when individual fitness varies according to focal traits. Extra-pair paternities (EPPs) can affect the intensity of selection by influencing variance in fitness among individuals. Studies of selection require that individual fitness is estimated using proxies of lifetime reproductive success (LRS).

Yolk vitamin E prevents oxidative damage in gull hatchlings.

Oxidative stress experienced during early development can negatively affect diverse life-history traits, and organisms have evolved complex defence systems against its detrimental effects. Bird eggs contain maternally derived exogenous antioxidants that play a major role in embryo protection from oxidative damage, including the negative effects on telomere dynamics. In this study on the yellow-legged gull (), we manipulated the concentration of vitamin E (VE) in the egg yolk and analysed the consequences on oxidative status markers and telomere length in the hatchlings.

Migration phenology and breeding success are predicted by methylation of a photoperiodic gene in the barn swallow.

Individuals often considerably differ in the timing of their life-cycle events, with major consequences for individual fitness, and, ultimately, for population dynamics. Phenological variation can arise from genetic effects but also from epigenetic modifications in DNA expression and translation. Here, we tested if CpG methylation at the poly-Q and 5'-UTR loci of the photoperiodic Clock gene predicted migration and breeding phenology of long-distance migratory barn swallows (Hirundo rustica) that were tracked year-round using light-level geolocators.

Contrasting effects of increased yolk testosterone content on development and oxidative status in gull embryos.

Hormone-mediated maternal effects generate variation in offspring phenotype. In birds, maternal egg testosterone (T) exerts differential effects on offspring traits after hatching, suggesting that mothers experience a trade-off between contrasting T effects. However, there is very little information on T pre-natal effects.

Antioxidants and embryo phenotype: is there experimental evidence for strong integration of the antioxidant system?

Organisms have evolved complex defense systems against oxidative stress. Bird eggs contain maternally derived antioxidants that protect embryos from oxidative damage. The antioxidant system components are thought to be integrated, but few studies have analyzed the covariation between antioxidant concentrations, embryo 'oxidative status' and morphology.

Sex-dependent carry-over effects on timing of reproduction and fecundity of a migratory bird.

Life of many organisms flows as a sequence of annual cycles. Timing of cyclical events is shaped by natural selection also via the domino effects that any life history stage has on the stages that follow. Such 'carry-over effects' have major consequences for evolutionary, ecological and demographic processes, but the causes that generate their individual-level variation, including the effect of sex, are poorly understood.