Aim Climatic gradients shape geographic variation in phenotypic traits that are involved in animal thermoregulation. Therefore, increasing temperatures under global warming are expected to cause change over time in traits that show predictable spatial patterns according to environmental clines (body and appendage size, tegument coloration), as well exemplified by biogeographic rules and shown by increasing literature at a loca...

Although the evolutionary ecology of melanin pigments and melanin-based coloration has been studied in great details, particularly in birds, little is known about the function of melanin stored inside the body. In the barn owl Tyto alba , in which individuals vary in the degree of reddish pheomelanin-based coloration and in the size of black eumelanic feather spots, we measured the concentration in melanin pigments in seven or...

Aim Pheomelanin is a pigment responsible for yellowish‐to‐reddish colours of vertebrate teguments. Its biosynthesis is favoured under high concentration of intracellular thiols, which, in turn, can depend on the environmental exposure to sulphur. Thus, pheomelanin production should be more intense and frequent in environments characterized by high level of sulphur, such as volcanic regions. In this study, we aimed at addressin...

The study of insular populations was key in the development of evolutionary theory. The successful colonisation of an island depends on the geographic context, and specific characteristics of the organism and the island, but also on stochastic processes. As a result, apparently identical islands may harbour populations with contrasting histories. Here, we use whole genome sequences of 65 barn owls to investigate the patterns o...

The climate fluctuations of the Quaternary shaped the movement of species in and out of glacial refugia. In Europe, the majority of species followed one of the described traditional postglacial recolonization routes from the southern peninsulas towards the north. Like most organisms, barn owls are assumed to have colonized the British Isles by crossing over Doggerland, a land bridge that connected Britain to northern Europe. H...

Bird nests are specialized habitats because of their particular composition including nest detritus and bird droppings. In consequence, they attract a specialized arthropod community considered as nidicolous, which includes species only found in bird nests (strictly nidicolous) or sometimes found in bird nests (facultatively nidicolous). Because the factors influencing the entomofauna in bird nests are poorly understood, in au...

Aim Insular populations face different conditions than those living on continents, thus, resulting in the evolution of typical insular phenotypes, like smaller body sizes or reduced colourations. However, the generality of the so‐called “island rule” has been questioned, and intraspecific analyses on the effects of insularity on cosmopolitan species are lacking. Here, we tested the predictions of the island rule in the cosmopo...

Aim The eco‐geographical Bergmann's rule predicts that animals have smaller body size in warmer regions than in cold environments because of thermoregulatory reasons. Although this rule has been widely investigated, intraspecific analyses on cosmopolitan taxa are rare. We examined whether geographical variation in wing length, a proxy of body size, shows a Bergmannian pattern and can be explained by three mechanisms known to a...

Aim The investigation of biogeographical patterns in the diet of widely distributed predators is essential to understand their ecology, life history traits and local adaptations. However, it is particularly challenging because of their wide distribution, broad trophic spectra and high ecological plasticity. Here, we described patterns of trophic ecology in a cosmopolitan nocturnal raptor, the common barn owl group, from a biog...

Aim Avian beak morphology is a good example of how anatomical structures have evolved in response to different selective pressures, such as diet and vocalizations, but also thermoregulation. The last of these functions was neglected until recently, but convincing evidence has been provided regarding the capacity of birds to regulate heat dissipation through their highly vascularized bills. According to this adaptive function a...

Disentangling the sources of variation in developing an effective immune response against pathogens is of major interest to immunoecology and evolutionary biology. To date, the link between immunocompetence and genetic variation at the major histocompatibility complex (MHC) has received little attention in wild animals, despite the key role of MHC genes in activating the adaptive immune system. Although several studies point t...

Aim The investigation of phenotypic diversity across geographical gradients is pivotal to understanding the evolution and adaptive functions of alternative phenotypes. The aim of the present study was to investigate whether the polymorphism in ventral plumage colouration observed in the cosmopolitan common barn owl group is determined by climatic factors, such as temperature and rainfall, consistent with Gloger’s and Bogert’s...

Aim Geological barriers within a species range play a key role in shaping patterns of genetic variation by restricting gene flow. Mountain ranges are particularly imposing barriers responsible for creating genetic differentiation across multiple taxa, from small amphibians to large mammals and birds. Here, we examined the population structure of North American barn owls ( Tyto alba ) and investigated whether the Rocky Mountain...

The melanocortin‐1 receptor ( MC 1R ) gene influences coloration by altering the expression of genes acting downstream in the melanin synthesis. MC 1R belongs to the melanocortin system, a genetic network coding for the ligands that regulate MC 1R and other melanocortin receptors controlling different physiological and behavioural traits. The impact of MC 1R variants on these regulatory melanocortin genes was never considered,...

Sexual conflict arises when selection in one sex causes the displacement of the other sex from its phenotypic optimum, leading to an inevitable tension within the genome – called intralocus sexual conflict. Although the autosomal melanocortin‐1‐receptor gene ( MC 1R ) can generate colour variation in sexually dichromatic species, most previous studies have not considered the possibility that MC 1R may be subject to sexual conf...