358 research outputs found
Alexandre Vinet Chateaubriand
No full textEtudes d'Alexandre Vinet sur Chateaubriand, avec une préface de Jean-Marie Roulin: "Le Microscope brisé".International audienc
Alexandre Vinet Chateaubriand
No full textEtudes d'Alexandre Vinet sur Chateaubriand, avec une préface de Jean-Marie Roulin: "Le Microscope brisé".International audienc
Female barn owls (Tyto alba) advertise good genes
No full textThe good genes hypothesis of sexual selection postulates that ornamentation signals superior genetic quality to potential mates. Support for this hypothesis comes from studies on male ornamentation only, while it remains to be shown that female ornamentation may signal genetic quality as well. Female barn owls (Tyto alba) display more black spots on their plumage than males. The expression of this plumage trait has a genetic basis and it has been suggested that males prefer to mate with females displaying more black spots. Given the role of parasites in the evolution of sexually selected traits and of the immune system in parasite resistance, we hypothesize that the extent of female plumage `spottiness’ reflects immunological defence. We assessed the genetic variation in specific antibody production against a non-pathogenic antigen among cross-fostered nestlings and studied its covariation with the plumage spottiness of genetic parents. The magnitude of the antibody response was positively correlated with the plumage spottiness of the genetic mother but not of the genetic father. Our study thereby provides the first experimental support, to our knowledge, for the hypothesis that female ornamentation signals genetic quality.
Contamination by neonicotinoid insecticides in Barn owls (Tyto alba) and Alpine swifts (Tachymarptis melba)
No full textAcknowledgements We thank all the students and volunteers who helped us in their fields. This study was supported by a Swiss National Science Foundation overheads grant, a grant from the Federal Office for the Environment and an SNSF-förderungs professor grant to FH. Photographs used in the graphical abstract are copyrights of Alexandre Roulin, Pierre Bize and Shirley Laurent. The authors bear sole responsibility for the content and declare no conflict of interest.Peer reviewe
Geographic variation in body size and plumage colour according to diet composition in a nocturnal raptor
No full textPredator–prey interactions are amongst the strongest selective forces that promote the evolution of local phenotypes in both predators and prey. However, intraspecific spatial covariation in phenotypic traits between predators and prey has been rarely investigated, especially at a large geographic scale. Here, we studied the covariation between prey composition and some phenotypic traits, such as wing length, bill length and plumage colour, of a widely-distributed nocturnal predator, the western barn owl Tyto alba. By using 3100 specimens collected across its entire range of distribution, spanning from Europe to Middle East and Africa, we showed that wing length positively covaries with prey size, but not with taxonomic composition. This finding suggests that larger prey might have selected for larger body size and/or that larger individuals might be more selective in hunting large prey. In addition, we also found that paler-plumaged populations generally hunt larger prey. Paler barn owls might be thus better specialized in capturing averagely larger prey and/or mainly hunt in habitats where larger prey are more abundant. In addition, considering that paler individuals are generally larger than brownish ones, it is possible that paler plumage colour might have evolved as a by-product of selection towards a large body size, which in turn have emerged in response to prey size composition. However, irrespectively of the direction of causality and the phenotypic target of selection, we showed that predator–prey interactions can affect spatial phenotypic variation by promoting the evolution of local adaptations
Generalized evidence for Bergmann’s rule: body size variation in a cosmopolitan owl genus
No full textThe 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 affect animal body size (heat conservation, resource availability and starvation resistance) in seven species of nocturnal raptors of the genusTyto. Location World. Taxon GenusTyto. Methods We measured wing length of 9,033 museum specimens covering the entire distributional range of each species and linked it with geographical (absolute latitude, elevation) and climatic predictors associated with heat conservation, resource availability and starvation resistance hypotheses of spatial variation in body size. Results All the species show a trend of increasing wing length with increasing latitude and/or elevation, and in five of them either or both geographical predictors are statistically significant. In all the species showing a Bergmannian pattern, wing length significantly decreases with temperature, thus supporting the heat conservation hypothesis. Conversely, we found less generalized support for the other hypotheses, although in some species significant trends between wing length and proxies of climatic seasonality and/or primary productivity emerged. Main conclusions Consistent clines in body shrinking in warm environments are observed in species living in different continents at different latitudinal and temperature ranges, as well as exploiting different habitats. These findings thus support the hypothesis that body size is, at least partly, selected for heat maintenance depending on the thermal environment, even in nocturnal species which are not directly exposed to solar radiation. However, different selective pressures may also have concomitantly acted to promote body size evolution in this bird group
Global biogeographical patterns in the diet of a cosmopolitan avian predator
No full textAim: 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 biogeographical perspective. We then compared variation in diet between barn owls living in the Americas (T. furcata), and those inhabiting Europe, Middle-East and Africa (T. alba), thus hunting on different assemblages of prey types. Location: World. Taxon: Barn owl species complex. Methods: We reviewed 790 studies reporting diet information of 971 locations (3,733,902 individual vertebrate prey), and investigated the variation in different diet parameters, reflecting taxonomic diversity, size of the prey and frequency of certain prey types according to geographical and climatic variables. Results: While confirming that the barn owl is a selective mammal hunter with variable taxa constituting its staple food in different regions, we also found significant geographical and climatic trends in several diet parameters. Although prey composition differed among continents, most of the patterns, including an increase in proportion of mammal prey in cold environments, an increase in diet diversity with elevation, a decrease in small prey consumption from high to low latitudes and at increasing temperature, and a decrease in rodent predation in humid habitats, were similar between T. furcata and T. alba. A strong island effect was observed for all diet parameters. Main conclusion: Our results indicate a generalized pattern of variation in barn owl diet across biogeographical regions, suggesting that similar prey communities occur in habitats with comparable ecological conditions and/or that different barn owl populations living in similar climate convergently evolved similar food preferences and hunting strategies
Data from: A melanin-based trait is more strongly related to body size in the tropics than in temperate regions in the globally distributed barn owl family
No full textLife history traits differ between organisms living in the tropics, northern and southern hemispheres, and sexual selection is thought to be stronger close to the equator than in temperate regions. Although birds are often supposed to be more brightly coloured in the tropics, the current evidence of geographic variation in the intensity of sexual selection and sex-specific natural selection is equivocal. Whether sex-specific traits signal aspects of individual quality better in the tropics than in the temperate regions of the northern and southern hemispheres therefore remains an open question. We examined predictions of this hypothesis in the Tytonidae family (barn owls and their relatives) because females, on average, display larger black spots on the tip of their ventral body feathers than males, and this trait is associated with aspects of individual quality. We measured the size of melanic spots and the wing length of 7893 Tytonidae skins collected worldwide and preserved in natural history museums. The covariation between spot size and wing length was stronger in females than in males, in large- than small-spotted Tyto taxa and close to the equator than in temperate regions. This suggests that selection for spot size, which can be used by owls as an additional cue to assess individual body size and other aspects of phenotypic quality, is stronger in females than in males, particularly near the equator
Evolution of wing length and melanin‐based coloration in insular populations of a cosmopolitan raptor
No full textAim 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 cosmopolitan common barn owl group.
Location World.
Taxon Barn owl species complex.
Methods We compared wing and bill length, as well as melanin-based plumage traits, between thousands of insular and continental barn owls living in the Afro-Palearctic region (Tyto alba), in the Americas (Tyto furcata) and in Australasia (Tyto javanica). We also tested whether the difference between insular and continental populations in these phenotypic traits varies among islands/archipelagos of different size and isolation.
Results In all the regions, we found differences between insular and continental owls in all the traits but bill length, with insular populations convergently evolving shorter wings and paler colourations. In addition, the difference in wing size between insular and continental populations is particularly marked on small and remote island systems, while melanin-based traits are less expressed especially on large islands.
Main conclusions We thus provide unprecedented evidence that insular conditions drive predictable phenotypic variations, even at the intraspecific level in different biogeographic regions, possibly promoting speciation events. In addition, our results also indicate that selective advantages of a given colouration can arise as the by-product of positive selection on individuals displaying phenotypic traits which can favour island colonization and are genetically linked to melanization
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