Gloger's rule in North American Barn Owls

Roulin, Alexandre; Randin, Christophe F.

doi:10.1642/auk-14-167.1

Cited by 26 publications

(35 citation statements)

References 41 publications

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“…Although these traits are partly genetically linked (Roulin & Jensen, ), this difference might be explained by the fact that black spots cover a small proportion of the plumage surface, thus limiting their scope to be involved in camouflage, feather resistance or body‐drying functions, and because spottiness seems to be more involved in mate choice and sexual selection than plumage colouration (Antoniazza et al, ; Roulin & Ducrest, ; Roulin, Jungi, Pfister, & Dijkstra, ; Roulin et al, ). However, this result apparently contradicts previous studies at smaller scales reporting that individuals with larger spots are more abundant in colder regions (Roulin & Randin, ). We cannot exclude that spot size can help to thermoregulate, as suggested in T. javanica , but in the other two lineages such a possible function might have been masked in the present analyses because populations living in tropical and warmer habitats are more spotted than those at temperate latitudes, as indicated by the negative trend of spot size with latitude consistently observed in all the lineages (Table ; Roulin et al, ).…”

Section: Discussioncontrasting

confidence: 98%

Climate‐driven convergent evolution of plumage colour in a cosmopolitan bird

Romanò

Séchaud

Hirzel

et al. 2019

Global Ecol Biogeogr

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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 biogeographical rules. Location World. Time period 1809–2017. Major taxa studied Tyto alba species complex. Methods We analysed the variation in heritable melanin‐based plumage colour according to annual temperature and rainfall in 9,110 individuals of the cosmopolitan barn owl, with three distinct evolutionary lineages representing its entire distribution range: the Afro‐European Tyto alba, occurring between Scandinavia and South Africa, the American Tyto furcata, found from southern Canada to Patagonia, and the Australasian Tyto javanica, living between the Himalayan Plateau and Tasmania. Results Although the geographical distribution of colour morphs is heterogeneous among the lineages, in all of them plumage colour becomes darker with increasing annual rainfall, indicating a convergent selection of darker morphs in humid habitats possibly to improve camouflage against the dark environment and/or to repel water more efficiently. Moreover, in T. alba and T. furcata, melanization increases at decreasing temperature, suggesting its possible role in thermoregulation. Discussion These findings provide convincing evidence of repeated evolution of similar body colouration patterns at a worldwide scale compatible with the main biogeographical rules, while emphasizing the possible role of melanin‐based traits in animal adaptation to climate change.

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Section: Discussioncontrasting

confidence: 98%

Climate‐driven convergent evolution of plumage colour in a cosmopolitan bird

Romanò

Séchaud

Hirzel

et al. 2019

Global Ecol Biogeogr

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“…The present study shows that, on the British Isles, barn owls display comparatively larger black feather spots on the ventral body side in cooler regions in summer. This result is consistent with what we found on the North American (Roulin & Randin, ) and European continents (Roulin, ). However, in another study considering the T. alba taxa as the unit of our statistics (instead of North‐American or European barn owl individuals), we found that, on the northern hemisphere, taxa located near the equator display larger black spots than taxa located towards the poles (Roulin, Wink & Salamin, ).…”

Section: Discussionsupporting

confidence: 93%

“…This work showed that, at the continental scale, variation in plumage traits is associated with climatic factors. For example, barn owls display larger black feather spots in regions where ambient temperatures are colder (Roulin & Randin, ). The same applies to the European continent, with barn owls having larger spots in the north‐eastern regions and being smaller‐spotted in the southern parts of the continent (Roulin, ).…”

Section: Introductionmentioning

confidence: 99%

Barn owls display larger black feather spots in cooler regions of the British Isles

Roulin

Randin

2016

Biol. J. Linn. Soc.

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Although, in many organisms, genotypes are adapted to specific environmental conditions, the identification of the ecological factors explaining patterns of local adaptation is not a trivial task. In relation to the cosmopolitan barn owl (Tyto alba), its plumage varies from white to dark pheomelanic and shows a difference in the number and size of black spots located at the tip of ventral feathers. The expression of these traits is strongly heritable and weakly sensitive to variation in body condition. Therefore, if owls located in cold or rainy regions are differently plumaged compared to owls living in warm or dry regions, this may not be a result of climate affecting the expression of plumage traits. Instead, different plumages might be selected under different environmental conditions. We have found that, on the British Isles, comparatively larger spots are present on barn owls found in regions that are cooler in summer. This is similar to the findings of a previous study performed in North America and on continental Europe, raising the possibility that larger-spotted barn owls better cope in cold temperatures during the rearing period or that they are better adapted to some environmental factors prevailing in cooler summers.

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“…Contrary to this, Bretagnolle (Bretagnolle ) found that plumage of petrels, albatrosses and allies (Procellariformes) became lighter with colder water temperatures, but selection patterns may be different for seabirds given the difference in environmental conditions when compared to terrestrial birds. In addition, intraspecific variation in colour can also correlate with temperature: darker individuals are found in in colder regions in barn owls Tyto alba (Roulin , Roulin and Randin , ), New Zealand bellbirds Anthornis melanura (Bartle and Sagar ), Australian eastern yellow robins Eopsaltria australis (Morales et al ), bearded vultures Gypaetus barbatus (Margalida et al ) and polymorphic species in general (Galeotti et al ). The opposite has been found in dark‐eyed juncos Junco hyemalis along an elevation gradient in Canada, where lighter birds were found at higher elevations with presumably lower temperatures (de Zwaan et al ).…”

Section: Discussionmentioning

confidence: 99%

Darker where cold and wet: Australian birds follow their own version of Gloger's rule

Delhey

2017

Ecography

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Gloger's rule is usually interpreted as predicting darker coloured animals in warmer and more humid/vegetated regions. The relative importance of temperature and rainfall or vegetation is however unclear, and often only one variable is tested at a time, mainly through proxies. Here, I assess the predictions of Gloger's rule for interspecific achromatic plumage variation (dark to light variation) for an entire avifauna (551 species of Australian landbirds). I tested the effects of climatic variables (temperature and rainfall) and vegetation structure on plumage reflectance at species and assemblage level (100 × 100 km cells), controlling for phylogenetic relatedness and spatial autocorrelation. To assess the robustness of these results I compared observed results with those of a null distribution of effects obtained from repeatedly simulating random plumage reflectance evolution on the phylogeny. At both the species and assemblage level, darker coloured birds were found in wetter and colder regions and in more densely vegetated habitats. Simulations confirm results at the species level and the effect of temperature at the assemblage level, but rainfall and vegetation effects at the assemblage level fall within the distribution of simulated effects and should be interpreted with care. Interspecific colour variation in Australian birds supports Gloger's rule for rainfall/vegetation, but shows the opposite pattern for temperature. Darker colours in wet and vegetated environments are consistent with the role of melanin pigmentation in preventing feather degradation by bacteria, but also with background‐matching for camouflage. Darker plumage might be beneficial in colder regions or detrimental in warmer regions if it affects thermoregulation, a selective force often only assumed to be of importance for ectotherms. The data highlight the need to test the generality of biogeographic rules across levels and at broad scale. Experimental work is needed to confirm the mechanisms linking plumage achromatic variation to climate.

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Gloger's rule in North American Barn Owls

Cited by 26 publications

References 41 publications

Climate‐driven convergent evolution of plumage colour in a cosmopolitan bird

Climate‐driven convergent evolution of plumage colour in a cosmopolitan bird

Barn owls display larger black feather spots in cooler regions of the British Isles

Darker where cold and wet: Australian birds follow their own version of Gloger's rule

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