Dressed for the Weather: Tawny Owl Feather Adaptations Across a Climatic Gradient.

Area of Science:

• Evolutionary biology
• Avian ecology
• Climate adaptation

Background:

• Populations are generally adapted to local environments through natural selection, counteracted by gene flow.
• Feather characteristics in birds, such as insulation and color, are potential indicators of local adaptation.
• The tawny owl (Strix aluco) is a suitable model for studying adaptation across its European range.

Purpose of the Study:

• To investigate whether feather properties and plumage color in tawny owls reflect local adaptation to environmental conditions.
• To compare phenotypic divergence (PST) of feather traits with genetic divergence (FST) to infer the role of natural selection versus genetic drift.
• To determine if climate influences specific feather characteristics, such as insulation capacity.

Main Methods:

• Studied feather properties (plumulaceous part, barb and barbule density) and plumage color (dark vs. light morphs) in tawny owls across nine European populations.
• Utilized eight microsatellite markers to infer genetic divergence (FST) among populations.
• Calculated phenotypic divergence (PST) for feather traits and compared it with FST to assess the influence of natural selection.

Main Results:

• Low overall genetic differentiation (FST = 0.022) was observed across populations.
• Phenotypic divergence (PST) for most feather structures exceeded FST, indicating potential local adaptation.
• Dorsal feather insulation (plumulaceous part) was larger in colder populations, suggesting climate-driven adaptation, while plumage color showed limited adaptive variation.

Conclusions:

• Feather structural properties, particularly in dorsal feathers, appear to be shaped by local adaptation to climate, potentially enhancing insulation in colder regions.
• Plumage color variation in tawny owls plays a limited role in adaptation at large spatial scales.
• Avian feather characteristics offer insights into the processes of local adaptation driven by environmental factors like climate.