Morphological variation under domestication: how variable are chickens?

Area of Science:

• Evolutionary biology
• Developmental biology
• Comparative anatomy

Background:

• Domestication rapidly alters morphology and behavior.
• Domesticated animals, like dogs and pigeons, exhibit greater morphological variation than wild ancestors.
• Chicken domestication offers a model to study evolutionary changes.

Purpose of the Study:

• Quantify skull morphology variation in chickens compared to wild fowl.
• Investigate skull modularity and integration in domesticated chickens.
• Identify skull regions with the highest variation during domestication.

Main Methods:

• Three-dimensional geometric morphometrics.
• Multivariate statistical analyses.
• Comparative analysis of domestic chickens and wild fowl skulls.

Main Results:

• Domestic chickens show a greater magnitude of skull shape variation than their ancestors.
• The cranial vault, formed by dermal and neural crest bones, is the most variable skull region.
• Neural crest-derived skull portions exhibit higher variation.
• The chicken skull demonstrates strong integration, unlike mammals.

Conclusions:

• Domestication drives significant skull shape diversification in chickens.
• Cranial vault variation may relate to brain shape differences, particularly in crested breeds.
• The integrated nature of the avian skull contrasts with mammalian modularity patterns.