The neck as a keystone structure in avian macroevolution and mosaicism

Area of Science:

• Evolutionary biology
• Paleontology
• Comparative anatomy

Background:

• Birds evolved from theropod dinosaurs, requiring significant body plan changes for flight.
• Mosaic evolution, where traits evolve independently, is a proposed mechanism for avian diversification.
• The role of the axial skeleton, specifically the neck, in avian macroevolution remains understudied.

Purpose of the Study:

• To conduct the first integrative analysis of avian neck evolution.
• To examine neck integration with the head and forelimb.
• To understand how these interactions influence macroevolutionary trends.

Main Methods:

• 3D geometric morphometrics
• Phylogenetic comparative methods
• Analysis of a broad sample of extant birds

Main Results:

• The avian neck is integrated with both the head and forelimb.
• Integration patterns vary across bird clades, with specific ecological groups showing head-neck or neck-forelimb integration.
• Groups with head-neck and neck-forelimb integration exhibit significant shifts in neck morphological evolution rates.

Conclusions:

• Trophic ecology and head-neck-forelimb mosaicism interact to influence avian neck evolutionary variance.
• The cervical vertebral column is a keystone structure in avian mosaicism and macroevolution.
• Understanding neck integration provides insights into the evolution of flight and bird diversity.