Data from: The neck as a keystone structure in avian macroevolution and mosaicism

BackgroundThe origin of birds from non-avian theropod dinosaur ancestors
required a comprehensive restructuring of the body plan to enable the
evolution of powered flight. One of the proposed key mechanisms that
allowed birds to acquire flight and modify the associated anatomical
structures into diverse forms is mosaic evolution, which describes the
parcelization of phenotypic traits into separate modules that evolve with
heterogeneous tempo and mode. Avian mosaicism has been investigated with a
focus on the cranial and appendicular skeleton, and as such we don’t
understand the role of the axial column in avian macroevolution. The long,
flexible neck of extant birds lies between the cranial and pectoral
modules and represents an opportunity to study the contribution of the
axial skeleton to avian mosaicism. ResultsHere we use 3D geometric
morphometrics in tandem with phylogenetic comparative methods to provide,
to our knowledge, the first integrative analysis of avian neck evolution
in context with the head and wing and to interrogate how the interactions
between these anatomical systems have influenced macroevolutionary trends
across a broad sample of extant birds. We find that the neck is integrated
with both the head and the forelimb. These patterns of integration are
variable across clades and only specific ecological groups exhibit either
head-neck or neck-forelimb integration. Finally, we find that ecological
groups that display head-neck and neck-forelimb integration tend to
display significant shifts in the rate of neck morphological evolution.
ConclusionsCombined, these results suggest that the interaction between
trophic ecology and head-neck-forelimb mosaicism influences the
evolutionary variance of the avian neck. By linking together the
biomechanical functions of these distinct anatomical systems, the cervical
vertebral column serves as a keystone structure in avian mosaicism and
macroevolution.