Evolutionary rates and shape variation along the anuran vertebral column with attention to phylogeny, body size, and ecology

The vertebral column is critical to a vertebrate species' flexibility
and skeletal support, making vertebrae a clear target for selection.
Anurans (frogs and toads) have a unique, truncated vertebral column that
appears constrained to provide axial rigidity for efficient jumping.
However, no study has examined how presacral vertebrae shape varies among
anuran species at the macroevolutionary scale nor how intrinsic
(developmental and phylogenetic) and extrinsic (ecological) factors may
have influenced vertebrae shape evolution. We used microCT scans and
phylogenetic comparative methods to examine the vertebrae of hundreds of
anuran species that vary in body size as well as adult and larval ecology.
We found variation in shape and evolutionary rates among anuran vertebrae,
dispelling any notion that trunk vertebrae evolve uniformly. We discovered
the highest evolutionary rates in the cervical vertebrae and in the more
caudal trunk vertebrae. We found little evidence for selection pressures
related to adult or larval ecology affecting vertebrae evolution, but we
did find body size was highly associated with vertebrae shape and
microhabitat (mainly burrowing) affected those allometric relationships.
Our results provide an interesting comparison to vertebrae evolution in
other clades and a jumping-off point for studies of anuran vertebrae
evolution and development.