Data and code from: Complete metamorphosis promotes morphological and functional diversity in Caudata

Metamorphosis, a common and spectacular developmental process, involves
major phenotypic changes often linked to environmental transitions.
Understanding how these changes affect morphological evolution is crucial
for examining metamorphosis's evolutionary impacts. In this study, we
analysed the role of metamorphosis and life cycle variation on the
morphological evolution of the mandible in Caudata (salamanders and
newts), a clade that exhibits a great diversity of life cycles and
ecologies. We focused on the mandible, a key component of the masticatory
apparatus, to investigate how life cycle variation may influence the
diversification of feeding mode. Using 3D geometric morphometrics on 317
extant species of Caudata, we found that both life cycle and size
influence mandible shape, with complex interactions between these factors.
The morphology of the mandibular bones evolved more independently in
species undergoing complete metamorphosis compared to those with partial
metamorphosis, likely facilitating feeding diversification in terrestrial
adults. On the other hand, high morphological integration in species
undergoing partial metamorphosis could promote the rapid evolution of
traits, resulting in the differentiation of more disparate morphologies,
potentially aiding paedomorphic species in adapting to challenging
environments. This study highlights the interplay between metamorphosis
and the environment in shaping morphological evolution among species and
provides new insights into the role of heterochrony in the morphological
diversification of organisms.