Data from: Integration and evolution of the cichlid pharyngeal skeleton: Seeking the causes and consequences of trait covariation

The evolutionary success of animals has been facilitated by the expansion
and diversification of serially homologous elements. The vertebrate
pharyngeal skeleton exemplifies this process. Evolved from a uniform
series of cartilaginous rods, different elements have evolved distinct
shapes and functions over time. This process implies that the evolution of
the pharyngeal skeleton involved the decoupling of its constituent
elements; however, to ensure functionality, a level of connectivity must
be maintained. Thus, the evolution of the pharyngeal skeleton is likely
influenced by a balance of diversifying and unifying forces. We probe
these ideas using East African cichlid fishes. Shape analyses in a sample
of 75 ecologically diverse species and a large F5 hybrid population showed
a conspicuous lack of independence. Nearly all elements were correlated, a
pattern reflected in the genotype-phenotype map and associated with
co-expression of the candidate gene, smad7. Results are discussed in the
context of the palimpsest model, whereby trait covariation is the result
of numerous, hierarchical forces of covariation. Given its broad
regulatory roles, we suggest that Smad7 may be involved in several layers
of the palimpsest, providing molecular insights into how serially
homologous elements may diversify while also maintaining functionality.