Evolutionary innovation and conservation in the embryonic derivation of the vertebrate skull

• Published in: Nature communications Vol. 5; no. 1; p. 5661
• Main Authors: Piekarski, Nadine, Gross, Joshua B., Hanken, James
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.12.2014; Nature Publishing Group; Nature Pub. Group
• Subjects: 13/1; 13/51; 14/35; 14/63; 631/136/818; 631/181/2806; 64/114; Ambystoma mexicanum - embryology; Animals; Biological Evolution; Humanities and Social Sciences; multidisciplinary; Neural Crest - embryology; Science; Science (multidisciplinary); Skull - embryology; Vertebrates - embryology; Xenopus laevis - embryology
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms6661

Development of the vertebrate skull has been studied intensively for more than 150 years, yet many essential features remain unresolved. One such feature is the extent to which embryonic derivation of individual bones is evolutionarily conserved or labile. We perform long-term fate mapping using GFP-transgenic axolotl and Xenopus laevis to document the contribution of individual cranial neural crest streams to the osteocranium in these amphibians. Here we show that the axolotl pattern is strikingly similar to that in amniotes; it likely represents the ancestral condition for tetrapods. Unexpectedly, the pattern in Xenopus is much different; it may constitute a unique condition that evolved after anurans diverged from other amphibians. Such changes reveal an unappreciated relation between life history evolution and cranial development and exemplify ‘developmental system drift’, in which interspecific divergence in developmental processes that underlie homologous characters occurs with little or no concomitant change in the adult phenotype. It is unclear whether the embryonic origin of skull bones is evolutionarily conserved. Here, the authors show that the pattern of cranial development of the Mexican axolotl is similar to that reported for other vertebrates, but the pattern in the African clawed frog, another amphibian, is unique.