Graphical AbstractEnvironmental oxygen might have been the key for the evolution of novel developmental mechanisms, such as the interdigital cell death of amniotes. Increased amount of oxygen can also induce cell death in interdigital regions of an amphibian that typically lacks it. To learn more about the role of environmental oxygen in the evolution of new traits, see the article number 2000025 by Ingrid Rosenburg Cordeiro and Mikiko Tanaka. Cover image by Itoko Tanaka and Mikiko Tanaka.

Oxygen is a key regulator of both development and homeostasis and a promising candidate to bridge the influence of the environment and the evolution of new traits. To clarify the various ways in which oxygen may modulate embryogenesis, its effects are reviewed at distinct organizational levels. First, the role of pathways that sense dioxygen levels and reactive oxygen species are reviewed. Then, the effects of microenvironmental oxygen on metabolism, stemness, and differentiation throughout embryogenesis are discussed. Last, the interplay between ecology (...) and development are reexamined with a focus on the evolution of tetrapods, including during the emergence of a novel mechanism that shapes amniote limbs—interdigital cell death. Both genetic and environmental components work together during the formation of organisms, highlighting the importance of a multidisciplinary approach for understanding the evolution of new traits. (shrink)