Large‐scale patterns of correlated growth in development are partially driven by competition for metabolic and informational resources. It is argued that competition between organs for limited resources is an important mesoscale morphogenetic mechanism that produces fitness‐enhancing correlated growth. At the genetic level, the growth of individual characters appears independent, or “modular,” because patterns of expression and transcription are often highly localized, mutations have trait‐specific effects, and gene complexes can be co‐opted as a unit to produce novel traits. However, body parts (...) are known to interact over the course of ontogeny, and these reciprocal exchanges can be an important determinant of developmental outcomes. Genetic mechanisms underlie cell and tissue behaviors that allow organs to communicate with one another, but they also create evolutionarily adaptive competitive dynamics that are driven by physiological and biophysical processes. Advances in the understanding of competitive and closely related coordinative interactions across scales will complement existing research programs that emphasize the role of cellular mechanisms in morphogenesis. Study of the large‐scale order produced by competitive dynamics promises to facilitate advances in basic evolutionary and developmental biology, as well as applied research in fields such as bioengineering and regenerative medicine that aim to regulate patterning outcomes. (shrink)

The question of whether the modern evolutionary synthesis requires an extension has recently become a topic of discussion, and a source of controversy. We suggest that this debate is, for the most part, not about the modern synthesis at all. Rather, it is about the extent to which genetic mechanisms can be regarded as the primary determinants of phenotypic characters. The modern synthesis has been associated with the idea that phenotypes are the result of gene products, while supporters of the (...) extended synthesis have suggested that environmental factors, along with processes such as epigenetic inheritance, and niche construction play an important role in character formation. We argue that the methodology of the modern evolutionary synthesis has been enormously successful, but does not provide an accurate characterization of the origin of phenotypes. For its part, the extended synthesis has yet to be transformed into a testable theory, and accordingly, has yielded few results. We conclude by suggesting that the origin of phenotypes can only be understood by integrating findings from all levels of the organismal hierarchy. In most cases, parts and processes from a single level fail to accurately explain the presence of a given phenotypic trait. The debate between the proponents of the modern and extended syntheses is somewhat reminiscent of the duck-rabbit illusion. The two sides are probably talking about the same thing, but from different perspectives. If not, then we argue that the challenge is to do an experiment that rules out the alternative view. (shrink)

Graphical AbstractThe exquisite morphology of a complex body results from the sum of competitive and cooperative interactions among its subsystems. More details can be found in article number 1900245 by Richard Gawne et al. The cover image shows immunohistochemical staining (in red) of the head of a tadpole of Xenopus laevis, showing the brain, nostrils, and peripheral innervation.