Allometry and size control: what can studies of body size regulation teach us about the evolution of morphological scaling relationships?

• Allometry describes the relationship between organ and body size.
• Changes in allometry generate the vast diversity of animal shapes.
• Understanding how allometry evolves has proven difficult.
• Elucidation of mechanisms underlying organ size regulation provides new perspectives on allometry evolution.
• Uncovering how genetic variation alters allometries is also needed.

The relationship between organ and body size, known as morphological allometry, has fascinated biologists for over a century because changes in allometry generate the vast diversity of organism shapes. Nevertheless, progress has been limited in understanding the genetic mechanisms that regulate allometries and how these mechanisms evolve. This is perhaps because allometry is measured at the population level, however adult organ and body size depends on genetic background and the developmental environment of individuals. Recent findings have enhanced our understanding of how insects regulate their organ and body sizes in response to environmental conditions, particularly nutritional availability. We argue that merging these developmental insights with a population genetics approach will provide a powerful system for understanding the evolution of allometry.