Volume 10, Issue 2, April 2026

The bones of the vertebrate skull come from two developmental sources: the mesoderm and the neural crest. This dual origin allows to study how development influences evolution. Using 3D scans of lizard skulls, including a species with exaggerated male traits linked to the neural crest, we examined patterns of skull variation. We found that neural crest-derived bones contribute to rapid changes driven by sexual selection. However, across different species, these same skull regions evolve more slowly and show less variation. This suggests that while neural crest cells may constrain long-term evolution because of their wide influence, they can also enable fast adaptations. The developmental biology of a trait therefore shapes its evolution.

Insect sensory traits (e.g., eyes and antennae) can shape their lifestyles. However, sensory traits are among the most expensive tissues to build and maintain, and investment in them is often shaped by ecological factors. In our study, we used butterflies as a model system to investigate patterns and drivers of eye size evolution across 100 million years. We quantified eye size using 3D micro-CT X-ray imaging of pinned museum specimens. We find that species body size largely dictates eye size, and closely related species have similar eye sizes. In fact, species relatedness alone explains 74% of eye size variation. Intriguingly, habitat of a species (i.e., whether they are found more in forest or open habitats) did not influence eye size. Overall, we show that eye size evolution in temperate butterflies is strongly driven by body size and species relatedness, not ecological factors. We also demonstrate how non-invasive micro-CT technology can be used on museum specimens to study evolutionary patterns and processes across millions of years.