EDGE CMT: How the Easter Egg Weevils (Pachyrhynchus) got their spots: the functional genomics of structural colors in beetles.

In many animals, including insects, coloration is formed by the animal’s nanostructure, which bends and reflects light, rather than by pigments. Studying how nature creates such so-called structural colors could provide inspiration for new optical materials. However, the development of nanostructures is poorly understood. For example, how do cells coordinate to form the structural colors found in nature? This project will study how cells in Easter Egg weevils collaborate during development to form intricate structures with unique optical properties. Examining these biological systems should inform development of new technologies that harness light for a wide variety of applications, including enhanced scattering layers in solar cells, advanced light-based signaling systems for anti-counterfeiting materials, bio-inspired optical components for defense applications, and the production of natural food dyes. The project will also provide training opportunities for students in cutting-edge genomic research, which has broad applications in human health. Easter Egg weevils in the genus Pachyrhynchus display elaborate patterning and iridescent colors in their hard cuticles, serving as elements in a mimetic system that helps defend against predation and may make the weevils distasteful to their predators. These beetles constitute a unique opportunity to study the extent to which convergent phenotypes arise from parallel mechanisms involving production of structural colors formed from 3D-photonic crystals and their patterning. Variation in the structural coloring will be explored as a multigenic trait to draw genome-to-phenome connections that might explain beetles’ adaptive radiation on evolutionary scales. Changes in genotype and associated genomic regions will be related to microscopic changes in structural colors at the nanoscale and macroscopic changes in beetle color patterns. The results will provide a foundational set of candidate loci for further study. The researchers expect to produce evidence for the repeatability/modularity of genomic mechanisms that produce these multigenic traits, thereby generating a testable framework for rapidly localizing the genetic basis of adaptive traits. Moreover, the project should reveal principles that apply to many other organisms with photonic crystals. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.