I am using forward genetic mapping to identify QTL controlling structural color in butterflies.
Structural color is caused by constructive interference of light as it interacts with nanoscale, regularly-spaced physical structures on or in the organism. This is in contrast to pigmentary color, caused by molecules that selectively absorb certain wavelengths. While the genetic basis of pigmentary coloration has been a fruitful research focus from the earliest days of genetics, almost nothing is known of the genetic architecture for structural color. There are a few examples where the inheritance pattern of a structural color is reported (i.e. Uta stansburiana, Colias eurytheme), but no implicated genes or pathways. Nevertheless, structural coloration is employed by many taxa as diverse as humans and Selaginella algae, and can be very adaptive, as when it is used for crypsis or mate attraction. Because the resulting color is strongly dependent on the thickness and regular arrangement of structural elements, structural color is also interesting from a morphogenetic perspective.
I have initiated analysis of the genetic architecture of structural color in the buckeye butterfly, Junonia coenia. I crossed two lines of buckeyes. One is a well characterized, plain brown line established by Fred Nijhout, for which a transcriptome exists and genome assembly is underway. The second line was artificially selected by butterfly breeder Edith Smith to be prominently covered with blue iridescent scales. The resulting F2 population segregates both percent wing coverage and hue of structurally colored scales. I am particularly excited that hue segregates; hue is a result of the thickness and spacing of the nanostructure and its segregation suggests I will be able to map not only upstream patterning loci, but also loci directly involved in creating the structures. I am also using electron microscopy to characterize the responsible nanostructures in this and closely related species.
Wings of Junonia coenia
A Blue Scale An SEM of a Blue Scale