From simplicity to complexity: The gain or loss of spot rows underlies the morphological diversity of three Drosophila species

To understand how novel animal patterning emerged, one needs to ask how the development of color patterns has changed among diverging species. Here we examine three species of fruit flies - Drosophila guttifera (D. guttifera), Drosophila palustris (D. palustris), and Drosophila subpalustris (D. subpalustris) - displaying a varying number of abdominal spot rows that were either gained or lost throughout evolutionary time. Through in situ hybridization, we examine the mRNA expression patterns for the pigmentation genes Dopa decarboxylase (Ddc), tan (t), and yellow (y) during pupal development. Our results show that Ddc, t, and y are co-expressed in identical patterns, each foreshadowing the adult abdominal spots in D. guttifera, D. palustris, and D. subpalustris.