How does complexity evolve?

Drosophila guttifera shows a complex spot pattern on the wings. What logic underlays this complex pattern on the DNA level, and what general conclusions can we draw about the evolution of living forms?

How does diversity evolve?

Drosophila guttifera, deflecta, and nigromaculata belong to the Drosophila quinaria group and show great diversity in their wing pigmentation patterns. What are the molecular causes for rapid evolutionary changes in closely related species?