Fig. 2. Dynamics of Dpp signaling in related fly species. (A) The evolutionary distance between Drosophila melanogaster (D. mel.) and three other Drosophila species with a different number of dorsal appendages. (B,C) Early and late patterns of P-Mad (green) and Br (red) in D. pseudoobscura (D. pse.). The eggshell has two appendages (D), as in D. melanogaster. (E,F) Early and late P-Mad and Br patterns in D. virilis (D. vir.). The eggshell has four dorsal appendages (G). (H-K) Dynamics of P-Mad and Br patterns in D. phalerata (D. pha.). (L-N) Dynamics of tkv expression in D. pha. The eggshell has three dorsal appendages (O). In all images the arrowhead marks the dorsal midline; anterior of the egg chamber is to the left.