Figure 7. Evolution of foraging behavior driven by new brain gene origination in Drosophila.

(A) Phylogenetic comparison of FSIs in closely-related Drosophila species that are color-coded according to the phylogeny in (D).

(B) MB-specific knock-down of Desr by the OK107 driver shows a significant decrease in FSI, correlating with the increase in foraging ability observed between nodes E and D (see also D and Figure S4B). Data are represented as mean +/− SEM. The asterisk denotes statistical significance (ANOVA, p < 0.01); n.s., not significant (ANOVA, p > 0.01).

(C) Scheme illustrating how the 11–25 Myr old MB gene Desr (orange) retroposed from the X-linked parent CoREST (green) into a genomic location on Chr. 2L adjacent to bib (grey), and recruited new 5′ and 3′ exons (deep orange). Gene models and distances are not drawn to scale.

(D) Protein sequence alignment of DESR showed homology to the CoREST N-terminal protein, resulting from retroposition of the CoREST short isoform. Regional alignment of DESR to its homologs showed evidence for rapid amino acid divergence; DESR arose after the D. pseudoobscura – D. melanogaster split and was lost in D. erecta. Amino acids color coded by conservation level. Only partial representative sequences are shown for simplicity.

(E) Expression pattern of Desr-Gal4 in the brain, particularly in MB axons (top panel) and calyces (ca, middle panel), the CB (top panel) and the AL (bottom panel).

(F) Xcbp1 and Desr (red stars) are shown on the Drosophila phylogeny. The node for the last common ancestor of the whole group (note E) is colored blue, while common ancestors younger than Desr but older than Xcbp1 (nodes C and D) are labeled yellow, and the common ancestors younger than Xcbp1 (nodes A and B) are labeled in green. Groups of animals with slow foraging behavior are highlighted in blue, fast foraging in green and intermediate foraging in yellow.

(See also: Figure S7)