Figure 1.

Strategy for screening for changes in hybrid-incompatible (HI) phenotypes in the F1 progeny from crosses between wild-type C. briggsae and C. nigoni introgression lines, as opposed to the F1 progeny from crosses between wild isolates of two parental species. Shown are schematics of crosses with C. briggsae (b) wild isolate (n) as a father (A) or a mother (B). Crosses with C. nigoni wild isolate (n) or its introgression line (ir) are shown on the top and bottom, respectively. GFP-linked introgression on autosomes or the X chromosome are shown separately. HI phenotypes were scored for the F1 GFP-expressing (introgression-bearing) progeny as indicated. Survival of B2 progeny in the crosses between the hybrid F1 progeny and C. briggsae wild isolate was also counted. Cross progeny were named as described previously (Woodruff et al. 2010). Briefly, progeny were named after their genotypes in parentheses, with paternal and maternal parents listed on the left and right, respectively.