How Can Satellite DNA Divergence Cause Reproductive Isolation? Let Us Count the Chromosomal Ways

Figure 1

Satellite block divergence between Drosophila melanogaster and D. simulans. Each chromosome pair, consisting of one homologous chromosome from each species, shows remarkable satellite differences: the D. melanogaster X contains a large block of the 359-bp satellite (red) and some AATAT (green) while the D. simulans X contains neither of these specific satellite monomers; dodeca satellite (blue) is present on the D. melanogaster 2nd chromosome and absent on the D. simulans 2nd chromosome; large regions of dodeca satellite are present on the 3rd chromosomes of both species, but only D. melanogaster 3rd chromosome has small regions of AATAT (green) and a small region of 359-bp variant (also red); AATAT satellite (green) is more abundant and distributed widely across the D. melanogaster 4th chromosome while the D. simulans 4th chromosome contains two primary regions of AATAT, which cannot be fully seen in this image, and in smaller amounts. Chromosomes were prepared from mitotic brain cells of hybrid larvae and stained by fluorescence in situ hybridization (FISH) as previously described [1].