Smoothed color density representations of the scatterplots of the (a,b) absolute and (c,d) relative numbers of tissues in which the genes of a duplicated gene pair are expressed, for both (a,c) 3R anchor points and (b,d) non-anchor points. From (a,c) we can conclude that many anchor point genes are both expressed in a high number of tissues, and that many of these tissues are actually identical. On the other hand, (b,d) show that non-anchor point genes frequently show asymmetric divergence because many genes are expressed in a high number of tissues, while their duplicate is not. The plots were made using the 'smoothScatter' function, implemented in the R package 'prada' , by binning the data (in 100 bins) in both directions. The intensity of blue represents the amount of points in the bin, as depicted in the legend.