Mean divergence (±95% confidence interval) versus mean length for different length categories of (A) introns, (B) 5′ intergenic sequences, and (C) 3′ intergenic sequences. Within each class of site, we divided the data into 20 categories, based on length, such that there were equal numbers of observations in each category. Divergence estimates were corrected for multiple hits using the method of Kimura (1980), and confidence intervals were obtained by bootstrapping 1000 times by observation. The dashed line for each class of site shows the linear regression of divergence on log length. The solid vertical line in A is drawn at the division between the long and short intron class (80 bp).
