Figure 2

Rate Classes and Partition of Variable Sites – Top: A visualization with pie graphs of the proportion of sites in each rate-class partition that are RNAs (white), first codon positions (light grey), second codon positions (dark grey), and third codon positions (black). Rate classes are listed across the top, from fastest (class 1) to slowest (class 6). Bottom: A bar-graph visualization of the numbers of each of these classes among partitions, using the same color coding, as indicated in the key. Constant sites, found only in rate class six, are indicated with hatched bars. Raw numbers of each of the values in the bar graph are given below the bars. Fifteen sites from the origin belong in rate class 6, one in rate class 4, and two in rate class 3 (not shown).