Discrepancies of stop codon usages between the inframe and C-terminal stop codons. The inframe stop codon usage is taken from the pre-filtering clusters, and the C-terminal usage is computed based on the annotated proteins of the organism. Red circle: an organism with pyrrolysine, blue; selenocysteine, yellow; both pyrrolysine and selenocysteine, white; neither pyrrolysine nor selenocysteine. The organisms are ordered by their discrepancy scores. The discrepancy score is the negative logarithm of a p-value of Fisher's exact test. The dotted line indicates significance level 0.05 after a correction for multiple testing.