Phylogenetic tree for the Transposase_21 domains of CACTA-like transposases. The tree was constructed by the neighbor-joining method using the three conserved regions indicated by boxes I to III in Figure 5 and excluding positions with gaps. Numbers represent the confidence of the branches assigned by bootstrap analysis (in 1,000 samplings); bootstrap values lower than 500 are omitted from the figure. The names indicate a transposon member of the CACTA or of the T ransposon R elated to C ACTA (TRC) family belonging to the organism indicated. Circles indicate the 3 different proposed families of transposons within the CACTA superfamily.