Correlation of genomic LTR retroelement and ZF domain content: Three panels show the number of detected LTR retroelements plotted against the number of detected ZF domains in different vertebrate groups or all groups combined. The lines show the linear least-squares best fit with its squared correlation coefficient R2. The fourth panel (lower right) shows the combined data after correction for phylogenetic relatedness by the method of independent contrasts. The line is the linear least-squares best fit forced to go through the origin and its associated R2 and P-value. The summed score cutoff for LTR retroelements was 50 (see Supplemental Methods). The ZF number was determined from all genomic open reading frames with four or more ZF domain matches with a minimum average score of 55. These counting criteria gave the maximum correlation for combined data, but a wide variety of other counting criteria also gave highly significant correlations (Supplemental Table S1).
