Evolutionary divergence of components of two selenium utilization traits extracted from the datasets identified in this work. Each graph contains 100 randomly selected organism pairs (points). The protein similarity (sequence divergence [SD]) of each component usually changes proportionally with the phylogenetic distance. Correlation coefficient (CC) is shown (number in the parentheses shows an updated CC after removing horizontal gene transfer [HGT] events). Points that are located above and distant from the reference line suggest potential HGT events. A reported HGT organism pair (Photobacterium profundum and Treponema denticola) of the Sec-decoding trait is shown with arrows for reference.