Hierarchical likelihood ratio tests (hLRTs). This figure illustrates an arbitrary hierarchy of LRTs for six different models. Within each LRT, the null model is depicted above the alternative model. When the LRT is not significant, the null model (above) is accepted (A), and it becomes the null model of the next LRT. When the LRT is significant, the null model is rejected (R) and the alternative model (below) becomes the null model of the next LRT. There are six possible paths depending on the outcome of the individual LRTs, and each path results in the selection of a different model. JC69: Jukes-Cantor model (Jukes and Cantor, 1969); K80: Kimura 1980 model (Kimura, 1980), also known as K2P; F81: Felsenstein 81 model (Felsenstein, 1981b); HKY85: Hasegawa-Kishino-Yano model (Hasegawa et al., 1985); SYM, symmetrical model (Zharkikh, 1994); GTR: general-time reversible model (Tavaré, 1986), also known as REV.