[i] ^aPairwise Mann-Whitney U tests among the different Muller's elements were significant for all the comparisons between Muller's element A and the rest after applying the Bonferroni correction for multiple tests and for all synteny definitions.

[ii] ^bThe observed distribution of the number of neighboring orthologous landmarks for any given landmark was compared with that obtained by simulations under a random breakage model (Methods). The G-tests for goodness-of-fit performed were subject to the William's correction. IGA, independent gene anchor; HCB, homologous collinear block.

[iii] GOO, gene order and orientation; GO, gene order; OLC, overall local contiguity. MGR, multiple genome rearrangement; MGR, multiple genome rearrangement.