Comparison of pathways I-VIII using optimal parameters by AIC.

The alternative pathways are distinguished by the representation of co-transcriptional splicing step 2 (column Co) as a reaction that involves feedback (F), multiple steps (M) or a single step (S); the representation of post-transcriptional splicing steps 1 and 2 (column Po) as a F, M or S reaction; and their representation of elongation (column El) as a M or S process. Total AIC is calculated from all pathway model residuals in all species, and normalised by subtracting the AIC for pathway I. Akaike weights are calculated from total AIC and represent the normalised likelihood of each of the eight pathways (see Materials and Methods, and Table 1 in Text S1 for parameter values).