Drivers of interlineage variability in mitogenomic evolutionary rates in flatworms (Platyhelminthes) are multifactorial

The forces driving interlineage variability in the evolutionary rates (both sequence and architecture) of mitochondrial genomes are often inconsistent and unpredictable. Herein we studied the impacts of multiple variables using 223 flatworm (Platyhelminthes) species and phylogenetic multilevel regression models. We found that: 1. Mitogenomic sequence evolution is faster in parasites associated with the thermally stable environment of endothermic hosts, but the overall impact of thermic habitat is small; 2. Mitogenome sizes are smaller in parasites of endothermic hosts, but the effects are small and inconsistent; 3. Mitogenomic gene order rearrangements (GORR) are positively correlated with mitogenomic size; 4. The expected positive correlation between GORR and sequence evolution is lineage-specific, and non-parasitic species exhibited a strong negative correlation; 5. Longevity has negligible impacts on mitogenomic evolution; 6. Parasitic (Neodermata) flatworm lineages exhibit higher evolutionary rates than non-parasitic lineages; 7. The effective population size has negligible impacts on mitogenomic evolution; 8. Comparatively, parasitism had by far the greatest impact on the mitogenomic evolution, but due to the monophyletic origin of this life-history strategy, alternative hypotheses cannot be rejected. A large number of factors impact the mitogenomic evolution in flatworms, with lineage-specific relative contributions, which sometimes produces incongruent lineage-specific mitogenomic evolution patterns.