Mitogenomic evolutionary rates in bilateria are influenced by parasitic lifestyle and locomotory capacity

The evidence that parasitic animals exhibit elevated mitogenomic evolutionary rates is inconsistent and limited to Arthropoda. Similarly, the evidence that mitogenomic evolution is faster in species with low locomotory capacity is limited to a handful of animal lineages. We hypothesised that these two variables are associated and that locomotory capacity is a major underlying factor driving the elevated rates in parasites. Here, we study the evolutionary rates of mitogenomes of 10,906 bilaterian species classified according to their locomotory capacity and parasitic/free-living life history. In Bilateria, evolutionary rates were by far the highest in endoparasites, much lower in ectoparasites with reduced locomotory capacity and free-living lineages with low locomotory capacity, followed by parasitoids, ectoparasites with high locomotory capacity, and finally micropredatory and free-living lineages. The life history categorisation (parasitism) explained approximate to 45%, locomotory capacity categorisation explained approximate to 39%, and together they explained approximate to 56% of the total variability in evolutionary rates of mitochondrial protein-coding genes in Bilateria. Our findings suggest that these two variables play major roles in calibrating the mitogenomic molecular clock in bilaterian animals. The diversity of mitogenomic evolutionary rates among animal lineages remains poorly explained. Here, an analysis of mitogenomes of almost 11,000 bilaterian species provides evidence that parasitism and locomotory capacity are major variables explaining elevation of mitogenomic evolutionary rates.

Automated summary

Parasitic species and those with low locomotory capacity exhibit faster mitogenomic evolutionary rates, suggesting that these variables play a major role in calibrating the mitochondrial molecular clock in bilaterian animals.