Is interlineage recombination responsible for low divergence of mitochondrial nad3 genes in Mytilus galloprovincialis?

The existence of mtDNA recombination in animals has been confirmed by several case studies. Still, for Mytilus mussels possessing two divergent mitochondrial genomes (M and F), which can recombine, no recombination between coding sequences of highly diverged M and F genomes has been shown. Based on the full sequences of both genomes, it has been suggested that particularly low divergence observed within the mitochondrial nad3 gene of the Mytilus galloprovincialis mussel may be caused by its exceptionally low evolutionary rate. Here, we contribute a new pair of mitochondrial genomes typical for M. galloprovincialis and show that this low divergence is not a sign of evolutionary conservation but is rather caused by the acquisition of an F-related sequence by the published M genome of M. galloprovincialis. The most likely scenario for this apparent mtDNA-coding region recombination case is an assembly artifact.