The fragmented mitochondrial genomes of two Linognathus lice reveal active minichromosomal recombination and recombination hotspots

Evidence for recombination between mitochondrial (mt) minichromosomes has been reported in sucking lice, but it is still not clear how frequent mt minichromosomal recombination occurs. We sequenced the mt genomes of the cattle louse Linognathus vituli and the goat louse L. africanus. Both Linognathus species have 10 mt minichromosomes, and seven of them have the same gene content and gene arrangement. Comparison of mt karyotypes revealed numerous inter-minichromosomal recombination events in the evolution of Linognathus species. Minichromosome merger, gene duplication and gene translocation occurred in the lineage leading to Linognathus lice. After the divergence of L. vituli and L. africanus, duplication, degeneration, deletion and translocation of genes also occurred independently in each species. Most of the recombination events in the Linognathus species occurred upstream of either cox3 or nad2, indicating these two locations were hotspots for inter-minichromosomal recombination. Our results provide an important perspective on mt genome evolution in metazoans.