Figure 1. Phylogenetic relationships based on mtDNA of the eight C. briggsae natural strains used for MA line progenitors (a) and schematic of the nad5Δ locus (b).

In (a), the three major intraspecific mtDNA clades and origin of the Ψnad5-2 element are indicated next to the relevant internal branches. The blue branches lead to MA line progenitors that encode the putative compensatory mutations associated with the nad5Δ locus [10]. In (b), the arrows indicate positions of the 21-bp direct repeats associated with deletion formation. The dashed line indicates DNA sequences missing in canonical nad5Δ molecules. The blue arrow indicates the position of the direct repeat bearing putative compensatory mutations. Clade III strains lack Ψnad5-2 elements and associated deletions, as indicated in the bottom mtDNA gene model.