Relative location of introns in the cox1 gene. DNA sequences were aligned base on protein sequence alignment. cox1 sequences are indicated by boxes. Intron locations are indicated by vertical bars. Numbers indicate the relative position of the introns in the alignment and not their position in their corresponding sequence. All introns are group I introns in these taxa. Introns aligned in Figure 3 are indicated in red. Introns containing a putative LAGLIDADG homing endonuclease are in black or red. Introns containing a putative GIY-YIG homing endonuclease are in green. Introns containing an unknown ORF are in blue. The alignment is provided in Additional file 1.