Host genes evolved from Ginger1 (for ' Gypsy INteGrasE Related 1') DNA transposon. (a) The phylogenetic relationship between Gin-1, Gin-2, and the Ginger1 elements (in red). The tree is constructed by the minimum evolution (ME) method (Poisson correction model, pairwise deletion, gamma parameter = 2, 1,000 bootstrap replicates). The sequences and alignment are shown in Additional file 3. C. intestinalis_1 gene refers to XM_002130131.1 gene; C. intestinalis_2 gene corresponds to expression sequence tag (EST) named FF869668.1. Integrases from Gypsy 412/Mdg1 lineage are included as outgroups. (b) The alignment of the local sequences around the three conserved introns in Ginger1-5_HM TPase and host proteins. The arrows point to the intron positions, the Arabic numbers (above) indicate the intron phase.