Figure 5.

Two extreme models for the pathway of cox1 intron transfer in plants and nonplants. (A) An all nonplant-to-plant transfer model. Left cladogram shows six donor organisms, all nonplants (F1–6). Arrows show donor-recipient relationships for six separate intron transfers to plants (P1–10 in Right cladogram). (B) Intron phylogeny based on the transfers diagrammed in A, showing phylogenetic interspersion of donor (F) and recipient (P) sequences. (C) An all-plant-to-plant transfer model. A single initiating transfer from the nonplant F3 lineage to plants is shown, followed by five successive plant-to-plant transfers. (D) Intron phylogeny based on C, showing a clade of 10 plant introns whose phylogeny is incongruent with that of the same plants in C. Branch lengths in these cladograms are not proportional to time.