species of angiosperms, we are confident that the intron has been horizontally acquired at least hundreds of times during angiosperm evolution and probably over 1,000 times. Equally remarkably, all of these transfers seem to have occurred very recently, in the last 10 million years or so of angiosperm evolution.
Many fascinating questions can be asked about the evolution of this wildly invasive group I intron. What does the inevitably complex historical network of horizontal transfers look like; i.e., who is the donor and who is the recipient in each specific instance of intron transfer? Phylogenetic evidence suggests at least one, perhaps initiating long-distance transfer of the intron from a fungus to a flowering plant (Cho et al., 1998). Have many or most of the transfers occurred via this long-distance route, in