My impression of this story is that Cano and co-workers
specifically selected the bee/Bacillus pair to study because their
evolution is restricted. That is, they 'co-evolve'. Cano et al expected
(or maybe hoped) that the Bacillus strain in this species of bee (even
though 25 My old or so) should be similar to the Bacillus strain in the
modern descent of that bee.
David
