Hybridisation and allopolyploidy can happen between lineages that diverged a long time ago. The 'widest' hybrids that I am aware of are a fern (xCystocarpium roskamianum; Rothfels et al. 2015) and a Viola (V. rostrata × violacea; Yoshida et al. 2015) whose parental lineages diverged ~60 and 15-20 Ma ago, respectively. Similarly, the 'widest' allopolyploids that I am aware of are two grasses (Ampelodesmos mauritanicus, Trikeraia pappiformis; Hochbach et al. 2015) which may be recent and whose parental lineages may have diverged >44 Ma ago.
Does anyone here know of other, and possibly more extreme, cases?
Thanks for your help.
Thomas