Complex sentence: An earlier study using amplified fragment length polymorphism (AFLP) fingerprinting showed a close association of wisent and American bison and probably with yak, but noted that the interbreeding of "Bovini" species made determining relationships problematic.
Split into simpler sentences: An earlier study, using amplified fragment length polymorphism (AFLP) fingerprinting, showed a close association of wisent and American bison and probably with yak. It noted that the interbreeding of "Bovini" species made determining relationships problematic.