The South African Hordeum capense is more closely related to some American Hordeum species than to the European Hordeum secalinum. This is based on differences in their 5S DNA unit class composition. The study found that H. capense shares similarities with American species containing the long Y2 unit class, rather than with H. secalinum, which lacks this unit class. This suggests that H. capense may have originated from a common stock with South American species like Hordeum muticum.