Crossing and Morphological Relationships among Native Clovers of Eastern North America

The Trifolium species of eastern North America now occupy a much reduced area in comparison to their earlier range. These species include T. reflexum L. (buffalo clover), T. stoloniferum Muhl. ex Eaton (running buffalo clover), T. carolinianum Michx. (carolina clover), T. virginicum Small ex Small and Vail (Kate's mountain clover), T. bejariense Moric., and a recently discovered species, T. calcarium Collins and Wieboldt. These species all have some potential for use as pasture, and may have desirable qualities for transfer to more widely used forages, such as T. repens L. (white clover). These species were examined to determine morphological and breeding system relationships in comparison with T. repens , and because several are threatened with extinction, to gain information that may optimize management schemes for their long‐term conservation. Based on morphological characteristics, breeding systems, crossing relationships, chromosome numbers, and forage yields, it was concluded that all species are quite distinct and unrelated to T. repens . All the native species had 16 somatic chromosomes. Two annual species, T. carolinianum and T. bejariense , are autogamously self pollinated, as is another annual, T. reflexum , but which may also be cross pollinated to a limited extent in nature. Trifolium stoloniferum set fewer seeds by selfing than by crossing, but self seed set was adequate to maintain the species in nature. Trifolium calcaricum also produced seeds via self‐pollination. One self population of T. stoloniferum produced less biomass than other self and cross populations, suggesting that inbreeding and subsequent loss of vigor may be a possible cause of its near extinction. However, there is insufficient reason to implicate factors other than habitat destruction and competition with other forage species as primary causes of near extinction.