Are white and purple flowers distinct species? -DNA answer

Onobrychis Mill. with more than 130 species is ranked as the second largest genus of the tribe Hedysareae after Hedysarum. The genus is distributed throughout temperate and subtropical regions of Eurasia, N and NE Africa. Most species of Onobrychis are distributed in the Flora Iranica area (77 species), the former USSR (62 species), Turkey (46 species) and Europe (23 species), respectively. Onobrychis cornuta (L.) grows in cushion form and develops an extended crown. This species, showing expansion in especially northward slopes exposed to erosion and heavy grazing in Iran –Turan floristic geography, can hardly be grazed by animals due to its thorn (when in short of forage sheep and goats can collect its fruits and leaves falling on the ground). Horned sainfoin (Onobrychis cornuta (L.) expands in northward slopes exposed to erosion and excessively grazed rangelands and stony and rocky lands in West Syria, Caucasia, Iran, Afghanistan, Turkmenistan and Turkey i.e. Iran-Turan floristic geography. This species growing naturally in many parts of Turkey is a perennial, cushion–formed and thorny plant. Horned sainfoin, a member of Onobrychis genera, is confused mainly with the thorny and cushion-formed members of Astragalus and Acantholimon genera. From a general view, plant resembles greatly these two forms. According to the definition of Davis (1970), Onobrychis cornuta (L.) species can grow up to 50 cm height and has double leaflet. Ends of its leave stems have thorny structures, length of double leaflets is 2 to 2.5 mm, its flowers are pink–purple, length of sepals is 4.5 to 6 mm and that of flag leaflets is between 12 and 15 mm.