Cardamine angustata var. ouachitana, a wildflower in the mustard family (Brassicaceae), was described by Smith in 1982 to include a form of Cardamine found only in the Ouachita Mountains of Arkansas. This variety is morphologically very similar to typical Cardamine angustata. The major difference noted by Smith for the two varieties was the complete lack of leaf hairs (trichomes) in the new variety, whereas typical Cardamine angustata normally possesses trichomes. However, Al-Shehbaz rejected the variety ouachitana and reduced it to synonymy with the typical C. angustata. The recommendation of Al-Shehbaz has been followed and the taxon Cardamine angustata var. ouachitana is currently not accepted by most plant taxonomists. We performed a preliminary evaluation of the status of Cardamine angustata var. ouachitana by comparing ribosomal internal transcribed spacer region DNA sequences from specimens of Cardamine angustata var. ouachitana with sequences of Cardamine angustata from the main range of the species and other related species of Cardamine. Phylogenetic analyses of these data produced an unexpected result; specimens of C. angustata var. ouachitana were actually closely related to C. concatenata, rather than the expected close relationship with C. angustata. However, C. angustata var. ouachitana is morphologically distinct from C. concatenata. These results suggest that Cardamine angustata var. ouachitana is actually a new species found only in the Ouachita Mountains of Arkansas.
Fawley, K. P.; Witsell, C. T.; Fawley, M. W.; Breedlove, J. S.; Brockman, R. J.; Humphrey, A. C.; Lawson, J. M.; McCallie, K. N.; Prescott, D. A.; Rushing, J. T.; and Whitaker, J. M.
"Possible new Arkansas endemic plant revealed by DNA sequence analysis, A,"
Journal of the Arkansas Academy of Science: Vol. 66, Article 12.
Available at: https://scholarworks.uark.edu/jaas/vol66/iss1/12