Some western colls. included here under angustifolium (in CALL, HARD, MARS) have been identified as the closely related aciculare, using older treatments. However, these colls. do not seem particularly distinct, and aciculare in its narrow sense occurs well south of Ky. (Hitchcock & Chase 1950, FNA 25); the range in W (2015) may be inaccurate. The two taxa were combined as subspecies of aciculare in FNA 25. The whole angustifolia complex has been supported by initial analysis of DNA, but traditionally defined aciculare did not emerge as a monophyletic segregate (Majure et al. 2023). Another southern taxon in the angustifolia complex is D. neuranthum (Griseb.) LeBlond, which has been recently reported from western Mo. but remains unlikely in Ky. (Thomas 2017).