ASTERACEAE

Weakley, Alan S., Kees, John C., Sorrie, Bruce A., Ward, Scott G., Poindexter, Derick B., Brock, Mason, Estes, L. Dwayne, Bridges, Edwin L., Orzell, Steve L., Levin, Geoffrey A., McClelland, R. Kevan Schoonover, Schmidt, Ryan J. & Namestnik, Scott A., 2023, Studies In The Vascular Flora Of The Southeastern United States. Ix, Journal of the Botanical Research Institute of Texas 17 (1), pp. 191-257 : 192-193

ASTERACEAE

SOLIDAGO : A new species of Solidago sect. Erectae from Tennessee Primary authors: Mason Brock and L. Dwayne Estes

While visiting the herbarium of the Botanical Research Institute of Texas (BRIT) in 2013, we came across an unusual specimen of Solidago L. The specimen was collected by Robert Kral in 1978 from phyllite boulders along the banks of the Hiwassee River in east Tennessee. Although identified by Kral as S. speciosa Nutt. (and as S. roanensis Porter in additional collections at NY and TENN), the specimens instead appear to instead bear a strong resemblance to the “riverscour” Solidago species of subsect. Erectae (G. Don) Semple & J.B. Beck ( S. arenicola B.R. Keener & Kral , S. plumosa Small , and S. racemosa Greene ) known from other river systems in the unglaciated southeastern United States. None of these three taxa had previously been documented in the Blue Ridge of Tennessee (with S. arenicola being restricted to the Cumberland Plateau, S. plumosa being endemic to the Yadkin River in the Piedmont of central North Carolina, and S. racemosa reported from northern Virginia and northwards and disjunct in the Cumberland Plateau of Tennessee and Kentucky).The presence of a “riverscour” Solidago in a region where none were known before spurred suspicion that it might represent an undescribed species.

In 2014 Tennessee Valley Authority botanist Adam Datillo visited the Hiwassee River, made collections of the Solidago , and deposited them at APSC. Close examination of this series of specimens provided additional clarity. Applying the most recent key at the time (Weakley 2020) to the Hiwassee River Solidago specimens resulted in a tentative determination as the single-site endemic S.plumosa . This determination could not be accepted however, as the Hiwassee River specimens differ from S. plumosa in having a distinctly puberulent inflorescence axis and broader basal leaves.

A second possibility for the Solidago was considered, which was that the Hiwassee River entity simply represented a disjunct population of S. arenicola , albeit with a smaller involucre than previously documented. However, the heads were not simply shorter, but denser as well. In addition, the Hiwassee River material has a more consistently hispid-puberulent inflorescence than the often scarcely puberulent to scabrid S. arenicola . While the Hiwassee entity also bears a resemblance to the more upland S. erecta , and has been previously identified as such on two specimens (NY, TENN), it can be readily distinguished by its glabrous leaf margin (as opposed to ciliate-scabrid).

With all identification possibilities eliminated, it appears that the Hiwassee River Solidago has a novel combination of characters not found in any other Solidago known in North America. The morphological distinctiveness, combined with its unusual riverscour habitat and significant geographic disjunction from its morphologically closest relatives ( S. arenicola , S. plumosa , and S. racemosa ), leads us to the conclusion that this population warrants recognition as a previously undescribed species.