The 2012 ASHS Annual Conference

Fothergilla (Hamamelidacea) is a small genus of uncommon, deciduous shrubs found exclusively in the Southeastern United States.  Two species of Fothergilla are currently recognized: F. gardenii and F. major.  However, variation in the genus is considerable and as many as four taxa have been recognized in the past.  Fothergilla gardenii is found in the coastal plains of North Carolina, South Carolina, Georgia, Florida, and Alabama and is tetraploid with 2n = 4x = 48.  In contrast, F. major is found on upland sites in the piedmont and mountains of North Carolina, South Carolina, Georgia, Alabama, Tennessee, and Arkansas and is hexaploid with 2n = 6x = 72.  No diploid cytotypes of Fothergilla have previously been known.  The objective of this study was to survey DNA contents and ploidy levels of Fothergilla spp. from throughout its range.  Samples from thirty populations were collected and tested.  Flow cytometry was used to determine DNA contents and associated ploidy levels.  As expected, tetraploid and hexaploid plants were identified, consistent with F. gardenii and F. major, respectively.  However, populations of diploid plants were also discovered in a few locations.  Considering that diploid plants differ morphologically and are isolated both geographically and cytogenetically from other Fothergilla spp., this cytotype may represent a new, distinct, and rare taxon.  Additional work is continuing to reassess the systematics and phytogeography of Fothergilla in order to elucidate the diversity and evolutionary relationships among species, properly classify this new cytotype, and to help guide future conservation efforts.