Ron Miller’s scientific contributions

Summary. Modern evolutionary research suggests that new species often arise rapidly from hybridization and chromosome doubling, augmenting the slow, divergent processes originally detailed by Darwin. Relationships between kindred species are thus best represented not by a simple branching candelabra or tree, as pictured in our old biology texts, but by a complex web of exchanges and ploidy variations. Such complexities seem especially evident in the highly compatible and multiploidal Southeastern deciduous azaleas, especially on those spectacular and much-visited mountaintops called "balds." We have conducted a survey of 92 samples taken from the azalea swarm on the bare top and adjacent woodlands of Gregory Bald within Great Smokies National Park. Flow cytometry was used to determine ploidy and published component traits of recognized species were used to elucidate mating interactions at that highly diverse site. A similar study was undertaken with 12 samples from along the interfaces be-tween the Rhododendron calendulaceum (tetraploid) and R. arborescens (diploid) colonies on Wayah/Wine Spring Bald, to the south of the Park. Cytometry revealed no tetraploids within the open bald area of Gregory, belying previous suggestions that R. calendulaceum is directly involved in that famous swarm. There were tetraploids keying out to R. calendulaceum, some with unusual variations (e.g., fragrance), within nearby woodlands. traits of several of the samples from Wayah/Wine Spring gave evidence for genetic exchanges be-tween the diploid and tetraploid species; one triploid, such as might serve as a two-way bridge between the azalea species, was in fact found. In addition, triploids had previously been discovered from R. calendulaceum-R. periclymenoides hybrids in northwestern South Carolina. mechanisms for gene exchange between diploid and tetraploid species do indeed exist. Examination of the complex diploids of Gregory was still more suggestive. Flower colors, odors, and forms evince origins in R. cumberlandense and R. arborescens and possibly R. viscosum. Diploid plants consistent with R. cumberlandense at this site could not, based on sizes and forms, be distinguished from tetraploid R. calendulaceum. e lack of differentiating morphological traits between R. cumberlandense and R. calendulaceum and similarity in average chromosome size suggests that tetraploid R. calendulaceum at this site is primarily derived from the diploid R. cumberlandense with limited genetic infusions from other species. Moreover, the indeterminacy of species upon this bald suggests that the present azalea species in the Southeast are likely to be recent products of cycles of migration and interaction attending the as many as 20 glaciations and warm periods since the beginning of the Pleistocene. Our contemporary list of recognized azalea species that seem so distinct and certain may simply be a momentary snapshot of a complex and rapidly changing evolutionary web that is the Pentanthera.

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.