Rhododendron colemanii: A New Species of Azalea ( section Pentanthera; ) from the Coastal Plain of Alabama and Georgia

Wenyu Zhou, Taylor Gibbons, Loretta 100 species of azaleas included in the the other eleven Pentanthera azalea species. Goetsch and Benjamin Hall evergreen sections Tsutsusi and Brachycalyx This group of seven included all five of the Department of Biology, University of (Chamberlain and Rae, 1990), while in Pentanthera species that Ranney’s lab had Washington, Seattle, Washington the deciduous section Pentanthera there found to be tetraploid, while all eleven are 16 to18 species also commonly known in the other group are diploid (Jones et Thomas Ranney as azaleas. Besides these well-delineated al. 2007). Further investigation of this Department of Horticultural Science, groups, a few additional species are also correlation has led us to conclude that Mountain Horticultural Crops called azaleas, as exemplified by R. vaseyi the tetraploid Pentanthera species have Research and Extension Center, North Gray, R. nipponicum Matsumura, R. long been evolving as a separate lineage, Carolina State University, Fletcher, schlippenbachii Maximowicz, R. albrechtii reproductively separated from all but two North Carolina Maximowicz, and R. albiflorum Hooker. of the known diploid species. These five deciduous azalea species share Ron Miller certain morphological traits with Tsutsusi Materials and Methods 1157 Ellison Dr., Pensacola, Florida azaleas, and recent DNA studies provided Taxon Sampling. The species and evidence that they are related to Tsutsusi clones studied for molecular and cytogenic a b s t r a c t . A new species of deciduous azaleas (Goetsch et al., 2005). Pentanthera components included all previously azalea, Rhododendron colemanii R. Miller azaleas, on the other hand, were found by described Pentanthera azaleas (Kron, 1993, (Red Hills azalea), from the upper Coastal DNA analysis to be the sister group to Kron and Creel, 1999), the Red Hills Plain of Alabama and Western Georgia, Hymenanthes (Kurashige azalea, and the related species R. canadense USA, has been characterized based on et al. 2001, Goetsch et al., 2005). (L.) Torrey. The molecular analyses also morphology, flowering phenology, habitat, In this article, we present findings included three, more distantly related native range, position in a molecular from two types of DNA analyses of species, which we used as outgroups to root phylogeny, and genome size. Though Pentanthera azaleas: relative genome our evolutionary trees: R. vaseyi, R. minus specimens have previously been confused size and gene sequence determinations. Michaux and R. maximum L. buds with Rhododendron alabamense Rehder These allow us to infer, respectively, the were collected from individual for or its hybrids, phylogenetic relationships ploidy number of each species and an DNA sequencing and relative genome based on sequences of the nuclear gene evolutionary tree that relates the different size determination. Except for the Red RPB2-I gene showed R. colemanii to be species to one another. This research Hills samples, which were collected either a coherent species in a clade of section began as a collaborative project to find from the wild or from Callaway Gardens, Pentanthera G. Don along with R. luteum out whether a deciduous azalea from the Georgia, USA, the remaining taxa were Sweet and the Southeastern U.S. azaleas Red Hills region of Alabama and Georgia, collected from the Rhododendron Species R. atlanticum (Ashe) Rehder, R. austrinum initially collected and propagated by S. Foundation Botanical Garden, Federal (Small) Rehder, and R. calendulaceum D. Coleman, Sr., is a new species. That Way, Washington, USA. The plants, (Michaux) Torrey. Flow cytometry turned out to be the case. (For a detailed grown there from wild-collected , had showed R. colemanii to be, like the other history of the Red Hills azalea, see Miller morphological characteristics consistent azaleas in this clade, tetraploid. A detailed and Yeatts, 2008.) As the scope of the with their published descriptions (Kron, morphological description and Latin investigation widened to include all species 1993). Morphological measurements of diagnosis are provided. in section Pentanthera, Clarence Towe put the Red Hills azalea were completed on the University of Washington researchers representative samples from throughout or the rhododendron community, as into communication with Tom Ranney its geographical range. Ffor the non-horticultural public, the of North Carolina State University. In Flow Cytometry and Ploidy name “azalea” is, unfortunately, a term discussions with Ben Hall, Clarence had Determination. Holoploid, 2C DNA shrouded in ambiguity. It has been applied noticed a surprising correlation. A group of contents (i.e., DNA content of the entire to two sizable groups of Rhododendron seven species, including the Red Hills azalea, non-replicated, chromosome complement species that bear little resemblance to had DNA sequences that were similar to irrespective of ploidy level) were determined one another. There are approximately one another, but markedly different from via flow cytometry following the methods

72 SPRING 2008 of Jones et al. (2007). Genome sizes Table 1. Relative genome sizes and ploidy levels of Pentanthera azaleas determined by were determined by comparing mean flow cytometry. relative fluorescence of each sample with an internal standard, Pisum sativum L. Taxa Accession - Source1 Relative 2C Ploidy Level (x) genome size2 ‘Ctirad’, with a genome size of 8.76 ρg (Greihuber et al., 2007) and calculated as: R. canadense Hootman - RSF 1.17 ± 0.00 2 2C DNA content of sample = 8.76 ρg × R. molle 80/091 - RSF 1.44 ± 0.02 2 (mean fluorescence value of sample/mean R. occidentale 77/388 - RSF 1.47 ± 0.01 2 fluorescence value of standard). Ploidy R. eastmanii 2004/037 - RSF 1.48 ± 0.07 2 levels from these samples were determined R. prinophyllum 98/155 - RSF 1.50 ± 0.03 2 based on the established relationship R. cumberlandense 2004/059 - RSF 1.50 ± 0.03 2 between relative DNA content and ploidy level in Rhododendron as reported by Jones R. prunifolium 2003/322 - RSF 1.50 ± 0.03 2 et al. (2007). R. periclymenoides 76/292 - RSF 1.51 ± 0.03 2 DNA Extraction, Sequencing and R. viscosum 2004/193 - RSF 1.51 ± 0.01 2 Phylogenetic Analysis. The methods R. flammeum 76/286 - RSF 1.53 ± 0.02 2 used for extracting DNA from or R. arborescens 80/012 - RSF 1.56 ± 0.01 2 flower bud tissue, DNA amplification R. canescens 76/278 - RSF 1.56 ± 0.00 2 by the Polymerase Chain Reaction R. alabamense 81/119 - RSF 1.57 ± 0.00 2 (PCR) procedure, DNA sequencing and phylogenetic analysis are all described in R. luteum 88/065 - RSF 2.61 ± 0.03 4 Goetsch et al. (2005). The gene sequences R. atlanticum 73/010 - RSF 3.02 ± 0.03 4 studied are those in the RPB2-I gene R. calendulaceum 76/292 - RSF 3.09 ± 0.02 4 (Figure 1), which codes for a subunit of R. colemanii A (Coleman/Callaway-Towe) 3.10 ± 0.06 4 the enzyme RNA Polymerase II. R. austrinum 2006/041 - RSF 3.11 ± 0.04 4 R. colemanii B (Grove Hill)-Towe 3.16 ± 0.06 4 Results R. colemanii C (Fountain)-Towe 3.22 ± 0.03 4 Flow Cytometry and Ploidy Determination. Relative genome sizes 1Sources: RSF - Rhododendron Species Foundation, Federal Way, Wash.; Clarence Towe, of the Pentanthera azaleas (Table 1) fell P.O. Box 212, Walhalla, SC 29691. 2 into one of two classes consistent with Values are mean 2C relative genome size ± SEM for two samples. either diploids (ranging from 1.17 to 1.57 ρg, mean = 1.48) or tetraploids corroborate those of Jones et al. (2007) for RPB2-I sequence for each, the vast (ranging from 2.61 to 3.22 ρg, mean = the species mentioned above. In addition, majority of it from intron (non-coding) 3.04), as established for Rhododendron we found R. molle (Blume) G. Don and sequences (Figure 1). A short segment of by Jones et al. (2007). Although we used R. canadense to be diploid (Table 1). In the alignment is shown in Figure 2, where similar methods to Jones et al. (2007), we view of previous reports of tetraploid R. a number of base changes can be seen to employed an updated estimate of genome canadense (Ammal et al., 1950; Sax, 1930), subdivide the species into groups that differ size for the internal standard (Pisum it remains to be seen whether the diploid in the base present at several positions. sativum L. ‘Ctirad’) of 8.76 ρg (Greihuber state is limited to the R. canadense clone This set of aligned RPB2-I sequences et al., 2007), that uniformly resulted in we studied. was used to infer an evolutionary tree by slightly lower values. Determination of the ploidy for three two different approaches. The first, called In a previous study that included different accessions of the Red Hills azalea maximum parsimony, uses the DNA data Pentanthera azaleas, Jones et al. (2007) showed that they were all tetraploids (Table to compute the evolutionary tree with confirmed the tetraploidy of R. 1). This raises the very interesting question the smallest number of steps (mutational calendulaceaum and R. luteum and further of the evolutionary relationship of the Red changes). The second method, maximum determined that R. austrinum and R. Hills azalea to other tetraploid Pentanthera likelihood, minimizes the total combined atlanticum were tetraploid species. All the azalea species (Jones et al., 2007). length of all tree branches, including other Pentanthera species they studied were DNA Sequencing and Phylogenetic terminal ones. With the RPB2-I sequence predominantly diploid. (These correspond Analysis. The sequence data set for 18 data, both analytical methods produced to Table 1, lines 3 to 13 in this paper.) The Pentanthera species and three outgroups the same tree (Figure 3). The outgroup research findings we report here (Table 1) consisted of 3200 base pairs of aligned species provide information about the root

JOURNAL AMERICAN RHODODENDRON SOCIETY 73 of the Pentanthera evolutionary tree. In this instance, the two clades of Pentanthera azaleas labeled A and B relate similarly to the outgroups. Thus, their DNA sequences do not indicate that either of them is clearly ancestral. Each of the phylogenetic analyses provides, in addition to a tree that best fits the DNA data, useful information regarding the degree of certainty of various features of the tree. For the parsimony analysis, this measure of statistical support is called bootstrap support, shown as numbers adjacent to the nodes where two branches of the tree diverge (Figure 3). A bootstrap figure of 100 indicates the highest degree of certainty for that node, while Figure 1. Structure of the Rhododendron RPB2-I Gene. The gene has 25 exons (black blocks) 50 or less indicates low certainty and 70 that make up the protein coding region. Between these are introns, indicated by a black line. or higher a reasonable degree of certainty. DNA sequences used in this study are marked by cross-hatched blocks. Except for exons 5, 14 and 15, most of the sequence analyzed comes from introns. The small arrows mark the The most striking result of the parsimony positions of DNA primers used to amplify DNA for sequencing. analysis is that there is 100% support for the tree nodes that define clades A, B and C (Figure 3). This means that the evidence possesses the morphological characteristics conceptually simple mechanism would be for these as distinct groups of genes is of section Pentanthera, it must then be a simply to have the pollen of one diploid unequivocal. All the more remarkable is new azalea species within this section. species fertilize the ovum of another the fact that at the organismal level, the Relationships within Section Pen- diploid species. Chromosomal doubling, species corresponding to DNA clades A tanthera. At an early point in the either pre-or post-fertilization, could have and C are homogeneous for ploidy, with evolutionary divergence of Pentanthera led to stable, fertile (4x) hybrids having all species in A being diploid and all in C azalea species, two lineages separated— the diploid complement of chromosomes being tetraploid. Rhododendron canadense one containing the common ancestor of from each parent. The net result would and R. molle, the two species remaining R. molle, R. canadense and clade C, the be a new tetraploid species formed from outside of clades B and C, are more other being the common ancestor of R. diploid ancestors. The results we have closely related to clade C than to clade B, occidentale (Torrey & Gray) Gray and all obtained do not support this mechanism suggesting a possible shared ancestry with of the remaining Pentanthera species of for the recent genesis of tetraploid the tetraploid azaleas. The phylogenetic the Eastern US. The lineages in question Pentanthera species. None of the tetraploid position of the Red Hills azalea is within are RPB2-I gene lineages, which may or species in clade C, including R. colemanii, the C clade. Thus, not only is the Red may not reflect relationships that apply contains an RPB2-I gene like that of any Hills azalea tetraploid (Table 1), all of its across the entire genome. To explore these diploid species. The fact that these five close relatives are tetraploid, as well (Table possibilities, further experiments, now in species make up a monophyletic group, 1). This clearly distinguished Red Hills progress, will determine whether analyses sharing a common ancestor unique only from R. alabamense, which is diploid and of other regions of the Rhododendron to them, has important implications. This is most closely related to other diploid genome recover the same evolutionary group contains both R. luteum, native to species (Figure 3, Table 1). tree. Asia Minor and Europe, and four North The Origin of Tetraploids, Ancient American species. It follows, therefore, that Discussion or Recent? The observation that hybrid this clade diverged from other Pentanthera The Red Hills Azalea. This study Pentanthera azaleas are frequently seen azaleas at least 40 million years ago, prior analyzed DNA sequences of the RPB2-I in natural populations (Towe, 2004; to the separation between Western Eurasia gene to categorize the Pentanthera section Skinner, 1955) has led many to consider and North America (Tiffney, 1985). The of deciduous azaleas and demonstrated the possibility that tetraploid species may demonstration that there is stable and that the Red Hills azalea is closely allied to, have originated recently in conjunction pervasive tetraploidy within clade C does but distinct from, the other Pentanthera with interspecific hybridization, i.e., not preclude the sporadic existence of species. Because the Red Hills azalea allopolyploidy (Li, 1957). One nascent polyloids within primarily diploid

74 SPRING 2008 Figure 2. Aligned Sequences for a 62 base pair region within intron 2 of RPB2-I. Note the base differences between groups of species at positions 641, 650, 691, and 698. Positions such as these serve to distinguish between clades in the phylogenetic analysis. A clade is a group of species that includes all descendants of one common ancestor. Clade and Monophyletic group are synonymous.

Figure 3. Phylogenetic tree of Pentanthera azaleas. The tree shown is that from maximum likelihood analysis. Branch lengths are proportional to the number of base changes on that branch. Maximum parsimony gave the same tree. Numbers indicate bootstrap support in the parsimony analysis. Authors of species not previously mentioned in this article: R. cumberlandense E. L. Braun, R. flammeum (Michaux) Sargent, R. periclymenoides (Michaux) Shinners, R. prinophyllum (Small) Millais, R. viscosum (L.) Torrey

Red = Rhododendron colemanii, Yellow = R. alabamense

Figure 4. Typical Rhododendron colemanii ; flower and Figure 5. Distribution of R. colemanii and R. alabamense in the Coastal vegetative buds; seed capsule; and form, , and habitat-- Plain of Alabama and Georgia. Monroe County, Alabama.

JOURNAL AMERICAN RHODODENDRON SOCIETY 75 species. For example, Rhododendron Table 2. Comparison of distinguishing features between Rhododendron alabam- occidentale was found recently (Jones ense and R. colemanii. et al., 2007) to exist both as a diploid in two accessions and as a tetraploid Rhododendron alabamense Rhododendron colemanii in the cultivar ‘Double Dig Twelve’. A Colonies in the Red Hills of Alabama and in Colonies in the Red Hills bloom from early to preliminary examination of the DNA of southwest Georgia bloom from early to mid mid May. April ‘Double Dig Twelve’ showed it to have the same sequences present as in diploid R. alabamense and its hybrids with R. Found primarily on sandy ridges or banks R. occidentale accessions. The occasional canescens are plants of dry ridges and along creeks or on north-facing bluffs in moist open, xeric oak woods with scattered Pinus woods along with Quercus laurifolia, Pinus tetraploidy of R. occidentale is thus shown spp., Oxydrendrum arboreum (L.)DC., and glabra Walt., Ilex vomitoria, Cyrilla racemifloria, to have a more recent origin than that of Vaccinium arboreum Marsh. Magnolia macrophylla, Hamamelis virginiana, Symplocos tinctoria, Myrica cerifera, Kalmia the species within clade C. latifolia, and Smilax spp. Conclusions.The conclusions of our research are: Though R. alabamense in southern Alabama Usually has 4-8 stems and can become 3-7 is a considerably larger plant than the low- m. tall, with a rounded, upright, dense form. • Those Pentanthera azaleas found growing, stoloniferous plant of Rehder’s type consistently as tetraploids make up a location in northern Alabama, it usually has monophyletic group that includes R. one or two main stems and an open, flat- topped “umbrella” form when mature. luteum from West Eurasia, as well as four Eastern North American species. Fully developed flower buds are shorter (0.8- Flower buds are longer (1.2-1.4 cm) and, 1.0 cm) and more rounded in the taper toward when immature, more elongated, without dark • The Red Hills azalea is a previously the tip. The distal ends of the bud scales, rims on the scales except in the winter, and undescribed tetraploid species within the when present, are usually outlined with distinct even then rimmed rather lightly. tetraploid clade. brown edges. • At an early point in the evolutionary Flowers are typically white, primarily with Flowers can be white, pink, or yellow, with divergence of Pentanthera azalea species, yellow blotches. The corollas occasionally or without blotches. The colors often spread two lineages separated—one containing exhibit eosin pink rims and are thin and almost across the entire corolla. Flower forms vary translucent. from tubular to broadly flared. Flower corollas the common ancestor of R. molle, R. are thicker and nearly opaque. canadense and the tetraploid clade—the Seed capsules are slim, cylindrical, with clear Though they have approximately the same other being the common ancestor of sutures, and are covered with unicellular hairs shape and size, R. colemanii capsules do R. occidentale and all of the diploid and occasional long, appressed multicellular not have the long appressed cilia and have Pentanthera species of the Eastern US. hairs. Glandular hairs are very rare on the surfaces, especially toward the distal end, and capsules. are marked by raised warts. Fresh capsules and pedicels, as opposed to material on herbarium sheets, are often covered with mulitcellular hairs tipped with glands.

DESCRIPTION OF RHODODENDRON COLEMANII Rhododendron colemanii R. Miller, non-rhizomatous except under stressed This species is placed inRhododendron sect. sp. nov. TYPE: U.S.A. Alabama: conditions; juvenile shoots cinnamon Penthanthera G. Don on account of the Monroe County, between Highway 41 brown, covered with sparse unicellular deciduous leaves, narrow corolla tube, and and Big Flat Creek , 2 May 2007, R. F. and sparse to dense (toward the tips) 5 exserted (Kron, 1993). In the Miller 24691 (holotype, TROY). Fig.4. appressed multicellular, eglandular field, the azalea can be distinguished from Species nova Rhododendron sectionis hairs. Vegetative bud scales glabrous R. alabamense and other coastal azaleas by Pentanthera distinguibili tetraploideo abaxially; margin densely unicellular- its late spring (early to mid May) flowering cum genome mango, multicaulis, deciduo, ciliate. Leaves membranaceous and time, its wide range of flower color (white, alabastris elongato, et capsules cum dull green to coriaceous and glossy pink or yellow), its mesic habitats, its verrucuosis glandulis. Species e habitatine green, 4-8 × 2-4 cm; blade obovate ovoid leaves with cuneate bases, its often humido, 3-7m elatus, 2C genome to occasionally oblong, base cuneate, warty seed capsules with glandular hairs, amplitude circa 3.16pg DNA, florescentiae apex broadly acute, mucronate, entire; and its taller stature (3-7 m). Its natural May praecox vel medius, flores colores adaxial surface and midvein sparsely distribution extends from southwestern vari, albus, roseus vel luteis, et affinis ad covered with multicellular hairs, with Alabama to the Chattahoochee Valley in fundamento R. atlanticum, R. austrinum, unicellular hairs near the petiole; abaxial Georgia in areas underlain by strata from R. calendulaceum, et R. luteum . surface sometimes glabrous, usually the Eocene, Paleocene, and Cretaceous Morphological Description. Many- covered with scattered unicellular and geological periods. stemmed or small tree to 7m tall, occasional appressed multicellular hairs,

76 SPRING 2008 the abaxial midvein with appressed wide at the base, densely covered with both R. alabamense and R. colemanii multicellular eglandular hairs; margin unicellular and multicellular eglandular bloom after the leaves are exerted; entire, ciliate with unicellular and and occasionally glandular hairs. Fruit therefore, no distinction can be made on appressed multicellular eglandular hairs; a capsule 1.3-3.0 cm long, 0.3-0.5 that basis. Their odors are both sweet and petioles 0.3-0.7 cm long, densely covered cm wide at base, cylindrical with somewhat lemony and can be confused. with unicellular hairs and appressed prominent sutures and raised warty However, compared to R. alamanense, R. multicellular eglandular hairs, often bumps toward the distal end, sparsely colemanii can also be distinguishing by a with scattered multicellular gland-tipped to densely covered with unicellular and later bloom time, its more mesic habitats, hairs on petioles and the bases of young multicellular eglandular hairs, often longer flower buds, a range of flower leaves. Flower buds 1.0-1.5 cm (long) with glandular-tipped multicellular colors, and fruit capsules that lack long, x 0.6-0.8 cm (wide), when immature hairs at the proximal end and on the appressed cilia but display small, raised rather narrow and tapered to a sharp peticels near the sepals, or often scattered warts and glandular hairs (see Table 2 apex. Bud scales awned, brownish-green along the entire capsule. pale for more detailed comparisons; Figure (drying chestnut brown), lacking dark brown, 1.5-3 mm long; testa expanded, 4). Rhododendron canescens occasionally rims except in winter; adaxial surface frayed on the ends, and dorsoventrally grows alongside R. colemanii, but can villous with unicellular hairs; abaxial flattened, surrounding the body, the easily be distinguished by observing the surface covered by minute unicellular cells elongate. former plant’s rough, elongate leaves; papillae; margin unicellular-ciliate, very its matted, rusty-colored current-year’s dense and shaggy toward the tip, non- Etymology. The epithet honors growth; its blunt, textured, flower buds; glandular. Inflorescence appearing after S. D. Coleman, Sr., of Fort Gaines, and its late March to early April blooming the leaves have expanded; a shortened Georgia, who collected, propagated, season. Rhododendron prunifolium, often a raceme of 8-10 flowers. Pedicels and distributed this azalea to gardens. cohort species within the Chattahoochee 0.5-0.7 cm long, densely covered with drainage, can be identified by its larger unicellular and multicellular glandular Distribution and Ecology. Southern bullate leaves; small flower buds; smooth, hairs. Sepals 0.05-0.1 cm long, margins Alabama and western Georgia in areas chocolate-brown current year’s growth; setose-fimbriate with multicellular underlain by Eocene, Paleocene, and and its red to orange, late summer eglandular hairs; abaxial surface sparsely Cretaceous strata—the so-called “Red flowers. The range of R. colemanii does to densely covered with unicellular Hills” (Figure 5)—on well-drained sandy not overlap with that of R. eastmanii Kron hairs and multicellular eglandular hairs, ridges and banks along watercourses or and Creel (Kron and Creel, 1999), which occasionally with glandular multicellular at the base of north-facing bluffs above blooms at a similar time; the latter azalea hairs. Corolla white with a yellow blotch streams. Associated species: Rhododendron occupies mesic sites in South Carolina on the upper corolla lobe, or uniformly canescens (Michaux) Sweet, Kalmia that are somewhat similar to, though white, pink with yellow blotch, or latifolia L., Stewartia malacodendron usually steeper and less heavily vegetated uniformly pink (rarely yellow); fragrance L., Hamamelis virginiana L., Fagus than, those occupied by R. colemanii. sweet, musky, and lemony; corolla 2.5-5 grandifolia Ehrhart, Pinus glabra Walter, Rhododendron eastmanii has a smaller cm wide, often reflexed, very variably R. prunifolium (Small) Millais [in the east], mature size and lacks the range of flower shaped; corolla tube 1.6-2.5 cm long, Illicium floridanum Ellis [in the west], color or multi-stemmed habit of the latter 0.25-0.4 cm wide at base; outer surface Quercus alba L., Q. laurifolia Michaux, azalea. At least occasionally, R. eastmanii of corolla covered with unicellular and Liriodendron tulipifera L., Magnolia displays glands on the edges of the flower- multicellular gland-tipped hairs, often macrophylla Michaux, M. virginiana bud scales whereas R. colemanni is totally in rows on the ridges of the tubes; inner L., Cyrilla racemifloria L., Ilex vomitoria without these glands. surface of corolla densely covered with Aiton, Symplocos tinctoria (L.) L’Héritier., unicellular hairs. Stamens 4.5-6.7 cm Myrica cerifera (L.) Small, and Alnus Paratypes. U.S.A. Alabama: Butler long, with flattened unicellular hairs the serrulata (Aiton) Willdenow. Flowering County, east of East Chapman at Mashy base of the filament, exserted 2.5-3.5 cm in early to mid May, occasionally in late Creek, 3 May 2007, R. F. Miller 24697 beyond the throat of corolla. Style 5-7 April and rarely into June. (TROY); U.S.A.: Georgia, Quitman cm long, exserted 3-4 cm beyond the Rhododendron colemanii is super- County, Georgetown, River Bluff Park, 4 throat, usually curved upward, with ficially similar to R. alabamense (Kron, May 2007, R. F. Miller 24696 (TROY); dense unicellular hairs on the proximal 1993), though they are found in different U.S.A.: Georgia, Quitman County, edge end, often light brown or reddish toward phylogenetic clades and R. colemanii is of Soapstone Creek at Highway 39 bridge, the distal end; stigma 0.1-0.2 cm wide. tetraploid while R. alabamense is diploid R. F. Miller 24696 (TROY). Ovary 0.20-0.35 cm long, 0.1-0.2 cm (Figure 3; Table 1). On the Coastal Plain, Literature Cited

JOURNAL AMERICAN RHODODENDRON SOCIETY 77 Ammal, E.K.J., I.C. Enoch, and M. Sectional relationships in the Rick Peterson for assistance in obtaining Bridgwater. 1950. Chromosome Rhododendron (Ericaceae): evidence samples. Special thanks are given to Dr. numbers in species of Rhododendron. from matK and trnK intron sequences. Paul Fantz for his review and assistance Rhododendron Year Book. 5:78-91. Plant Systematics and Evolution 228:1- with the manuscript. Chamberlain, D.F. and S.J. Rae. 1990. A 14. Revision of Rhododendron IV. Subgenus Li, H. Chromosome studies in the azaleas Tsutsusi. Edinb. J. Bot. 47(2): 89-200. of eastern North America. 1957. Am. J. Wenyu Zhou is currently a Greihuber, J., E.M. Temsch, and J.C.M. Bot. 44(1):8-14. graduate student, Taylor Gibbons is Loureiro. 2007. Nuclear DNA content Miller, R. and S. Yeatts. Rhododendron an undergraduate at the University of measurement, 67-101. In: J. Doležel, colemanii: a detective story. J. Ameri. Miami, Miami Florida, Loretta Goetsch is J. Greihuber, and J. Suda (eds.). Flow Rhododendron Soc. 62:79-85. a research scientist and Benjamin Hall is cytometry with plant cells: Analysis of Sax, K. 1930. Chromosome stability in a professor of Biology. WZ, LG and BH genes, chromosomes and genomes. Wiley- the genus Rhododendron. Amer. J. Bot. can be reached at Department of Biology, VCH, Weinheim. 17(4):247-251. University of Washington box 35-1330 Goetsch. L.A., A.J. Eckert and B.D. Hall. Skinner, H. T. 1955. In search of native Seattle, WA 98195-1330. Wenyu Zhou: 2005. The molecular systematics of azaleas. Morris Arboretum Bulletin [email protected], Taylor Gibbons: Rhododendron (Ericaceae): a phylogeny 6:1-2. [email protected], Loretta based upon RPB2 gene sequences. Sys. Tiffney, B. H. 1985. The Eocene North Goetsch: [email protected], Benjamin Bot. 30(3): 616-626. Atlantic land bridge: its importance in Hall: [email protected] Jones, J.R., T.G. Ranney, N.P. Lynch, Tertiary and modern phytogeography of Thomas G. Ranney is a professor and S.L. Krebs. 2007. Ploidy levels the Northern hemisphere. Jour. Arnold of Horticultural Science and member and relative genome sizes of diverse Arboretum 66:243-273. of the Southeastern Chapter. He can species, hybrids and cultivars of Towe, L. C. 2004. American Azaleas. be reached at the following address: Rhododendron. J. Amer. Rhododendron Timber Press, Portland and Cambridge, Department of Horticultural Science, Soc. 61(4):220-227. 146pp. Mountain Horticultural Crops Research Kron, K.A. 1993. A revision of and Extension Center, 455 Research Rhododendron section Pentanthera. Acknowledgements Drive, North Carolina State University, Edinb. J. Bot. 50: 249-364. Recognition and appreciation is given Fletcher, NC 28732-9244. tom_ Kron, K.A. and M. Creel. 1999. A to Alvin Diamond, Buddy Lee, R. [email protected] new species of deciduous azalea O. Smitherman, Bob Stevens, John Ron Miller is currently a retired (Rhododendron section Pentanthera; Thornton, Clarence Towe, and Steve Yeatts professor of English literature and can be Ericaceae) from South Carolina. Novon: for their efforts, insights, and assistance reached at: 1157 Ellison Dr., Pensacola, A Journal of Botanical Nomenclature in understanding and describing this FL 32503. [email protected] 9(3):377-380. species. Thanks to Jeff Jones and Nathan Kurashige, Y., J.I. Etoh, T. Handa, K. Lynch for completing flow cytometry Takayanagi, and T. Yukawa. 2001. analyses. We thank Steve Hootman and

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