Delineation and Distribution of Zephyranthes en USA

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Delineation and Distribution of Zephyranthes

Species (Amaryllidaceae) Endemic to theSoutheastern United StatesRaymond O. Flagg1* and Gerald L. Smith2

1Carolina Biological Supply Company, Burlington, North Carolina 27215-33982Department of Biology, High Point University, High Point, North Carolina 27262-3598

ABSTRACT Three closely related, midwinter to spring-flowering, mesic species of Zephyr-anthes (Amaryllidaceae) are endemic to the southeastern United States: Z. atamasca, Z. treatiae,and Z. simpsonii. The taxonomic level of the distinctiveness of Z. treatiae from Z. atamasca is

discussed. Based on herbarium, cytological, and field studies, and on Principal ComponentAnalysis and pictorialized scatter diagram analysis, we conclude that all three taxa are distinctat the species level. They are distinguished by differences in relative lengths of floral elements.Illustrations, a distribution map, and a key are provided.

INTRODUCTION Zephyranthes (Amarylli-daceae) was established by William Herbert(1821), and is an American genus of some 40species (Mabberley 1997) with native distri-bution from Maryland to Argentina. Threeclosely related, midwinter to spring-flowering,mesic species of Zephyranthes are endemic tothe southeastern United States: Z. atamasca(L.) Herb. (1821), Z. treatiae S. Watson (1879),and Z. simpsonii Chapm. (1892). All threespecies have linear stigmatic lobes, greenperianth tubes and white perianth segments.The perianth segments may be variouslyflushed with pink.

Zephyranthes atamasca (Figure 1) and Z.treatiae (Figure 2) have been generally treatedas though the flowers were not significantlydifferent from one another, and were distin-guished by their leaves and their habitats.Although Z. atamasca tends to be associatedwith hardwoods and to grow in clumps, andZ. treatiae tends to be associated with pineflatwoods and to grow singly or looselyclumped, these general distinctions have beenrecognized as not always true; therefore, thebasic test to tell them apart has been in theleaves, as reflected in the keys of Small (1933),Godfrey and Wooten (1979) and Clewell(1985).

In the seeming absence of recognizedsignificant differences in the flowers of Z.atamasca and Z. treatiae, it has been thought(Flagg 1961, Spencer 1973, and Flory 1978)that Z. treatiae might be only an ecotypicvariant of Z. atamasca. Meerow (1985) de-scribed differences in the leaves and habits of the two taxa, and agreed that there was noconsistent distinguishing floral variation;therefore, he made the combination ‘‘Zeph-yranthes atamasco var. treatiae (S. Wats.)Meerow, comb. et stat. nov.’’ [page 94].

Although the perianth of Z. simpsonii(Figure 3) was originally described as palepink, many flowers observed in nature areoften strongly infused with pink or purpledistally, grading to white with a yellow-green

base. Other flowers are predominantly whiteand cannot be distinguished from the other two taxa by color. Nevertheless, Z. simpsoniiwith its narrowly funnelform flowers andlittle, if any, reflexing of the perianth seg-ments, and with its stigma among (or within2 mm of) the anthers has always beenrecognized as florally distinct from Z. ata-masca and Z. treatiae with their broadlyfunnelform flowers, reflexed perianth seg-ments and obviously exserted (3 mm or more

beyond the anthers) stigmas. It is interestingto note that Z. simpsonii, which is found inassociation with pine flatwoods in Florida andGeorgia, and maritime forests in NorthCarolina and South Carolina, tends to grow

*email address: [email protected]

Received September 4, 2007; Accepted May 24, 2008.

CASTANEA 73(3): 216–227. SEPTEMBER 2008

216



singly or loosely clumped and has a leaf type

like Z. treatiae, but with larger stomata (ca.63 mm vs. ca. 43 mm long).

MATERIALS AND METHODS Over a peri-od of decades we examined specimens of

Zephyranthes from a large number of herbar-

ia. In preparing materials for Flora of NorthAmerica (Flagg, Smith, and Flory 2002), werestudied specimens from The Florida StateUniversity (FSU), the Missouri Botanic Garden(MO), the University of Florida (FLAS), The

Figure 1. Zephyranthes atamasca (L.) Herb. A. Habit and flowering scape. B. Leaf cross section. C. Flower frontalview. D. Section of flower (l. s.). E. Tepal. (Drawn by Melanie Darst).

2008 FLAGG, SMITH: SOUTHEASTERN ZEPHYRANTHES 217



University of Georgia (GA), the Universityof North Carolina-Chapel Hill (NCU), andthe University of North Carolina-Charlotte(UNCC). The preponderance of the morpho-

metric data were taken from specimens atFLAS and MO.

As a rule, we quickly determined the speciesand then recorded data. Zephyranthes simpsonii

Figure 2. Zephyranthes treatiae S. Watson. A. Habit and flowering scape with frontal and side view of flower. B.Leaf cross section. C. Section of flower (l. s.). D. Tepal and stamen. (Drawn by Melanie Darst).

218 CASTANEA VOL. 73



Figure 3. Zephyranthes simpsonii Chapm. A. Habit and flowering scape. B. Leaf cross section. C. Frontal view of flower. D. Section of flower (l. s.). E. Capsule with pedicel and sheath. (Drawn by Jean Putnam Hancock).




was readily recognized by its relatively longperianth tube and its stigma among or within2 mm of the anthers. Zephyranthes atamascawas instantly identified when broad (5 mm or

more) leaves were present on the sheet.Zephyranthes treatiae was readily determinedwhen the stigmatic lobes were notably long(over 4 mm). Overall, the flowers of Z. ata-masca and Z. treatiae looked different to us;e.g., the free filaments of Z. treatiae seemednotably shorter and the perianth tube seemedlonger as compared to Z. atamasca.

To obtain some of the data we routinelyused strong backlighting of the herbariumspecimens. While not always necessary, shin-

ing a bright light up through the specimengreatly facilitated many determinations.Many sheets left us with partial data. Partswere missing from some specimens, and inspite of various lighting techniques, we couldnot always measure each element as desired.We recorded width and length of leaves whenthey were present, and recorded the lengths of floral elements when we were confident of themeasurements. Complete floral data onlengths of spathe, pedicel, total perianth,

perianth tube, free filament and style, andposition of the stigma relative to the antherswere obtained from 33 specimens of Z.atamasca, 45 specimens of Z. treatiae and 46specimens of Z. simpsonii, and this data wasused in the analysis and is presented in Tablesand Figures.

RESULTS

Morphometrics

Table 1 is a summary of all relevant mea-

surements obtained in the study. The lengthsof each element overlap among the threetaxa, but some differences can be noted.Among the three taxa, the widest leaves, thelongest pedicels and the shortest perianth

tubes occur in Z. atamasca, and the longestperianth tubes and the shortest styles occur inZ. simpsonii. In comparison with Z. atamasca,longer perianth tubes, shorter free filaments

and longer stigmatic lobes occur in Z. treatiae.A Principal Component Analysis (PCA)

demonstrated variation with Component 1containing 44.7% of the variance and Com-ponent 2 containing 24.2% of the variance(the remaining percentage is in the other fivecomponents). Character weightings are givenin Table 2. The PCA analysis (Figure 4) showsthe taxa as three clusters with less overlapbetween Z. atamasca and Z. treatiae thanbetween Z. treatiae and Z. simpsonii. The plot

of the first principal component as comparedwith the second principal component demon-strates that the variation within each taxon isless than the variation between taxa. Individ-uals of the three taxa can be defined as threeclusters supporting a concept of three species.

Because relative lengths of floral elementswere particularly revealing in analyzing rela-tionships of Zephyranthes species of the TexasGulf Coast (Flagg 1961, Flagg and Flory1976), we pursued this with the three south-

eastern species. Table 3 is a summary of theratios found when the lengths of specific floralelements were divided by the length of theperianth tube. Restated as simple generalities

Table 1. Widths of leaves and lengths of floral elements in millimeters in herbarium specimens of Zephyranthes species endemic to southeastern United States

Z. atamasca Z. treatiae Z. simpsonii

Leaf (2) 3–7 (8) 1–3 1–4

Spathe (20) 22–32 (36) (18) 21–33 (36) (17) 21–40 (42)Pedicel (0) 4–16 (34) 0–10 (12) 0–6 (15)Perianth (55) 66–90 (101) (61) 66–95 (108) (40) 43–85 (101)Perianth tube (8) 11–20 (21) (17) 19–28 (31) (14) 16–33 (40)Filament (29) 32–44 (47) (16) 22–39 (46) (15) 16–28 (32)Style (52) 58–74 (78) (50) 55–82 (87) (31) 33–57 (62)Stigmatic lobe (0.8) 1.1–3.0 (4.0) (1.4) 2.3–4.3 (5.5) (1.0) 1.6–2.9 (4.3)

Table 2. Principal component matrix (characterweightings) for Zephyranthes species endemic tosoutheastern United States

Component 1 Component 2

Spathe length .179 .535Perianth length .887 .381Style length .906 .155Leaf width .559 2.428Perianth tube length .008 .904Filament length .915 2.154Pedicel length .576 2.460




in relationship to perianth-tube length: totalperianth length in Z. atamasca is always morethan 4 times the perianth-tube length, in Z.treatiae it is 3 to 4 times, and in Z. simpsonii itis usually less than 3 1/5 times perianth-tubelength; filament length in Z. atamasca is atleast 1 2/3 times and usually 2 to 3 times (or more) perianth-tube length, in Z. treatiae it is

usually 1 to 1 1/2 times and occasionally asmuch as 1 2/3 times, and in Z. simpsonii it is2/3 to 1 1/3 times; the style in Z. atamasca isalways more than 3 times the perianth-tubelength, in Z. treatiae it is about 2 1/2 to 3 1/3times, and in Z. simpsonii is always less than 21/2 times; in Z. atamasca spathe length is

usually at least 1 1/2 times the perianth-tubelength, in Z. treatiae it is usually less than 11/2 times, and in Z. simpsonii it ranges from2/3 to 2 times.

Using records of specimens under study for which there were complete data on lengths of perianth, perianth tube, filament, style andspathe, we created a pictorialized scatter

diagram (Figure 5) based on the relativelengths of the floral elements in individualspecimens. Within each taxon every speci-men could not be depicted because onoccasion one glyph would partially obscureanother. If the overlapping glyphs of a taxonwere not identical, we used the one most

Figure 4. Principle components analysis of the morphological characters of h: Zephyranthes atamasca, X: Z.treatiae, %: Z. simpsonii.

Table 3. Ratios of lengths of floral elements to length of perianth tube in Zephyranthes species endemic tosoutheastern United States

Z. atamasca Z. treatiae Z. simpsoniiPerianth/Perianth tube (4.1)4.3–6.4 (8.5) (3.0)3.1–4.0(4.1) (2.2)2.4–3.1(3.2)Filament/Perianth tube 1.7–3.4 (4.6) (0.8) 1.0–1.5(1.7) 0.7–1.1(1.3)Style/Perianth tube 3.2–5.3 (7.5) 2.5–3.3(3.4) (1.4)1.6–2.4Spathe/Perianth tube 1.4–2.4 (3.0) (0.7)0.9–1.4(1.5) (0.7)0.8–1.7(2.0)




different from the majority of glyphs for thattaxon, which illustrates the morphologicaldiversity but also somewhat exaggerates theamount of variation within a taxon. The

pictorialized scatter diagram produced apattern similar to the PCA cluster analysis,but with even less indication of morphologi-cal overlap between species. We concludedthat there are three closely related species

distinguished by suites of floral characteris-tics.

Cytology

The somatic chromosome number of both Z.atamasca and Z. treatiae is 2n5 24 (this paper,Flory 1940 and 1943, Flagg 1961) (Figure 6Aand 6B). We have prepared karyotypes of both species and conclude that the chromo-

Figure 5. Pictorialized scatter diagram using floral characteristics of Zephyranthes endemic to southeasternUnited States.




some types are remarkably similar in size andcentromere position. Even though some slightchromosomal differences are observable be-tween Z. atamasca and Z. treatiae, we thinkthat the morphological distinctions discussedin this paper are largely the result of genemutations that have become established inpopulations through selection in each species.The divergence of Z. atamasca and Z. treatiaeinto distinctive habitats suggests to us thatthey have speciated as a response to their environmental conditions. We believe that

gene sequencing of variable genes and DNAfingerprinting techniques (ISSR) are likely toreveal those suspected genetic differences asdemonstrated by Meerow et al. (2000) for other species of Zephyranthes .

The cytological distinction of Z. simpsonii isa more clear-cut case. The somatic number is2n 5 48 (this paper, Flory 1940 and 1943,Flagg 1961) (Figure 6C). We hypothesize thatZ. simpsonii is of autopolyploid origin from Z.treatiae. They have nearly indistinguishable

leaf forms, although Z. simpsonii has larger stomata and may possess a thicker leaf.Further supporting our idea of Z. simpsoniiorigin is that floral distinctions between Z.simpsonii and Z. treatiae are less than those of Z. simpsonii and Z. atamasca (Figures 4 and 5).It is conceivable to us that, as Z. simpsoniievolved, the perianth tube continued toelongate and effectively shortened the freesegments of the perianth resulting in thetrumpet form. There is widespread evidence

in Zephyranthes that as chromosome numbersincrease style exsertion decreases placing thestigma at or below the anthers and support-ing self pollination (Flagg and Smith, pers.obs.). We believe that gene studies will also

reveal genetic differences between Z. simpsoniiand Z. treatiae.

Distribution

Zephyranthes atamasca is found in the CoastalPlain and Piedmont from southeastern Mary-land to northern Florida and west to thesoutheastern corner of Mississippi (Figure 7).Zephyranthes treatiae occurs between centralFlorida and southern Georgia (Figure 7).Zephyranthes simpsonii occurs disjunctly inthe Coastal Plain in southeastern North

Carolina and northeastern South Carolina,from southeastern Georgia to south-centralFlorida, and with two very small populationson the Alabama-Mississippi border (Figure 7).

In reviewing the morphological data acrossthe distribution, we did not find a generaltendency for Z. atamasca to be more like Z.treatiae in north-to-south or west-to-east di-rections. Our studies indicate that there is notwidespread hybridization between Z. ata-masca and Z. treatiae. Nevertheless, in Darien

(McIntosh Co.), Georgia, where it was appar-ent that both Z. atamasca and Z. treatiae hadbeen brought in and planted together, asingle specimen of Z. atamasca found in alawn had perianth element ratios that nearlyproximated the most extreme ratios found inZ. treatiae. The leaf width and short stigmaticlobes of that specimen placed it in Z. ata-masca, but we suspect some hybridization hasbeen involved in Darien, Georgia, and wecannot rule out natural hybridization in the

vicinity of Jasper, Florida in ecotonal zonesbetween the two species. This is likely to occur in other counties where Z. atamasca and Z.treatiae are both present (Figure 7) and inwhich habitats are adjacent to one another.

Figure 6. Somatic chromosomes of (A) Zephyranthes atamasca (Smith 1398, Bladen County, North Carolina) (B)Z. treatiae (Smith s.n., Brooks County, Georgia) and (C) Z. simpsonii (Flory s.n., De Soto County, Florida, Greenhouseaccession – 849).




However, it is also important to point out thatthere are counties where populations of eachoccur, but that they are spatially isolated indifferent habitats, and the opportunity for

hybridization is not as likely. Measurementsof specimens, which have been taken fromvouchers documenting populations as report-ed above, support the distinctiveness of eachspecies.

SUMMARY/DISCUSSION The three mid-winter to spring-flowering, mesic species of Zephyranthes endemic to the southeasternUnited States, were described in the 19th

century: Z. atamasca in 1821 establishing thegenus, Z. treatiae in 1879, and Z. simpsonii in1892. Since Chapman (1892) described Z.simpsonii, as ‘‘stamens and style equal, in-cluded,’’ it has been recognized as florally

Figure 7. Distributions of Zephyranthes species endemic to southeastern United States.




distinct from the other two species. Zephyr-anthes atamasca and Z. treatiae have beendistinguished from one another primarily bytheir leaves: broad, shiny green, slightlychanneled, margins sharp-edged in Z. ata-masca; and, narrow, dull green, semi-terete,margins rounded in Z. treatiae. For some planttaxonomists, the seeming lack of floral differ-ences has called into question the specific

status of Z. treatiae.While we suspect that some hybridization

has occurred between Z. atamasca and Z.treatiae, we don’t accept that as justificationfor lumping together the two taxa. Broyles andWyatt (1991) reported that Z. atamasca is fullyself-compatible [self-compatibility is mostcommon in the genus (Flagg and Smith,personal observation)], but also sets a similar number of viable seed in cross-pollinations.This breeding system would offer the potential

for hybridization, which would not be unex-pected considering the natural hybridization(Flagg 1961, Flagg and Flory 1976) that hasoccurred between such morphologically differ-ent rain-lilies as Z. pulchella J. G. Sm. (1895)and Z. chlorosolen (Herb.) D. Dietr. (1840).Because of the great floral morphologicaldifferences between these parents, and in spiteof their recognized natural hybridization,some authors continue to recognize Cooperiaincluding Z. chlorosolen [5 Cooperia drummon-

dii Herb. (1836)] as a separate genus (Diggs etal. 2006, Correll and Johnston 1970); althoughwe considered Cooperia to be congeneric withZephyranthes (Flagg, Smith, and Flory 2002).Clearly, putative natural hybridization alone

would not be sufficient reason to deny specificstatus to a rain-lily.

Broad leaves (5 mm or more) generallydistinguish Z. atamasca from Z. treatiae andZ. simpsonii. A stigma among or near (within2 mm) the anthers distinguishes Z. simpsoniifrom Z. atamasca and Z. treatiae. The threespecies are further distinguished by floralcharacteristics related, by and large, to the

degree of fusion of the perianth into a tube(Figure 8).

PCA of the taxa demonstrates that thevariation between Z. atamasca and Z. treatiaeis greater than the variation between Z.treatiae and Z. simpsonii. A pictorialized scatter diagram using lengths of floral elementsrelative to perianth-tube length supports theconcept of three species.

Our conclusion supports taxonomists, suchas Chapman (1892), Small (1933), Hume

(1935), Godfrey and Wooten (1979), Clewell(1985) and Wunderlin (1998), who treated Z.atamasca, Z. treatiae and Z. simpsonii as threedistinct species.

KEY TO ZEPHYRANTHES SPECIESENDEMIC TO THE SOUTHEASTERN

UNITED STATES

1. Stigma exserted more than 4 mm be-yond anthers; perianth-tube length

usually less than 1/3 of the totalperianth length . . . . . . . . . . . . . . . . . . 2

2. Leaf greater than 4.5 mm inwidth . . . . . . Zephyranthes atamasca

2. Leaf less than 4.5 mm in width . . . . 3

Figure 8. Floral diagrams of Zephyranthes species endemic to southeastern United States.




3. Perianth-tube length less than 1/4of the total perianth length, about1/2 (1/3–2/3) of the filamentlength . . . . Zephyranthes atamasca

3. Perianth-tube length at least 1/4 of

the total perianth length, aboutequal (2/3–1J) to the filamentlength . . . . . . Zephyranthes treatiae

1. Stigma very near, among or below anthers; perianth-tube length usually1/3 or more of the total perianthlength . . . . . . . . Zephyranthes simpsonii

ACKNOWLEDGEMENTS We are particu-larly grateful to Walter S. Flory, Jr. (deceasedJune 8, 1998) for his steady encouragement

and for his contributions to the formativestages of this paper. We thank the Curators of FLAS, FSU, GA, MO, NCU, USF, UNCC for making loans available; and, we particularlythank Richard Wunderlin and Bruce Hansen(USF), and Kent Perkins (FLAS) for their patience in granting to us several specificloan requests. We thank Charles K. Smith(Biology Department, High Point University)for assistance in performing the PrincipalComponent Analysis of our data. JacquelynReaves and several taxonomy classes at HPU

collected data in the early stages of thisproject from herbarium and field collectedspecimens that proved helpful to the artists indeveloping the illustrations. Robert Godfrey(deceased), Angus Gholson, Melanie Darst,Mark Garland, and Gary Knight participatedin field studies in March of 1992 to collectZephyranthes specimens. Melanie Darst andJean Putnam-Hancock provided the fine illus-trations. Funding for the field work andartwork was provided by NC Board of Science

and Technology grant, no. 90SE010.

LITERATURE CITED

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