Documentation of the Chromosome Number for the California Endemic, Toxicoscordion exaltatum (Liliales: Melanthiaceae)

2010·3.2 MB·English

by  Dale W Mcneal

Madrono, Vol. 57, No. 3, pp. 180-183, 2010
DOCUMENTATION OF THE CHROMOSOME NUMBER FOR THE CALIFORNIA
ENDEMIC, TOXICOSCORDION EXALTATUM {\AIAAI.BS\ MELANTHIACEAE)
Dale W. McNeal
Department ofBiological Sciences, University ofthe Pacific, 3601 Pacific Avenue, Stockton,
CA
95211-0197
Wendy B. Zomlefer'
Department of Plant Biology, University of Georgia, 2502 Miller Plant Sciences, Athens,
GA
30602-7271
[email protected]
Abstract
The mitotic chromosome count for Toxicoscordion exaltatum {2n = 22), documented for the first
timehere, matchesthenumberformerlyreportedforotherspeciesinthegenus. Abasenumberof.v =
11 is synapomorphic for Toxicoscordion. An updated overview ofthis recently resurrected segregate
genus is given.
Key Words: California endemic, chromosome number, Melanthiaceae, Toxicoscordion, Zigadenus.
Tribe Melanthieae (Liliales: Melanthiaceae) inner three) and one obovate gland per tepal
comprises seven genera (ca. 65-95 spp.) of (Fig. IB; Zomleferet al. 2001; ZomleferandJudd
predominately woodland and/or alpine perennial 2002). Toxicoscordion comprises ca. eight species
herbs occurringmainly in the temperate to Arctic (Table 1) restricted to the midwestern United
zones of the Northern Hemisphere: Aniicmthiimi States to western North America (Fig. lA) and
A. Gray (1 sp.), Anticlea Kunth (9-11 spp.), includes the widely distributed poisonous "death
Schoenocciulon A. Gray (26 spp.), Stemmtliium camas" plants of the rangelands such as T.
(A. Gray) Kunth (3 spp.), Toxicoscordion Rydb. nuttalia (A. Gray) Rydb., T. paniculatum (Nutt.)
(8 spp.), Veratrum L. s.l. (17^5 spp.), and Rydb., and T. venenosum (S. Watson) Rydb. (see
Zigadenus Michx. s.s. (1 sp.). These generic Marsh et al. 1915, 1926).
circumscriptions (most novel) are supported by However, the focal taxon of this paper, T.
DNA
parsimony analyses of/rnL-F(plastid) and exaltatum (Eastw.) A. Heller (giant deathcamas),
ITS (nuclear ribosomal) sequence data (Zomlefer has a more limited distribution: mid-elevations
et al. 2001, 2003, 2006a, b). A significant (1000 to 1800 m) along margins of mixed
consequence of the molecular studies was the coniferous forest on the western slopes of the
reassessment of the traditional Zigadenus s.l., a Sierra Nevada Mountains in California (Fig. lA;
poorly defined assemblage with a complex Walsh 1940; Preece 1956; Schwartz 1994, 2002).
taxonomic history involving several segregate (Reports of this taxon from the foothills of the
genera (summaries in Zomlefer 1997; Zomlefer Sierra Nevada near Chinese Camp, Tuolumne
et al. 2006a). Contemporary treatments (e.g., Co. [see Preece 1956] are based on several
Schwartz 2002) have typically accepted the collections of T. frenjontii, a species otherwise
monotypic segregate Aniianthiuni with the re- known only from the Coast Ranges in CaHfornia
maining ca. 20 species maintained in Zigadenus [McNeal and Zomlefer 2009].) Toxicoscordion
s.l. Based on these molecular data, however, exaltatum is the largest species in the genus with
Zigadenus s.l. is polyphyletic and forms five relatively large bulbs (6-10 cm long; 3-5 cm in
strongly supported clades correlating with certain diam.) and long flowering stems to 100 cm tall
geographical distribution, morphological charac- (McNeal 1993). These robust plants often occur
ters, and chromosome number. in large popu—lations ofhundreds to thousands of
One well-defined clade corresponds to Tox- individuals creating a remarkable display
icoscordion, originally described by Rydberg (McNeal personal observation).
(1903), and sometimes recognized as Zigadenus The chromosome number 2n = 22 (or n = 11)
sect. Chitonia (Salisb.) Baker (Preece 1956; has been verified for all species of Toxicoscordion
dSecfhiwnaerdtzby19t9h4e).moTrhpihsoloZgiigcaadlenussynaspeogrmeograptheieiss e(Txaabllteatu1;mFwigi.th2;anseeunZdoomlceufmeernt20e0d3)c,iteaxtcieopntoffonr T=.
of conspicuously clawed tepals (especially the 11 by McNeal (1993; Schwartz 2002). Since
chromosome number is a significant and likely
an invariable apomorphy for genera of tribe
'Corresponding author. Melanthieae (e.g., Zomlefer and Smith 2002;
1
2010] MCNEAL AND ZOMLEFER: TOXICOSCORDION EXALTATUMCHROMOSOME NUMBER 181
Fig. 1. Distinctive characteristics of Toxicoscordioii. A. General distribution map of Toxicoscovdion (gray
shading) with dots indicating localities of the California endemic T. exaltatwn. (The south-midwestern disjunct
range ofthe genus comprises T. uuttallii.) Data from Walsh (1940), Preece (1956), and Schwartz (1994, 2002). B.
Adaxial surface ofan outer (left) and an inner (right) tepal of T. exaltatwn showing the generic autapomorphies:
claw plus a single obovate gland. Dashed ellipse = filament insertion. The claws ofthe inner tepals are typically
more pronounced than those ofthe outer whorl. Drawn from live material (McNeal& Smith 4749: CPH, GA) by
W. B. Zomlefer.
Zomlefer 2003), 22 is the predicted mitotic count months, and then placed on moist peat moss in a
for all Zigadeims species now transferred to growth chamber at 4 C with 16 hr of light and
Toxicoscordioii. We here document the chromo- 8 hr of darkness per day. Growing root tips
some number of T. excdtcitum. (12 cm long) were collected at ca 7:00 a.m. and
soaked in 0.2% colchicine for 26 28 hr, rinsed in
Materials and Methods deionized water, and fixed in Carnoy's solution
(3 ethanol: 1 acetic acid). Root tips thus prepared
Several bulbs ofToxicoscordioii exaltatum were were stored in the freezer for at least 24 hr,
collected during field work by the first author on transferred to 70% ethanol to slow tissue
12 May 2006, stored in paper bags for three hardening, and returned to the freezer. Squash
Table 1. The Speciesof Toxicoscordiona^otweOriginal Documentationofthe Mitotic(2n)and/or
Meiotic {n) Chromosome Numbers. See also Zomlefer (2003).
Chromosome number
Taxon // 2n Original source(s)
T. hrevihracteatus (M. E. Jones) R. R. 1 1 Lewis (1959); Cave (1970)
Gates
TT.. feoxnatltaamtmwin((EEaassttww..))ZAo.mlHeeflelrer& Judd 11 1 Pthriesecpeap(e1r956, asZigadenus veueuosusvar. foutanus);
Cave (1970)
T.fremontii (Torr.) Rydb. 11 Miller (1930); Preece (1956, as Zigadenusfrenumtii
vav.fremontii); Cave (1970, as Z. fremontii var.
fremontii and var. inezianus)
T. micranthwn (Eastw.) A. Heller 11 Preece (1956, as Zigadenus venenosus var.
micranthus)
T. nuttallii (A. Gray) Rydb. 22 Zomlefer (2003)
T. pauiciilatwn (Nutt.) Rydb. 11 22 Preece (1956)
T. venenoswn (S. Watson) Rydb. 11 22 Preaencde(v1a9r.56,veansenZoisguas)d;enCuasvveen(e1n9o7s0)u;svTaary.lgorra&mineus
Taylor (1977, as Z. venenosus var. gramineus);
Hartman &Crawford (1971, asZ. venenosusvar.
gra)ni)ieus)
MADRONO
182 [Vol. 57
A B C
AVv;
^c,
10 Mm
Fig. 2. Summary illustration ofpreviously documented meiotic {n = 11) and/or mitotic (In = 22) chromosomes
ofToxicoscordion(A-B, D-I)and thenew reportfor T. exaltatwn (C: 2n = 22). A. T. hrevihracteatus^ diakinesis{n
= 11). B. T.fontammr, anaphase II (n = 11). C. 7". exaltatum, metaphase {2n = 22), {McNeal& Smiths.n. [12 May
2006], CPH). D. T. fremontii, metaphase \ {n = 11). E. T. micranthum, metaphase I (n = 11). F. T. mittallii,
metaphase {2n = 22). G. T. pcmiculatimi, metaphase {2n = 22). H. T. paniculatum, metaphase I (/? = 11). I. T.
venenosum, metaphase I (;? = 11). A, B, and I modified from Cave (1970); D, E, G, and H modified from Preece
(1956); F from Zomlefer (2003).
preparations were made within 30-60 days ac- Results and Discussion
cording to protocols outlined by Brooks et al.
(1963). Following fixation, roots were rinsed The mitotic chromosome number of 2t2 = 22
several times in deionized water and hydrolyzed for Toxicoscordion exaltatimi is confirmed with
in 1.0 N HCL at 60'C for 5 min and rinsed plants from a population in El Dorado Co.,
several times again. Root tips were trimmed to Cahfornia (Fig. 2C; Table 1), and the previous
ca. 3 mm and placed on slides in saturated iron report by McNeal (1993) isnowdocumented with
aceto-carmine and macerated with fine-tipped a voucher specimen. The validation ofthe diploid
forceps. After application of a cover slip, the number for T. exaltatum strengthens support for
preparation was squashed using thumb pressure. the monophyly of Toxicoscordion, as well as the
Slides were mounted with euparal for future phylogenetic significance of chromosome num-
reference. Well-spread metaphase chromosomes bers as generic synapomorphies for tribe Mel-
were traced by the second author under a Leica anthieae.
DMLB Research Microscope with a camera A probable basechromosome numberofx = 8
lucida attachment. The herbarium voucher spec- is often cited for the tribe (summary in Zomlefer
imen, McNeal & Smith s.n. (12 May 2006), is et al. 2006a). The diploid numbers of 22 for
deposited at CPH. Toxicoscordion (Zomlefer 2003) and 20 for
2010] MCNEAL AND ZOMLEFER: TOXICOSCORDION EXALTATUMCUKOUOSOME NUMBER 183
Stenanthium (Zomlefer and Judd 2002) are Miller, E. W. 1930. A preliminary note on the
exceptions to the multiples of eight prevalent in cytology of the Melanthioideae section of the
the other genera (Sen 1975; Tamura 1995; Lowry Liliaceae. Proceedingsofthe University ofDurham
ea3t2n)d,al.AVnet1ir9ca8l7te;rauZm(o2/m(7li=encfle3u2rd),in1S9g9c7hM)oe:c/anAnomtci/aiauinlutomnh;i{u2Imnn ={=2n1166)=,, PreeWZPcihaegis,alhodiSse.nongJpu.thsoi.1cn9a,5lP6h.PS.uAoDlc.licmeyatdtnyio,st8sa:Wer2xAt6oa.7nt-oi2om7ni1.c.sSttuadtyeoCfotlhleeggeenuosf
32, 64, 80, 96). Due to the small size of the Rydberg, p. a. 1903. Some generic segregations.
chromosomes of this tribe (ca. 2.0^.0 |am in Bulletin ofthe Torrey Botanical Club 30:271-281.
length), the few detailed karyological studies Schwartz, F. C. 1994. Molecular systematics of
(e.g., Lee 1985) lack the detail to infer mecha- Zigadenus section Chitonia (Liliaceae). Ph.D. dis-
nisms ofchromosomal evolution, although these sertation. University ofWashington, Seattle, WA.
chromosome numbers indicate the prevalence of . 2002. Zigadenus. Pp. 81-89 in Flora of North
polyploidy and/or aneuploid variation of the America Editorial Committee (eds.). Flora of
prospective basic number. North America north of Mexico, Vol. 26, Magno-
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Acknowledgments University Press, Oxford, U.K.
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countswhileenrolled in Undergraduate Research under orders Asparagales and Liliales (Monocotyledo-
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