Table Of ContentA Reconsideration of Chaunanthus (Brassicaceae)
Robert A. Price
Department of Botany, University of Georgia, Athens, Georgia 30602, U.S.A.
Ihsan A. Al-Shehbaz
Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299, U.S.A.
Abstract. Three Mexican endemic species of distant from Cardamine and I. pinnatifidus. On the
shrubby habit and apparent thelypodioid affinities basis of morphological evidence and molecular
(.fodanthus acuminatus, /. mexicanus, and /. petiol- data, we have reassessed the Mexican species pre¬
atus) are separated from the eastern North Ameri¬ viously placed in lodanthus and treat them below
can herli lodanthus pinnatifidus as the genus as the separate genus Chaunanthus.
Chaunanthus O. E. Schulz. The new combinations Chaunanthus differs from lodanthus by having
Chaunanthus acuminatus and C. mexicanus are basally woody stems, wingless petioles, non-aurie-
proposed. The distinguishing features ami geo¬ ulate cauline leaves, pubescent leaves and stems,
graphic distribution of the genus Chaunanthus are petals undifferentiated into claw and blade, sepals
discussed, and a key to species and synopsis of its half as long as to subequaling petals, obtuse non-
three included species are presented. apiculate anthers, well-developed median nectar
Key words: Brassicaceae, Chaunanthus, lodan¬ glands confluent with the lateral nectaries, often se-
thus, Mexico. cund fruits, and incumbent cotyledons. By contrast,
lodanthus has herbaceous stems, winged petioles,
auriculate cauline leaves, glabrous leaves and
Beginning with the revision of Rollins (1942),
stems, petals strongly differentiated into a blade
lodanthus Torrey & A. Gray included four species,
and claw and more than twice as long as the sepals,
three endemic to Mexico (/. acuminatus Rollins, I.
strongly apiculate anthers, median nectaries totally
mexicanus Rollins, and /. petiolatus (Hemsley) Rol¬
lacking, spreading, non-secund fruits, and accum-
lins) and one, the type species /. pinnatifidus (Mi-
bent cotyledons. In our opinion, these morpholog¬
chaux) Steudel, widely distributed in riverine and
ical differences are quite significant, and they
moist wooded habitats in the eastern half of the
clearly support the removal of the Mexican species
United States (Al-Shehbaz, 1988; Rollins, 1993).
of lodanthus sensu Rollins (1942, 1993) to Chaun¬
Alternatively, the one Mexican species published
anthus. Chaunanthus is distinguished from Thely¬
prior to Rollins (1942) was originally treated as a
podium, in which C. petiolatus was originally
thelypodioid mustard (Thelypodium petiolatum
placed, by its suffrutescent habit, long petiolate,
Hemsley), and later transferred to the monotypic
undivided, dentate, non-auriculate cauline leaves,
genus Chaunanthus by Schulz (1924). Prantl
yellow to creamy-white petals, included stamens,
(1891) allied the monotypic lodanthus with Car-
and non-torulose sessile fruits. In contrast, Thely¬
damine L. and relatives, whereas Schulz (1936)
podium is characterized by a biennial herbaceous
placed it in a heterogeneous tribe Matthioleae. Mo¬
habit, sessile auriculate or petiolate and pinnately
lecular sequence comparisons for the ehloroplast
divided (rarely only toothed) cauline leaves, purple,
gene ndhY (Price & Sweeney, 1998) strongly indi¬
lavender, or white flowers, exserted stamens, and
cate that the eastern North American /. pinnatifidus
is in fact closely related to Cardamine L., with torulose fruits that are often short-stipitate.
which it shares an herbaceous habit, glabrous to Rollins (1942) examined only nine specimens of
sparsely pubescent leaves, white to purplish flow¬ the three Mexican species that he placed in lodan¬
ers, and a tendency to grow in rnesic habitats. In thus. Although only the type collection of Chaun¬
contrast, the three Mexican species are suffrutes- anthus mexicanus is currently known, many collec¬
cent in habit, have markedly pubescent leaves and tions of C. petiolatus and C. acuminatus have been
yellow to creamy white flowers, and often occur in made since Rollins’s account, so we present below
drier montane habitats. They clearly group in all an updated summary of the ecology, distribution,
molecular comparisons to date (Price, unpublished) and phenology of the latter two species based upon
with Thelypodium and relatives in a clade quite a much expanded set of collections.
Novon 11: 329-331. 2001.
330 Novon
Key to the Species of Chaunanthus dalupe, Rzedowski 32182 (MEXU); Ecatepec, Sierra de
Guadalupe, 3 km N Ecatepec, Division Tecuexcomac, en-
la. Fruit strongly flattened, long hirsute, attenuate to
trando por Col. Ampliacion, Garcia 1477 (AKIZ, MEXU,
beak-like apex; stigma sessile; stem apex ending
MO, TEX); entre Cuatepec y San Cristobal Ecatepec, Si¬
in a leafy, paniculate inflorescence .
erra de Guadalupe. Mntuda 25702 (GH, IEB. MEXU,
.3. C. mexicanus
TEX); Sierra de Guadalupe, al N de la Ciudad de Mexico,
lb. Fruit terete, glabrous or minutely puberulent, cu-
Paray 1165 (MEXU); Mt. Guadalupe, near Mexico, Bour-
neate to apex; stigma on a distinct style; stem
geau 762 (E, GH). Puebla: Boca de Monte, Purpus 3692
apex ending in leafless racemes.
(UC, US). Queretaro: parte alta del Cerro La Temblad-
2a. Stems hirsute; leaf trichomes exclusively
era, 10.5 km al N de Pena Blanca, Mun. Penamiller. P^rez
simple; petals 2—3 mm wide . . 1. C. petiolatus
A Zamudio 3238 (IEB).
2b. Stems glabrous or puberulent; leaf trichomes
stalked-forked at least on abaxial surface;
petals ca. I mm wide .2. C. acuminatus 2. Cliaiinnnthus acuminatus (Rollins) R. A.
Price & Al-Shehbaz, comb. nov. Basionym: lo¬
1. Chuuiiantliii.s petiolatus (Hemsley) (). E. danthus acuminatus Rollins, Contr. Dudley
Schulz, in Engler, Pflanzenreich IV. 105 (Heft Herb. 3: 212. 1942. TYPE: Mexico. Jalisco:
86): 159. 1924. Basionym: Thelypodium pe- Sierra Madre Occidental, San Sebastian, Ar¬
tiolatum Hemsley, Diagn. PI. Nov. Mex. 2. royo Seco, thicket near stream, 15 Jan. 1927,
1878. lodanthus petiolatus (Hemsley) Rollins, Ynes Mexia 1491 (holotype, UC).
Contr. Dudley Herb. 3: 211. 1942. TYPE:
Phenology. Flowering November through June,
Mexico. Hidalgo: Zimapan, ./. M. Coulter 684
fruiting January through October.
(holotype, K; isotype, (/II).
Habitat. Clay soil in steep volcanic slopes and
Phenology. Flowering July through early Oc¬ flats in forests, deep shade in forest understory; el¬
tober, fruiting September through October. evation 1200-2600 m.
Habitat. Steep rocky volcanic outcrops, open
scrub-oak forests with andesite and basalt boulders; Specimens examined. MEXICO. Colima: Rancho el
Jabali, 20 km N de la Cd. de Colima, cerca de la Haci¬
elevation 2000—2850 m.
enda San Antonio, ].9°26'N, 103°40'W, R. A K. Martinez
Specimens examined. MEXICO. Distrito Federal: 960 (K); Mun. de Comala, Rancho El Jabali, 22 km NNW
of Colima in SW foothills of Vulcan de Colima. I9°26.9'N,
Vertiente E del Cerro de Santa Catarina, cerca de Sta.
103°42.7'W, Sanders, Charlton, Phillips A' Rothschild
Catarina, delg. Tlahuac, Rzedowshi 26063 (CAS. MEXU,
10656 (GH, MICH), Vazquez 524 (GH. MEXU), Vazquez
MICH); Deleg. Tlahuac, 3 km NO de San Francisco Tlal-
A Phillips 891 (MEXU), Vazques 971 (MO): Rancho El
tengo, Ladera SSE del cerro de Sta. Catarina, Garcia 1675
Jabali, 25 km NNW of Colima. Lago, Epazote, I9°26.6'N,
(MEXU); Lomas de Mixcoac, Lyonnel 1386 (CAS, MEXU).
103°40.7'W, Sanders, Daniel A Phillips 11017 (MICH);
Guanajuato: 2 km al NW de La Gavia, sobre el eamino
Rancho El Jabalf, 22 Km NNW' Colima, Lago Jabali,
a Gortazar, Rzedowski 40948 (IEB); 14 km de San Luis de
19°26.9'N, 103°41.8'W, Sanders, Daniel A Phillips 11108
la Paz, vers Victoria, pr, vers Victoria, prfes de la Pres-
(GH, MICH). Jalisco: 5 mi. NNE of la 1 pa de Allende, E-
nsita, 21°18'N, l()0o26,W, Caranza Gonzales A: Lahat
facing slopes N of road-summit, McVaugh 20183 (GH,
2530 (IEB). Hidalgo: Cerro Grande, al SE de Epazoyu-
MEXU, MICH); 10— 12 km N La Cuesta, below the pass
can, Rzedowski 29322 (MEXU); Cerro Alto, 2 km al S de
to Talpa de Allende, McVaugh 233371 (MICH); Sierra Ma¬
Epazoyucan, Rzedowski 31127 (AKIZ, MEXU, MICH);
dre Occidental, San Sebastian, E of Segundo Arroyo, Mex¬
Cerro Xihuingo, cerca de Los Cides, Mun. Tepeapulco,
ia 1565 (UC); Jocotepec, Cerro Viejo, paraje El Quinto,
Rzedowski 31504 (MEXU); 2 km al N de Huixmi, Mun.
enfrente de Zapotitan de Hidalgo, Machuca 6366 (MICH);
Tlaxiaca. Rzedowski 36956 (IEB. MEXU); Metztitldn, head
Cerro Viejo, vereda a Barranca del Agua, Machuca 3533
of descent into Barranca de Metztitlan between Zoquital
(MICH).
and Los Venados, Moore & Wood 4217 (GH. UC); Zima¬
pan, Cerrote, 10 km sur del entronque de la carr. de Zi¬
mapan, Hernandez & Rodriguez 5020 (CAS, MEXU, MO); 3. Chuimunlhiis mexicanus (Rollins) R. A. Price
Pachuca, Pttrpus 6512 (F, GH, MO, UC); Cerro Tecajete,
& Al-Shehbaz, comb. nov. Basionym: lodan¬
Mun. de Zempoala, Ventura 332 (CAS, MEXU, MICH);
thus mexicanus Rollins, Contr. Dudley Herb.
Cerro Xihuingo, Mun. de Tepeapulco, Ventura 473
(MEXU, MICH), Ventura 2161 (MEXU); Mun. San Agus- 3: 213. 1942. TYPE: Mexico. Puebla: Coxca-
tin Tlaxiaca, Sierra del monte alto de Temoaya, 5 km des- tlan, Sep. 1909. C. A. Purpus 4158 (holotype,
pu6s de la desviacion de la carretera Benito Juarez-Chap- GH; isotypes, MO, UC).
ulte, 20°05'N, 99°01'45"W, Diaz 834 (MEXU); Mun.
Ajacuba, cerro al NE del poblado Emiliano Zapata, ver¬ Known only from the type collection.
tiente S de la Sierra de Chicavasco, ejido San Nicolas
Teeomatlan, 20°08'50”N, 99°00'45"W, Diaz 672 (MEXU); Acknowledgments. We thank the curators and
Cerro de Santa Monica, N of Santa Monica, 40 km NW
directors of the herbaria cited in this work. We are
of APAM. on Pachuca highway. West P-26 (MICH). Mex¬
grateful to Jerzy Rzedowski for his critical review
ico: San Andrds, 5 km al SW de San Cristobal Ecatepec,
Rzedowski 27633 (MEXU, MICH, TEX); 6 km al W de of the manuscript and for sending photocopies of
San Cristdbal Ecatepec, parte alta de la Sierra rle Gua¬ specimens deposited at IEB.
Volume 11, Number 3 Price & Al-Shehbaz 331
2001 Chaunanthus (Brassicaceae)
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