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A 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) Literature Cited Rollins, R. C. 1942. A systematic study of lodanthus. Al-Shehbaz, I. A. 1988. The genera of Arabideae (Cru- Contr. Dudley Herb. 3: 209-215. ciferae; Brassicaceae) in the southeastern United States. -. 1993. The Cruciferae of Continental North Amer¬ J. Arnold Arbor. 69: 85-166. ica. Stanford Univ. Press, Stanford. Prantl, K. 1891. Cruciferae. In A. Engler & K. Prantl Schulz, O. E. 1924. Cruciferae—Sisymbrieae. In A. Engler (editors), Nat. Pflanzenfam. III. 2: 145—206. (editor), Pflanzenreieh IV. 105 (Heft 86): 1-388. Price, R. A. & P. W. Sweeney. 1998. Relationships in the -. 1936. Cruciferae. In A. Engler & K. Prantl (ed¬ tribe Cardamineae (Brassicaceae) from trnh-Y and ndhF itors), Nat. Pflanzenfam., ed. 2., 17B: 227-658. Verlag sequence comparisons. Amer. J. Rot. 85(6, Suppl.): 152. von Wilhelm Engelmann, Leipzig.