The taxonomy of Chenopodium desiccatum and C. nitens, sp. nov.1 Nuri Benet-Pierce2 and Michael G. Simpson Department of Biology, San Diego State University, San Diego, CA 92182-4614, USA Oldest Botanical Journal in the Western Hemisphere Journal of the Torrey Botanical Society 141(2), 2014, pp. 161–172 The taxonomy of Chenopodium desiccatum and C. nitens, sp. nov.1 Nuri Benet-Pierce2 and Michael G. Simpson Department of Biology, San Diego State University, San Diego, CA 92182-4614, USA BENET-PIERCE,N.AND M. G. SIMPSON (Department of Biology, San Diego State University, San Diego, CA 92182-4614, USA). The taxonomy of Chenopodium desiccatum and C. nitens, sp. nov.: J. Torrey Bot. Soc. 141: 161–172. 2014.—Fruits and seeds of the genus Chenopodium have been considered taxonomically important but have not been fully studied or utilized. We discuss the importance of describing fruit and seed morphology at low magnification to improve the identification and taxonomy of North American taxa of Chenopodium, which in a large part remains unresolved. A new species, Chenopodium nitens Benet-Pierce & M. G. Simpson, is described, integrating these reproductive characters with general vegetative characters. Key words: Chenopodiaceae, Chenopodium, Chenopodium leptophyllum var. oblongifolium, fruits, seeds. Chenopodium, of the Chenopodiaceae (5 American species. Part of this difficulty arises Amaranthaceae s.l. in APG III, 2009), a genus from the highly variable vegetative features of of approximately 150 species worldwide, these plants. Chenopodium species are well includes species of economic importance such known for being able to fruit as small plants if as the South American C. quinoa Willd., an conditions are less than optimal, contributing important ‘‘pseudocereal.’’ Phylogenetic stud- in part to their variation in stem habit and ies of the Chenopodiaceae have demonstrated other vegetative features. In addition, they that Chenopodium as traditionally treated is present similar leaf characteristics across taxa, not monophyletic (Kadereit et al. 2010). In the and most mature plants lose primary leaves as most recent molecular phylogenetic analyses they enter the fruiting stage, making it difficult (Fuentes-Bazan et al. 2012a, b), species of to find fruits and primary leaves to aid in several clades formerly treated in Chenopodi- identification. Incomplete taxonomic treat- um have been transferred to the genera Blitum ments have added to the confusion. At present, L., Chenopodiastrum S. Fuentes, Uotila, & we lack descriptions detailed enough to fully Borsch, Lipandra Moq., and Oxybasis Kar. & differentiate some taxa present in North Kir. In addition, the largest clade of the America, as not all is known about the traditional Chenopodium s.l. is treated as a variation in each. With incomplete descriptions monophyletic Chenopodium s.s. This study and the absence of clear identification keys, also confirmed the genus Dysphania Mosyakin many determinations remain controversial. & Clemants, with its distinctive glandular Historically, fruits and seeds of Chenopodium trichomes, as a well-supported clade. The taxa have been deemed highly relevant and even from North America discussed in this paper essential for identification, but have been are all included in the Chenopodium s.s. clade. underutilized in taxonomic keys. A number Whether treated in the broad or narrow of new fruit characters have been recently sense, Chenopodium has often been considered defined and investigated with success for their taxonomically difficult, particularly its North taxonomic value across Chenopodium s.l. (Sukhorukov and Zhang 2013). Fruits and seeds of North American Chenopodium s.s. 1 Our most sincere thanks and appreciation to the have not been properly described even for well- following herbaria for allowing us to examine and known species, having been considered exceed- sample material, including type specimens, and for ingly variable or difficult to assess, possibly as the use of their images: ASU, CAS-DS, CDA, the result of hybridization. For some species CHSC, GH, JEPS, MO, NY, OBI, PAC, RM, RSA- POM, SD, SDSU, TEX, UC, UNM and US. We that are still poorly known, fruit characteristics especially want to thank our reviewers for their help have yet to be detailed at all. Most of the in improving this paper. We thank Lee M. Simpson characters we are using here are new, and some for acquiring most of the images. others we define somewhat differently for 2 Author for correspondence, E-mail: nuribpierce@ North American taxa. gmail.com Received for publication July 6, 2013, and in Mature fruits and seeds of Chenopodium s.s. revised form March 8, 2014. from North America are generally somewhat 161 162 JOURNAL OF THE TORREY BOTANICAL SOCIETY [VOL.141 lenticular, small at ca. 1 (0.6–2.4) mm in studies (Crawford and Reynolds 1974, Craw- diameter, and exhibit variable shapes, fruit ford 1975, Crawford and Julian 1976, Craw- wall, and seed coat reticulation; these charac- ford and Wilson 1979, La Duke and Crawford ters may all be observed with a field lens at 1979, Reynolds and Crawford 1980), has gone 203 but preferably with a microscope, with no into trying to conclusively distinguish what further preparation required. The seed is have been called the ‘‘narrow-leaved’’ Cheno- always horizontal, with very few exceptions, podium taxa, mainly present in this region. and varies across taxa in a number of Even authors of recent phylogenetic molecular additional features, including size (diameter), studies (Fuentes-Bazan et al. 2012a) concluded outline shape in face view (oval to round), that more morphological studies of Chenopo- level of compression as seen in side view (from dium are needed to better resolve its taxono- flat to globose), three-dimensional shape of my. The detailed study of fruits and seeds the basal face (adjacent to the attachment of could open new avenues for more accurate the hilum) and of the upper face (apical or circumscription of taxa. stylar, frequently evident as the sepals open), In this study, we describe a set of fruit and sculpturing of the seed coat and degree of seed morphological characters that are stable shine, and the presence, shape, and thickness and can be observed at relatively low magni- of a marked equatorial margin. fication in order to obtain more reliable The fruit wall (pericarp) is also variable and, identifications. We employ a subset of these in many taxa, among the most informative of characters in delimiting Chenopodium desicca- all characters. Fruit wall attachment to the tum, which is one of the most misidentified seed varies in that it may be (1) fully adherent, taxa in North America and is among the if it can only be removed forcefully or not at ‘‘narrow-leaved’’ Chenopodium of the western all, (2) semi-adherent, if it remains mostly United States, a loose group in which many attached to the seed but partially falls off in species remain mired in confusion. We assess big pieces or is relatively free at the upper and confirm the usefulness of fruit and seed (stylar) or basal (funicular) region, or (3) free, characters to improve the taxonomy of this if it falls completely off the seed coat when group, and also present the discovery of a new rubbed with fingers or touched with forceps. species, identified and circumscribed using The pericarp may also vary in thickness, seed morphological features. dryness, hardness, sculpturing (ranging from somewhat smooth to highly reticulate), tex- Materials and Methods. We observed and ture, color, and color patterning. Usually, the sampled numerous specimens from herbaria at fruit wall texture is variously papillate, but ASU, CAS-DS, CDA, CHSC, GH, JEPS, these papillae dry and collapse, remaining as a MO, NY, OBI, PAC, RM, RSA-POM, SD, membranous or a dry pericarp if not adherent SDSU, TEX, UC, UNM and US (Holmgren or as a series of pits or reticulations that take and Holmgren 1998, onwards), including type many forms and levels of breakdown if it specimens. In addition to making observa- remains attached to the seed. tions of vegetative features, we photographed Taxonomic treatments of the genus Cheno- fruits and seeds of many specimens at high podium in North America (including Watson magnification and resolution using a Vision- 1874, Nelson 1902, Rydberg 1912, 1917, ary Digital BK Plus photomicroscope and Standley 1916, Aellen 1929, Aellen and Just prepared composite images with Helicon 1943, Wahl 1954, Bassett and Crompton 1982, Focus. All specimens were conventionally Mosyakin and Clemants 1996, Clemants and photographed and, when possible, images of Mosyakin 2003) and phylogenetic studies of sampled herbarium specimens were digitized the Chenopodiaceae (Kadereit et al. 2003, on an inverted, flat-bed scanner in order to Kadereit et al. 2010, Fuentes-Bazan 2012a, b) have good reference images. The identity of have greatly added to our knowledge of the herbarium specimens was assessed employing classification of the group; however, enhanced original taxon descriptions, past floristic taxonomic precision is still needed for many treatments (cited below), and the key of the species in the western United States, an area Flora of North America treatment of Cheno- rich in Chenopodium taxa. An enormous podium s.l. (Clemants and Mosyakin 2003). amount of work, including numerical, mor- We used inflorescence and other vegetative phological, flavonoid chemistry, and other characters to confirm or help with conclusive 2014] BENET-PIERCE AND SIMPSON: TAXONOMY OF CHENOPODIUM 163 identification, but always in conjunction with original description, many Chenopodium spec- seed and fruit characters, as the latter are imens of similar habit have been identified as proving more reliable. this species; however, fruit and seed morphol- We studied the primary literature in order to ogy does not always support this determina- elucidate the delimitation of ambiguous Che- tion. Several issues, we believe, contributed to nopodium taxa. In addition, we collected C. desiccatum being immersed in taxonomic original material from localities in western confusion since its inception.