New Combinations in North American Desmodium (Leguminosae: Tribe Desmodieae)

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1 J. Jpn. Bot. 88: (2013) New Combinations in North American Desmodium (Leguminosae: Tribe Desmodieae) Hiroyoshi Ohashi Herbarium, Botanical Garden, Tohoku University, Sendai, JAPAN (Accepted on May 11, 2013) Three species groups in Desmodium of North America: D. ciliare group, D. paniculatum group and D. procumbens group are revised for Flora of North America. Each of them is treated as a single species containing one or two varieties. The following four new combinations are published: D. marilandicum var. ciliare (Willd.) H. Ohashi, D. marilandicum var. lancifolium (Fernald & B. G. Schub.) H. Ohashi, D. paniculatum var. fernaldii (B. G. Schub.) H. Ohashi, and D. procumbens var. neomexicanum (A. Gray) H. Ohashi. Desmodium obtusum (Willd.) DC. is regarded to be a synonym of D. marilandicum var. lancifolium; D. glabellum (Michx.) DC. and D. perplexum B.G. Schub. to be synonyms of D. paniculatum; and D. procumbens var. exiguum (A. Gray) B. G. Schub. to be a synonym of D. procumbens var. procumbens. Key words: Desmodium, Fabaceae, Leguminosae, new combinations, North America. Recently, Desmodium of North America has been the subject of much study, notably by Schubert (1940, 1950a, 1950b, 1970) and Isely (1983, 1990, 1998). Desmodium traditionally is considered a difficult genus (Isely 1990, p. 163). Isely (1990) further stated that Desmodium contains groups of species whose taxonomy is presently ambiguous or among which the differentiation of kinds is unsatisfactory or overlapping. In such cases, confidently keying a plant to a name is often difficult. Thus, I have borrowed a device from Flora Europaea (Tutin et al. 1968, p. xv): Where it is difficult to distinguish between a number of closely similar species in a genus, an ad hoc group has been made, and these groups... are keyed out in the main species key.... For example, if the identity of a specimen in the Desmodium paniculatum (L.) DC. group is uncertain, one can at least identify it with the group. Under this framework, Isely recognized D. ciliare (Willd.) DC., D. paniculatum (L.) DC. and D. procumbens (Mill.) Hitchc., along with each of their related taxa, as species groups. The difficulty in classifying these groups is, however, not satisfactorily solved by this approach. Taxa attributed to these groups appear to have been recognized by over-weighting such variable characters as type and degree of density of indumentum on the stems and leaves and by the size and shapes of the leaves. The problems in the North American species groups are similar to those in the Asian species of Desmodium. For example, Desmodium heterocarpon (L.) DC. includes many synonyms that were initially distinguished by over-emphasizing superficially discontinuous characters (Ohashi 1973, 1991). To correctly distinguish natural taxa, further 166

2 June 2013 The Journal of Japanese Botany Vol. 88 No analyses of morphological characters and genetic features of the groups are necessary. Until that time when such detailed studies can be carried out, I have decided to regard each of the groups as single species, D. paniculatum, D. marilandicum, and D. procumbens, in my treatment of Desmodium for the Flora of North America. Their so-called related species are treated as synonymous or as varieties of the recognized species. 1. The Desmodium ciliare Group Plants described in this group as separate species are characterized by having similar 2 or 3 segmented loments. They include Desmodium ciliare (Willd.) DC., D. marilandicum (L.) DC., and D. obtusum (Willd.) DC. with D. ciliare D. marilandicum and D. ciliare D. obtusum (Isely 1990, 1998). Isely (1998), Krings (2004), and Raveill (2006), each presented keys to the D. ciliare group, all based on vegetative characters, of which Isely s is as follows: 1. Leaflets times as long as wide D. ciliare? 1. Leaflets times as long as wide Terminal leaflet generally distinctly longer and narrower than others; medial stems sparsely to densely uncinate-pubescent D. obtusum 2. Terminal leaflet similar to lateral ones; medial stems glabrous to pilose or also with uncinate pubescence. 3. Stems glabrous(-sparsely uncinatepuberulent); petioles cm long; leaflets glabrous or with a few hairs; pedicels filiform, generally cm long D. marilandicum 3. Stems generally pilose; petioles and pedicels shorter than above or plants lacking the above combination of characters Stems conspicuously or thinly pilose(- uncinate-puberulent); petioles 1 3 mm long, shorter than rachis; leaves subappressedpubescent(-glabrate); pedicels 3 8 mm long, commonly stout... D. ciliare 4. Stems and leaves with various combinations of characters of D. ciliare and D. marilandicum, e.g., stems and leaflets glabrate but petioles 1 3 mm long or stems pilose but petioles well developed; pedicels various in length D. ciliare D. marilandicum Isely (1998) noted, however, that many populations of Desmodium ciliare are of, or include, plants with various features of D. marilandicum (p. 538). Some plants of D. marilandicum throughout its range exhibit various combinations of the characters of D. marilandicum and D. ciliare and are relegated to postulated D. ciliare D. marilandicum category (p. 546). This presumed hybrid includes (1) plants with the aspect of D. ciliare, but which are glabrate or have some pubescence; (2) those with the aspect of D. ciliare, including pubescence, but leaves well petioled; and (3) those with the aspect of D. marilandicum but somewhat pilose (p. 558). Desmodium ciliare D. obtusum is presumed to be plants with foliage intermediate between Desmodium ciliare and D. obtusum and with a mixture of uncinate and pilose pubescence (p. 558). Isely s (1998) comments indicate that D. ciliare, D. marilandicum and D. obtusum are indistinguishable without recognizing the intermediate forms between them as presumed hybrids. No evidence of hybrid origin of these intermediate forms was presented. I recognize this group as a single polymorphic species, D. marilandicum, with three varieties, although the distinction between the vaieties is sometimes ambiguous. A key to the varieties is as follows: 1. Terminal leaflet elliptic-ovate to narrowly ovate, cm, apex acute to obtuse... var. lancifolium 1. Terminal leaflet elliptic, ovate, ovate-rhombic or broadly ovate, cm, apex obtuse Leaves nearly sessile, petioles 1 15 mm

3 168 植物研究雑誌第 88 巻第 3 号 2013 年 6 月 Fig. 1. Holotype of Desmodium ciliare var. lancifolium Fernald & B. G. Schub. (GH).

4 June 2013 The Journal of Japanese Botany Vol. 88 No long; stems and petioles uncinate-puberulent and mostly pilose; pedicels 3 8 mm long var. ciliare 2. Leaves petiolate, petioles mm long; stems essentially glabrous, petioles sparsely uncinate-puberulent; pedicels (6 )8 19 mm long... var. marilandicum Desmodium marilandicum (L.) DC., Prodr. 2: 328 (1825); Schub. in Gray s Man. ed. 8: 920 (1950); Schub. in Man. Vasc. Pl. Texas: 864 (1970); Isely, Vasc. Fl. SE US 3(2): 175 (1990); Isely, Native Natur. Leg. US: 546 (1998); Krings in Vulpia 3: 145, fig. 8 (2004); Raveill in Vulpia 5: 20 (2006). Hedysarum marilandicum L., Sp. Pl. 2: 748 (1753). Meibomia marilandica (L.) Kuntze, Revis. Gen. Pl. 1: 198 (1891). var. marilandicum Stems essentially glabrous. Leaves mostly petiolate; petioles sparsely uncinate-puberulent, mm long; terminal leaflet ovate, ovaterhombic or suborbicular, ( 4) cm, apex obtuse. Pedicels (6 )8 19 mm long. D. marilandicum var. ciliare (Willd.) H. Ohashi, comb. nov. Hedysarum ciliare Willd., Sp. Pl. 3(2): 1196 (1802). Desmodium ciliare (Willd.) DC., Prodr. 2: 329 (1825); Isely, Native Natur. Leg. US: 538 (1998); Krings in Vulpia 3: 145, fig. 6 (2004). Meibomia ciliaris (Willd.) S. F. Blake in Bot. Gaz. 78: 275 (1924). M. ciliaris var. acutifoliola Schindl. in Repert. Spec. Nov. Regni Veg. 23: 357 (1927). M. ciliaris var. albiflora Schindl. in Repert. Spec. Nov. Regni Veg. 23: 357 (1927). Stems uncinate-puberulent and patent longpilose. Leaves nearly sessile, petioles uncinatepuberulent and patent long-pilose, 1 15 mm long; terminal leaflet elliptic, ovate or ovaterhombic, cm, apex obtuse. Pedicels 3 8 mm long. D. marilandicum var. lancifolium (Fernald & B. G. Schub.) H. Ohashi, comb. nov. D. ciliare var. lancifolium Fernald & B. G. Schub., Rhodora 40: 437 (1938). [Fig. 1] Hedysarum obtusum Willd., Sp. Pl. 3(2): 1190 (1802). H. rigidum Elliott, Sketch Bot. S. Carolina 2: 215 (1823). D. obtusum (Willd.) DC., Prodr. 2: 329 (1825); Isely, Native Natur. Leg. US: 547 (1998); Krings in Vulpia 3: 144, fig. 9 (2004). D. rigidum (Elliott) DC., Prodr. 2: 330 (1825). Meibomia obtusa (Willd.) Vail in Bull. Torrey Bot. Club. 19: 115 (1892); Schind. in Repert. Spec. Nov. Regni Veg. 23: 357 (1927). Meibomia rigida (Elliott) Kuntze, Revis. Gen. Pl. 1: 198 (1891). Stems and petioles sparsely to densely uncinate-puberulent. Leaves shortly petiolate; petioles sparsely to densely uncinate-puberulent, 2 20 mm long; terminal leaflet elliptic-ovate to narrowly ovate, cm, apex acute to obtuse. Pedicels 4 10 mm long. 2. The Desmodium paniculatum Group Schubert (1950a, 1950b) treated Desmodium paniculatum (L.) DC. and its related species and clarified the classification of the group by recognizing D. glabellum (Michx.) DC. and describing D. perplexum B. G. Schubert. Isely (1983) surveyed the taxonomic relations among these species in detail and recognized them as distinct within his Desmodium paniculatum group. These species are characterized by having straight loments with 3 5, angled articles. Morphologically, however, as pointed out by Isely (1990) Desmodium paniculatum fades into both D perplexum and D glabellum, and authors have interpreted the species variously. Isely (1998) considered the relationships among these species as a continuum with variation between the members of the group suggesting introgression through various hybrid combinations: D. paniculatum D. perplexum;

5 170 植物研究雑誌第 88 巻第 3 号 2013 年 6 月 Fig. 2. Holotype of Desmodium perplexum B. G. Schub. (GH). Fig. 3. Holotype of Desmodium fernaldii B. G. Schub. (GH). D. paniculatum D. glabellum; and D. glabellum D. perplexum. Krings (2004) characterized the abaxial leaf surface of the D. paniculatum group in North Carolina as follows: D. glabellum: abaxial midvein with dense, long, spreading, straight trichomes, and uncinate trichomes lacking or nearly so; D. fernaldii: abaxial midvein with dense uncinate trichomes, and scattered appressed, straight trichomes; D. paniculatum: abaxial midvein with appressed, straight trichomes of ca. 0.2 mm long; and D. perplexum: abaxial midvein with long, straight, spreading or appressed trichomes and shorter uncinate trichomes. Through the wide range of morphological variations in the D. paniculatum group, I recognize the members merely as forms of a single polymorphic species, because these species are basically uniform in flowers and fruits. I consider that D. fernaldii should be recognized as distinct from D. paniculatum, but at the rank of variety, even though they are distinguished by somewhat continuous or overlapping characteristics: 1. Abaxial leaf surface sparsely strigillose, uncinate-puberulent on veins; stems and petioles glabrous or uncinate-pubescent var. fernaldii 1. Abaxial leaf surface slightly strigose to conspicuously subappressed-villous and sometimes uncinate-pubescent; stems and petioles glabrescent to conspicuously pilose or uncinate-pubescent... var. paniculatum Desmodium paniculatum (L.) DC., Prodr. 2: 329 (1825); B. G. Schub. in Rhodora 52: 152 (1950); in Gray s Manual ed. 8: 922 (1950); Isely, Vasc. Fl. SE US 3(2): 173 (1990); Isely, Native Natur. Leg. US: 550 (1998); Krings in

6 June 2013 The Journal of Japanese Botany Vol. 88 No Vulpia 3: 144, fig. 2 (2004); Raveill in Vulpia 5: 19 (2006). Hedysarum paniculatum L., Sp. Pl. 2: 749 (1753). H. glabellum Michx., Fl. Bor. Amer. 2: 73 (1803). Desmodium glabellum (Michx.) DC., Prodr. 2: 329 (1825); Isely, Native Natur. Leg. US: 541 (1998); Krings in Vulpia 3: 146, fig. 13 (2004). D. dillenii Darl., Fl. Cestr. ed. 2: 414 (1837). Meibomia paniculata (L.) Kuntze, Revis. Gen. Pl. 1: 198 (1891). M. glabella (Michx.) Kuntze, Revis. Gen. Pl. 1: 198 (1891). D. perplexum B.G. Schub., Rhodora 52: 154 (1950); Isely, Native Natur. Leg. US: 551 (1998); Krings in Vulpia 3: 144, fig. 20 (2004). [Fig. 2] D. paniculatum var. epetiolatum B. G. Schub. in Rhodora 52: 153 (1950). D. paniculatum var. dillenii (Darl.) Isely, Amer. Midl. Naturalist 49: 927 (1953). D. dichromum Shinners, Spring Fl. Dallas- Fort Worth Area: 409 (1958). var. paniculatum D. paniculatum var. fernaldii (B. G. Schub.) H. Ohashi, comb. nov. D. fernaldii B. G. Schub. in Rhodora 52: 147 (1950); Isely, Native Natur. Leg. US: 540 (1998); Krings in Vulpia 3: 146, fig. 12 (2004). [Fig. 3] 3. The Desmodium procumbens Group Desmodium procumbens (Mill.) Hitchc. occurs from SE Arizona to Trans-Pecos Texas in the southwestern United States, southward through Mexico, Central America to the northern half of South America and in the West Indies. It is introduced and naturalized in the Philippines, Maluku (Ambon) and tropical Africa. The species is characterized by having twisted loments, which are strongly so when young. Desmodium procumbens became known in North America when Schubert (1940) newly circumscribed the species including D. exiguum A. Gray. Desmodium procumbens is divided into four varieties based on differences in the leaves; one variety is in North America north of Mexico. The North American representative of the species, regarded as var. exiguum (A. Gray) B. G. Schub., has broad, unifoliolate lower leaves and linear to narrowly ovate leaflets on the upper leaves. Isely (1998) commented on D. procumbens as follows: [Desmodium procumbens] var. exiguum, which extends north to the United States, differs from the others in the extraordinary development of the broad unifoliolate lower leaves, which contrast with the narrow leaflets of the upper stem leaves. Although D. procumbens appears well-defined in the United States, this may not be true in Mexico and southward (McVaugh 1987). McVaugh (1987) reports D. procumbens to be a variable species with respect to leaf-form and indument as well as to plant-habit. The habit of Desmodium procumbens varies locally. It is described as an erect or ascending perennial in North America (Isely 1998), or as an erect or procumbent annual (Schubert 1940, 1980; McVaugh 1987). The epithet, procumbens is derived from Hedysarum procumbens Mill. described from Jamaica. Desmodium procumbens var. exiguum was distinguished from var. procumbens by having variously shaped leaflets versus uniform leaflets in the latter (Schubert 1940), but the leaflets of var. exiguum are polymorphic, exhibiting continuous variation with those of var. procumbens. Isely (1998) grouped Desmodium procumbens with D. neomexicanum A. Gray and D. rosei B. G. Schub. in the D. procumbens group. Desmodium neomexicanum is united with D. procumbens by having twisted loments, but is recognized at the rank of variety, distinguished as follows: 1. Margin of loments not involute; articles glabrous, abaxial margin rounded...d. rosei 1. Margin of loments involute; articles

7 172 植物研究雑誌第 88 巻第 3 号 2013 年 6 月 Fig. 4. Holotype of Desmodium exiguum A. Gray (GH).

8 June 2013 The Journal of Japanese Botany Vol. 88 No Fig. 5. Holotype of Desmodium bigelovii A. Gray (GH).

9 174 植物研究雑誌第 88 巻第 3 号 2013 年 6 月 uncinate-puberulent (terminal one sometimes glabrous), abaxial margin angled or sometimes rounded at maturity D. procumbens 2. Loments distinctly spirally twisted, stipitate (stipe mm long); primary bracts mm long; leaves 1- and 3-foliolate var. procumbens 2. Loments slightly spirally twisted, subsessile or stipitate (stipe mm long); primary bracts mm long; leaves mostly 3-foliolate... var. neomexicanum Desmodium rosei B. G. Schub., Contr. Gray Herb. 129: 22, pl. 1, fig. A Desmodium procumbens (Mill.) Hitchc. in Ann. Rep. Missouri Bot. Gard. 4: 76 (1893); Schub., Contr. Gray Herb. 129: 5, pl. 1, fig. B1 7 (1940) as var. typicum; Schub. in Ann. Missouri Bot. Gard. 67: 651 (1980); McVaugh, Fl. Novo- Galic. 5: 481 (1987). Hedysarum procumbens Mill., Gard. Dict. ed. 8, Hedysarum no. 10 (1768) [Type. Jamaica. Houstoun, 1730 (BM; photo GH). fide Schubert (1980)]. D. exiguum A. Gray, Smithsonian Contr. Knowl. 5(6): 46 (1853). [Fig. 4] Meibomia exigua (A.Gray) Kuntze, Revis. Gen. Pl. 1: 198 (1891). M. procumbens (Mill.) Schind. in Repert. Spec. Nov. Regni Veg. 20: 151 (1924). D. procumbens var. exiguum (A. Gray) B. G. Schub. in Contr. Gray Herb. 129: 12, pl. 1, fig. B8 9 (1940); Schub. in Ann. Missouri Bot. Gard. 67: ; Isely, Native Natur. Leg. US: 552 (1998). var. procumbens Herbs, perennial. Stems uncinate-puberulent and sparsely pubescent. Leaves 1- and 3-foliolate, apex acute or acuminate, both surfaces uncinatepuberulent and villose. Primary bracts caducous or partly persistent, mm long. Loments distinctly spirally twisted, stipitate, stipe mm long; articles 2 3. D. procumbens var. neomexicanum (A. Gray) H. Ohashi, comb. nov. [based on autonym D. neomexicanum A. Gray var. neomexicanum (1879)]. Desmodium neomexicanum A. Gray, Smithsonian Contr. Knowl. 3(5): 53 (1852), as Neo-Mexicanum ; Schub. in Cont. Gray Herb. 129: 21, pl.1, fig. C, 1 9 (1940); McVaugh, Fl. Novo-Galic. 5: 475 (1987); Isely, Native Natur. Leg. US: 546 (1998). Desmodium bigelovii A. Gray, Smithsonian Contr. Knowl. 5(6): 47 (1853). [Fig. 5] D. neomexicanum var. bigelovii (A. Gray) S. Watson, Rep. US Geogr. Surv., Wheeler 6 (Botany): 101 (1879). Meibomia neomexicana (A. Gray) Kuntze, Revis. Gen. Pl. 1: 198 (1891). M. bigelovii (A. Gray) Kuntze, Revis. Gen. Pl. 1: 197 (1891). Herbs, annual. Stems inconspicuously uncinate-pubescent or glabrescent. Leaves mostly 3-foliolate, apex obtuse, both surfaces uncinate-puberulent. Primary bracts usually persistent, mm long. Loments slightly spirally twisted, subsessile or stipitate; stipe mm long; articles (1 )2 5. This study was mainly based on specimens of Desmodium in the Harvard University Herbaria (A, GH, NEBC), which had long been studied by Dr. Bernice G. Schubert ( ) who carefully annotated almost all of them collected in North America. I would like to thank Dr. D. E. Boufford and Ms. E. W. Wood (Harvard University Herbaria) for various help when I worked on the treatment for FNA at Harvard in 2007, 2010 and I am grateful to Drs. T. Azuma (Hokkaido University), Y. Endo (Ibaraki University), Y. Iokawa (Jyoetsu Kyoiku University), T. Kajita (Chiba University), T. Nemoto (Ishinomaki Senshu University), R. E. Spangler (Harvard University), M. Suzuki (Tohoku University), Y. Tateishi (Ryukyu University), and J. Yokoyama (Yamagata University) for their collaboration

10 June 2013 The Journal of Japanese Botany Vol. 88 No in my field work in the United States in 1995, 1996 and I thank Dr. J. Raveill (University of Central Missouri) for his help in editing the original manuscript of Desmodium for Flora of North America, which includes the new combinations proposed here. I am also grateful to Dr. Boufford for comments on the original manuscript. References Isely D The Desmodium paniculatum (L.) DC. (Fabaceae) complex revisited. Sida 10: Isely D Vascular Flora of the southeastern United States. 3(2) Leguminosae (Fabaceae). The University of North Carolina Press, Chapel Hill and London. Isely D Native and Naturalized Leguminosae (Fabaceae) of the United States exclusive of Alaska and Hawaii. Monte L. Bean Life Science Museum, Brigham Young University, Provo, Utah. Krings A Abaxial foliar vestiture of Desmodium Desv. (Fabaceae) in North Carolina and vegetative recognition of the species. Vulpia 3: Ohashi H The Asiatic Species of Desmodium and Its Allied Genera (Leguminosae). 318 pp., 76 pls. Ginkgoana 1. Academia Scientific Book, Inc., Tokyo. Ohashi H Taxonomic studies in Desmodium heterocarpon (L.) DC. (Leguminosae). J. Jap. Bot. 66: Raveill J. A Identification of Missouri species of the tribe Desmodieae (Fabaceae) using vegetative characters. Vulpia 5: Schubert B. G Desmodium: Preliminary studies-i. Contr. Gray Herb. 129: Schubert B. G. 1950a. Desmodium: Preliminary studies III. Rhodora 52: Schubert B. G. 1950b. Desmodium. In: Fernald M. L., Gray s Manual of Botany, 8th ed. pp American Book. Co., New York. Schubert B. G Desmodium. In: Correll D. S. and Johnston M. C., Manual Vasc. Pl. Texas. pp Texas Research Foundation, Renner, Texas. Schubert B. G Desmodium. In: Dwyer J. D. and collaborators. Flora of Panama, part 5, Fam. 83 Leguminosae subfam. Papilionoideae. Ann. Missouri Bot. Gard. 67(3): Woods M The genera Desmodium and Hylodesmum (Fabaceae) in Alabama. Castanea 73(1): 大橋広好 : 北アメリカ産シバハギ属 ( マメ科ヌスビトハギ連 ) の新組み合わせ Flora of North America vol. 11 のマメ科シバハギ属 Desmodium を執筆した際に Desmodium marilandicum (L.) DC., D. paniculatum (L.) DC. および D. procumbens (Mill.) Hitchc. について種の範囲を新たに設定した. これに伴って 4 個の新組み合わせを行ったので, これらを本文中で発表した. また,D. marilandicum では近縁種とされていた Desmodium obtusum (Willd.) DC., D. paniculatum では D. glabellum (Michx.) DC. と D. perplexum B. G. Schub., および D. procumbens では D. procumbens var. exiguum (A. Gray) B. G. Schub. を異名と見なした.Desmodium paniculatum (L.) DC. は北アメリカ東部に広く分布し, もっとも普通に見られる種 (Isely 1990) である. 日本でアレチヌスビトハギと呼ばれていて, 東北地方南部以西沖縄まで広く帰化していて北 海道胆振からも報告がある. 市街地で見られるもっとも普通のシバハギ属植物で, 荒れ地のありふれた雑草となっている. 小葉は多型で, 狭長卵形が典型的な形であるが, 線形から広卵形, ほぼ円形あるいは菱形までの変異が見られる. 日本に帰化している形を見ても小葉にはかなりの変異が見られる.D. marilandicum と同種と見なした Desmodium obtusum (Willd.) DC. も日本に帰化しており, 1940 年大阪府茨木市で採集され, 今日ではアメリカヌスビトハギと呼ばれている ( 日本の帰化植物 p 平凡社 ). この種は D. marilandicum の変種である var. lancifolium (Fernald & B. G. Schub.) H. Ohashi に当たると考えられる. ( 東北大学植物園津田記念館 )