Desmodium arechavaletae Burkart, Darwiniana, Spec. Nov.
Creators: name: Lima, Laura Cristina Pires
name: Queiroz, Luciano Paganucci De
name: Tozzi, Ana Maria Goulart De Azevedo
name: Lewis, Gwilym Peter
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Fabales
Fabaceae
Desmodium
Desmodium arechavaletae

description: 4. Desmodium arechavaletae Burkart, Darwiniana 3(2): 216. 1939. Desmodium ramosissimum Arechav., Flora Uruguaia 1, Anales Mus. Nac. Montevideo 3: 362. 1901, nom. illeg., non Don, 1832. Meibomia ramosissima (Arechav.) Schindl., Repert. Spec. Nov. Regni Veg. 20: 149. 1924. Type:— URUGUAY. Tacuarembó: Tacuarembó, Gruta de los Cuervos, December 1898, J. Arechavaleta s.n (holotype MVM1124*!). Fig. 6.   
 Desmodium asperum f. longipetiolata Chodat & Hassl., Bull. Herb. Boissier, sér. 2, 4(9): 889. 1904. Lectotype (designated here):— PARAGUAY. Amambay: Bella Vista, February, E. Hassler 8254 (lectotype G0070275![3 sheets], isolectotypes BM!, NY!). Remaining syntype: Paraguay. Amambay: Bella Vista, February, E. Hassler 8507 (G!).   
 Desmodium asperum f. lanata Chodat & Hassl., Bull. Herb. Boissier, sér. 2, 4(9): 889. 1904. Lectotype (designated here):— PARAGUAY. San Pedro: flumen Capibary, Dec, E. Hassler 5911 (lectotype G00070273!, isolectotypes BM!, G![3 sheets], K![2 sheets], NY!, P![4 sheets], W!).   
Erect, slightly branched subshrub, 0.5–2.5 m tall, with a xylopodium; stems not virgate, slender, cylindrical, striate, sparsely puberulous-uncinate, not glaucous; internodes 1.1–1.7 cmlong. Stipules 6.4–15 × 0.5–2 mm, narrowly triangular, not auriculate, not amplexicaul, inserted perpendicularly at the base of the leaf petiole, free from each other, apex caudate, margin ciliate, glabrescent or glabrous, veins slightly conspicuous, caducous. Leaves unifoliolate; petiole 5–6 mm long, cylindrical, sulcate, sparsely puberulous-uncinate; stipels 9–11 mm long, subulate, margin straight, sparsely uncinate or sericeous on the outer surface, persistent; leaflets discolorous, coriaceous, venation brochidodromous, primary, secondary and tertiary veins prominent on the abaxial surface, indumentum densely velutinous on the primary and secondary veins, tomentose on the tertiary veins on the abaxial surface, adaxial surface puberulous, uncinate hairs covering both surfaces, terminal leaflet 9.5–12 × 4.5–6.5 cm, ovate, base obtuse, apex obtuse or subacute. Inflorescence a terminal paniculate; the main axis longer than the adjacent leaves, 25–30 cm long, densely puberulous-uncinate, 2 flowers per node; primary bract 2–3 mm long, ovate, margin straight, puberulous-uncinate on the outer surface, caducous, veins conspicuous on the outer surface; secondary bract ca. 1.5 mm long, narrowly triangular, margin straight, sericeous on the outer surface, caducous, veins inconspicuous on the outer surface; pedicel 2 mm long, sparsely puberulous-uncinate. Flowers 5–7 mm long; calyx bilabiate, tube campanulate, 1–1.5 mm long, puberulous-uncinate and hirsute on the outer surface; upper lip bifid, slightly fused, the 2 teeth joined for ca. ¾ of their length, acute, ca. 0.2 mm long; lower lip trifid, lateral tooth lanceolate, 1.5–2.2 mm long, central tooth triangular, 2.2–2.5 mm long; corolla purple, standard 5–6 × 4–5 mm, obovate, apex obtuse or retuse, maculate at the base, claw 1–1.5 mm long; wing petals 5–6 × 1.5–2 mm, oblong, apex obtuse, without callosities, claw 0.8–1 mm long; keel petals 6–6.5 × 1–2 mm, narrowly obovate, apex obtuse or subacute, with callosities, claw 2–3 mm long; androecium monadelphous, 5–7 mm long, vexillary stamen partially fused with the other from the base 2.5–3.5 mm long; ovary 3–4 mm long, sparsely tomentose na margin, stipe 0.8–1.3 mm long, glabrescent. Loment 1.5–2 cm long, stipe 2–3 mm long, sericeous, isthmus marginal, upper suture straight, lower suture sinuate; articles uniform 2–4, 4–5 × 2–3 mm, elliptic, not tortuous, indehiscent, membranaceous, veins insconspicuous, sparsely puberulous-uncinate. Seed ca. 3.5 × 2 mm, ovate, hilum subcentral.  
 DESMODIUM (LEGUMINOSAE, PAPILIONOIDEAE) IN BRAZIL   
 Phytotaxa 169 (1) © 2014 Magnolia Press • 25 26 • Phytotaxa 169 (1) © 2014 Magnolia Press   
 LIMA ET AL.   
 Selected specimens examined:— BRAZIL. Mato Grosso do Sul: Ponta Porã: ca. 22 km Ponta Porã, Caminho para Bela Vista, 5 December 1970, fl., A . Krapovickas et al. 14072 (CTES). Paraná: Ponta Grossa: PR-151, 3 km após saída de Ponta Grossa em direção a Castro, 12 December 1998, fl., S . T. S. Miotto 1659 (ICN). Rio Grande do Sul: Manoel Viana: ca. 1,3 km do entroncamento de acesso secundário da RS-377 e a fazenda Berleze (ex Esquina do Silva), 10 December 2008, fl., fr., L . C. P. Lima et al. 465 (HUEFS). São Paulo: Itapetininga: ca. 4 km de Itapetinga, 21 January 1960, fl., fr., S . M. de Campos 161 (G, RB, SP).   
 Distribution and Ecology:— Uruguay, Paraguay, Argentina, Bolivia and Brazil (Chodat & Hassler 1904, Izaguirre & Beyhaut 1998, Vanni 2001, Lima et al. 2010). In Brazil the species has been collected in subtropical regions of the States of Mato Grosso do Sul, Paraná, Rio Grande do Sul, and São Paulo. It grows in stony fields.   
 Conservation Assessment:— LC (Least Concern), not endangered (IUCN 2001).   
 Phenology:— flowering and fruiting from November to February.   
 Etymology:— chosen by Burkart in honor of José Arechavaleta, who greatly contributed to the Flora of Uruguay.   
 Common Name:— pega-pega.   
 Taxonomic notes:— ovate or long-elliptic, unifoliolate leaves, flowers to about 7 mm long, and membranaceous fruits help to distinguish Desmodium arechavaletae. The asperous, coriaceous, ovate or longelliptic unifoliolate leaves and paniculate inflorescences make D. arechavaletae morphologically similar to D. guaraniticum. However, the purple flowers to about 7 mm long (vs. lilac or rose coloured flowers more than 8 mm long in D. guaraniticum) and elliptic, membranaceous articles (vs. orbicular, coriaceous articles in D. guaraniticum) help to differentiate the two species.   
 Chodat & Hassler (1904) described Desmodium asperum f. longipetiolata Chodat & Hassl. and D. asperum f. lanata Chodat & Hassl. as forms of D. asperum (currently D. distortum). However, these forms were synonymised by Schindler (1928) under Meibomia ramosissima, a name associated with Desmodium arechavaletae as confirmed in this study.
description: Published as part of Lima, Laura Cristina Pires, Queiroz, Luciano Paganucci De, Tozzi, Ana Maria Goulart De Azevedo & Lewis, Gwilym Peter, 2014, A Taxonomic Revision of Desmodium (Leguminosae, Papilionoideae) in Brazil, pp. 1-119 in Phytotaxa 169 (1) on pages 25-27, DOI: 10.11646/phytotaxa.169.1.1, http://zenodo.org/record/10089817