Desmodium burkartii L.C.P.Lima & Vanni, 2012

Lima, Laura C. P., Vanni, Ricardo O., De Queiroz, Luciano P. & Tozzi, Ana M. G. A., 2012, An overlooked new species of Desmodium (Fabaceae, Papilionoideae) from Argentina, Phytotaxa 40, pp. 55-59 : 56-57

Desmodium burkartii L.C.P.Lima & Vanni , sp. nov., Fig. 1

Haec species D. riedelii accedit , sed foliolo elliptico-lanceolato (nec lanceolato aut oblongo), petiolo 8–11 mm longo (non 2–3 mm longus), pedicello 7–9 mm longo (non 2–4 mm longo) et lomento oblongo 2–6 articulato (nec reniformi 1–2 articulato) praecipue differt.

Type:— ARGENTINA. Corrientes: Arroyo Riachuelo, Ruta 12, Km 17, 2 December 2008, fl., fr., L.C. P. Lima & R. Vanni 444 (holotype HUEFS, isotypes CTES, K, NY, UEC)

Subshrubs with xylopodium; stem decumbent or erect, cylindrical, striate, glabrescent or puberulousuncinate; internodes 2.6 – 5.3 cm long; stipule 3 – 4 × 2 mm, ovate, apex caudate, margin entire, glabrescent, caducous, free from each other. Leaves trifoliolate; petiole (5 –) 8 – 11 mm long, striate, puberulous-uncinate; stipels 2 – 3mm long, linear, apex acute, margin entire, glabrescent, persistent; petiolule 1 – 2 mm long, puberulous-uncinate; leaflets elliptic-lanceolate, base rounded, apex mucronate, glabrescent or puberulousuncinate on both surfaces, secondary venation brochidodromous, secondary and tertiary veins conspicuous on the adaxial surface, uncinate around the main vein on the abaxial surface, terminal leaflet 2.8 – 5.0 × 0.5 – 1.2 cm, lateral leaflets 2.1 – 4.1 × 0.6 – 0.8 cm. Inflorescence a laxly flowered terminal pseudoraceme, 18.2 – 33.0 cm long, puberulous-uncinate, 2 – 3 flowers per node; primary bracts 3 – 4 × 1 mm, ovate-lanceolate, tomentose, striate, 5 veined, caducous; secondary bracts ca. 3.0 × 0.5 mm, narrowly-lanceolate, tomentose, striate, 1 – 2 veined, caducous; pedicel 7 – 9 mm long, tomentose-uncinate. Flowers ca. 10 mm long.; calyx bilabiate, tube campanulate, 2.0 – 2.5 mm long, outer surface tomentose; upper lip almost entire, ca. 1mm long, apex sub-acute; lower lip trifid, teeth ovate-lanceolate, ca. 3mm long; petals purple, standard ca. 9.5 × 8.0 mm, obovate, apex obtuse, claw ca. 0.5 mm long, wing petals ca. 9 × 4 mm, obovate, apex obtuse, claw ca. 1 mm long, keel petals 7 – 8 × 3 mm, narrowly-obovate, apex obtuse, claw ca. 4mm long; androecium pseudomonadelphous, ca. 10mm long; ovary ca. 8mm long, puberulous-tomentose. Loment 2.7 – 6.2 cm long, stipitate, stipite 2 – 3 mm long, isthmi excentric, articles 2 – 6, 11 – 15 × 7 – 9 mm, oblong, reticulate, puberulousuncinate. Seeds ca. 3.2 × 2.5 mm, broadly oblong, brown.

Distribution and habitat:— Desmodium burkartii occurs in the Province of Corrientes, northeastern Argentina, in grasslands with palms ( Butia spp. ) on sandy soil.

Phenology:—Flowering and fruiting specimens were recorded from November to February.

Conservation assessment:—According to the IUCN (2001) conservation criteria Desmodium burkartii can be considered as Critically Endangered (CR). It has a restricted distribution, occurring only on sandstone in grassland of northeastern Argentina, near the Riachuelo River.

Etymology:—It is named in honor of Arturo Burkart, who left an impressive contribution to legume systematics in Argentina.

Additional specimens examined (paratypes):— ARGENTINA. Corrientes: Arroyo Riachuelo, y Ruta 12, 5 December 1976, fl., fr., C.Quarín 3513 (CTES, G). Conceição, Estância Santa Rosalia, 4 January 1955, fl., fr., T.M.Pedersen 3107 (BR, CTES, P, SI, US); Riachuelo, 3 November 1986, fl., fr., A.Charpin & U.Eskuche 2070 (G [2 sheets]); 12 October 1967, fl., fr., A.Krapovickas & C.L.Cristóbal 13560 (MBM); 10 January 1976, fl., A.Schinini & O.Ahumada 12389 (CTES, G [2 sheets]); 25 November 1978, fl., fr., M.S.Ferruci et al. 80 (CTES, K); without date, fl., R.M.Crovetto & A.Schinini 10240 (G); 17 December 1981, fl., fr., R. Vanni et al. 158 (CTES, G); 27 February 1985, fl., fr., R. Vanni 457 (CTES);

The combination of the leaflets elliptic-lanceolate, flowers ca. 10 mm long and stipitate loment with 2 – 6 oblong articles allows easily distinguishing Desmodium burkartii from other Argentinean species. Although D. burkartii was treated as D. riedelii for more than 70 years ( Burkart 1939, Vanni 2001), these species are not particularly alike except for the terminal pseudoracemose inflorescence, as can be seen in the comparison presented in the Table 1 . Among the species of Desmodium in Argentina, D. burkartii is most similar to D. glabrum (Mill.) Hitchc. They share the same large loment with ca. 7 – 9 mm wide, but D. burkartii differs by presenting leaflets elliptic-lanceolate (× rhomboid in D. glabrum ), flowers ca. 10 mm long (× ca. 3mm long), loments with 2 – 6 oblong-articles (× 2 – 4 reniform or rhomboid articles).

Figures

FIGURE 1. Desmodium burkartii. A. Habit. B. Leaflet. C. Detail of the lower surface of the leaflet highlighting indumentum and venation. D. Primary (left) and secondary bracts (right). E. Flower. F. Calyx opened out. G. Standard petal. H. Wing petal. I. Keel petal. J. Fruit. K. Seed (all from C.Quarín 3513, paratype). Drawn by R.Pinto.