Stemodia diplohyptoides Sosa & Dematteis, 2014

Sosa, María De Las Mercedes & Dematteis, Massimiliano, 2014, Stemodia diplohyptoides (Plantaginaceae, Gratiolae): a new diploid species from South America, Phytotaxa 186 (5), pp. 271-278 : 272-275

Stemodia diplohyptoides Sosa & Dematteis , spec. nov. Figs. 1 , 3 , 4 .

Stemodia hyptoides affinis sed numero chromosomatico diploideo, 2n=22 (non tetraploideo, 2n=44), foliis obovatis, 23–65 x 8–35 mm (non oblanceolatis, 40—90 x 10–45 mm), caulibus minoribus, corolla 8–10 mm longa (non 7.5 mm) differt.

Type:— ARGENTINA. Misiones: Parque Nacional Iguazú , 14 December 2004; M. M. Sosa, R. O. Vanni & M. G. López 123 (holotype CTES, isotype MICH, CANB) .

Perennial herbs, procumbent with ascending stems, 50–180 cm high. Stem 4-ribbed, 1.5–4 mm diameter at base, several axillary branches, basal internodes 14–45 mm long, with glandular and eglandular trichomes. Leaves opposite, narrowly elliptical, 20–60 x 8–35 mm, sessile, attenuate at base, basally clasping to auriculate, margin serrate, barely pubescent. Flowers arranged in bi-bracteate spiciform inflorescence, shortly pedicellate, pedicels 1 mm long, bracteole 5 mm. Sepals 5 all alike, 5 to 6 mm long, linear-lanceolate, glandular-pubescent. Corolla tubular of 8–10 mm long, inferior lip trilobate, pubescent in the throat with long hairs within, superior lip emarginate. Stamens 4, with short filaments (1.2–2 mm), and 2 long (4 mm); anthers separated by enlarged connective. Ovary ovoid, style straight, 4 mm, stigma laterally broadened. Capsule ovoid, 3–4 mm, 4-valvate. Seeds oblong-ovoid to ellipsoid with rounded margins, 340 x 150 µm, dark brown; exotesta reticulate with cells generally isodiametrical, hexagonal, anticlinal and periclinals walls straight, raised and thickened, with protuberances in the angles; secondary sculpture (fine relief of the cell wall) of micro-papillae (= “verrucose”). Ovules 98–133 µm long, stomata anomocytic of ± 30 µm long and with anticlinal walls of the upper epidermis of the leaf sinuate. 2n=22.

Distribution and ecology:— Stemodia diplohyptoides has been found in the northeastern extreme of Argentina, specifically in the north and center of Misiones province ( Fig. 2 ). This species grows in marginal vegetation of Parana River, on sandbar next to the river, near streams, with modified soils. Following field observations, we hypothesize that S. diplohyptoides is adapted to ecological conditions that are different from the typical habitat of the other members of Stemodia , which prefer humid soils. Some specimens grow over rocky soils with permanent water, such as the terrace of the San Martin Island that receives water from the Iguazú falls. Other specimens were collected on rocky basalt and were found to have horizontal stems and rootlets at the nodes. We interpret the development of adventitious roots as adaptations to a soil poor in nutrients exposed to for leaching.

Phenology: —flowering August to December.

Additional specimens examined: ARGENTINA. Prov. Misiones, Eldorado, Pto. Eldorado, 17 October 1977, Cabrera et al. 28805 (CTES; SI); 8 September 1985, Múlgura et al. 496 (BAB); Eldorado, Puerto Eldorado, 11 October 1999, Keller 79 (CTES); 1 Km al S del puerto, 20 November 2003, Sosa & Keller 121 (CTES); Sosa & Keller 124 (CTES); 11 April 2006, Sosa & Rodriguez 248 (CTES); Parque Schwelm, Balcón de las Guayabas, 26 March 2006, Sosa & Rodriguez 247 (CTES); Iguazú, P. N. Iguazú, en cantera vieja, 14 February 2004, Sosa et al. 131 (CTES), Isla San Martín, 8 August 1991, Vanni et al. 2827 (CTES); 31 March 1995, Vanni et al. 3372 (CTES); 14 February 2004, Sosa et al. 133; 8 April 2008, Múlgura de Romero et al. 4429 (CTES, SI); San Martín, Puerto Rico, 12 April 2006, Sosa & Rodríguez 251 (CTES); Montecarlo, Puerto Piray, 12 April 2006, Sosa & Rodríguez 249 (CTES); 13 November 1996, Vanni et al. 3832 (CTES); Puerto Montecarlo, 17 August 1997, Vanni et al. 4067 (CTES); 12 April 2006, Sosa & Rodríguez 250 (CTES).

Figures

FIGURE 1. Stemodia diplohyptoides.A. Habit. B. Stem detail. C Detail of a stem. D. Flower. E. Corolla (inner view). F. Long stamen. G. Short stamen. H. Detail of ovary. I. Node with fruits. J. Fruit. K. Detail of sepal. L. Detail of fruit (A-L: Sosa et al. 123 CTES, illustrated by Mirtha Gómez).

FIGURE 2. Geographic distribution of Stemodia diplohyptoides (stars), S. stricta (circles) and S. hyptoides (squares) in southern South America.

FIGURE 3. Seed morphology observations under SEM of Stemodia. A, B. Seed and detail of ornamentation on the seed surface of S. diplohyptoides. C, D. Seed and detail of ornamentation on the seed surface of S. hyptoides. (A-B: Sosa & Keller 121 CTES; C-D, Sosa 134 CTES).

FIGURE 4. Mitotic chromosomes in species of Stemodia. A. S. diplohyptoides, 2n=2x=22. B. S. hyptoides, 2n=4x=44. Bar= 2 μm. (A, Sosa et al. 123 CTES; B, Sosa 272 CTES).