Microstachys nana M.J.Silva & Esser, 2011

Silva, Marcos José Da & Esser, Hans-Joachim, 2011, Two new taxa and two new combinations in Microstachys (Euphorbiaceae) from South America, Phytotaxa 32, pp. 18-26 : 20

Microstachys nana M.J.Silva & Esser , sp. nov. ( Fig. 1 )

Microstachyde glandulosa similis sed habitu diminuto atque caespitoso, ramulis puberulis, floribus pistillatis distincte pedicellatis et stylis elongatis basaliter connatis distinguenda.

Typus:— BRAZIL. Paraná: Município de Porto Amazonas, localidade de Caiacanga, 13 October 1963 (fl, fr), G . Hatschbach 10280 (holotype B!, isotypes MBM!, UEC!) .

Herb 6–13 cm tall, branched at the base into up to five shoots; root system well developed with a main root up to 11 cm long. Branches cylindrical to angulate, glabrous to glabrescent. Trichomes simple, multicellular, adpressed, ca. 1 mm long. Leaves alternate; stipules 0.7–0.9 mm long, persistent; petiole 1.3–1.9 mm long, glabrescent; blade elliptic to rarely oblong-elliptic, 1.6–2.8 × 0.8–1.2 cm, membranaceous, base obtuse and usually truncate, margin thickened and irregularly crenate, apex rounded, uniform in colour and glabrous on both sides, with up to 3 submarginal circular glands, 0.3 mm in diameter in each basal section of the lower surface on each side of the midvein, penninerved, brochidodromous, with 4–5 pairs of indistinct secondary veins. Inflorescences terminal or leaf-opposed, erect, 5.5–6 cm long when adult, glabrous, with up to 2 pistillate flowers at the base and up to 26 staminate cymules apically, the pistillate flowers often separated and inserted at nodes below the staminate part; axis compressed-angulate, glabrous; pistillate bracts 0.9–1.0 mm long, staminate bracts 0.7–0.8 mm long, both broadly ovate with an irregularly dentate-lacerate margin, obtuse apex, and a pair of basal glands. Pistillate flowers: pedicel 1.3–1.4 mm long; sepals 1.0–1.1 × 0.8–0.9 mm, broadly ovate, the margin shallowly and irregularly lacerate-dentate; ovary 1.0– 1.1 mm long, with 6 appendages on each mericarp; stigmas 2.2–2.5 mm long, erect and united at base for ca. 0.5 mm. Staminate cymules with 1 (rarely 2) flowers, staminate flowers subsessile, glabrous; sepals 1.0–1.1 × 0.8–0.9 mm, obovate-spatulate, with a distinct central vein, the margin discretely dentate apically; stamens completely free with filaments up to 0.6 mm long, anthers 0.3–0.4 mm long. Fruits (immature) 2.6–3 mm long, glabrous, with 6 erect appendages on each mericarp. Seeds not seen.

Distribution and ecology:— Microstachys nana hitherto has only been found in the Brazilian state of Paraná, municipios Caiacanga and Serrinha, in campo limpo vegetation, and is most probably endemic there. Flowering and fruiting in October.

Etymology:—The specific epithet refers to the diminuitive aspect of the plant.

Conservation Status:—This species is known only from two collections, both collected on campo limpo that are continuously being substituted by agricultural lands. Therefore the species is classified here as vulnerable according to the IUCN categories ( IUCN 2001).

Relationships:— Microstachys nana can be recognized and characterized by its size (to 13 cm tall) small even within this genus, the leaves with thickened and irregularly crenate margins, distinctly pedicellate pistillate flowers (pedicel 1.3–1.4 mm long), and stigmas 2.2 to 2.5 mm long. Morphologically it resembles Microstachys glandulosa in several characters related to the leaf (shape, base, apex and absence of hairs), shape of glands, and the glabrous ovary. However, M. nana is a herb with glabrous to glabrescent branches, adpressed trichomes, completely free stamens, pedicellate pistillate flowers, ovaries with well-developed and erect appendages, and inflorescences 5.5–6 cm long with spaced flowers. Microstachys glandulosa is a subshrub to shrub (up to 1 m tall), has branches with short uncinate-filiform trichomes, stamens with filaments very slightly united at base, sessile pistillate flowers, ovaries with small and curved appendages, and inflorescences 0.9–4 cm long with more condensed flowers.

Paratype:— BRAZIL. Paraná, Serrinha in campis, 24 October 1908 (fl, fr), P . Dusén 6960 ( K!) .

Figures

FIGURE 1. Microstachys nana. A. Habit. B. Lower side of leaf base with a pair of glands. Ba. Detail of leaf margin. C. Detail of inflorescence, staminate part. D. Staminate flower. E. Sepal of staminate flower. F. Bract of staminate cymule. G. Pistillate flower. H. Sepal of pistillate flower. I. Bract of pistillate flower. J. Fruit. (G. Hatschbach 10280).