Microstachys ditassoides subsp. villosa 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 : 22

Microstachys ditassoides subsp. villosa M.J.Silva & Esser , subsp. nov. ( Fig. 2 )

Microstachyde ditassoide similis sed ramis densiter villosis, laminis foliorum utrinque densiter villosis, marginibus planis et sparsim serratis distinguenda.

Typus:— BRAZIL. Piauí: Rio Preto , September 1841 (fl, fr), G . Gardner 2954 (holotype K!, isotype BM!) .

Subshrub ca. 70 cm tall, densely branched. Branches cylindrical, conspicuously villous and slightly ridged. Trichomes simple, multicellular, 1–2 mm long. Leaves spirally alternate; stipules 0.8–0.9 mm long, ovatelanceolate, acuminate, externally sericeous, persistent; petiole 4.9–5.2 mm long, subcylindrical, villous; blade ovate, chartaceous, 7.8–10 × 4.9–6 mm, base cordate, margin flat, sparsely serrate with projections directed upwards, apex acute, uniform in colour on both sides, with a pair of circular glands on the lower surface near the base, villous on both surfaces, trichomes ca. 2 mm long, more dense on the veins, venation penninerved, brochidodromous, midrib conspicuous, secondary veins 1–3 pairs, inconspicuous. Inflorescences leafopposed, erect, the main axis puberulous, the staminate part with ca. 20, spirally arranged, staminate cymules apically, and 1 pistillate flowers at the base or separated from it and then inserted at lower nodes; pistillate bracts 0.8–0.9 mm long, ovate, scarious, with two globose basal-lateral glands, margin entire, apex acute, ciliate, shortly sericeous outside; staminate bracts 0.5–0.6 mm long, broadly ovate, with two digitifom glands at base, margin entire, scarious, apex short-acuminate, glabrous outside. Pistillate flowers sessile, sepals 0.8 × 0.7 mm, broadly elliptic, margin slightly denticulate, apex obtuse to shortly acuminate, glabrous and with two basal-lateral, cylindrical and well-developed glands ovary ca. 0.7 × 0.6 mm, glabrous, with six appendages each mericarp, style ca. 0.8 mm long, cylindrical, erect, free, upward. Staminate cymules 1–2-flowered; flowers subsessile (pedicel ca. 0.1 mm long), sepals 0.7–0.8 × 0.5 mm, oblong-obovate, apex obtuse, discretely veined in centre, margin entire, glabrous; stamens with filaments up to 0.4 mm long, free, anthers 0.3 mm long. Capsules 4.2–4.5 × 2.9–3 mm, oblong, glabrous, with appendages similar to the ovary. Seeds unknown.

Distribution and ecology:— Microstachys ditassoides subsp. villosa seems to be endemic to Piauí state, where it grows in cerrado vegetation. Flowering in September.

Etymology:—The epithet refers to the villous pubescence, very characteristic in this taxon.

Conservation status:— This species is only known from its type locality, and there is no information about its current status. Due to that, its IUCN Conservation Status should be DD (Data Deficient) according to IUCN Red List criteria ( IUCN 2001) .

Relationships:— Microstachys ditassoides subsp. villosa is morphologically similar to typical M. ditassoides ( Didrichsen 1853: 88) Esser (1998: 958) . It can, however, easily be distinguished by the densely villous branches and leaves, the latter with flat margins and sparsely serrate (vs. strongly revolute and entire in M. ditassoides ), staminate sepals oblong-obovate and obtuse at the apex (vs. suborbicular and emarginate at the apex), pistillate sepals glabrous outside and with two basal-lateral, cylindrical and well-developed glands (vs. pistillate sepals pubescent, glands flattened and rudimentary). The leaves are ovate with a broadly cordate base and are villous on both surfaces, which also distinguishes subsp. villosa from typical M. ditassoides . In M. ditassoides s. str. the leaves are ovate-lanceolate or linear with the base cordate to sagittate, glabrous on both surfaces or tomentose on the lower surface only. Microstachys ditassoides can be recognized as a specific complex that includes specimens which are usually caespitose, glabrous or densely tomentose but never villous, with ovate leaves which are basally cordate to sagittate, glabrous to tomentose on the lower surface, short to long (to 8 cm) inflorescences, and glabrous to tomentose ovary. The typical species occurs in rocky fields and savannas mostly in the states of Minas Gerais, Goias, Bahia and São Paulo, but it also reaches Bolivia. Microstachys ditassoides subsp. villosa is, however, restricted to the state of Piauí.

Sebastiania ditassoides var. villosa Glaziou (1913: 632) , an invalid name based on the collection Glaziou 22096 from Goias, ‘Serra das Divisões ou do Urbanom’, could not be studied.

Figures

FIGURE 2. Microstachys ditassoides subsp. villosa. A. Flowering branch. B. Detail of branch showing trichomes. C. Leaf. Ca. Lower side of leaf base with a gland. D. Inflorescence. E. Staminate flower. F. Sepal of staminate flower. G. Bract of staminate cymule. H. Pistillate flower. I. Sepal of pistillate flower. J. Bract of pistillate flower. K. Fruit. (A–K: G.Gardner 2954).