Astiella desseinii Groeninckx, 2017

Groeninckx, Inge, Janssens, Steven, Smets, Erik & Verstraete, Brecht, 2017, Description of 11 new Astiella (Spermacoceae, Rubiaceae) species endemic to Madagascar, European Journal of Taxonomy 312, pp. 1-40 : 18-20

Astiella desseinii Groeninckx sp. nov.

http://www.ipni.org/urn:lsid:ipni.org:names:77161720-1

Figs 2F , 4D , 5 E–F, 9

Diagnosis

Astiella desseinii sp. nov. resembles A. latifolia sp. nov. in having sessile flowers, elongated placentas, ovoid capsules, identical seed and pollen morphology, but differs in the erect habit (vs creeping), the linear leaves with secondary veins invisible (vs ovate to broadly ovate leaves with prominent secondary veins), and the cylindrical corolla tubes with the stamens exserted beyond the corolla throat in brevistylous flowers (vs funnel-shaped corolla tubes with the stamens always included).

Etymology

The species is named in honour of Dr. Steven Dessein, who was the first to observe and collect Astiella desseinii .

Type

MADAGASCAR: Toliara province, Menabe region, Morondava district, RN 35, at Antsehase bridge/ river, on elevated sandy bank near river, without herb or shrub vegetation, 197 m, 23 Jan. 2007, De Block et al. 2247 (holo-: BR; iso-: MO, P, TAN).

Description

Herb, up to 25 cm tall; stems quadrangular in cross section, glabrous or beset with minute trichomes with characteristic rounded apex towards the nodes, reddish green. Stipule base 0.4–0.8 mm long,covered with short trichomes with characteristic rounded apex; fimbriae often absent, sometimes 2 clearly visible and then 0.5–0.7 mm long, colleter-tipped. Leaves sessile, anisophyllous; blades linear, large leaves 6–22 × 0.7–1.5 mm, small leaves 3.2–12 × 0.6–1.2 mm, beset with short trichomes with characteristic rounded apex above,glabrous below, yellow-green; base attenuate;apex acute; margin revolute when dry, beset with short trichomes with characteristic rounded apex; midvein prominent, purplish or reddish brown below; secondary veins invisible; intersecondaries invisible. Inflorescences pseudo-axillary, 1–2-flowered; peduncle absent. Flowers sessile, heterostylous. Calyx green; tube reduced; lobes 4, narrowly ovate to ovate with acute apex, 0.9–1.2 × 0.3–0.5 mm, glabrous or with a few trichomes, margin beset with short trichomes with characteristic rounded apex. Corolla yellow-green before anthesis, creamy white after; tube cylindrical, widened at the apex, 4–11 mm long, 0.7–1.2 mm wide at the throat, 0.4–0.6 mm wide at the base, glabrous; lobes 4, broadly ovate, 1.2–1.7 × 0.9–1.2 mm, papillose outside, densely pubescent inside. Stamens inserted near the base of the corolla lobes and exserted for 0.8–1.2 mm beyond the corolla throat in brevistylous flowers, inserted in the lower half of the corolla tube and included in longistylous flowers. Anthers ellipsoid, 1–1.2 mm long; filaments dorsifixed, ca 0.5 mm long. Pollen tricolporate, prolate spheroidal to subprolate spheroidal; E 26.5 μm in brevistylous flowers, 19–24 μm in longistylous flowers; P 27 μm in brevistylous flowers, 24–26 μm in longistylous flowers; ectocolpi long; endocolpi long; tectum bireticulate; suprareticulum microreticulate to reticulate, mostly ornate, smooth or with granules; infrareticulum microreticulate with granules. Ovary 2-locular, ovoid, 1.2–1.5 × 0.8–1 mm, glabrous for the most part, covered with short trichomes with characteristic rounded apex towards the base; placenta fused with the septum, elongated, bearing 6–7 ovules per locule embedded in the placental tissue. Style 5 mm long and exserted for 0.2–1.3 mm beyond the corolla throat in brevistylous flowers, 4.8–6.5 mm long and exserted for 1.3–1.8 mm beyond the corolla throat in longistylous flowers, glabrous; stigma bilobed, lobes 0.5 mm long in longistylous flowers, 1–1.2 mm long in brevistylous flowers, papillate, white. Capsules ovoid, 3.4–3.8 × 1.8–2.3 mm, crowned with the persistent calyx lobes, glabrous for the most part, covered with short trichomes with characteristic rounded apex towards the base, green becoming reddish brown, dehiscence loculicidal. Seeds 6–7 per locule, elliptic in outline, ventral groove absent, 5 × 0.7–0.8 × 5 mm, black; seed coat surface reticulate, testa cells with undulating radial walls, microsculpturing granulate.

Distribution

W Madagascar: Toliara province, Menabe region, Morondava district.

Habitat

Plateau grassland-wooded grassland mosaic; elevated sandy bank near river; laterite; at 197 m elevation.

Conservation status

The species is only known from its type locality. The species was collected from an elevated sandy bank. No threat could be identified, but as very little is known about the ecology of the species, we categorise the species as data deficient (DD).

Figures

Fig. 2. Distribution maps. A. Astiella antongilensis Groeninckx sp. nov. B. A. antsalovansis Groeninckx sp. nov. C. A. confusa Groeninckx sp. nov. D. A. deblockiae Groeninckx sp. nov. E. A. delicatula Jovet. F. A. desseinii Groeninckx sp. nov. G. A. homolleae Groeninckx sp. nov. H. A. latifolia Groeninckx sp. nov. I. A. longifimbria Groeninckx sp. nov. J. A. perrieri Groeninckx sp. nov. K. A. pulla Groeninckx sp. nov. L. A. tsaratanensis Groeninckx sp. nov.

Fig. 4. Scanning electron microscopy micrographs of pollen in polar view (PV), the apocolpium (AC), pollen in equatorial view (EV) and the mesocolpium (ME). A. Astiella antsalovansis Groeninckx sp. nov. B. A. deblockiae Groeninckx sp. nov. C. A. delicatula Groeninckx sp. nov. D. A. desseinii Groeninckx sp. nov. Scale bars for A and C: PV, EV = 5 µm, AC = 1 µm, ME = 2 µm; for B and D: PV, EV = 5 µm, AC, ME = 1 µm.

Fig. 5. Scanning electron microscopy micrographs of seeds and a detail of their surface. A–B. Astiella antsalovansisGroeninckx sp. nov.C–D.A. deblockiaeGroeninckx sp. nov.E–F.A. desseiniiGroeninckx sp. nov. G–I. A. delicatula Jovet. J–K. A. homolleae Groeninckx sp. nov. L–M. A. latifolia Groeninckx sp. nov. N–O. A. perrieri Groeninckx sp. nov. P–R. A. tsaratanensis Groeninckx sp. nov. Scale bars for A, C, E, J, L, N = 100 µm; B, I = 50 µm; D = 10 µm; F, K, M, O, R = 20 µm; G, H, P, Q = 200 µm.