Homollea furtiva De Block, 2018

Block, Petra De, 2018, Revision of the Madagascan endemic Homollea (Rubiaceae - Pavetteae), with description of two new species, European Journal of Taxonomy 423, pp. 1-24 : 7-9

Homollea furtiva De Block , sp. nov.

urn:lsid:ipni.org:names:77177485-1

Figs 1 , 6A

Diagnosis

Resembling H. longiflora Arènes and H. leandrii Arènes because of the glabrous vegetative and reproductive parts, but differing from both species by the inflorescences with fewer flowers (1–3 vs 3–12); similar to H. longiflora because of the reddish brown shoots but differing from this species by the shape and size of the vegetative leaves (broadly obovate, broadly elliptic, or, rarely obovate, elliptic or ovate, 4–7 × 2.5–4 cm vs narrowly elliptic or narrowly ovate, (5.5–)7–12 × (1.3–)1.7–3(–4) cm) and the number of secondary veins on each side of the midrib (4–6(–7) vs 7–12); similar to H. leandrii because of the calyx lobes which are sparsely ciliate at their bases and the shape of the blades of the first order bracts (broadly ovate or ovate with cordate to truncate base), but differing from this species by the reddish brown shoots (vs fawn or pale beige).

Etymology

The specific epithet comes from the Latin adjective furtivus (secret, clandestine). It refers to the fact that the species was only recently collected for the first time.

Type material

Madagascar, Antsiranana Province, Diana Region, commune Mahavanona, fokontany Andranomanitra, Montagne des Français, vers 5 km NE d’Andranomanitra, 325 m, 29 Mar. 2004 (fr), Razafitsalama, Ratovoson, Randrianasolo, Rakotondrajaona, Jullet, Rasolofo, Flavien & Tombondrainy 583 (holo-: MO; iso-: K, P).

Other material studied

MADAGASCAR: Antsiranana Province: Diana Region, Montagne des Français, forêt d’Antaolanaomby , 385 m, 22 Mar. 2007 (fr), Ratovoson, Benjara & Jaovoavy 1279 (CNARP n.v., MO scan, P n.v., TAN n.v.).

Description

Small shrub, ca 2 m tall; vegetative and reproductive parts glabrous (externally); young shoots smooth, brown; older shoots reddish brown, flaking. Leaves with petioles 0.5–1.2 cm long; blades broadly obovate or broadly elliptic, rarely obovate, elliptic or ovate, 4–7 × 2.5–4 cm, thinly coriaceous, drying somewhat glossy and brown or greenish brown above, paler below; apex acuminate, acumen 0.3–1.2 cm long; base attenuate; secondary veins 4–6(–7) on each side of midrib; ciliate pit domatia present; stipules 0.5–0.8 cm long, basal cone 2–4 mm long, free parts of sheaths 1.5–4 mm long, triangular with acute, obtuse or somewhat rounded tips, or, ovate with acuminate tips, acumen up to 2 mm long. Inflorescences 1–3-flowered; peduncle 2–4 cm long; first order axes up to 3 mm long but mostly absent; first order bracts consisting of 3–4 mm high, ovate sheaths and blades broadly ovate, 1–3.5 × 1–3 cm with cordate or truncate bases and petioles up to 1 mm long; higher order bracts and bracteoles absent. Flowers shortly pedicellate, pedicels up to 2 mm long; calyx tube 1–1.5 mm long, glabrous and without colleters inside; calyx lobes 10–15 × ca 1 mm, sparsely ciliate at the base outside (trichomes usually absent in fruiting stage), glabrous inside, tips obtuse to acute; corolla, style and stigma and anthers unknown; ovary ca 2 mm long; 4–7 ovules per locule. Fruits at least ca 6 × 6 mm (persistent calyx not included); pyrenes thin, crustaceous; septum not stony; seeds 2–6 per fruit, 3–5 × 2.5–3 mm.

Distribution

Only known from Montagne des Français, a limestone massif close to Antsiranana in the Diana Region (Antsiranana Province) in North Madagascar ( Fig. 6A ).

Habitat and phenology

Lowland dry semideciduous or deciduous forest; on limestone. Fruiting: March.

IUCN status

Critically Endangered: CR B2ab(iii). Since only two specimens of H. furtiva sp. nov. are known, the extent of occurrence (EOO) could not be calculated. Its area of occupancy (AOO) is estimated to be 18 km 2 using a cell width of 3 km. The two known specimens are recent and were collected after the year 2003. All the collecting sites fall within the Montagne des Français New Protected Area (created in 2013). However, protection of the Montagne des Français is weak and its dry forests are under threat by logging for timber and charcoal for the population of the city of Antsiranana. With a very limited geographic range, threats which lead to infer a continuing decline in the quality of habitat, and a single location, H. furtiva sp. nov. is assessed as Critically Endangered (CR).

Notes

Homollea furtiva sp. nov. has only been collected twice. Flowers are unknown.

This species combines characters from both H. leandrii (calyx lobes sparsely ciliate at the base; broadly ovate leaves subtending the inflorescences) and H. longiflora (reddish brown shoots).

Figures

Fig. 1.Homollea furtivaDe Block sp. nov.A. Fruitingbranch.B. Stipule.C. Firstorderbract.D. Ovary and calyx.E. Detailof D showing the sparsely ciliate base of the calyx lobes. F. fruit.Drawn by Mr.A. Fernandez. From Razafitsalama et al. 583 (MO).

Fig. 6. Distribution maps of Homollea. A. H. furtiva De Block, sp. nov. (★), H. leandrii Arènes (●) and H. longiflora Arènes (▲). B. H. perrieri Arènes (▲), H. SeptentrionaliS De Block sp. nov. (●) and unplaced material coll. ignot. 25309-SF (★).