Homollea perrieri Arènes

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 : 13-16

Homollea perrieri Arènes

Figs 4 , 6B

Notulae Systematicae 16: 15, f. 3 (14–20) ( Arènes 1960). – Type: Madagascar, Mahajanga Province, Boeny Region, Manongarivo, Ambongo , Jan. 1904 (fl, fr), Perrier de la Bâthie 3633 (holo-: P; iso-: P).

Other material studied

MADAGASCAR: Mahajanga Province: Betsiboka Region, forêt de Kasijy, Kelifely , Nov. 1974 (fl), Morat 4700 (P, TAN) ; Boeny Region, Majunga, 30 Mar. 1912 (fr), Afzelius 259 (P); Soalala, Réserve Naturelle Intégrale de Namoroka, ca 40 km S of Soalala , 3 Feb. 2000 (fr), Davis, Rakotonasolo & Wilkin 2529 (BR, K, TAN); Majunga, dunes , Feb. 1915 (fl, fr), Perrier de la Bâthie 3504 (P); Ambongo , 17 Feb. 1841 (fr), Pervillé 680 (P) ; Réserve Naturelle Intégrale de Namoroka, canton Andranomavo , district Soalala, 2 Mar. 1952 (fr), Rakotovao 4067-RN (P, TAN, TEF).

Description

Shrub 1–4 m tall; vegetative and reproductive parts pubescent with trichomes 0.2–0.5 mm long (the longest trichomes occurring on ovary and fruit); young shoots brown, densely hirsute; older shoots fawn, greyish or dull brown, glabrous. Leaves with petioles 0.2–0.8 cm long, densely hirsute; blades narrowly elliptic, narrowly obovate, linear or, more rarely, elliptic or obovate, (3–)5.5–17 × 0.8–4 cm, subcoriaceous to coriaceous, drying somewhat glossy and brown or greenish above, somewhat paler below, moderately to densely hirsute, scabrid or ± glabrous with trichomes restricted to the veins above, densely hirsute below; margins ciliate; apex acuminate or, more rarely, acute, acumen 0.2– 0.6 cm long; base attenuate or cuneate; secondary veins 5–10 on each side of midrib; ciliate pocket domatia sometimes present; stipules 0.3–0.8 cm long, sparsely to moderately hirsute outside, basal cone 1.5–4 mm long, free parts of sheaths 2–4 mm long, ovate with acuminate tips, acumen up to 2 mm long. Inflorescences 3–12-flowered, with peduncle, axes and pedicels densely hirsute; peduncle 0.5–9 cm long; first order axes up to 5 mm long; first order bracts consisting of 1–2 mm high triangular sheaths and blades linear, elliptic or ovate, 0.4–3.5 × 0.1–1.5 cm with cuneate or attenuate bases and 1.5–3 mm long petioles; higher order bracts usually absent, if present, then linear, 2–4 mm long; bracteoles absent. Flowers shortly pedicellate, pedicels 1–6 mm (1–3 mm long in flowering stage, up to 6 mm long in fruiting stage); calyx tube (1.5–) 2–2.5 mm long, moderately to densely hirsute outside, sparsely to moderately sericeous just below the lobes (further down hairs sparse or almost absent) and without colleters inside; calyx lobes 5–8(–10) × 0.3–0.8 mm, sparsely to moderately hirsute outside, inside moderately sericeous at the base, higher up pubescence identical to that on outside, margins ciliate, tips usually obtuse to rounded (rarely acute); corolla tube 15–20 mm long, moderately to densely hirsute outside, sparsely to moderately villose in the upper third inside; corolla lobes 8–11 × 2 mm, sparsely to moderately hirsute outside, sparsely to moderately sericeous at the base and glabrous higher up inside, margins ciliate; tips obtuse to rounded; anthers 4–6 mm long, exserted for most of their length but their bases included in the corolla tube at anthesis, inserted ca 1 mm below the level of the throat; ovary (1–) 1.5–2 mm long, densely hirsute; 2–3 ovules per locule; stigma exserted from corolla tube for 4–7 mm at anthesis, receptive zone 15 –16 mm long. Fruits 4–6 × 6–8 mm (persistent calyx not included), moderately to densely hirsute; pyrene stony, breaking up into 4 valves along 4 preformed longitudinal germination slits (two along the lines of fusion of the two locules and two perpendicular to those); septum not stony; seeds 2–4 per fruit, 3–4 × 2–3 mm.

Distribution

Known from the Boeny and Betsiboka Regions in western Madagascar (Mahajanga Province), collected from the surroundings of Mahajanga and Ambongo and from the Namoroka and Kasijy Reserves ( Fig. 6B ).

Habitat and phenology

Lowland dry semideciduous or deciduous forest, on sandy soil, from the upper level of the beach to limestone formations further inland, alt. 0– 200 m. Flowering: November–January; fruiting: February– March.

Vernacular name

Dingadingana (Rakotovao 4067-RN).

IUCN status

Endangered: EN B2ab(iii). The extent of occurrence (EOO) of H. perrieri is estimated to be 10,176 km 2, and its area of occupancy (AOO) 54 km 2 using a cell width of 3 km. Over a period of ca 175 years (first collection in 1841 by Pervillé) only seven specimens were collected: four specimens were collected before 1915, three between 1950 and 1975, the most recent specimen dates from the year 2000. The older specimens do not have detailed locality data, e.g., Majunga or Ambongo, which renders the assessment somewhat less reliable. The species occurs in five localities, three of which are in protected areas: Tsingy de Namoroka National Park, Kasijy Reserve and Mahavavy Kinkony New Protected area (created in 2015). The main threat to the species is decline of its habitat both inside and outside the protected areas as a result of logging for timber and charcoal, burning for grazing and slash-andburn agriculture. Considering these threats, and the fact that the species occurs in only five locations, H. perrieri is assessed as endangered (EN).

Notes

In the protologue, Arènes (1960) described the flowers of H. perrieri as having a corolla tube of 11 mm long and corolla lobes of 5 mm long. Very few mature flowers are available for study (one on the isotype Perrier de la Bâthie 3633 and old, incomplete flowers in the envelopes on Morat 4700 and Perrier de la Bâthie 3504). None of these flowers show the measurements given by Arènes (1960). Their corolla tubes range between 15 and 20 mm and the corolla lobes between 8 and 10 mm long.

One specimen, Morat 4700, has long, linear leaves (up to 17 × 0.8 cm), whereas the other specimens have shorter wider leaves (5–12 × 1.2–4 cm). The specimen Morat 4700 occurs in the southernmost locality for the species.

Figures

Fig. 4. Homollea perrieriArènes.A. Fruiting branch.B. Stipules. C. Ovary and calyx. D. Fruit. Drawn by Mr.A. Fernandez.A, C–D from Afzelius 259 (P); B from Perrier de la Bâthie 3633 (P).

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 (★).