Homollea longiflora 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 : 11-13

Homollea longiflora Arènes

Figs 3 , 6A

Notulae Systematicae 16: 16, f. 3 (1–8) ( Arènes 1960). – Type: Madagascar, Mahajanga Province, Boeny Region, canton Tsaramandroso, district Ambato-Boeni, N de Bevazaha , 8 Feb. 1949 (fl), Saboureau 7 (holo-: P; iso-: P, TAN, isotypes labelled as coll. ignot. 1857- RN).

Other material studied

MADAGASCAR: Mahajanga Province: Boeny Region, Réserve Naturelle Intégrale d’Ankarafantsika, Station Forestière d’Ampijoroa , 14 May 1952 (fr), Coll. ignot. 4952-SF ( P); district Morovoay, Réserve Naturelle Intégrale d’Ankarafantsika, Station Forestière d’Ampijoroa, trail C towards Jardin Botanique , 200 m, 24 Jan. 2000 (fl), Davis, Rakotonasolo & Wilkin 2504 ( BR, K); Réserve Naturelle Intégrale d’Ankarafantsika, Station Forestière d’Ampijoroa, Jardin Botanique, section B , 9 Feb. 1999 (fl, fr), De Block & Rakotonasolo 767 ( BR, G, K, MO, P, TAN, WAG); Réserve Naturelle Intégrale d’Ankarafantsika, Station Forestière d’Ampijoroa, Jardin Botanique, section B , 9 Feb. 1999 (fl), De Block & Rakotonasolo 768 ( BR, G, K, MO, P, TAN, WAG); Réserve Naturelle Intégrale d’Ankarafantsika, Station Forestière d’Ampijoroa, Jardin Botanique, section A , 10 Feb. 1999 (fl), De Block & Rakotonasolo 781 ( BR, K, MO, P, TAN, WAG); Réserve Naturelle Intégrale d’Ankarafantsika, Station Forestière d’Ampijoroa , 3 km N d’Andranofasika, 12 Apr. 1984 (fr), Dorr & Koenders 3017 ( K, MO, P, WAG); Réserve Naturelle Intégrale d’Ankarafantsika, Station Forestière d’Ampijoroa , 2 Feb. 1972 (fl), Jacquemin 908 ( P); Réserve Naturelle Intégrale d’Ankarafantsika, Station Forestière d’Ampijoroa , 15 Feb. 1973 (fl), Jacquemin 1223 ( P); Réserve Naturelle Intégrale d’Ankarafantsika, Station Forestière d’Ampijoroa, edge of Ankarafantsika plateau, trail around lake , 75 m, 14 Feb. 1987 (fr), Nicoll 378 ( K, MO, P, TAN, WAG); Réserve Naturelle Intégrale d’Ankarafantsika, Station Forestière d’Ampijoroa, edge of Ankarafantsika plateau , 100 m, 15 Feb. 1987 (fr), Nicoll 400 ( K, MO, P, TAN); Ambato-Boina, Andranofasika, Parc National d’Ankarafantsika , E of lac Ravelobe, 28 Jan. 2007 (fr), Ralimanana, Andriamampandry, Rapanarivo & Raharison 826 ( BR, K, MO, P, TAN, TEF); Bevazaha, canton Tsaramandroso, district Ambato-Boeni , 8 Feb. 1949 (fl), Ramamonjisoa 1857-RN ( P, TAN); Ankarafantsika, 6 Feb. 2000 (fl), Thulin, Kornhall, Popp & Rivolala 10382 (UPS); Bongolava Region, Bongolava , 18 Mar. 2010 (fr), De Block, Groeninckx & Rakotonasolo 2341 ( BR, TAN).

Description

Small tree or shrub, up to 5 m tall; vegetative and reproductive parts glabrous (externally); young shoots brown, smooth; older shoots reddish brown, glossy, flaking. Leaves with petioles 0.5–1.5 cm long; blades narrowly elliptic or narrowly ovate, (5.5–)7–12 × (1.3 –)1.7–3(–4) cm, coriaceous, drying glossy and greenish brown or, more rarely, brown above, glossy and somewhat paler below; apex acuminate or, more rarely, acute, acumen 0.3–1.2 cm long; base attenuate; secondary veins 7–12 on each side of midrib; ciliate pit domatia sometimes present; stipules 0.5–1 cm long, basal cone 1.5–2.5 mm long, free parts of sheaths 2.5–5 mm long, triangular with acute tips. Inflorescences 3–12-flowered; peduncle 1.5–13.5 cm long; first order axes up to 2 mm long, rarely up to 35 mm long; first order bracts consisting of 1–2 mm high, triangular sheaths (but up to 5 mm high and keeled in case of long first order axes) and blades linear, narrowly elliptic, narrowly ovate or, more rarely, ovate, 0.3–3.5 × 0.1–1.5 cm with attenuate bases and 3–6 mm long petioles or, more rarely, similar in size and shape to the vegetative leaves; higher order bracts usually absent, if present, then linear, 3–4 mm long; bracteoles absent. Flowers sweetly scented, shortly pedicellate, pedicels 2–8 mm long; calyx tube 1–2 mm long, glabrous and without colleters inside; calyx lobes 4.5–10 × 0.3–0.75(–1) mm, not ciliate at the base outside, glabrous inside, tips rounded; corolla tube (10–) 22–30 mm long, moderately villose in the upper half inside; corolla lobes 8–11 × 2–3 mm, tips obtuse to rounded; anthers 4.5–5.5 mm long, only the tips (1–2 mm) exserted from the corolla tube at anthesis, inserted ca 2 mm below the level of the throat, white; ovary 1–2 mm long, sometimes faintly ribbed longitudinally (when dry); 3–7 ovules per locule; stigma exserted from corolla tube for 4–6 mm at anthesis, receptive zone 15 –25 mm long. Fruits 4–6 × 7–8 mm (persistent calyx not included); pyrene thin, crustaceous, without preformed germination slits; septum not stony; seeds 2–6 per fruit, 3.5–4.5 × 2.5–3 mm.

Distribution

Known from Mahajanga Province in western Madagascar, centred in the Boeny Region with one collection from the Bongolava Region; mostly collected from the Ankarafantsika Reserve and surroundings ( Fig. 6A ).

Habitat and phenology

Lowland dry semideciduous or deciduous forest; on sandy soil, alt. 0– 200 m. Flowering: January– February, with peak in February; fruiting: March–May.

IUCN status

Endangered: EN B1ab(iii) + 2ab(iii). The extent of occurrence (EOO) of H. longiflora is estimated to be 1,209 km 2 and its area of occupancy (AOO) 36 km 2 using a cell width of 3 km. All collecting localities fall within the Ankarafantsika National Park and the Bongolava New Protected Area (created in 2006). The major threat for this species is habitat loss since both protected areas are under threat by logging for charcoal and timber, burning for grazing and slash-and-burn agriculture ( Nicoll & Langrand 1989). The sandy soil, once denuded, erodes quickly and vegetations do not recover. The distribution of this species is insufficiently known since all but three of the 15 specimens available at this time are from the Ankarafantsika National Park (mostly from the Ampijoroa Forest station near Lake Ravelobe), an area easily accessible to collectors. Considering the threats, and the fact that the species is distributed in only three locations, H. longiflora is assessed as Endangered (EN).

Note

The holotype, Saboureau 7, bears a handwritten label by Saboureau. Duplicates are available at P and TAN (with similar handwritten labels), but are labelled as coll. ignot. 1857-RN.

Figures

Fig. 3. Homollea longifloraArènes. A. Flowering branch. B. Stipules. C. Ovary and calyx. D. Corolla, stamens, style and stigma. E. Placenta with ovules,abaxial view. F. Placenta with ovules, adaxial view. G. Fruit. H. Transverse section through fruit.I. Seed, lateral view. J. Seed, adaxial view.Drawn by Mr. A. Fernandez.A, C–D from Saboureau 7 (P); B, H–J from De Block et al. 2341 (BR); E–F from De Block et al. 768 (BR); G from Dorr & Koenders 3017 (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 (★).