Homollea septentrionalis 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 : 16-19

Homollea septentrionalis De Block , sp. nov.

urn:lsid:ipni.org:names:77177486-1

Figs 5 , 6B

Diagnosis

Homollea septentrionalis sp. nov. is similar to H. perrieri in that the young stems, petioles, leaves, stipules, inflorescence parts, ovary, calyx and corolla are pubescent. It differs from H. perrieri by the longer trichomes ((0.3–) 0.5–1.5 mm vs 0.2–0.5 mm), the longer calyx lobes ((9 –12–)17–25 vs 5–8(–10) mm), the longer corolla tubes and lobes (20–27 and 13–18 mm, respectively, vs 15–20 and 8–11 mm) and by the higher number of ovules per locule (4–6 vs 2–3).

Etymology

The specific epithet refers to the distribution area of the species in the northernmost part of Madagascar.

Type material Madagascar, Antsiranana Province, Sava Region, sous-préfecture de Vohemar, commune rurale de Daraina, Daraina, forêt d’Ampondrabe, à 1220 m du point côté 594, au 185°, 338 m, 14 Feb. 2005 (fl), Nusbaumer & Ranirison 1468 (holo-: G scan; iso-: BR).

Other material studied

MADAGASCAR: Antsiranana Province: Diana Region, forêt de Sahafary, bassin de la Saharenena , 7 Nov. 1966 (fl), Capuron 24489-SF ( P, TEF) ; Antsiranana II, Antsampano, Beately, Antsisinala , 11 Aug. 2005 (fr), Rakotonasolo & Rapanarivo 1033 ( BR, K, TAN) ; Irodo, Sahafary forest , 118 m, 4 Jan. 2008 (fl), Rakotonasolo & Nowak 1147 ( BR, K, TAN) ; Sava Region, Vohemar district, Daraina commune, Daraina, Bekaraoka South , 9 Apr. 2008 (fr), Bremer, Mouly, Ravelonarivo & Kainulainen 5125 (S); sous-préfecture de Vohemar, commune rurale de Daraina , Daraina, forêt de Bekaraoka, partie Sud , 1,2 km S du point côté 330, 150 m, 16 Mar. 2003 (fr), Gautier, Wohlhauser & Nusbaumer 4410 ( G, K); Vohemar, Ampisikina, Tsaratanana, forêt d’Ampondrabe, à 1 km au NW du village d’Ambaribe, 200 m, 4 Nov. 2005 (fr), Rakotonandrasana, Ratovoson, Guittou & Jaovelo 965 (CNARP n.v., G, MO n.v., P n.v., TAN n.v.) ; sous-préfecture de Vohemar, commune rurale de Daraina , Daraina, forêt de Bekaraoka, partie Sud , à 1000 m du point côté 237, au 40°, 160 m, 16 Mar. 2005 (fr), Ranirison & Nusbaumer 961 (BR, G scan) .

Description

Shrub 1–2 m tall; vegetative and reproductive parts pubescent with trichomes (0.3–) 0.5–1.5 mm long (the longest trichomes occurring on ovary and fruit); young shoots reddish brown, densely hispid; older shoots reddish brown, flaking, glabrous. Leaves with petioles 0.5–1 cm long, densely hispid; blades elliptic, rarely ovate or obovate, 5–11 × 2.5–5 cm, subcoriaceous or rarely coriaceous, drying greenish or brownish above, discolourous or somewhat paler below but sometimes young leaves drying blackish on both surfaces, moderately to densely hispid or villose or rarely ± glabrous with trichomes restricted to the veins above, densely hispid below; margins ciliate; apex acuminate, acumen 0.3–0.8 cm long; base cuneate to obtuse or,more rarely, unequal; secondary nerves5–9 on each side of midrib; higher order veins sometimes dark or blackish brown in young leaves; domatia absent or inconspicuous; stipules 0.6–1 cm long, at the base densely hispid and higher up sparsely to moderately villose or, more rarely, ± glabrous outside, margins ciliate, basal cone 2.5–5 mm long, free parts of sheaths 2.5–5 mm long, triangular with acute tips or, more rarely, ovate with acuminate tips, acumen up to 2 mm long. Inflorescences 3–12-flowered, with peduncle, axes, pedicels and bracts densely hispid; peduncle 1–2(–4.5) cm long; first order axes up to 2 mm long; first order bracts consisting of 1–2 mm high triangular sheaths and blades sessile or subsessile, broadly ovate to ovate, 0.8–3.5 × 0.5–2.5 cm with cordate or truncate bases; higher order bracts usually absent, if present, then linear, up to 5 mm long; bracteoles absent. Flowers scented, sessile or subsessile; calyx tube 1–1.5 mm long, moderately to densely hispid outside, densely sericeous and without colleters inside; calyx lobes (9–12–)17–25 × 0.5–0.8 mm, sparsely to moderately hispid outside, inside densely sericeous in the basal 5 mm, higher up pubescence identical to that on the outside, margins ciliate, tips acute; corolla tube 20–27 mm long, sparsely to moderately hirsute and with up to 5 mm long longitudinal lines of appressed hairs below the sinuses of the corolla lobes outside, moderately villose in the upper half inside; corolla lobes 13–18 × 2 mm, sparsely to moderately hirsute outside, sparsely to moderately sericeous at the base and glabrous higher up inside, margins ciliate, tips obtuse or acute; anthers 4.5–5 mm long, mostly included in the corolla tube at anthesis (only ca 1 mm exserted), inserted ca 3 mm below the level of the throath; ovary ca 2 mm long, densely hispid; 4–6 ovules per locule; stigma exserted from corolla tube for 4–5 mm at anthesis, receptive zone ca 14 mm long. Fruits ca 9 × 9 mm (persistent calyx not included), moderately to densely hispid; 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 ca 5 per fruit, ca 4.5 × 2.5–3 mm.

Distribution

Only known from the Diana and Sava Regions in northern Madagascar (Antsiranana Province; Fig. 6B ).

Habitat and phenology

Lowland dry semideciduous or deciduous forest, on sandy soil; alt. 150– 350 m. Flowering: November– February; fruiting: March–August.

IUCN status

Endangered: EN B1ab(iii) + 2ab(iii). The extent of occurrence (EOO) of H. septentrionalis sp. nov. is estimated to be 3,495 km 2, and its area of occupancy (AOO) 54 km 2 using a cell width of 3 km. Seven of the eight known specimens are recent (collected after the year 2003) and are the result of the intensified collection effort made in this region mainly by the Conservatoire & Jardin Botaniques de la Ville de Genève. The species occurs in five localities, two of which fall within the Loky-Manambato New Protected Area (Daraina), created in 2005 and managed by a Madagascan non-governmental organization, Association Fanamby. The main threat to the species is loss of habitat as a result of subsistence farming, logging for timber and charcoal and fires. Furthermore, the region is also subject to traditional mining for gold ( Rakotondravony 2009; Nusbaumer et al. 2010). Considering these treats, and the fact that the species occurs in only five locations, H. septentrionalis sp. nov. is assessed as Endangered (EN).

Note

The specimens Bremer et al. 5125, Gautier et al. 4410, Nusbaumer & Ranirison 1468, Rakotonandrasana et al. 965 and Ranirison & Nusbaumer 961 have long and narrow calyx lobes, 17–25 mm long. As such, they are clearly different from H. perrieri , the calyx lobes of which vary in length between 5 and 8(–10) mm. The specimens Capuron 24489-SF, Rakotonasolo & Rapanarivo 1033 and Rakotonasolo & Nowak 1147 have shorter calyx lobes, ranging in length between 9 and 12 mm. Their other characters, however, are identical to those of the typical specimens of H. septentrionalis sp. nov.: reddish brown shoots (vs fawn, greyish or dull brown in H. perrieri ), trichomes (0.3–) 0.5–1.5 mm long (vs 0.2–0.5 mm long) and sessile or subsessile flowers (vs pedicels 2–6 mm long). Furthermore, with the exception of Bremer et al. 5125, they possess the subsessile, broadly ovate or ovate blades of the first order bracts with cordate to truncate base typical for H. septentrionalis sp. nov. (vs shortly petiolate, linear, elliptic or ovate blades with cuneate or attenuate base in H. perrieri ). The three specimens also share the same distribution area as the typical specimens of H. septentrionalis sp. nov. and are, for all these reasons, considered to belong to this species.

Figures

Fig. 5. Homollea SeptentrionaliS De Block sp. nov. A. Flowering branch. B. Stipule. C. Detail of lower surfaceof leaf, showing pubescenceon midriband blade.D. Flower.E. Fruit.F.Apical viewof discand pubescent adaxial surface of calyx tube and lobes (base only). Drawn by Mr.A. Fernandez.A–D from Nusbaumer & Ranirison 1468 (BR); E–F from RaniriSon & NuSbaumer 961 (BR).

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 (★).