Helictosperma malacophylla (Drake) De Block, 2018

Block, Petra De, Rakotonasolo, Franck, Ntore, Salvator, Sylvain G. Razafimandimbison, & Janssens, Steven, 2018, Four new endemic genera of Rubiaceae (Pavetteae) from Madagascar represent multiple radiations into drylands, PhytoKeys 99, pp. 1-66 : 1

Helictosperma malacophylla (Drake) De Block comb. nov. Figs 2E, F , 6 , 8 , 9E-H, N

Ixora malacophylla Drake, Bull. Mens. Soc. Linn. Paris 2: 1309 (1897) & Hist. Phys. Madagascar, Atlas 4: t. 422 (1897). Tarenna malacophylla (Drake) Homolle, Bull. Soc. Bot. France 85: 606, fig. 1.5 (1938); Capuron, Rév. Rub. Mad. Com.: 173 (1973). Type: MADAGASCAR. s.loc., s.dat. (fl.), Grevé 112 (lectotype: P!, designated here; isolectotypes: BM!, K!, P!).

Description.

Shrub 2-6 m tall, more rarely tree up to 12 m tall with trunk up to 6 m tall and dbh up to 10 cm; young shoots quadrangular, often bisulcate, brown, densely covered with erect to spreading hairs; older branches brown, pale brown, greyish or fawnish, glabrous, often flaking. Leaves often immature at time of flowering, 6-15 × 4-8.5 cm, ovate, more rarely broadly ovate, elliptic or obovate; blades papyraceous, drying brown to dark brown, more rarely greenish-brown above, brown and often somewhat paler below, densely covered with erect hairs on the lower surface, moderately to densely covered with erect or spreading hairs on the upper surface, pubescence denser on the midrib and secondary nerves on both surfaces; base rounded, subcordate, cordate or unequal, more rarely truncate or obtuse; apex acuminate, acumen 3-18 mm long; hair tuft domatia present; midrib and secondary nerves raised on the lower leaf surface; midrib impressed especially in the basal half on the upper leaf surface; 10-14 secondary nerves on each side of the midrib. Petioles densely covered with erect hairs, 14-45 mm long. Stipules caducous; densely covered with erect hairs outside but rapidly becoming corky and losing the pubescence; stipules of vegetative nodes with sheaths 3-5 mm long and awns 3-6 mm long, those of inflorescence-bearing nodes ovate with acute to shortly acuminate tips, 4-6 mm long. Inflorescences consisting of 25-90 flowers, 2.5-8 × 2-7 cm; peduncle, inflorescence axes and pedicels densely covered with erect hairs; peduncle 1-5.5 cm long; first order axes up to 2(-4) cm long; first order bracts with stipular parts narrowly triangular and leaves long-petiolate and identical in shape and size to the vegetative leaves or somewhat smaller; second order bracts of the central axis often similar to the first order bracts but leaves considerably smaller and narrower with acute to attenuate base, 1-6.5 × 0.3-3.2 cm; second order bracts of lateral axes reduced or absent; higher order bracts and bracteoles linear, moderately to densely covered with erect hairs on both surfaces, no colleters present inside; bracts up to 1.2 cm long; bracteoles subopposite on the pedicel, 0.2-0.4 cm long; first order branching often shifted above the first order bracts (up to 1 cm higher); bracts sometimes adnate to axis for up to 5 mm. Flowers pedicellate, pedicels 1-5 mm long. Calyx green, moderately to densely covered with erect hairs outside; tube ca. 0.5 mm long, with a sparse ring of appressed hairs at the base but without colleters inside; lobes erect in young bud, but rapidly becoming reflexed, oblong, 3-5 × 1-1.5 mm, the upper half sparsely covered with erect hairs inside, bases not overlapping but closely joining, tips obtuse. Corolla tube 7-8 mm long, ca. 1 mm in diameter at the base, ca. 1.5 mm in diameter at the throat, moderately to densely covered with erect hairs outside, the upper 2/3 moderately to densely covered with erect hairs inside; lobes 4-5 × 3-3.5 mm, glabrous on both surfaces, margins ciliate. Anthers 3.5-5 mm long; filaments 1-1.5 mm long. Ovary 1-1.25 mm long, green, densely covered with erect hairs. Style and stigma white, exserted from the corolla tube for 7-10 mm at anthesis; style densely covered with spreading, upwardly directed hairs in the upper half; stigma with upper 4-5 mm fusiform, longitudinal papillate lines running down for a further 3-4 mm. Fruits 4-6 mm in diameter (persistent calyx not included), moderately to densely covered with erect hairs, drying brown and glossy when ripe; seeds 3-5 mm in diameter, dark brown.

Habitat.

Lowland dry deciduous and semi-deciduous forest on calcareous soil, usually on sand; alt. 30-800 m.

Distribution.

Helictosperma malacophylla is known from the Boeny, Betsiboka and Sofia Regions (Mahajanga Province), from the Ihorombe (Fianarantsoa Province) and from the Atsimo-Andrefana and Menabe Regions (Toliara Province). Fig. 14B .

Phenology.

Flowering: November-February(-April); Fruiting: (November-)January-May.

Vernacular names.

Ampale (dialect Masikoro; coll. ignot. 21707-SF); nofotrakoho (coll. ignot. 19382-SF); talinala (dialect Masikoro; coll. ignot. 21708-SF); voloiravy (Randriamiera 8770-RN); zamanimbato (Rakotovao 3898-RN).

Uses.

Construction wood for houses and cattle enclosures (coll. ignot. 19146-SF, 19382-SF, 21707-SF, 21708-SF); fire wood (coll. ignot. 21707-SF, 21708-SF).

Critical note.

Helictosperma resembles Exallosperma by the Terminalia -branching pattern, the pedunculate, pseudo-axillary inflorescences and the basally attached placentas from which three collateral ovules arise. The genera differ by pollen (tectum microreticulate to perforate in Helictosperma vs. psilate in Exallosperma ) and fruit/seed characters (fruit with two pyrenes, each with a single laterally flattened seed with irregularly distributed surface ridges vs. fruit with single pyrene falling apart into four valves and containing a single seed that is rolled-in on itself). Helictosperma malacophylla resembles E. longiflora by the general hairiness of the whole plant but differs from it by the larger number of flowers per inflorescence (25-90 in H. malacophylla vs. 3-12 in E. longiflora ), the longer pedicels (1-5 mm vs. 0-2 mm long), the shorter bracteoles (2-4 mm vs. 4-10 mm long) and the shorter corolla tubes (7-8 mm long vs. 26-37 mm long) and calyx lobes (3-5 mm long vs. 12-16 mm long).

Preliminary IUCN assessment.

Near Threathened: NT. The extent of occurrence (EOO) of Helictosperma malacophylla is estimated to be 273.476 km2, which falls outside any threat category, but its area of occupancy (AOO) is 261 km2, which complies with the Endangered category under the sub-criterion B2. The species occurs in ten locations and is known from more than fifty collections, twelve of which were collected recently (after 1989). The distribution of these recent collections coincides with the distribution of the older specimens (from 1892 till 1975), indicating that the species remains present throughout its original distribution area. Only few specimens were collected from protected areas, notably Ankarafantsika National Park, Tsingy de Namoroka Strict Nature Reserve and Kirindy Mitea National Park. Despite its large extent of occurrence, Helictosperma malacophylla is threathened locally by reduction of its habitat through slash-and-burn agriculture, logging for timber and charcoal and burning to improve grazing. Based on the above observations, the species is assessed as Near Threathened.

Additional specimens examined.

MADAGASCAR. Mahajanga Province: 2 km N of Tsarahasina , 30 m, 10 May 2006 (fr.), Andriamahay & Rakotoarisoa 1359 (K); canton Bemanevika, Analafaly forest, 6 km E of Marotaolana, 384 m, 10 May 2005 (fr.), Birkinshaw, Andrianjafy & Raha-Jean 1525 (BR, MO, P, TAN); Réserve Naturelle VII, Ankarafantsika, 120-150 m, s.dat. (fl.), coll. ignot. 30-SF (P); vallée de Marivoraona, village le plus proche Ambodifiakarana, canton Betsandraka, district Tsaratanana, bord E du sentier d’Ambatobe à Ambodifiakarana, 30 Nov 1958 (fr.), coll. ignot. 19146-SF (P, TEF); forêt d’Anatialabe, village le plus proche Kamakama, canton Ankirihitra, district Ambatoboeni, 30 Nov 1958 (fr.), coll. ignot. 19382-SF (P, TEF); Soalala district, Reserve Naturelle Integrale de Namoroka ( Réserve Naturelle 8), c. 38.5 km S of Soalala, 120 m, 2 Feb 2000 (fr.), Davis, Rakotonasolo & Wilkin 2520 (BR, K, TAN); forêt de Marohogo, 22 m, 13 Feb 1999 (fr.), De Block & Rakotonasolo 799 (BR, C, G, K, MO, P, TAN, WAG); Réserve Naturelle VIII, Tsingy de Namoroka , canton Andranomavo, district Soalala , 24 Apr 1952 (fl.), Rakotovao 3898-RN (P, TAN); Réserve Naturelle VIII, Tsingy de Namoroka , Andranomavo, district Soalala , 29 Dec 1952 (fl.), Rakotovao 4918-RN (P, TAN); Ambatofolaka, Réserve Naturelle VIII, Tsingy de Namoroka , canton Andranomavo, district Soalala , 28 Mar 1954 (fr.), Rakotovao 6154-RN (BR, P, TEF); Ambatofolaka, Réserve Naturelle VIII, Tsingy de Namoroka , canton Andranomavo, district Soalala , 26 Jan 1954 (fr.), Rakotovao 6239-RN (BR, P, TEF); canton Andranomavo, district Soalala , 25 Feb 1957 (fr.), Randriamiera 8770-RN (BR, P, TEF); canton Andranomavo, district Soalala , 10 Nov 1958 (fl.), Randriamiera 9724-RN (BR, P, TEF) ; Fianarantsoa Province: de Ihosy 47-49 km ad SE per viam ad Ivohibe in nemorosis parvis residuis juxta pascua ignita, 650-700 m, 5 Nov 1967 (fl.), Bernardi 11197 (G, K, P); bassin de la Menarahaka, près du carrefour des routes d’Ihosy à Ivohibe et Iakora, 650 m, 10 Feb 1963 (fr.), Capuron 22618-SF (P, TEF); haut bassin de la Menarahaka, E d’Ihosy, 5 Nov 1967 (fr.), Capuron 27850-SF (BR, P, TEF); vallée de la Menarahaka, E d’Ihosy, 19 Dec 1968 (fl.), Capuron 28479-SF (P, TEF); 10 km NE d’Ihosy entre Ihosy et Ambararata, 22 Feb 1970 (fr.), Capuron 29068-SF (BR, P, TEF); road Antananarivo-Ihosy, a few km before reaching Ihosy , 4 Jan 1999 (fl.), De Block & Rakotonasolo 534 (BR, K, MO, TAN); haute vallée de la Menarahaka, E d’Ihosy, 700-800 m, 28 Jan-10 Apr 1955 (fr.), Humbert 29886 (BR, P) ; Toliara Province: Sakaraha, commune Mahaboboka, Marotsiraka, forêt d’Analaraty, 469 m, 24 Mar 2013 (fr.), Andriamihajarivo, Miandry & Rakotoarivony 1879 (BR, MO, P, TAN); c. 10 km N of Befandriana-Sud, 150 m, 28 Nov 1962 (fl.), Appert 108 (MO, Z); Morombe district, Tanandava-Tatalavalo, 70 m, 10 Mar 1963 (fr.), Appert 114 (MO, Z); Fotivolo, Ankazobe, Feb 1963 (fr.), Bosser 17287 (BR, P, TAN); environs de Berenty, 18 Feb 1970 (fr.), Bosser 19934 (BR, P); Betsipotika, E de Morondava, 18 Jan 1962 (fl.), Capuron 20872-SF (BR, P, TEF); N de Dabara , Mahabo , 1 Apr 1970 (fr.), Capuron 29141-SF (BR, P, TEF); forêt de Mavozobe, village le plus proche Mavozobe, canton Befandriana-Sud , sous-préfecture Morombe, 22 Feb 1964 (fr.), coll. ignot. 21707-SF (TEF); forêt de Mavozobe, village le plus proche Mavozobe, canton Befandriana-Sud , sous-préfecture Morombe, 22 Feb 1964 (fr.), coll. ignot. 21708-SF (P); Kirindi forest , N part - Conoco, 7-16 m, 19 Jan 2007 (fl.), De Block, Rakotonasolo, Groeninckx & Dessein 2194 (BR, G, MO, P, TAN); Morondava , 1892 (fl.), Grevé s.n. (K); Morondava , close to site of baobabs amoureux, 27 m, 22 Jan 2007 (fl.), Groeninckx, Rakotonasolo, De Block & Dessein 132 (BR, G, MO, P, TAN, WAG); bassin de la Malio, affluent de Mangoky, près d’Ambalabe, 400-450 m, Nov 1946 (fl.), Humbert 19447 (BR, P); bassin moyen du Fiherenana entre Lambomakandro et Sakaraha, 400 m, 10 Dec 1946 (fl.), Humbert 19681 (BR, P); N of Tulear, near Mangoky river , 50 m, 1 Jan 1989 (fl.), Phillipson 3068 (BR, K, MO, P, TAN, WAG); Horombe, Beroroha, Tsivoko, forêt humide de Makay dans la zone de Menapanda, 495 m, 9 Dec 2010 (fr.), Rakotovao & Andriantiana 5558 (BR, MO, P, TAN); district Ankazoabo, commune Ankazoabo, canton Morafeno, village le plus proche Ampanihimahasoa, route Sakaraha-Ankazoabo, 12 km SE d’Ankazoabo, 599 m, 11 Mar 2004 (fr.), Randrianaivo, Ratodimanana, Razafindraibe, Randrianarisoa, Edodoky & Tsimanoa 1058 (BR, G); Sakaraha , Mahaboboka, canton Marotsiraka Betsileo, S of Ambinanintelo village and S of the intersection of the two rivers Bevoalavo and Andranoheza, 417 m, 21 Feb 2011 (fr.), Randrianasolo, Andriamihajarivo, Razanatsima, Rakotoarivony, Randrianarivony, Fagnarena, Bruno & Redilike 1417 (BR, MO, P, TAN); forêt d’Anosilamy, canton Beronono, commune Beronono, 448 m, 13 Jan 2010 (fr.), Razakamalala, Rakotovao & Andriantiana 5161 (BR, MO, P, TAN); Unplaced localities: forêt de Moailake, Feb 1892 (fl.), Douilot s.n. (P); Nandrosia, May 1897 (fr.), Perrier de la Bâthie 234 (P); Boiny, not readable further, Jan 1902 (fl.), Perrier de la Bâthie 1011 (BR, P); Without locality: s.dat. (fr.), Baron 4612 (K, P); Central Madagascar , s.dat. (fr.), Baron 4673 (K); s.dat. (fr.), Baron 4679 (P); s.dat. (st.), Douilot s.n. (P); s.dat. (fr.), Homolle 1427 (P); s.dat. (fr.), Homolle 1473 (P); s.dat. (fr.), Homolle 1495 (P) .

Figures

Figure 2. Exallosperma and Helictosperma. A-C Exallosperma longiflora: A flowering branch B inflorescence C infructescence from herbarium specimen Gautier et al. 4257 D Helictosperma poissoniana, flowering branch E, F Helictosperma malacophylla: E inflorescence F detail of inflorescence. Photographs: P. De Block (A, D), S. Dessein (E, F), L. Nusbaumer (B, C, ©: Conservatoire et Jardin botaniques de la Ville de Geneve).

Figure 6. Helictosperma malacophylla. A, flowering branch B fruiting branch C flower D bract, bracteole, ovary and calyx E longitudinal section through ovary and calyx F longitudinally opened corolla showing the position of stamens and style G stamens H placenta and ovules, abaxial view I placenta and ovules, adaxial view J fruit. A-C, E-G, J reproduced or adapted from Drake del Castillo (1897: Pl. 422) D De Block et al. 534 H, I De Block et al. 797.

Figure 8. Helictosperma malacophylla: pyrene and seed. A pyrene showing four preformed germination slits, lateral view B pyrene falling apart into four valves along preformed germination slits, lateral view C seed, adaxial view, with embryo position indicated D transverse section through seed. A-D coll. ignot. 19146 - SF.

Figure 9. Pollen of Exallosperma and Helictosperma. A-D, M Exallosperma longiflora E-H, N Helictosperma malacophylla I-L H. poissoniana. A, E, I polar view B, F, J equatorial view C, G, K mesocolpium D, H, L ectoaperture M, N pollen grain wall. A, M Nusbaumer & Ranirison 1992 B-D De Block et al. 1132 E-H, N Phillipson 3068 I-L Leandri 573.

Figure 14. Distribution maps. A Exallosperma longiflora B Helictosperma malacophylla C H. poissoniana D Pseudocoptosperma menabense E Tulearia splendida F T. capsaintemariensis.