Croton loucoubensis Baill.
Creators: name: Kainulainen, Kent
name: Ee, Benjamin van
name: Razafindraibe, Hanta
name: Berry, Paul E.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Malpighiales
Euphorbiaceae
Croton
Croton loucoubensis

description: Croton loucoubensis Baill. in Adansonia 1: 155. 1861 [as loucoubense] (Fig. 1E, 2C, 4 I-J, 8).
Ξ Croton adenophorus var. loucoubensis (Baill.) Müll. Arg. in A. DC., Prodr. 15(2): 589. 1866.
Lectotypus (designated here): MADAGASCAR. Prov. Antsiranana: Diana Reg., Nossibé, forêt de Loucoubé, III.1851, Boivin s.n. (P [P00133453]!). Syntypus: FRANCE. Dept. Mayotte: sine loc., VI.1848, Boivin 3382 (P [P00133452]!).
= Croton adenophoroides Radcl.-Sm., Gen. Croton Madag. Comoro 117. 2016. Typus: M ADAGASCAR. Prov. Antsiranana: Besinkara, Ambalafary, Andvakena: premier cours d’eau sur le chemin de Bekolosy, 14°04’S 48°17’E, 500 m, 12.XI.1994, Gautier & Derleth 2529 (holo-: K!; iso- G [G00341696]!, MO!, P [P00433174]!), syn. nov.
Shrubs or trees 1.5-10 m tall, dichotomously branching, internodes sometimes so short as to give the appearance of whorled branches; in all parts covered in whitish to ferrugineous, stellate trichomes many of which have a bristly, porrect (to c. 3 mm) central radius. Branches ± flattened and striate on new growth but becoming terete with age, reddish-brown to gray, with stellate trichomes, with orange latex. Stipules 0.8-2.0 cm long, lanceolate, fimbriate, glandular, caducous. Leaves alternate to ± opposite along stem, opposite at the apex. Petioles 3-15(-20) cm, adaxially canaliculate, densely stellate, usually with a pair of acropetiolar, ± reclined, stipitate (to 2.5 mm long), stellate-pubescent glands with a concave discoid apex (0.3-0.5 mm diam.). Leaf blades chartaceous, glandulardenticulate or undulate, ovate, 5-20 × 3-13.5 cm, apex acute to acuminate, base rounded to truncate or rarely cordate; adaxial surface velvety to bristly stellate-pubescent, pale green when fresh (turning orange in old leaves) and drying matte pale green to brown; venation with 4-9 pairs of brochidodromus, ± penninerved secondary veins (the lowermost pairs congested and appearing palmate), and cross-venulate tertiary venation; abaxial surface velvety stellate-pubescent, matte, paler than the adaxial side when dry; venation prominent and very distinct, with stipitate glands in some of the axils of the secondary veins (Fig 1E). Inflorescences terminal, raceme-like thryses 3.5-22.5 cm long, with numerous staminate flowers towards the distal end and 0-6 pistillate flowers towards the base; axes densely stellate-pubescent, flattened and striate; bracts awn-shaped, 1-5 mm long, usually persistent. Staminate flowers with brown, hirsute-stellate, subglobose buds 2.0- 3.5 mm diam., pedicels elongating from bud to anthesis, 1-8 mm long; sepals 5, yellowish pale green, shortly connate at base, lobes broadly triangular-ovate, 2.2-2.8 × 1.3-2.0 mm, apex acute to rounded, abaxially stellate-pubescent, adaxially cilate towards apex, margins densely ciliate; petals 5, white, elliptic to spatulate, 2.4-3.5 × 1.2-2.2 mm, recurved at anthesis, abaxially and adaxially ciliate, margins densely ciliate; disc glands 5, opposite the sepals, sessile, ellipsoidal, c. 0.4 × 0.4 mm, pale yellow; stamens 16-18, white, filaments c. 2.5 mm long, ciliate, anthers broadly elliptic, c. 1.0 × 0.8- 1.0 mm; receptacle pilose. Pistillate flowers with stellatepubescent buds c. 2.5 mm diam., pedicels 1-6 mm long; sepals 5, triangular to ovate, spreading at anthesis, 2.5-5.0 × 1.8-3.0 mm, apex acute to rounded, somewhat inflexed, shortly connate at base, abaxially and adaxially stellate, pale green, persistent in fruit; petals absent or reduced to short filaments c. 1 mm long; disc glands 5, opposite the sepals, sessile, ellipsoidal, 0.4-0.6 × 0.8-1.2 mm, pale yellow; ovary densely covered in bristly, stellate trichomes, green, globoid, 2-6.5 mm in diameter, styles 3, 4- 5.5 mm long, each branch flattened and 3-4 times bifurcate, with the first bifurcation congested and fused, spreading, recurved at the apices, abaxially stellate-pubescent, adaxially glabrous, yellowish, turning brown, persistent. Capsules 1-1.5 × 1-1.5 cm, smooth, pale greenish-brown, hirsute, exocarp separating, endocarp woody, c. 2 mm thick (Fig. 4I); columella 7-10 mm long, cornute. Seeds ± compressed-ellipsoid, apiculate, 6.3-6.9 × 4.4-4.8 × 2.5-3.4 mm (Fig. 4J); testa matte brown, diagonally ridged, verrucose; caruncle reniform, 0.5-0.8 × 1.1-1.7 mm.
Phenology. – There are specimens in flower collected in September to December and in March, which suggests either a bimodal flowering season, or else just a lack of collections from the generally rainy months of January and February.
Distribution, habitat and ecology. – Croton loucoubensis is known from northwestern Madagascar, from sea level to about 900 m elevation, where it is found in moist evergreen forests as well as secondary vegetation. It appears to be restricted to the subhumid Sambirano Domain, following the phytogeographical domains described by HUMBERT (1955), and has mainly been collected in Ampasindava Peninsula, the Manongarivo RS, and on the islands of Nosy Be and Nosy Komba (Fig. 2C). The syntype from Mayotte (Boivin 3382) is unfortunately sterile, and, in this condition, it is not clear if it represents this species or C. mayottae.
Conservation assessment. – Croton loucoubensis occurs in the protected areas of Ampasindava, Lokobe, and Manongarivo. Only one recent collection has been made outside these areas (Gillespie et al. 10646). We estimate that the extent of occurrence is no more than 3000 km 2, and we therefore consider this species as “Near Threatened” (NT), according to IUCN Red List Categories and Criteria (IUCN, 2012).
Vernacular names. – “Hazomafaika” (Reserves Naturelles 9215), “Kimiramira” (Gautier et al. 3078), “Lazakatalaotra” (Reserves Naturelles 4896), “Tsimiramira” (Ammann et al. 91a).
Notes. – The species epithet loucoubensis refers to the type locality in the Lokobe forest on the island of Nosy Be in Antsiranana Province.
BAILLON (1861), followed by LEANDRI (1939), included a specimen of Croton loucoubensis (Boivin 2185) in C. muricatus Vahl, a species from southeastern Madagascar, a factor that has contributed to the confusion surrounding these species and the taxonomy of the Adenophorus Group as a whole. LEANDRI (1939) treated C. loucoubensis as a synonym of C. adenophorus, but his concept of C. adenophorus, as shown in his key and description, conforms here to the type of C. loucoubensis. RADCLIFFE-SMITH (2016) also failed to recognize the type of C. loucoubensis as distinct from C. adenophorus; instead he described C. adenophoroides based on newer material. Croton loucoubensis is readily distinguished from C. adenophorus by its fimbriate stipules, velvety leaves, stipitate and pubescent petiolar glands, and larger woody capsules (10-15 × 10-15 mm vs 5-6 × 5.5-8 mm) with bristly pubescence (Fig. 4I).
Additional specimens examined. – MADAGASCAR. Prov. Antsiranana: Diana Reg., Ambanja Distr., Ampasindava, Bongomihiravavy forest, 13°46’07”S 48°05’52”E, 323 m, 27.XI.2008, Ammann et al. 91a (G, MO, TEF); Ampasindava, Betsitsika forest, 13°46’09”S 48°04’06”E, 317 m, 7.XII.2008, Ammann et al. 159 (G, MICH, MO, TEF); Ampasindava, Andranomatavy forest, 13°40’02”S 47°59’13”E, 205 m, 24.XI.2009, Ammann et al. MYA 378 (G, K, MICH, MO, P, TEF); Nosy Be, Lokobe Reserve, 13°24’46”S 48°18’45”E, 0-100 m, 5.IX.1994, Antilahimena 154 (MO, P); Ampasindava, Ambohimirahavavy forest, 13°45’43”S 48°05’40”E, 410 m, 13.XI.2008, Bernard et al. 1192 (G, MICH, MO, P, TAN); Nosy Be, n.d., Boivin 56 (P); Nosy Komba, VII.1850, Boivin 2185 (P); Nosy Be, Lokobe forest, X.1960, Bosser 14738 (MO, P, TAN); Manongarivo Reserve, 14°02’S 48°18’E, 880 m, 20.IX.1996, Gautier et al. 3078 (G, MO, P); Nosy Be, Lokobe forest, 1.IX.1967, Jacquemin H457J (K, P); Ampasindava, Bongomihiravavy forest, 13°45’43”S 48°05’25”E, 435 m, 11.XI.2008, Madiomanana et al. MAD 110 (G, MO, P, TEF); ibid. loc., 13°45’28”S 48°04’10”E, 270 m, 26.XI.2007, Nusbaumer 2536 (G, MO, TEF); ibid. loc., 13°45’36”S 48°06’36”E, 505 m, 28.XI.2007, Nusbaumer 2600 (G, MICH, TEF); Ampasindava, Betsitsika forest, 13°44’37”S 48°01’18”E, 333 m, 22.XI.2008, Nusbaumer & Tahinarivony 2955 (G, K, MO, P, TEF, WAG); Manongarivo Reserve, 14°03’09”S 48°17’03”E, 240 m, XII.1993, Rakotomalala et al. 16 (G, MO, P); [Ampasindava], 13°46’59.5”S 48°04’33.0”E, 317 m, 2.V.2012, Rasoanaivo et al. 50 (G, MO); Lokobe Reserve, 28.IX.1952, Réserves Naturelles 4360 (K, P); Nosy Be, 17.XI.1952, Réserves Naturelles 4896 (P); Lokobe Reserve, 5.XII.1953, Réserves Naturelles 5936 (K, P, TAN); Nosy Be, Andranokomba, 30.X.1956, Réserves Naturelles 9215 (G, K, MO, P, WAG); Nosy Be, Hellville, 30.X.1956, Réserves Naturelles 9441 (G, K, MO, P); Nosy Be, 12.III.1971, Schmitt 255 (P); ibid. loc., 13.III.1971, Schmitt 272 (P). Prov. Mahajanga: Sofia Reg., Analalava Distr., 111 km N of Antsohihy along RN 6, S of Ankaromyhely, 14°04’31”S 48°06’25”E, 245 m, 21.X.2012, Gillespie et al. 10646 (CAN, MICH, MO, TAN); Andranomohavelona, Ambaliha, Ambanja, 18.X.1953, Service Forestier 7702 (P).
description: Published as part of Kainulainen, Kent, Ee, Benjamin van, Razafindraibe, Hanta & Berry, Paul E., 2017, A revision of the Adenophorus Group and other glandular-leaved species of Croton (Euphorbiaceae) from northern Madagascar and Mayotte, including three new species, pp. 371-402 in Candollea 72 (2) on pages 390-392, DOI: 10.15553/c2017v722a15, http://zenodo.org/record/5722061