Croton plurispicatus P.E. Berry, Kainul. & B.W. van Ee, 2016

Kainulainen, Kent, Ee, Benjamin van, Antilahimena, Patrice, Razafindraibe, Hanta & Berry, Paul E., 2016, New species and species reports of Croton L. (Euphorbiaceae) from the eastern forest corridor of Madagascar, Candollea 71 (2), pp. 327-356 : 342-344

Croton plurispicatus P.E. Berry, Kainul. & B.W. van Ee , spec. nova ( Fig. 1B , 7 C-D, 10, 12A-F).

Typus: MADAGASCAR. Prov. Toamasina: Alaotra- Mangoro Region. Moramanga Distr., along road heading S from RN 2 towards Lakato, c. 9.8 km S by line-ofsight from RN 2, 19°03’05”S 48°21’32”E, 1030-1060 m, 13.VIII.2015, van Ee, Berry & Razafindraibe 2198 (holo-: MICH [ MICH1513198 ]!; iso-: G!, MAPR!, MO!, MICH [ MICH1513199 ]!, P,! TAN!).

Croton plurispicatus P.E. Berry, Kainul. & B.W. van Ee is similar in pubescence and habit to Croton chrysodaphne Baill. and C. submetallicus Baill. , but differs in its smaller flowers grouped in multiple, axillary, spicate thyrses along the distal nodes of the fertile stems.

Shrubs or small trees to 8 m tall, to 7 cm diam. at base, densely branched with sharply ascending branches producing copious red sap when cut. Branches ± flattened on new growth, ridged and furrowed, densely covered by overlapping, copperyferrugineous lepidote trichomes. Stipules absent or vestigial. Leaves alternate, ± congested towards the branch tips. Petioles 1.0-2.5(-4.0) cm long, adaxially canaliculate. Leaf blades subcoriaceous, elliptic to narrowly elliptic-oblanceolate, 3-5 × 5-15 cm (to 6 × 20 cm on vigorous basal branches), apex obtuse to broadly acute or rounded, base acute to cuneate, margin entire, with a pair of prominent globoid glands 0.6- 1 mm diam. at the junction of the blade and petiole, usually on the abaxial side, the top of the gland generally with a narrow hollowed opening, sometimes with a second or a third pair of similar but smaller glands on the edge of the blade shortly above the base; venation brochidodromous, with 9-11 pairs of secondary veins, barely noticeable on adaxial side but more visible and subprominent on abaxial side, adaxially coppery-lepidote (young leaves densely coppery-lepidote, but as the leaf expands the scales become more sparse and the underlying green cuticle becomes visible), abaxially silvery-white-lepidote with ± evenly dispersed brown lepidote trichomes, the midvein raised and prominent on abaxial side, with more coppery-lepidote trichomes than rest of blade. Inflorescences spicate-thyrsoid, ascending, 3-8(-9) cm long, axillary with up to 12 in successive leaf axils on a single branch, the rachis slightly flattened or ridged, sometimes entirely staminate or else with 1-3 basal pistillate flowers followed by many cymules of staminate flowers in the distal portion. Staminate flowers with densely coppery-lepidote, orbicular buds c. 2 mm diam., pedicels 1-3(-4) mm long at anthesis; sepals 5, valvate, deltate, c. 1.5 × 1.5 mm, inflexed at anthesis, abaxially coppery-lepidote; petals 5, ligulate, c. 1.2 × 1.5 mm, recurved at anthesis, abaxially coppery-lepidote, adaxially glabrous, margins densely crispate-villous; disc glands/nectaries 5, opposite the sepals, sessile, ellipsoid, c. 0.8 × 0.4 mm, yellow; stamens 15-25, white to pale yellow, filaments 1.5-2 mm long, densely villous towards the base and on the receptacle, anthers oblong, c. 0.5 mm long. Pistillate flowers with short pedicels 0.5-1.5 mm long, with a narrowly lanceolate bracteole c. 0.2 × 1.0 mm at base, sepals 5, valvate, narrowly triangular, patent at anthesis, abaxially coppery-lepidote, adaxially pale-greenish lepidote with coppery dots, dorsally ridged, 1.5-2.0 × 3.0- 4.0 mm; petals absent; disc glands/nectaries 5, opposite the sepals, sessile, ellipsoid, c. 0.6 × 0.4 mm, yellow; ovary densely coppery-lepidote, globoid, 2.5 mm diam.; styles 3, to 3 mm long, up to five times bifurcate with numerous stigmatic tips, pale greenish-cream on upper surface, patent at anthesis. Capsules ( Fig. 7C ) densely coppery-lepidote, globoid, 7- 8 mm diam.; columella 5-6 mm long, cornute, fimbriate. Seeds ( Fig. 7D ) dark grey or brown, lenticular, 4-6 × 3-4 mm, caruncle c. 0.5 × 1.0 mm, with a conspicuous raphe on ventral side below the caruncle.

Etymology. – The specific epithet refers to the multiple, spike-like inflorescences that are clustered along the flowering branches of this species.

Phenology. – So far, this species has been found in flower and fruit in February, March, May, June, and August, so it is likely that it flowers fairly continuously throughout the year.

Distribution, habitat and ecology. – Croton plurispicatus is known from a relatively restricted area of primary montane moist forest from adjoining areas of the Alaotra-Mangoro and Atsinanana regions of Toamasina Prov., at elevations of 600- 1100 m ( Fig. 1B ). So far it has mainly been found south of Andasibe (principally along the road to Lakato), but it has also been collected in a locality north of Route Nationale 2 near the southeastern corner of Mantadia National Park. Along the Lakato road, it grows in association with the more common and widespread C. submetallicus .

Notes. – Within Malagasy Croton , C. plurispicatus belongs to a diverse group of species that have in common large penninerved leaves with a dense covering of coppery- or silvery-lepidote trichomes on the underside. LEANDRI (1972) published a note about this group in which he recognized seven species from Madagascar and one from the Comoro Islands. BERRY et al. (2011) clarified the tangled history of one of these, C. chrysodaphne Baill., and BERRY & VAN EE (2011) established C. multicostatus Müll. Arg. as the correct name for another member of this group. Nonetheless, there are quite a few other specimens from various parts of the island that fall into this morphological group that still remain unidentified, often because they lack sufficient flowering or fruiting material.

We believe that the most distinctive character of this new taxon are the multiple narrow thyrses that appear individually in the axils of successive leaves on young branches, whereas most Croton species have a single main axillary or terminal inflorescence ( Fig. 10 E-F). The young stems and leaves are characterized by a very dense, coppery-lepidote indumentum that changes as the leaves expand and develop ( Fig. 10E, I ). On the leaf undersurface, the trichomes completely cover the blade at maturity, but the outer fringes of the scales then become visible and are lighter in color than the coppery center of the scales. On the upper surface, the scales are less dense and they degenerate more, leaving some of the underlying green cuticle exposed and visible when fully expanded. The basal leaf glands are unusual in having a narrow hollow opening on top ( Fig. 10F ). The stems and inflorescences are noticeably ridged and partially flattened ( Fig. 10D ). The paucity of pistillate flowers in this species is noteworthy (only 1-3 per inflorescence when present, with some inflorescences being entirely staminate); the pistillate flowers also have very short, stout pedicels, small calyces, a lepidote inner surface, and intricate, highly divided styles. In contrast, the staminate flowers are far more numerous and longer-pedicellate, with numerous (15-25) stamens.

Where we collected C. plurispicatus along the road from Andasibe to Lakato, it was most often growing in association with the more abundant and widespread C. submetallicus . That species is generally a lower-growing and more spreading shrub or tree, with the pistillate flowers having much larger sepals and much more elongate pedicels, as well as leaves with much sparser indumentum on the underside, but the two do seem to intergrade and possibly hybridize in this area. In particular, van Ee et al. 2203 (MAPR, MICH, MO, P, TAN) was a plant that had many intermediate characters between the two species.

Paratypi. – MADAGASCAR. Prov. Toamasina: Alaotra-Mangoro Region, Moramanga Distr., Ambatovola, Fanovana , forêt de Vohimana , 18°55’13”S 48°30’49”E, Andriatsiferana et al. 2559 ( MO, P, TAN); Lakato, VII.1973, Guillaumet 4274 ( P); village d’Ambodigavo , forêt d’Analanjahana à l’W d’Ambodigavo , 19°07’39’’S 48°23’51’’E, 900 m, 31.V.2007, Razanatsima et al. 290 ( MO); Lakato, village Manasamena , forêt corridor Ankeniheny , 19°04’02’’S 48°22’02’’E, 1041 m, 19.IX.2007, Razanatsima et al. 369 ( MO); Atsinanana Region, Vatomandry Distr., Ambalabe , Ambinanindrano II , le long de la piste vers SW du Tobin’I Foara, 19°10’11”S 48°34’40”E, 610 m, 12.III.2005, Ranaivojaona & Razanatsima 1173 ( K, MICH, MO); ibid. loc., 19°09’08’’S 48°34’47’’E, 610 m, 14.III.2005, Randrianasolo et al. 1028 ( K, MICH, MO); Sahanionaka, forêt de Vohibe , chute Tsitondroina , 19°10’49”S 48°32’27”E, 763 m, 2.VI.2010, Razanatsima 858 ( MO); Alaotra-Mangoro Region, Moramanga Distr., along unpaved road from RN 2 to Lakato, 19°03’35’’S 48°21’49’’E, 1015 m, 27.II.2009, van Ee et al. 981 ( MAPR, MICH, MO, P, TAN); ibid. loc., van Ee et al. 982 ( MAPR, MICH, MO, P, TAN); ibid. loc., 19°04’25”S 48°22’04’’E, 906 m, 27.II.2009, van Ee et al. 984 ( MICH, TAN); ibid. loc., 19°03’05”S 48°21’32”E, 1030-1060 m, 13.VIII.2015, van Ee et al. 2199 ( MAPR, MICH, MO, P, TAN); ibid. loc., van Ee et al. 2200 ( MAPR, MICH, MO, P, TAN); ibid. loc., van Ee et al. 2202 ( MAPR, MICH, MO, P, TAN).

Figures

Fig. 1. – Distribution maps. The grey squares or white arrow on the inset maps of Madagascar show the location of the area depicted. A. Croton ferricretus Kainul., B.W. van Ee & P.E. Berry (red); B. Distribution of Croton droguetioides Kainul. & Radcl.-Sm. (turquoise) (Cours 4111 not shown), C. enigmaticus P.E. Berry & B.W. van Ee (light green) (Ralimanana et al. 1402 not shown), C. indrisilvae Kainul., B.W. van Ee & P.E. Berry (yellow), and C. plurispicatus P.E. Berry, Kainul. & B.W. van Ee (light purple); C. Croton ankeranae Kainul. (yellow), C. radiatus P.E. Berry & Kainul. (red), and Croton lasiopyrus Baill. (white). The collection in gray represents presumed hybrids between C. lasiopyrus and C. enigmaticus (van Ee et al. 2215 and 2216); D. Croton hypochalibaeus Baill. in Madagascar. [Google Earth Image © 2016 DigitalGlobe.Reproduced per attribution guidelines]

Fig. 7. – Croton ferricretus Kainul., B.W. van Ee & P.E. Berry (A-B), C. plurispicatus P.E. Berry, Kainul. & B.W. van Ee (C-D), C. hypochalibaeus Baill. (E-F), C. indrisilvae Kainul., B.W. van Ee & P.E. Berry (G-H), and C. enigmaticus P.E. Berry & B.W. van Ee (I-J). A, C, E, G, I. Capsule; B, D, F, H, J. Seed. [A-B: van Ee et al. 2436; C: van Ee et al. 2198; D: Ranaivojaona & Razanatsima 1173; E-F: van Ee et al. 2472; G-H: van Ee et al. 2176; I-J: van Ee et al.2214]

Fig. 10. – Croton plurispicatus P.E. Berry, Kainul. & B.W. van Ee. A. Top of felled tree with dense ascending branches; B. Cross-section of woody stem, showing reddish sap at cambial layer; C. Young twig cut to show reddish latex that is exuded; D. Twig with flattened and angled shoots; E. Flowering branch showing the multiple thyrses along a single stem, some of them entirely staminate; F. Inflorescence with staminate flowers and buds. Note also the basilaminar glands (lower right); G. Pistillate flower at anthesis showing the lepidote inner surface of the sepals and the intricately divided, patent styles; H. Inflorescence with three basal pistillate flowers at varying stages of fruit development; I. Inflorescence with a basal fruit and a staminate flower above it. [Photos: P.Berry].