Croton ankeranae Kainul., 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 : 329-331

Croton ankeranae Kainul. , spec. nova ( Fig. 1C , 2 ).

Typus: MADAGASCAR. Prov. Toamasina: Atsinanana Region, Distr. Brickaville, Commune Maroseranana, Fokontany Ambodilendemy, Andrangato River , 18°26’37”S 48°46’31”E, 446 m, 13.III.2011, Antilahimena 7554 (holo-: MICH [ MICH1513200 ]!; iso-: MO!, P, TAN).

Croton ankeranae Kainul. can be distinguished from the similar small-leaved shrub Croton indrisilvae Kainul., B.W. van Ee & P.E. Berry by its taller habit (to 12 m vs. <1 m) and smaller leaves (4.5-10.5 × 3.9-6.3 mm vs. 9-28 × 5-12 mm) that are entire (vs. crenate) with the apex acute to obtuse (vs. obtuse to rounded).

Shrubs to small trees 0.8-12 m tall, dichotomously branching, internodes sometimes contracted giving the appearance of whorled branches. Branches ± flattened on new growth and densely covered by dark gray-brown fasciculate trichomes with rays c. 0.2 mm long, pale gray to whitish, becoming terete and glabrous with age. Stipules absent or vestigial. Leaves subopposite, ± congested at nodes. Petioles 0.7-1.8 mm, adaxially canaliculate, sometimes with a pair of acropetiolar, stipitate (0.2-0.4 mm long), discoid (c. 1.5 mm diam.) glands. Leaf blades thinly coriaceous, entire, (broadly) elliptic to obovate, 4.5-10.5 × 3.9-6.3 mm, apex acute-obtuse, base cuneate; adaxial surface glabrous, glossy, dark green when fresh and drying dark green; secondary venation indistinct; abaxial surface sparsely fasciculate, pale green when fresh and drying pale brown; secondary venation indistinct, midrib prominent. Inflorescences comprising 1-2 staminate flowers or a solitary pistillate flower, axillary or terminal; bracts triangular, c. 3.0 × 0.2 mm. Staminate flowers with fasciculate, subglobose buds c. 0.9 mm diam., pedicels to 1.5 mm long; sepals 5, shortly connate at base, lobes triangular to ovate, c. 0.7 × 0.3 mm, apex acute, inflexed at anthesis, abaxially fasciculate, adaxially glabrous, margins densely ciliate, pale green; petals 5, white, narrowly obovate to spatulate, c. 1.0 × 0.2 mm, recurved at anthesis, abaxially sparsely papillate, adaxially glabrous, margins densely ciliate; disc glands/nectaries 5, opposite the sepals, sessile, ellipsoid, c. 0.1 × 0.05 mm; stamens 3-5, white, filaments c. 1.5 mm long, ciliate, anthers broadly elliptic, c. 0.2 mm long; receptacle pilose. Pistillate flowers with fasciculate-pubescent buds c. 0.9 mm diam., pedicels 0.5- 0.9 mm long; sepals 5, elliptic, spreading at anthesis, 1.2 × 0.6 mm, apex rounded, abaxially stellate-pubescent, abaxially sparsely fasciculate, pale green; disc glands/nectaries 5, opposite the sepals, sessile, ellipsoid, c. 0.3 × 0.2 mm; glandular filaments (in petal position alternating with the nectary lobes) 5, linear, c. 0.5 × 0.07 mm, erect; ovary globose, c. 0.8 mm diam., densely stellate, styles 3, c. 2.5 mm long, bifurcate, spreading, recurved at the apices, with some fasciculate trichomes and a few pilose trichomes at the base, white, turning brown, persistent. Capsules 3-4 × 6-7 mm, smooth, with fasciculate trichomes; columella 2.8-3.5 mm long, cornute, capitate. Seeds not seen.

Etymology. – The specific epithet refers to the Ankerana forest where this species is found.

Distribution, Habitat and Ecology. – Croton ankeranae is to date only known from the Ankerana-Vohimanana montane forest in the Antsinanana Region of Toamasina Prov., at 400- 1050 m elevation ( Fig. 1C ).

Notes. – This species is probably most closely related to C. indrisilvae Kainul., B.W. van Ee & P.E. Berry described below, which has similar whitish stems with brown-fasciculate pubescence, small leaves with indistinct venation, and reduced inflorescences. However, both the leaves and flowers of C. ankeranae are smaller and among the smallest of any Malagasy Croton , and the staminate flowers have only 3 to 5 stamens.

Paratypi. – MADAGASCAR. Prov. Toamasina: Atsinanana Region. Brickaville Distr., Anjahamamy, Anivoranokely , Ankerana forest , 18°24’46”S 48°49’24”E, 768 m, 28.I.2012, Antilahimena 8108 ( MO, P, TAN); Maroseranana, Ambodilendemy, piste vers Vohimanana , 18°25’08”S 48°47’20”E, 1011 m, 24.III.2011, Ravelonarivo et al. 3838 ( MICH, MO); Ambatolampy, Vohimanana forest , 18°24’05”S 48°48’43”E, 927 m, 19.I.2012, Ravelonarivo & Edmond 4082 ( MICH, MO, P, TAN); Ankerana forest , 18°25’42”S 48°48’38”E, 695 m, X.2005, Razakamalala et al. 2260 ( 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. 2. – Croton ankeranae Kainul. A. Flowering branch with two staminate flowers; B. Staminate flower; C. Pistillate flower. Note bifurcate stigmas and greenish sepals; D. Branch with nearly mature capsule; E. Staminate flower; F. Staminate flower with stamens removed to show the five nectaries; G. Pistillate flower, showing bifurcate stigmas and filamentous structure in the position of petals; H. Pistillate flower with ovary and two sepals removed to show the five nectaries. Note the glandular filament in the petal position. [A, C-H:Antilahimena 7554; B: Ravelonarivo & Edmond 4082] [Photos: A, C-D: P. Antilahimena; B: D. Ravelonarivo]