Croton indrisilvae Kainul., B.W. van Ee & P.E. Berry, 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 : 338-339

Croton indrisilvae Kainul., B.W. van Ee & P.E. Berry , spec. nova ( Fig. 1B , 7 G-H, 9).

Typus: MADAGASCAR. Prov. Toamasina: Alaotra- Mangoro Region, Moramanga Distr., Analamazaotra National Park , on trail to the east of the visitor center, 18°56’45”S 48°25’33”E, 975 m, 11.VIII.2015, van Ee, Berry & Razafindraibe 2175 (holo-: MICH [ MICH1513201 ]!; iso-: G!, MO!, TAN!).

Croton indrisilvae Kainul., B.W. van Ee & P.E. Berry is distinguished from C. droguetioides Kainul. & Radcl. -Sm. by its whitish branches with brown, fasciculate trichomes (vs. gray branches with villous, whitish trichomes); obovate crenate leaves with obtuse to rounded apex and cuneate base (vs. ovate dentate leaves with apiculate apex and rounded to cordate base); the absence of stipitate petiolar glands; and the lower number of stigma lobes (6 vs.>30). It is sometimes confused with Croton incisus Baill. but is differentiated by its crenate leaves (vs. incised to lobed) with obtuse to rounded (vs. acute) apex and the absence of stipitate petiolar glands.

Shrubs 0.3-0.8 m tall, dichotomously branching, internodes sometimes contracted giving the appearance of whorled branches. Branches ± flattened on new growth and densely covered by dark reddish-brown, fasciculate trichomes with rays c. 0.5 mm long, pale gray-whitish, becoming terete and glabrous with age. Stipules absent or vestigial. Leaves whorled at apex and nodes. Petioles 1-3 mm long, adaxially canaliculate, without any apparent glands. Leaf blades thinly coriaceous, slightly revolute, crenate towards apex, obovate, 9-28 × 5-12 mm, apex obtuse to rounded or emarginate, base cuneate; adaxial surface glabrous, glossy, dark green; secondary venation indistinct, with 2-5 pairs of brochidodromus, ± penninerved secondary veins, midrib prominent except near apex; abaxial surface sparsely covered with a mixture of white and brown fasciculate trichomes, glossy, pale green when fresh and drying gray-green; venation ± indistinct except for the midrib. Inflorescences racemose, reduced, to 3 mm long, terminal or axillary, bracts linear to lanceolate, 0.5-1.0 mm. Staminate flowers with stellate-pubescent, subglobose buds c. 1.1 mm diam., pedicels c. 1.0 mm long; sepals 5, shortly connate at base, lobes triangular to ovate, c. 0.9 × 0.7 mm, apex acute, inflexed at anthesis, abaxially stellate-pubescent, adaxially glabrous, margins ciliate; petals 5, narrowly obovate to spatulate, c. 1.2 × 0.4 mm, recurved at anthesis, abaxially sparsely papillate, adaxially glabrous, margins ciliate; disc glands/nectaries 5, opposite the sepals, sessile, triangular, c. 0.2 × 0.1 mm; stamens c. 5, filaments c. 1.3 mm long, ciliate, anthers broadly elliptic, c. 0.4 mm long; receptacle pilose. Pistillate flowers with pedicels 1.5- 7.0 mm long; sepals 5, oblong-spatulate, 2.3-3.3 × 0.7- 1.5 mm, apex rounded, abaxially stellate, adaxially glabrous, pale green, persistent in fruit; disc glands/nectaries 5, opposite the sepals, sessile, ellipsoid with an apical depression, c. 0.5 × 0.3 mm, yellowish; glandular filaments (in petal position alternating with the sepals) 5, fusiform, c. 0.4 × 0.1 mm, reddish; ovary globose, 1.0- 1.5 mm diam., densely stellate; styles 3, c. 1.6 mm long, bifurcating 1-2 times, stellate-pubescent, persistent. Capsules 4.3-4.8 × 2.8-6.3 mm ( Fig. 7G ), smooth, pale brown, brown stellate-pubescent, exocarp not separating, endocarp woody, c. 0.2 mm thick; columella c. 2.5 mm long, cornute, capitate. Seeds ellipsoid ( Fig. 7H ), c. 3.6 × 3.0 × 2.9 mm; testa glossy, rugulose, pale brown; caruncle elliptic, c. 0.6 × 0.2 mm.

Etymology. – The specific epithet refers to the forests where this species grows, which are inhabited by the large, tail-less lemur species, Indri indri Gmelin, 1788 .

Distribution, habitat and ecology. – Croton indrisilvae is only known from Analamazaotra in the Alaotra-Mangoro Region at 900-1000 m elevation, where it forms part of the primary montane forest understory ( Fig 1B ).

Notes. – This is one of several Malagasy Croton shrubs with small leaves (<30 mm long) from moist montane forests in eastern Madagascar, including C. ambanivoulensis Baill. , C. ankeranae , C. incisus Baill. These species all have pale stems with contrasting dark fasciculate trichomes and leaves with cuneate bases and ± indistinct venation. They are mainly distinguished on the basis of the shape and size of the leaves. Both C. ankeranae and C. indrisilvae have obovate leaves, but the leaves of C. indrisilvae are larger (<28 × 12 mm vs. <10.5 × 6.3 mm), somewhat revolute, and crenate (vs. entire). The poorly known (and possibly conspecific) C. ambanivoulensis and C. incisus have rhombic leaves that are serrate in the former and incised in the latter. Unlike C. indrisilvae they also have stipitate petiolar glands.

Paratypi. – MADAGASCAR. Prov. Toamasina: Alaotra-Mangoro Region, Moramanga Distr., Station forestière d’Andasibe (Périnet) , 900 m, 8.XII.1989, Evrard 11244 ( P, TAN); Analamazaotra , 18°56’14”S 48°25’62”E, 910 m, 20.IV.2010, Rajaovelona 258 ( K, P, TAN); Perinet , Rauh 477 ( TAN); Analamazaotra , 8.III.1950, Service Forestier 715 ( K, P); ibid loc., 8.VIII.1961, Service Forestier 20317 ( P); Analamazaotra NP , 18°56’42”S 48°25’28”E, 929 m, 11.VIII.2015, van Ee et al. 2176 ( 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]