Croton orangeae Kainul. & P.E. Berry, 2017

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, Candollea 72 (2), pp. 371-402 : 394-395

Croton orangeae Kainul. & P.E. Berry , spec. nova ( Fig. 1F , 2D , 4 K-L, 10).

Typus: MADAGASCAR. Prov. Antsiranana: Diana Reg. , Ramena , Ankorikakely , Baie des Sakalava , 12°16’40”S 49°23’01”E, 25 m, 9.XII.2004, Razafitsalama et al. 692 (holo-: MICH [ MICH1517188 ]!; iso-: CNARP, MO!, P [ P05484901 ]!, TAN) .

Croton orangeae Kainul. & P.E. Berry is similar to C. adenophorus Baill. in its denticulate, cordate leaves and glabrous stems, but differs in its stipules that are awn-shaped (vs foliaceous), its mature leaves that are scabrously stellate-pubescent (vs subglabrous), and the bark of the branches matte and tan to gray (vs ± glossy and reddish brown) and soon turning flaky (vs smooth).

Shrubs 1-4 m tall, dichotomously branching, internodes sometimes so short as to give the appearance of whorled branches. Branches flattened on new growth but becoming terete with age, pale green and sparsely covered with whitish stellate indument, soon turning tan to gray, glabrous, matte. Bark flaky, gray to brown ( Fig. 10B ). Stipules 5-10 mm long, awn-shaped, early caducous. Leaves opposite, deciduous. Petioles 0.5-10 cm long, adaxially canaliculate, stellate-pubescent, usually with a pair of subsessile, concave, discoid glands 0.4-0.6 mm diam. at the junction with the lamina. Leaf blades chartaceous, (subentire) dentate to denticulate, ovate, 2.2-14.0 × 2.5-14 cm, apex (acute) acuminate, base (truncate) cordate; both sides with a persistent, scabrous stellate indument, green when fresh, drying matte pale green to brown; venation evident, with 6-10 pairs of brochidodromus, ± penninerved secondary veins (the lowermost pairs congested and appearing palmate), and cross-venulate tertiary venation; venation prominent, sometimes with glands in some of the axils of the secondary veins on the lower surface ( Fig. 1F ), but absent in most leaves. Inflorescences terminal, racemelike thryses 1-6.5 cm long, bisexual with pistillate flowers towards the base and staminate flowers towards the distal end, axes stellate-pubescent, flattened; bracts narrowly triangular, c. 2.5 mm long, caducous. Staminate flowers with stellate-pubescent, subglobose buds, c. 1.8 mm diam., pedicels elongating from bud to anthesis, 1-5 mm long; sepals 5, pale green, shortly connate at base, lobes broadly triangular-ovate, 2-2.5 × 1.5-1.8 mm, apex acute, inflexed at anthesis, abaxially stellate-pubescent, adaxially glabrous, margins ciliate; petals 5, elliptic to spatulate, 1.5-2.5 × 0.7-0.9 mm, recurved at anthesis, abaxially glabrous and papillose, adaxially ciliate towards apex, margins densely ciliate; disc glands 5, opposite the sepals, sessile, ellipsoidal, c. 0.4 × 0.6 mm, yellow; stamens 13-21, white, filaments 1.5-2.5 mm long, ciliate, anthers broadly elliptic, c. 0.8 × 0.7 mm; receptacle pilose. Pistillate flowers with stellate-pubescent buds 2-2.5 mm diam., pedicels 1.5- 5.5 mm long; sepals 5, elliptic, not spreading at anthesis, 1.8-2.8 × 1-1.7 mm, apex acute, shortly connate at base, abaxially and adaxially stellate-pubescent, persistent in fruit; petals sometimes absent or reduced, when present 1.4-1.8 × 0.7-0.9 mm, spatulate, glabrous except for the ciliate margin, abaxially papillose; disc glands 5, opposite the sepals, sessile, ellipsoidal, 0.3 × 0.7 mm, yellow; ovary densely covered by ferrugineous to dark brown, stellate trichomes, globoid-ellipsoid, 2-3 mm diam., styles 3, c. 2 mm long, each branch flattened and twice bifurcate, spreading, recurved at the apices, abaxially stellate-pubescent, adaxially glabrous, persistent. Capsules broadly globoid, 5 × 6.5 mm, smooth, pale brown, covered with contrasting dark brown stellate trichomes ( Fig. 4K ), exocarp not separating, endocarp woody, c. 0.5 mm thick; columella 4-5 mm long, cornute, capitate. Seeds ± compressed-ellipsoid, c. 3.5 × 3 × 2 mm; testa matte, verrucose, pale brown; caruncle narrowly reniform c. 0.4 × 1 mm ( Fig. 4L ).

Etymology. – The epithet refers to the Orangea (Oronjia) Peninsula in Antsiranana Province, where the type was collected and the species is apparently restricted.

Phenology. – Only a few specimens are known, collected in bud in March, in flower in August-December, and in fruit in December.

Distribution, habitat and ecology. – This species is so far only known from the Orangea (Oronjia) Peninsula in northern Antsiranana Province where it grows in dry scrub vegetation and littoral forest on limestone and sand, from sea level to c. 50 m in elevation ( Fig. 2D ).

Conservation assessment. – Croton orangeae is known only from the Orangea Peninsula. The deciduous forests of Orangea are currently threatened by deforestation despite their recent additon to Madagascar’s protected area network. Deforestation is mostly related to agricultural practices. Given this and the extent of occurrence is <5000 km 2, the new species is assigned as “Endangered” [EN B1 ab(iii)], according the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Croton orangeae is distinct for its glabrous, grayish branches with flaky bark, and dentate to denticulate leaves with a persistent, scabrous indument on both sides. In the shape of the leaves and in the pale brown capsules with white and contrasting brown stellate trichomes, it may appear similar to C. adenophorus , but that species has a glossy reddish bark and subglabrous leaves, and also differ in its usually longer inflorescences (1.5-22 cm vs 1-6.5 cm in C. orangeae ), and distinctly foliaceous stipules and calyces. No vernacular names have been noted for this species.

Additional specimens examined. – MADAGASCAR. Prov. Antsiranana: Diana Reg., Antsiranana Distr., Orangea , 25.XI.1970, Debray 1525-D ( K, P) ; ibid. loc., 12°14’20”S 49°21’49”E, 13 m, 29.VIII.2001, Rabenantoandro & Razanatsoa 579 ( MO, P) ; ibid. loc., 12°14’08.2”S 49°21’40.3”E, 50 m, 25.X.2009, van Ee et al. 1080 ( MICH) ; ibid. loc., 12°13’54”S 49°21’28”E, 19 m, 5.III.2016, van Ee et al. 2343 ( MICH, TAN) ; ibid. loc., 12°14’08”S 49°21’41”E, 30 m, 5.III.2016, van Ee et al. 2351 ( MICH, TAN) ; ibid. loc., 5.III.2016, van Ee et al. 2352 ( MICH, TAN) ; ibid. loc., 5.III.2016, van Ee et al. 2353 ( MICH, TAN) .

Figures

Fig. 1. Abaxial side of leaves showing laminar glands and pubescence A. Croton nudatus Baill.; B. Croton stanneus Baill.; C. Croton adenophorus Baill.; D. Croton bathianus Leandri; E. Croton loucoubensis Baill.; F. Croton orangeae Kainul. & Berry; G. Croton sahafariensis Kainul. & Berry; H. Croton scoriarum Leandri; I. Croton tsiampiensis Leandri. [A: van Ee et al. 2340; B: van Ee et al. 2160; C: van Ee et al. 1135; D: van Ee et al. 1138; E: Ammann et al. 378; F: van Ee et al. 2353; G: van Ee et al. 1089; H: van Ee et al. 2329; I: Nusbaumer LN 902]

Fig. 2. Distribution maps. A. Croton nudatus Baill. (white), C. stanneus Baill. (yellow); B. Croton adenophorus Baill. (green) and C. tsiampiensis Leandri (white); C. Croton bathianus Leandri (light blue), C. loucoubensis Baill. (yellow), and Croton scoriarum Leandri (red); D. Croton orangeae Kainul. & Berry (red) and C. sahafariensis Kainul. & Berry (yellow); E. Croton mayottae P.E. Berry & Kainul. [Google Earth Image © 2017 DigitalGlobe. Reproduced per attribution guidelines]

Fig. 4. Capsules (A, C, E, G, I, K, M, O); Seeds (B, D, F, H, J, L, N, P). A-B. Croton nudatus Baill.; C-D. Croton stanneus Baill.; E-F. Croton adenophorus Baill.; G-H. Croton bathianus Baill.; I-J. Croton loucoubensis Baill.; K-L. Croton orangeae Kainul. & P.E. Berry; M-N. Croton sahafariensis Kainul. & P.E. Berry; O-P. Croton tsiampiensis Leandri. [A: Randrianaivo et al. 1424; B: Gautier & Chatelain 4898; C: Gillespie 10802; D: Nusbaumer LN 906; E: van Ee et al. 1165; F: van Ee et al. 2294; G: van Ee et al. 2406; H: van Ee et al.1138; I: Nusbaumer 2536; J: Bernard et al. 1192; K-L: Razafitsalama et al. 692; M-N: van Ee et al. 2314; O-P: Nusbaumer 902]

Fig. 10. Croton orangeae Kainul. & Berry A. Leaves; B. Bark; C. Underside of leaves; note the scabrous, stellate, indument and the laminar glands (arrow); D. Young inflorescences; E. Flowering branch with staminate flower and young fruits; F. Staminate flower and young fruits; G. Staminate flower in anthesis and mature fruits below. [A-B: van Ee et al. 2351; C-E: van Ee et al. 1080; F-G: Razafitsalama et al. 692] [Photos: A-D: P. Berry; E: B. van Ee; F-G: R. Randrianaivo]