Croton enigmaticus P.E. Berry & 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 : 333-335

Croton enigmaticus P.E. Berry & B.W. van Ee , spec. nova ( Fig. 1B , 5 A-G, 6, 7I-J).

Typus: MADAGASCAR. Prov. Toamasina: Alaotra- Mangoro Region, along dirt road N of RN 2, past the village of Savahoana, [ Analantrongy ], 984 m, 18°55’00”S 48°20’41”E, 14.VIII.2015, van Ee, Berry & Razafindraibe 2214 (holo-: MICH [ MICH1513196 ]!; iso-: MICH [ MICH 1513197 ]!, MO!, P!, TAN!).

In its sometimes elongate, bracteate inflorescences and hispidpubescent stems, Croton enigmaticus P.E. Berry & B.W. van Ee is closest to Croton bracteatus Lam. but differs in its much more serrate leaf margins, larger and more conspicuous stipules, shorter petioles, and the fewer bifurcations of the stigmas. In its pubescence, leaves, and somewhat foliaceous pistillate sepals it is also similar to C. fianarantsoae Leandri , but differs in its more serrate leaves, more numerous pistillate flowers, and more conspicuous stipules.

Subhrubs to shrubs 0.3-2 m tall or occasionally lianescent 3-4 m tall, often with a profusion of adventitious roots in the leaf litter layer ( Fig. 6B ). Stems, leaves, and inflorescence rachis densely pubescent, with stellate-lepidote trichomes having a stiff, porrect, whitish central ray 2-3 mm long, the basal portion of the trichomes brown to coppery. Stipules lanceolate to falcate, often somewhat recurved, 5-10 mm × 2-4 mm, light green, foliaceous, caducous, or sometimes seemingly absent. Leaves alternate at the base of stems, but becoming more congested near the tips and then becoming opposite or whorled, persistent, varying from patent to often ± drooping from the stems; petioles 6-15(-20) mm long, hispid, with a pair of laterally divergent, stipitate glands at the apex, each 2-3.5 mm long, with a glandular, knobby tip. Leaf blades papyraceousmembranous, (broadly) ovate to elliptic, 5-9(-12) × 2.5-6 cm, apex acuminate, base rounded, venation brochidodromous with 6-7 pairs of secondary veins, these ± impressed on upper surface, margins dentate-serrate, both surfaces and margins densely hispid. Inflorescences terminal, erect to drooping when elongate, 1-8(-14) cm long (very variable from plant to plant), unisexual or bisexual, with or without conspicuous light green to brown bracts resembling the stipules; pistillate flowers from 1-10 numerous in proximal portion, staminate flowers distal and in single or in few-flowered cymules of varying pedicel lengths, the pedicels of both sexes usually ± divergent (perpendicular) from the rachis. Staminate flowers with hispid, globose buds 2-3 mm in diam., pedicels usually variable in length on same inflorescence, 1-5(-8) mm long; sepals 5, valvate, c. 3 × 1.5 mm, triangular, inflexed at anthesis; petals 5, ligulate, white, pubescent, c. 2 × 1 mm, slightly recurved at anthesis; stamens 15-20, white to pale yellow, filaments 2.5-3.5 mm long, ciliate, anthers elliptic, c. 0.8 mm long. Pistillate flowers with hispid pedicels 3-8(-15) mm long; sepals usually 5 but up to 7-9 on some flowers, imbricate, somewhat unequal in size, 8-10(-15) × 3-5 mm, narrowly triangular to elliptic-lanceolate, acuminate, foliaceous and green on both sides, the midvein and two additional lateral veins visible, hispid on both sides and along margins, persistent in fruit; glandular filaments (in petal position alternating with the sepals) 5, c. 1 mm long ( Fig. 5G ); ovary hispid, green, with scattered coppery-based scales, globoid-ellipsoid, c. 3 mm diam., styles 3, each bifurcating 2-3 times near the base with a total of c. 24 stigmatic tips, curled when young, creamy-white, turning coppery-brown, patent. Capsules ellipsoid to subgloboid, greenish, densely hispid, c. 10 mm diam.; columella c. 7 mm long, with a fimbriate tip. Seeds ± compressed-ellipsoid ( Fig. 7J ), c. 5.5 × 4.0 × 2.5 mm, covered by a thin, translucent-white, fleshy coating when fresh; testa glossy, rugulose, dark brown; caruncle reniform, white when fresh, c. 1.0 mm wide, 0.7 mm long.

Etymology. – The specific epithet refers to the enigmatic nature of the species, showing at times unusual characters such as foliaceous, curved stipules, prominent bract-like pistillate calyces, elongate inflorescences, markedly serrate leaves, and mats of adventitious rootlets in the leaf litter, but other times the inflorescences are short, the stipules absent, and the leaf margins are subentire. Individuals of this species can either appear to be nearly herbaceous, scraggly shrubs, or even lianas.

Phenology. – From the four sets of specimens available, C. enigmaticus is known to flower and fruit in January, June, August, and October, so it appears to be quite aseasonal in its phenology.

Distribution, habitat and ecology. – Croton enigmaticus is known from just two sites in the mountains of Moramanga Distr. in the Alaotra-Mangoro Region of Toamasina Prov. ( Fig. 1B ) and from the Tsarahonenana forest near Didy, at elevations of 950-1075 m. One of these sites is in the Ambatovy mine area, the second is about 15 km due south in a similarly forested region, and the Didy collection is considerably farther north. In the two Moramanga Distr. sites, C. enigmaticus grows in the understory or along road cuts of dense, montane evergreen forest, often together with lianescent bamboos prevalent in the understory.

Notes. – This species is remarkable for its densely hispid pubescence and variable-sized inflorescences, which can be very congested or quite elongate. It also has unusual foliaceous stipules and bracts, however, these may be lacking (or early caducous?) on some plants. Finally, it shows extensive local vegetative reproduction by proliferous production of adventitious roots in the litter layer. It co-occurs with plants that are included here under C. lasiopyrus Baill. , but they have intermediate traits that indicate they may be hybrids between these two species.

Paratypi. – MADAGASCAR. Prov. Toamasina: Alaotra-Mangoro Region, Moramanga Distr ., Andasibe , Ambatovy , Analantrongy , 18°55’13”S 48°20’26”E, 997 m, 9.VI.2009, Antilahimena et al. 7106 ( MICH, MO, P, TAN); ibid. loc., Antilahimena et al. 7107 ( MICH, MO, P, TAN); Ambatovy, 18°48’11”S 48°20’49”E, 1075 m, 9.X.2007, Bernard & Phillipson 605 ( MICH, MO, P, TAN); Ambatondrazaka Distr., Didy , Tsarahonenana forest , 4.3 km NE from Didy, 18°05’05”S 48°34’17”E, 15.I.2010, Ralimanana et al. 1402 ( BR, G, K, MO, TAN); Moramanga Distr., dirt road N of Route Nationale 2 past village of Savahoana, 18°55’28”S 48°20’57”E, 972-989 m, 14.VIII.2015, van Ee et al. 2209 ( MICH, MO, P, TAN); ibid. loc., van Ee et al. 2210 ( MICH, MO, P, TAN); ibid. loc., van Ee et al. 2211 ( MICH, MO, P, TAN); ibid. loc., 18°55’06”S 48°20’38”E, 981 m, van Ee et al. 2212 ( MICH, MO, P, TAN); ibid. loc., van Ee et al. 2213 ( 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. 5. – Croton enigmaticus P.E. Berry & B.W. van Ee (A-G) and C. ferricretus Kainul., B.W. van Ee & P.E. Berry (H-M). A. Side view of staminate flower; B. Top view of staminate flower; C. Top view of staminate flower with the stamens removed to show the nectaries; D. Side view of pistillate flower with one of the sepals removed; E. Top view of pistillate flower with one of the sepals removed; F. Top view of pistillate with the ovary removed to show the five nectaries; G. Close-up of the base of a pistillate flower with the ovary and sepals removed, showing the five glandular filaments in the position of the petals (alternating with the sepals); H. Side view of staminate flower; I. Top view of staminate flower; J. Top view of staminate flower with stamens removed to show the five nectaries; K. Side view of pistillate flower. Note basally connate sepals and parallel sides; L. Top view of pistillate flower, showing the patent, bifurcating stigmas; M. Top view of pistillate flower with ovary removed to show the five nectaries. [A-G: van Ee et al. 2214; H-M: van Ee et al. 2436]

Fig. 6. – Croton enigmaticus P.E. Berry & B.W. van Ee. A. Climbing habit, here together with a climbing bamboo; B. Adventitious roots emerging from the stems; C. Typical trichotomous branching; D. Leaves; E. Close-up of the densely hirsute newly emergent leaves. Note the falcate stipules and stipitate acropetiolar glands; F. Inflorescence with the pedicels of the staminate flowers perpendicular to the axis of the rachis; G. Pistillate flower. Note the somewhat unequal, foliaceous sepals and thrice bifurcating stigmas; H. Inflorescence showing an immature fruit, foliaceous bracts along the rachis, and staminate pedicels of varying lengths. [Photos: P.Berry]

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]