Croton ramosissimus Sodré & M. J. Silva, 2017

Sodré, Rodolfo Carneiro & Silva, Marcos José Da, 2017, An overlooked new species of Croton section Geiseleria (Euphorbiaceae) from the Brazilian Cerrado, with a key to the species of this section occurring in the state of Goiás and in the Distrito Federal, Phytotaxa 329 (2), pp. 127-138 : 128-131

Croton ramosissimus Sodré & M. J. Silva , sp. nov. ( Fig. 1 , 2 )

Type: ___ BRAZIL. Goiás: Corumbá de Goiás, hillside opposite to the belvedere of Salto de Corumbá , to the left of BR-414 road, towards Cocalzinho, 15º50’53.2”S 48º46’07”W, 1050 m elev., 10 October 2016, fl., fr., R. C. Sodré, R. D. S. Nabarro & F. Roa 2668 (holotype: UFG!; isotypes: CEN!, K!, MICH!, NY!) .

Diagnosis: ___ Croton ramosissimus is most similar to C. tamberlikii from which it differs by its densely branched stems (vs. poorly branched), stipules 1.5–3.5 mm long (vs. 0.5–1 mm long), staminate bracts 1.1–2.7 mm long (vs. 4–6.5 mm long), villous filaments (vs. glabrous), and oblongoid seeds without spots (vs. ovoid, with spots).

Subshrubs 0.75–2 m tall, erect, monoecious, not aromatic, with a xylopodium, the main stem growing in a monopodial aspect with several shortened lateral branches; young branches light green to ferrugineous, adult branches brownish, both covered with multiradiate stellate, subsessile trichomes, with 12–15 lateral rays, the central one usually indistinguishable from the others; indument tomentose to the touch; latex clear. Leaves alternate, simple, blade 3.4–8.8 × 1.5–5.3(–6.5) cm, oblong, oblong-lanceolate, sometimes elliptic, base slightly cordate, sometimes obtuse, apex acute or acuminate, margin serrate or doubly serrate, with quite prominent teeth, with cupuliform to patelliform glands in the sinuses and ovoid glands on the tip of the teeth, faces concolorous, greenish, with sessile multiradiate stellate-porrect trichomes on both surfaces, the porrect central radius usually indistinguishable from the others; venation brochidodromous, with 4–6 pairs of secondary veins, impressed on the adaxial surface and prominent on the abaxial surface; stipules 1.5–3.5 × 0.2–0.3 mm, linear or lanceolate, margin entire, with 1 or 2 subglobose to ellipsoid sessile glands, covered with multiradiate stellate-porrect trichomes along the margin and on the abaxial surface; petiole 2–7 mm long, without glands or very rarely with 2 patelliform sessile glands at the apex. Thyrses 1.2–3.5 cm long, terminal, bisexual, flowers continuous along the inflorescence axis, (2–)3–5 pistillate flowers distributed at the basal ¼ to ½ of the axis, and numerous staminate flowers densely arranged in the apical portion; staminate bracts 1.1–2.7 × 0.3–0.5 mm, linear, linear-lanceolate, or linear-oblanceolate, staminate bracteoles 0.2–0.4 × 0.1–0.2 mm, linear, oblong, or ovate; pistillate bracts 1.1–2.6 × 0.4–0.7 mm, narrowly triangular, linear-lanceolate, or oblong, both bracts and bracteole without glands, adaxial surface glabrous, abaxial surface with multiradiate stellate-porrect trichomes. Staminate flowers 3.5–6(–8) mm long, yellow-greenish; pedicels 0.7–2.5(–3.5) mm long; sepals 5(–6), subequal or conspicuously unequal, 1.5–2 × 0.7–1 mm, ovate or oblong-ovate, apex obtuse, glabrous internally, stellate-porrect externally; petals 5, 1.9–2.5× 0.5–1 mm, oblanceolate to elliptic-obovate, villous to glabrescent on both surfaces, ciliate on the margin and barbellate near the base; stamens 11(–15), filaments 2.5–3 mm long, villous, anthers 0.6–0.7 mm long, glabrous, disk with 5 segments, yellowish, receptacle villous. Pistillate flowers 3.3–4.5 mm long, light green; pedicels 0.5–1.5 mm long; sepals 5(–6), subequal, 1.8–2.6 × 0.6–1.7 mm, ovate or ovate-lanceolate, sometimes lanceolate, apex acute, margin entire without glands, stellate-porrect externally and glabrescent internally; petals 0.4–2 × 0.1–0.3 mm, linear or narrowly lanceolate, with stellate trichomes, or glanduliform, ca. 0.2 mm long, ovoid or subulate; ovary 1.1–1.3 × 1.4–1.5 mm, subglobose or oblongoid, covered with stellate-porrect trichomes, light green, styles 3, 1,9–2,3 mm long, 2-fid, stellate-porrect; disk with 5 segments, ovoid, whitish, receptacle glabrous. Capsules 4.3–5.2 × 4.3–5.1 mm, oblongoid, light green, fruiting calyx not exceeding half of the capsule length, pedicels 0.8–2 mm long; seeds 3.3–4.0 × 2–2.7 mm, oblongoid, dark brown, without spots, slightly foveolate, caruncle 0.4–0.5 × 1–1.3, mm long, reniform, cream, sessile.

Distribution and ecology: ___ Croton ramosissimus is found in the state of Goiás and in the Distrito Federal, both in the midwestern region of Brazil ( Fig. 3 ). It grows in open areas of typical Cerrado or Cerrado ralo (sparse), on clay or rocky soils, near rock outcrops, between 950 and 1,100 m of elevation. Although it grows sympatrically with C. abaitensis Baillon (1864: 337) and C. spica Baillon (1864: 362) , these two species are morphologically very different from the new species and have a broader geographic distribution (Sodré & Silva 2015).

Phenology: ___ The new species has been collected with flowers and fruits from September to December.

Etymology: ___ The specific epithet alludes to the conspicuously branched stems of the new species, with distal secondary or tertiary branches oriented upwardly or perpendicularly ( Fig. 2A ).

Preliminary conservation status: ___ Since Croton ramosissimus has been found in an area larger than 20,000 km 2, which encompasses six municipalities, and it grows in vegetation types very common in midwestern Brazil, we suggest provisionally considering it as a Least Concern (LC) species ( IUCN 2017). However, we emphasize that the area where it grows is usually exposed to anthropogenic pressures.

Specimens examined (paratypes): ___ BRAZIL. Distrito Federal: Brasília, Pipiripau waterfall, 12 km from Planaltina Leste , 31 December 1974, fl., fr., E. P. Heringer 14274 ( CEN, IBGE, K, NY, UB, US) ; Condominium Mini Chácaras , near Paranoá dam, 15º48’20”S, 47º47’32”W, 1,100 m, 5 October 2001, fl., G. Pereira-Silva 5501 ( CEN, SP) ; Lago Sul, Rasgado Ecological Park, near Setor de Mansões Dom Bosco , 15º50’12”S, 47º29’04”W, 1,062 m, 28 October 2003, fr., M. A. Silva & D. Alvarenga 5584 ( IBGE, SP) ; Sucupira farm, campo sujo near the goat pen, 15º54’51”S, 48º0’4”W, 1,146 m, 11 September 2006, fl., fr., G. D. Vale, C. G. Fontes & J. B. Pereira 37 ( CEN, UFG) ; Recanto das Emas, dirt road to the right on km 13 of BR-060 road, towards Brasília, DF, after the Federal Highway Police station, before the interchange road to Santo Antônio do Descoberto, 15º55’53”S, 48º9’51”W, 1,066 m, 12 December 2016, fl., fr., R. C. Sodré 2892 ( UFG), 2893 ( UFG), 2894 ( UFG), 2896 ( UFG). Goiás: Corumbá de Goiás , hillside opposite the belvedere of Salto de Corumbá , to the left of BR-414 road, towards Cocalzinho, 15º50’53.2”S 48º46’07”W, 1,050 m, 10 October 2016, fl., fr., R. C. Sodré, R. D. S. Nabarro & F. Roa 2669 ( UFG), 2670 ( UFG), 2671 ( UFG), 2672 ( UFG), 2673 ( UFG), 2674 ( UFG), 2675 ( UFG), 2676 ( UFG) ; Leopoldo de Bulhões , exiting the town, near the railway, 16º37’44”S, 48º44’6”W, 1,040 m, 8 December 2011, fl., fr., M. J. Silva et al. 3999 ( UFG) ; Cerrado after the railway, ca. 500 m after Leopoldo de Bulhões , 24 May 2013, fl., R. C. Sodré et al. 763 ( UFG), 764 ( UFG) ; Mossâmedes, Serra Dourada, at the boundaries of the municipalities of Mossâmedes to the south and Goiás to the north, area of the Universidade Federal de Goiás, 8 November 1969, fl., fr., J. A. Rizzo 4556 ( UFG) ; Santo Antônio do Descoberto, dirt road to the right, ca. 1,000 m from the bridge on the river Alagado , 16º11’45”S, 48º11’29”W, 950 m, 6 November 2002, fl., fr., G. Pereira-Silva et al. 6866 ( CEN) ; Silvânia, Silvânia National Forest , ca. 2 km to the northwest of the reserve office, after an interdicted iron gate, 16º38’11.7”S, 48º40’28”W, 1,040 m, 7 December 2012, fl., fr., R. C. Sodré et al. 322 ( UFG), 326 ( UFG), 327 ( UFG), 329 ( UFG) ; M. J. Silva et al. 4594 ( UFG), 4599 ( UFG) ; 27 November 2013, fl., fr., R. C. Sodré et al. 1015 ( UFG), 1016 ( UFG), 1017 ( UFG), 1018 ( UFG) .

Figures

FIGURE 1. Croton ramosissimus. A. Flowering branches. B. Stipule showing the porrect trichomes and glands at the base. C. Detail of the base of a leaf showing the glands at the apex of the petiole. D. Detail of the margin of the abaxial surface of a leaf showing a patelliform gland in one of the sinuses.E. Staminate flower.F. Staminate petal, adaxial surface.G. Staminate petal, abaxial surface. H. Pistillate flower.I. Fruit. J. Seed, ventral surface showing the raphe and caruncle. K. Seed, dorsal surface. Drawn by Cristiano Gualberto from the holotype.

FIGURE 2. Croton ramosissimus. A. Habit. B. Inflorescence showing pistillate and staminate flowers. C and D. Inflorescences showing pistillate flowers and staminate buds. E. Fruits. Photographs by the authors.

FIGURE 3. Distribution map of Croton ramosissimus. DF = Distrito Federal, GO = Goiás State.