Croton stellatoferrugineus Caruzo & Cordeiro, 2010

Caruzo, Maria Beatriz Rossi, Cordeiro, Inês, Berry, Paul E. & Riina, Ricarda, 2010, A new species of Croton section Cleodora (Euphorbiaceae s. s.) from Minas Gerais, Brazil, Phytotaxa 3, pp. 27-33 : 28-32

Croton stellatoferrugineus Caruzo & Cordeiro , sp. nov. ( Figs. 1A–E , 2A–H )

Crotoni sphaerogyno Baill. affinis sed indumento ferrugineo, bracteis foliaceis, floribus femineis campanulatis, stylis multifidis ca. 24-partitis differt.

Type:— BRAZIL: Minas Gerais: Santo Antônio do Itambé , estrada para as cachoeiras e para a ponte de pedra, próximo à ponte, 18°27’16,2’’S e 43°18’29,4’’W, 750 m, fl., fr., 25 June 2008, M. B. R . Caruzo , L. R . Lima , S. E . Martins & A. L . Santos 120 (holotype SP, isotypes K, MICH, MO, NY, SPF) .

Shrub 1–3 m tall, monoecious, indument ferrugineous; branchlets flattened, covered by stellate and multiradiate trichomes. Leaves alternate; lamina 3–11.5 x 1–4.5 cm, narrowly ovate to ovate-elliptic, slightly discolorous, apex narrowly acute, base slightly cordate, margin entire, upper surface pubescent, covered by stellate trichomes, with less than 10 radii, usually with a long central erect ray, lower surface densely pubescent, covered by multiradiate trichomes, with more than 10 radii, venation pinnate, brochidodromous, secondary veins abruptly upturned towards the next ones, tertiary veins sinuous; petiole 0.5–2 cm long, with a pair of sessile basilaminar chestnut-brown glands; stipules ca. 5 mm long, linear. Inflorescence 5–20 cm long, terminal; inflorescence axis flat, striate, pubescent; proximal cymules pistillate, with a single pistillate flower, distal cymules staminate, with 1–2 staminate flowers, bracts from 0.4 cm long in terminal and youngest cymules, up to 2 cm long in the basal and oldest ones, foliaceous, prophylls 1–3 mm long, linear. Staminate flowers 5 mm long, campanulate; pedicels 2 mm long; calyx 2 mm long, pubescent externally, covered by stellate and multiradiate trichomes, glabrate internally; sepals 5, valvate, united up to half their length, then free for 1 mm long, entire, equal, ovate, apex acute; petals 5, 2 mm long, ovate to ovate-lanceolate, apex acute to rounded, reflexed; disk 5-segmented; stamens 15, filaments subulate, glabrate; receptacle villose with simple trichomes. Pistillate flowers 5 mm long, campanulate; sessile; calyx 4 mm long, pubescent externally, covered by stellate and multiradiate trichomes, glabrate internally; sepals 5, quincuncial, united up to half of their length, then free for the terminal 3 mm, equal, ovate-lanceolate, slightly fleshy, covered by ferrugineous trichomes, pale trichomes extending up to the central part of the sepals, margins villose; petals absent; disk 5- segmented; ovary globose, pubescent; styles 3, multifid, connate into a short column at the base, then branching into 24–30 terminal arms about ⅓ the way up the style. Capsules 0.7–1 cm long, globose, pubescent, calyx slightly accrescent, not inflated; seeds 4–5 mm long, subglobose, smooth; caruncle small, reniform.

Distribution and habitat: —So far only known from the “Pico do Itambé”, in the Espinhaço range, Minas Gerais state, southeastern Brazil, where it grows in seasonally dry forests, at 700–900 m elevation.

Etymology: —The specific epithet refers to the rusty color of its stellate indument.

The species can be recognized in the field by its densely ferrugineous indumentum and the foliaceous bracts with glands similar to those found at the base of the leaves.

From the results of an ongoing taxonomic revision of Croton section Cleodora by the senior author, and following the sectional synopsis of Croton by Webster (1993), Croton stellatoferrugineus clearly belongs to that section. The features shared by members of section Cleodora are the arborescent or shrubby habit, presence of basilaminar or acropetiolar glands, stamens between 15–25, pistillate sepals quincuncial or imbricate, usually accrescent, and sometimes fused at the base or up to half of their length, and quadrifid or multifid styles fused at the base or higher up. This new species has a shrubby habit, basilaminar glands ( Fig. 2A ), 15 stamens, quincuncial sepals united up to half of their length ( Fig. 1C , 2C ), and multifid styles fused at the base ( Fig. 1D ), all features indicating that C. stellatoferrugineus belongs to section Cleodora .

Croton stellatoferrugineus is morphologically most similar to Croton sphaerogynus Baillon (1864: 326) , a species from “restinga” forests of Brazil (São Paulo, Rio de Janeiro, Espírito Santo and Bahia), but differs from it in several features that are shown in Table 1. The main features that easily distinguish C. sphaerogynus from C. stellatoferrugineus are the indumentum color (whitish with some sparse points slightly ferrugineous in C. sphaerogynus vs. strongly ferrugineous in C. stellatoferrugineus ; see Figs. 2 and 3 ), type of trichomes (appressed stellate in C. sphaerogynus vs. stellate or multiradiate in C. stellatoferrugineus ), bracts subtending the pistillate and staminate cymules (foliaceous in C. stellatoferrugineus vs. linear, not foliaceous in C. sphaerogynus ; see Figs. 1B and 1G ), and seed shape (subglobose in C. stellatoferrugineus vs. globose in C. sphaerogynus ; see Figs. 1E and 1J ). Besides these morphological differences, C. stellatoferrugineus occurs in seasonally dry forests in Minas Gerais, whereas C. sphaerogynus occurs in moist forests in seashore plains (“restinga” forests) in the states of São Paulo, Rio de Janeiro, Espírito Santo, and Bahia (see Table 1).

Another species morphologically similar to Croton stellatoferrugineus is C. heterocalyx Baillon (1864: 324) , which has a disjunct distribution between dry forests and “restinga” forests in southeastern and northeastern Brazil (Caruzo & Cordeiro, in prep.). Both these species occur in dry forests and have similar ferrugineous indument. However, C. stellatoferrugineus can be easily distinguished from C. heterocalyx due to the different characters listed in Table 1, among which leaf shape (ovate to cordate in C. heterocalyx vs. narrowly ovate to ovate-elliptic in C. stellatoferrugineus ), morphology of branchlets (cylindric in C. heterocalyx vs. flat in C. stellatoferrugineus ), and staminate flowers (cupola-shaped in C. heterocalyx vs. campanulate in C. stellatoferrugineus ; see Figs. 2D and 3F ) are the most notable.

Additional specimens examined (paratypes): — BRAZIL: Minas Gerais: Serra do Espinhaço, southeastern drainage of Pico do Itambé, about 5 km directly west and north of Santo Antônio do Itambé , 9 February 1972, fl., fr., W. R . Anderson et al. 35673 ( MBM, MICH, NY, UB, US, VEN) ; Santo Antônio do Itambé , ponte de pedra sobre o riacho mãe-d’água, 1833’8.4’’ S e 4320’15.8’’ W, 811 m , fr., 18 February 2009, I . Cordeiro et al. 3033 ( SP) .

Figures

FIGURE 1. Comparison of Croton stellatoferrugineus and C. sphaerogynus. A–E. Croton stellatoferrugineus. A. Flowering branch. B. Floral bract, dorsal and ventral views. C. Pistillate flower. D. Gynoecium. E. Seed, dorsal view; A–E. Cordeiro et al. 3033 (SP). F–J. Croton sphaerogynus. F. Flowering branch. G. Floral bract, dorsal view. H. Pistillate flower. I. Gynoecium. J. Seed, dorsal view; F–J. Caruzo & Lima 121 (SP).

FIGURE 2. Morphological features of Croton stellatoferrugineus. A. One of the two basilaminar glands. B. Habit, showing senescent orange leaves (first plant to the right). C. Pistillate flower. Note ferrugineous indument, basally connate sepals with quincuncial aestivation of the lobes, and styles branched into at least 24 terminal tips. D. Staminate flowers. Note reflexed petals. E. Bracts with basal gland. F. Stipule partly hidden by ferrugineous trichomes. G. Infructescence. H. Detail of fruit, with slightly accrescent calyx. A- B, E-H. Cordeiro et al. 3033 (SP).C-D. Caruzo et al. 120 (SP).

FIGURE 3. Morphological features of Croton sphaerogynus and C. heterocalyx. A-E. Croton sphaerogynus. A. Habit. B. Basilaminar glands. C. Pistillate flower, showing revolute sepal lobes, stylar column, and ca. 12 terminal tips. D. Staminate flower. E. Fruits; A. Caruzo et al. 65 (SP, WIS); B-D. Caruzo & Lima 121 (SP); E. Sant’Ana et al. 1122 (CEPEC). F-I. Croton heterocalyx. F. Staminate flowers. G.Stipule. H. Inflorescence. I. Fruit; F-I. Caruzo et al. 140 (HUEFS).