Croton restingae Sodré & Riina, 2023

Sodré, Rodolfo Carneiro, Silva, Marcos José da, Caruzo, Maria Beatriz Rossi & Riina, Ricarda, 2023, Croton restingae sp. nov. (Euphorbiaceae), a new species of section Adenophylli from the state of Rio de Janeiro, Brazil, and its phylogenetic relationships, European Journal of Taxonomy 864, pp. 104-116 : 108-111

Croton restingae Sodré & Riina sp. nov.

urn:lsid:ipni.org:names:77315910-1

Figs 2 , 4P–T

Diagnosis

Croton restingae Sodré & Riina sp. nov. shares with C. echioides and C. laceratoglandulosus a fruit columella with three non-inflated, flat or slightly ascending apical appendages; however, it differs by having entire stipules with 2 sessile glands at the base, 2(–6) sessile or shortly stipitate acropetiolar / basilaminar leaf nectaries, entire bracts, 2–2.3 × 1.5–1.6 mm, staminate flowers with 15–18 stamens, revolute and eglandular pistillate sepals, 4.2–5 × 2.6–3 mm, styles 2-fid with 6 apical terminal arms, basally united forming a column ca 0.8 mm long, and larger capsules, 7.5–8 × 8.5–9.3 mm, vide Table 2 .

Etymology

The specific epithet refers to the restinga vegetation where the species occurs.

Material examined

Type

BRAZIL – Rio de Janeiro • Saquarema, Reserva Ecológica Estadual de Jacarepiá ; 18 Nov. 1992; fl.; C. Farney et al. 3290; holotype: RB[299275] ; isotypes: ASE[17676] , SLUI[5310] .

Paratypes

BRAZIL – Rio de Janeiro • Arraial do Cabo, Pontal do Atalaia ; 2 Jan. 2000; M.F. Vasconcelos s.n.; BHCB[035062] • Saquarema, Reserva Ecológica Estadual de Jacarepiá ; 22 Jan. 1993; J. Fontella, R. Paixão, C. Farney & D. Garcia 2899; SP • ibid.; J. Fontella, R. Paixão, C. Farney & D. Garcia 2900; RB • ibid.; Sep.–Dec. 1992; C. Farney et al. 3663; RB • ibid.; 20–21 Aug. 1990; A. Souza et al. 3163; R • ibid.; 20–21 Aug. 1990; A. Souza s.n.; R[174495] • ibid.; 21 Aug. 1990; fl.; A. Souza et al. 3161; R • ibid.; restinga de Ipitanga , 2º cordão; s.d.; s.col., s.n.; R[203793] • Reserva Ecológica de Massambaba , estrada do Joazeiro , trilha dos Micos Leões ; 8 Apr. 1995; M.G. Bovini, V.S. Fonseca & L.C. Giordano 757; RB, SP • without locality [probably Rio de Janeiro State]; s.d.; s.col., s.n.; R[99957] .

Description

Shrub 1.7–3.5 m tall, latex yellowish, orange or reddish; stems erect, dichotomous or trichotomous, cylindrical, slightly striate, puberulent, sometimes hirsute, hirtellous or glabrescent, yellow-ferrugineous, trichomes stellate-porrect, 6–11 lateral rays 0.3–0.6(–0.9) mm long, one or two whorls, central ray (0.2–) 0.4–2.1 mm long, with stipe 0.05–0.25 mm long, or with simple trichomes 1–2 mm long. Leaves alternate; stipules 4–10 × 0.5–0.8 mm, linear or narrowly lanceolate, dorsal surface pubescent or puberulent with trichomes multiradiate, stellate-porrect or simple, sessile, ventral surface puberulent or glabrescent with the same trichomes, with 2 ovoid, sessile colleters at the base, and an ovoid or subglobose colleter at the apex; petioles 1.5–6 cm long; 2(–6) acropetiolar /basilaminar nectary glands, two of them facing the abaxial surface, 0.8–1.3 mm diam., sometimes another two or four facing the adaxial surface, 0.35–0.6 mm diam., both patelliform, sessile or with stipe 0.1–0.4 mm long; leaf blade 6.7–9.5 × 3.2–6.3 cm, 1.7–4 times as long as petioles, ovate or ovate-lanceolate, membranaceous, base truncate, rounded, obtuse or cordate, apex acute or acuminate, margin serrulate, sometimes entire, with subglobose colleters usually at the apex of teeth, subsessile, venation brochidodromous with 4–6 pairs of secondary veins impressed on the adaxial surface and prominent on the abaxial surface, leaf blade discolorous, dark-green adaxial surface, pubescent, with simple trichomes, 0.1–0.3 mm long, with 4–12 quadrangular glands (idioblasts) at the base, stellate or multiradiate trichomes, in both rays 0.2–0.6 mm long, sessile or with stipe 0.05 mm long, abaxial surface clear green, tomentose or pubescent, with multiradiate trichomes, stipe 0.2–0.7 mm long, or subsessile stellate-porrect trichomes. Thyrses 9.5–21 cm long, bisexual, terminal or in the dichotomies or trichotomies of branches, sessile or with peduncle up to 1.5 cm long, sparse flowers, bisexual cymules in the basal portion with 1 pistillate flower and 6–8 staminate flowers, followed by staminate cymules with (4–)6–8 flowers; bracts of both flowers 2–2.3 × 1.5–1.6 mm, elliptic or oblong, entire, with globose glands at the base, tomentose on ventral surface and pubescent on dorsal surface, both with stellate or multiradiate trichomes; bracteoles 0.7–1.1 × 0.2–0.5 mm, triangular, linear or lanceolate, with globose glands at the apex, indument similar to those of bracts. Staminate flowers 3.5–4.2 mm long; pedicel 1–2 mm long; receptacle villous; sepals 5, 2.7–3.4 × 2.1–2.8 mm, slightly unequal, shortly united at the base, ovate or largely elliptic, apex acute, obtuse or rounded, dorsal surface pubescent with stellate-porrect trichomes, shortly villous at the apex, ventral surface glabrous; petals 2–2.5 × ca 1 mm, oblong, apex rounded, glabrous on both surfaces, villous apex; stamens 15–18, ca 2 mm long, anthers elliptic or largely elliptic; nectary disk with 5 segments. Pistillate flowers 5–6.7 mm long; pedicel ca 1.2 mm long; sepals 5, 4.2–5 × 2.6–3 mm, slightly unequal, free, ovate or oblong, acute apex, margin entire, eglandular and revolute, dorsal surface shortly tomentose with trichomes stellate-porrect or multiradiate, ventral surface pubescent with trichomes fasciculate, stellate-porrect or simple; petals 5, ca 0.15 mm diam., reduced to ovoid glands, glabrous, whitish; ovary ca 1.6 × 2.2 mm, globose, hirsute-tomentose, trichomes stellateporrect or multiradiate, shortly stipitate; styles 3, ca 3 mm long, united basally in a column ca 0.8 mm long, 2-fid, with 6 terminal arms; nectary disk with 5 segments oblong. Capsules 7.5–8 × 8.5–9.3 mm, globose, hirsute-tomentose, ferrugineous, pedicel 1–1.5 mm long, apex of columella with three discrete, flat or slightly ascending appendages, seeds not seen.

Distribution, habitat and phenology

Croton restingae Sodré & Riina sp. nov. is endemic to the coast of Rio de Janeiro ( Fig. 3 ), in the municipalities of Saquarema and Arraial do Cabo, where it grows in restinga vegetation, on sandy soil, between 5–50 m of elevation. This vegetation is included in the Brazilian Atlantic Forest Domain and is floristically highly diverse and includes different phytophysiognomies such as forest, dense shrubland, open shrubland, savanna and pasture ( Eiten 1983; Araújo 1992). The new species was collected with flowers in January, April, August and November.

Preliminary conservation status

Croton restingae Sodré & Riina sp. nov. has a limited Extent of Occurrence (45.7 km 2) and is tentatively categorized as Critically Endangered (CR; B1ab[iii]). Although the new species occurs in the Massambaba Environmental Protection Area (EPA), a special Conservation Unit called ʻsustainable useʼ that covers 9000 hectares of the coastal strip between the municipalities of Saquarema and Arraial do Cabo, in general EPAs are very poorly preserved and urbanization is allowed without major restrictions ( Macedo et al. 2019). Sá (2002) in a series of studies on the regeneration of restinga in the municipality of Saquarema reported significant disturbance in the area of occurrence of C. restingae , even within the limits of an Ecological Reserve (former Jacarepiá Ecological Reserve). Such disturbance was caused by deforestation to plant pineapple, opening of roads, logging, extractivism of ornamental plants, in addition to the use of plants for various purposes by the local community. Additionally, the only record of C. restingae for the municipality of Arraial do Cabo, comes from a region with intense tourism, representing a potential risk to its natural populations.

Figures

Fig. 2. Croton restingae Sodré & Riina sp. nov.A. Flowering branch. B. Indument of branch.C. Trichomes of branches. D. Stipule. E. Leaf. F–G. Foliar base (adaxial surface) showing the nectaries. H. Foliar base (abaxial surface) showing the nectaries. I. Trichomes of adaxial and adaxial surfaces of the leaf blade. J. Pistillate bract, dorsal surface. K. Pistillate bract, ventral surface. L–M. Pistillate bracteoles, dorsal surface. N. Pistillate flower. O. Pistillate sepal, dorsal surface. P. Pistillate sepal, ventral surface. Q. Gynoecium. R. Nectary disk of pistillate flower and glandular petals. S. Staminate flower. T. Calyx of staminate flower, dorsal view. U. Capsule.V. Carpophore showing the columella with discrete appendages at the apex. Drawn by Renato Galhardo Neto. A–R, T from M.F. Vasconcelos s.n.; S from J. Fontella 2899; U from s.col. s.n. R[99957]; V from A. Souza et al. 3163.

Fig. 4. Morphological comparison of C. restingae Sodré & Riina sp. nov. and related species. A–E. Croton echioides Baill. A. Basilaminar nectaries.B. Pistillate flower. C. Gynoecium. D. Nectary disk and glandular petals (arrows) of pistillate flower. E. Carpophore showing the columella, detail of the apical appendages. – F–J. C. gracilipes Baill. F. Basilaminar nectaries. G. Pistillate flower. H. Gynoecium. I. Nectary disk and glandular petals (arrows) of pistillate flower. J. Carpophore showing the columella, detail of the apical appendages. – K–O. C. laceratoglandulosus Caruzo & Cordeiro. K. Basilaminar colleters. L. Pistillate flower. M. Gynoecium. N. Nectary disk of pistillate flower. O. Carpophore showing the columella, detail of the apical appendages. – P–T. C. restingae sp. nov. P. Basilaminar nectaries. Q. Pistillate flower. R. Gynoecium. S. Nectary disk and glandular petals (arrows) of pistillate flower. T. Carpophore showing the columella, detail of the apical appendages. Photos: A–E from R.C. Sodré 3314; F–J from R.C. Sodré 3413; K–O from R.C. Sodré 3461; P–S from M.F. Vasconcelos s.n.; T from A. Souza et al. 3163.

Fig. 3. Distribution map of C. restingae Sodré & Riina sp. nov. State abbreviations: BA = Bahia; ES = Espírito Santo; GO = Goiás; MG = Minas Gerais; PR = Paraná; RJ = Rio de Janeiro; SP = São Paulo.