Croton aemulus Barbosa & Carn.

Barbosa, Bárbara Laís Ramos, Oliveira, Reyjane Patrícia, Mascarenhas, Ana Angélica Silva, Dórea, Marcos Da Costa, Martins, Fabiano Machado & Carneiro-Torres, Daniela Santos, 2018, Croton aemulus and C. graomogolensis (Euphorbiaceae): Two new species from Minas Gerais, Brazil, based on distinct lines of evidence and their relation to C. muscicapa and C. longibracteatus, Phytotaxa 365 (3), pp. 259-272 : 262

Croton aemulus Barbosa & Carn. -Torres, sp. nov. ( Fig. 1 , 2 A–E , 3 A–F , 4 B )

Type:— BRAZIL: Minas Gerais: Jequitinhonha. Serra de areia no topo da serra, 16º20’11.2”S, 41º5’25.4”W, 1088 m, 21 November 2015, B.L.R. Barbosa, D.S. Carneiro-Torres, M.S. Silva & J.F.C. Oliveira 19 (holotype HUEFS!; isotypes ALCB!, K!, M!, MBM!, MO!, NY!, P!, RB!, SP!, SPF!) .

Diagnosis:— Croton aemulus differs from C. longibracteatus by having leaf blades with a pubescent adaxial surface, leaf margins with 3–4 glands at the apex of each tooth, staminate and pistillate flowers with smaller stamens and bracts, and sepals of pistillate flowers with short-stipitate glands (vs. leaf blades with a subglabrous adaxial surface, leaf margins with one sessile gland at the apex of each tooth, staminate and pistillate flowers with larger stamens and bracts, and sepals of pistillate flowers with long-stipitate glands).

Description:—Shrubs, monoecious, erect, to 1 m tall, foliage viscid, green-vinaceous, pubescent, trichomes stellate-rotate, porrect, radii 6–8. Leaves simple, alternate; stipules lanceolate, glandular, 1.5–4 × 1–2 mm; petiole 8.5–30 mm long, hirsute-pubescent, eglandular; blade ovate, 31.5–71 × 21–47 mm, apex acuminate, base cordate to subcordate, margin with 3–4 glands at the apex of each tooth, pubescent on both surfaces; venation actinodromous. Inflorescences terminal, bisexual, 25.5–83 mm long, hirsute, with proximal pistillate flowers and distal staminate flowers, distributed continuously along the rachis; bracts lanceolate, staminate flower bracts 1.5–4.5 mm long, pistillate flower bracts 1.5– 7 mm long, fimbriate-glandular, glands long-stipitate, concentrated at the base. Staminate flowers yellowish green, 5.5–7 mm long; pedicels 2–5 mm long; sepals 5, ovate, 2.5–4 × 1.5–2.5 mm; adaxial surface glabrous, abaxial surface pubescent with trichomes at the apex; petals 5, ovate, 3–4 × 2–3 mm; stamens 11–12, 4.5–6.5 mm long. Pistillate flowers green, 7.5–8 mm long; pedicels 3–4.5 mm long; sepals 5, lanceolate, 6.5–9 × 1–2 mm, pubescent, margin glandular, glands short-stipitate, reduplicate; petals absent; ovary globose, pubescent, styles 3, united at the base, multifid, with 8–11 terminal tips, glabrous. Capsules globose, 6.5–7 × 5.5–6 mm, pubescent; seeds globose, 3.5–4 × 2.5–3 mm, smooth, carunculate.

Etymology: —The epithet aemulus refers to the general and confusing morphology of this new species, which is quite similar to Croton longibracteatus and C. graomogolensis .

Morphological comments: —In general, Croton aemulus is morphologically similar to C. longibracteatus ( Fig.5F–J ). These species share several characters, such as lanceolate and glandular stipules, leaf blades with a dentate margin, and a similar number of stamens. They differ mainly because C. aemulus has leaf blades with a pubescent adaxial surface, margins with 3–4 glands at the apex of each tooth, pistillate flowers 7.5–8 mm long, and lanceolate sepals with short-stipitate glands (vs. leaf blades with a subglabrous adaxial surface, margins with one gland at the apex of each tooth, pistillate flowers 9–17.5 mm long, and lanceolate sepals with long-stipitate glands in C. longibracteatus ). Although both species have some similar leaf anatomical characters, as discussed below, they also exhibit differences that support our taxonomic decisions.

Croton aemulus is also similar to C. graomogolensis ( Fig. 2 F–L ) by the size of pistillate and staminate flowers and small bracts ( Tab. 2). Croton aemulus differs by having pubescent leaf blades on the adaxial surface, margins with 3–4 glands at the apex of each tooth, staminate flowers 5.5–7 mm long, and stamens 11–12 (vs. leaf blades glabrous to subglabrous on the adaxial surface, margin with 1–3 glands at the apex of each tooth, staminate flowers 3–4.5 mm long, and stamens often 15–17 in C. graomogolensis ).

Geographic distribution, habitat and conservation: — Croton aemulus is restricted to the state of Minas Gerais, in southeastern Brazil, and is only known from the municipality of Jequitinhonha ( Fig. 1 ). It was only found in the Mata Escura Biological Reserve, in cerrado de altitude vegetation (mountain savannah), which occurs from 1,088 to 1,134 m elevation and typically grows on sandy soil ( Tab. 2). This species is here considered Endangered CR (B1 B2 ab (ii)), according to IUCN (2012) criteria, because it is only known from three locations and has an estimated area of occupancy (AOO) of less than 15 km 2.

Paratypes:— BRAZIL. Minas Gerais: Jequitinhonha, Reserva Biológica da Mata Escura , 16º26’2”S, 41º0’12”W, 31 December 2004, R. de Mello-Silva et al. 437 ( RB, SP, SPF) ; Reserva Biológica da Mata Escura , 16º20’18”S, 41º05’23”W, 25 March 2008, T.E. Almeida et al. 1308 ( BHCB) .

Figures

FIGURE 1. Map showing known distribution of the four species.

FIGURE 2. C. aemulus and C. graomogolensis. A–E. C. aemulus (Barbosa et al.19, HUEFS). A. Habit; B. Stipules, glandular, lanceolate; C. Bracts; D. Staminate flower; E. Pistillate flower. F–L. C. graomogolensis (Barbosa et al. 17, HUEFS). F. Habit; G. Glandular stipules, resembling a bunch of grapes; H. Bracts in frontal view; I. Bracts in lateral view; J. Staminate flower; K. Pistillate flower; L. Ovary and styles. Drawing by Natanael Nascimento.

FIGURE 3. C. aemulus (Barbosa et al. 19, HUEFS) and C. graomogolensis (Barbosa et al. 17, HUEFS). A–F. C. aemulus. A. Habit; B. Inflorescences with staminate flowers and bracts; C. Inflorescences with flower buds, staminate and pistillate flowers; D. Leaf and stipules, branch pubescent; E, F. Pistillate flowers. G–L. C. graomogolensis. G. Habit; H. Inflorescences with flower buds and open staminate flower; I. Inflorescences with flower buds, staminate flowers, and fruit; J. Pistillate flowers and stipules; K. Pistillate flowers; L. Branch. Photos by D.S. Carneiro-Torres and B.L.R Barbosa.

FIGURE 4. Morphological comparison of species. Leaf margin, stipules, sepals, and bracts. A. C. longibracteatus (Barbosa et al. 11, HUEFS). B. C. aemulus (Barbosa et al. 19, HUEFS). C. C. muscicapa (Barbosa et al. 4, HUEFS). D. C. graomogolensis (Barbosa et al. 17, HUEFS). Scale bars = 1 mm.

FIGURE 5. C. muscicapa (Barbosa et al. 4, HUEFS) and C. longibracteatus (Barbosa et al. 11, HUEFS). A–E. C. muscicapa: A. Habit; B. Glabrous leaf; C. Glandular stipules, resembling a brunch of grapes; D. Staminate flower; E. Pistillate flower; F–J. C. longibracteatus. F. Habit; G. Leaf with details of the subglabrous adaxial surface and pubescent abaxial surface; H. Glandular, lanceolate stipules; I. Staminate flower; J. Pistillate flowers with one sepal removed. Drawing by Lucas Menezes.