Acalypha chaquensis Cardiel & I.Montero, 2018

Cardiel, José María, Muñoz, Iris Montero & García, Irene Sancho, 2018, Three new species of Acalypha (Euphorbiaceae, Acalyphoideae) from Argentina, Bolivia, Brazil and Paraguay, Phytotaxa 356 (2), pp. 158-166 : 160-162

Acalypha chaquensis Cardiel & I.Montero sp. nov. ( Figs. 1 , 4a ).

Diagnosis:— Acalypha chaquensis Cardiel & I.Montero is morphologically close to A. variabilis Klotzsch ex Baillon (1865: 226) , but it differs by the indumentum of the young branches (puberulous to subglabrous vs hispid), leaf blade folding (non-conduplicate vs conduplicate), and the presence of exudate on the leaf lower surface (none vs bright exudate).

Type:— ARGENTINA. Chaco: Departamento Bermejo, Municipio Isla del Cerrito , isla Brasilera , 50 m, 27º20´S, 58º40´W, 29 May 1977. C.L. Cristóbal et al.1543 (holotype F [1837994]!; isotypes CTES, G [G00405503]!) .

Description:— Rhizomatous shrub or suffrutex to 50 cm high, monoecious; young branches slender, puberulous, with simple,short, curved hairs;older branches early glabrescent. Stipules linear-lanceolate, to 0.6 cm long, acute,hispidulous, caducous. Petiole 2.5–4.0 cm long, with indumentum similar to that found on the young branches. Leaf blade (5–)6–8 × (3–) 4–5 cm, ovate-lanceolate, membranaceous, base rounded to cordate; apex acute to sub-acuminate; margin serrate, teeth rounded to triangular, upper and lower surface laxly pubescent to sub-glabrous, with some appressed simple hairs on veins; venation pinnipalmate, with 7 basal veins, and 5–6 veins per side; stipels absent. Inflorescences unisexual. Male inflorescences axillary, to 4.5 cm long, spicate; peduncle to 0.8 cm long, appressed pubescent; rachis hidden by the flowers; flowers densely glomerate; bracts minute, to 0.05 cm long, linear, ciliate–hispidulous. Female inflorescences terminal, erect, to 12 cm long, spicate; peduncle to 0.5 cm long, appressed pubescent; rachis clearly visible, appressed pubescent; female bracts at fruiting stage, to 0.35 × 0.45 cm, hispidulous to subglabrous; margin divided into 10–12 linear teeth, c. ½ to 2/3 of the bract length, rounded at apex, covered by minute stellate crystalliferous papillae, flowers solitary. Male flowers inconspicuous; pedicel to 0.05 cm long, buds c. 0.1 cm diameter, hispidulous. Female flowers sessile; sepals 3, triangular, c. 0.1 cm long, joined at the base, hispidulous-ciliate; ovary c. 0.08 cm diameter, densely pubescent; styles c. 0.5 cm long, free at base, glabrous, papillose at base, each divided into 12–13 slender segments. Capsule <0.2 cm diameter, pubescent and papillose; seeds c. 0.15 × 0.10 cm, minutely foveolate. Allomorphic female flowers present at the apex of some male and female inflorescence, and solitary, axillary in the basal nodes; pedicels filiform, <2 cm long, sparsely pubescent; sepals 3 irregular; ovary cylindrical, to 0.5 cm long, bilaterally symmetrical, fimbriate at the ends, finely pubescent; style single, sub-basal.

Distribution and habitat: — Argentina and Paraguay. This species has been found in two different localities: in the banks of the Paraná River, at 50 m of elevation, near the city of Corrientes in Argentina; and in the Cerro León massif, which is a group of isolated hills of low altitude in the northwest of Paraguay. Both localities are within the Chaco biome.

Etymology: —The specific name refers to the Gran Chaco Region, in eastern Bolivia, western Paraguay and northern Argentina, where this species has been found.

Conservation status: —Specimens labels do no indicate frequency or abundance of this species at the collection site. In the absence of additional information, the status of this species can only be provisionally classified as Data Deficient (DD). The material from Argentina was collected in a highly disturbed area. Conversely, the specimen from Paraguay was collected in a relatively well-preserved and protected area in Cerro León massif which is within the Defensores del Chaco National Park limits.

Additional specimens examined (paratypes):— PARAGUAY. Alto Paraguay: Macizo Cerro León, 166 m, 20º26´S, 60º15´W, 3 October 1979. A. Schinini & E. Bordas 17839 (MO!).

Figures

FIGURE 1. Acalypha chaquensis. A. Habit. B. Detail of the floral node and stipules. C, Detail of the leaf upper surface and margin. D. Detail of the leaf lower surface and margin. E. Female bract (at fruiting stage). F. Allomorphic female flower. G. Ovary and styles. H. Calyx of female flower. I. Capsule. J. Seed. Illustrations by Juan Castillo, from the holotype.

FIGURE 4. Scanning electron microscope images.A.Teeth of the female bract of Acalypha chaquensis showing the stellate crystalliferous papillae (from A. Schinini & E. Bordas 17839, MO). B. Detail of stellate crystal on the female bract of Acalypha communis subsp. apicalis (Nicholas Edward Brown) Cardiel & P.Muñoz (2013: 1296) (from J.C. Solomon 6911, MO).