Acalypha amithii Mart.Gord., Fragoso & K.Velasco, 2022

Martínez-Gordillo, Martha, Fragoso-Martínez, Itzi & Velasco-Gutiérrez, Kenia, 2022, A new species of Acalypha (Euphorbiaceae) from Guerrero, Mexico, Phytotaxa 539 (3), pp. 223-228 : 224-226

Acalypha amithii Mart.Gord., Fragoso & K.Velasco sp. nov. ( Fig. 1 ).

Diagnosis: Similar to A. stenoloba but differs from it by being a subshrub of up to 1 m tall, with axillary and terminal pistillate inflorescences, pistillate flowers with free ovate-lanceolate sepals, pistillate bracts with cuneate base, and styles glabrous, ca. 12 times longer than the ovary.

Type:— MEXICO. Guerrero: Mpio. San Luis Acatlán, Yoloxóchitl , paraje El Cacao Rojo, entrando por el Cerro Copete Chico, 576 m, 16°50’55.5714”N, 98°39’4.5714”W, 29 May 2017, K. Velasco G. 40441 (holotype: FCME!; isotypes: HUAP!, MEXU!, US!) .

Subshrubs up to 1 m tall, monoecious; young branches thin, glabrescent, axillary buds densely hispid, trichomes simple and whitish, mature stems lenticellate; stipules persistent earlier reddish to dark brown, 2–9.6 cm long, subulate, pubescent, with antrorse trichomes; petioles thin, 1–5.5 cm long, pubescent, with antrorse trichomes; leaf blade (5–)10–22 × 1.2–6.7 cm, elliptic to elliptic-lanceolate, membranous; apex caudate, margin denticulate, base cuneate, lower surface glabrous, upper surface mostly glabrous, with trichomes dispersed on the nerves, venation pinnate, three-veined from the base. Inflorescences unisexual; staminate inflorescences 3.1–8 cm long, axillary, peduncle 4–7 mm long; pistillate inflorescences 4.5–6.1 cm long, axillary and terminal, peduncles thin, 0.7–1 cm long, pubescent, trichomes simple, antrorse, adpressed; pistillate bracts not fully developed, 2–2.8 mm long, sessile, accrescent, ovate, divided up to the middle, with ca. 7 unequal teeth, hispid with erect trichomes, 1–1.2 mm long, with spheric sessile glands. Staminate flowers pedicellate, perianth white-hyaline, sepals 4, ovate-lanceolate, buds less than 1 mm long. Pistillate flowers subsessile, sepals 3-4, 0.3–0.7 mm long, free, subulate, hispid; ovary densely pubescent, with trichomes simple, large, adpressed; styles 3, 6.3–7.4 mm long, free, laciniate, with laciniae 2–3 mm long, white, reddish when mature. Capsules and seeds not seen.

Distribution and ecology: — Acalypha amithii occurs in Guerrero, in the Pacific slope, growing along streams, at 576 m of elevation, in tropical subdeciduous forests, near the transition zone with Pinus -Quercus forests. It has been collected with flowers from April to May. During the field work, that encompassed the collection of all the other flowering plant species of the region, A. amitthi was not observed growing in other areas. In the collection sites, the species formed groups of no more than 10 individuals, which suggest that its distribution range is narrow and its local abundance scarce. These factors combined with wood extraction and the expansion of agricultural and livestock activities seen in the region could potentially threaten the new species. However, a more detailed study to ascertain its conservation status is needed.

Etymology: —The new species is dedicated to Jonathan D. Amith, anthropologist and linguist who studies the Mixtec, Totonac, and Nahua languages and cultures, and who has especially dedicated himself to the ethnobiology of these communities in the states of Guerrero and Puebla.

Additional specimen examined (paratype): — MEXICO. Guerrero: San Luis Acatlán, Yoloxóchitl, en el paraje Cacao Rojo o Colorado, a 4.4 km en línea recta al NE de Yoloxóchitl , camino a Arroyo Cumiapa , 576 m, 16°50’43.6194”N, 98°39’25.8474”W, 22 April 2016, K. Velasco G. 40060 ( FCME!, HUAP!, MEXU!, US!) .

Taxonomic comments: —The new species belongs to subgenus Acalypha due to the presence of sessile pistillate flowers and accrescent pistillate bracts. The species that Acalypha amithii resembles the most morphologically is A. stenoloba Müller-Argoviensis (1872: 41) , a Peru and Bolivia endemic, which thrives in the Amazonian and Andean regions ( Cardiel 2007, 2013). Both species share the glabrous, petiolate, and penninerved leaves, unisexual inflorescences and pistillate bracts with 9 or less teeth. The new species differs from A. stenoloba in the habit, being a subshrub up to 1 m high (vs. shrubs or small trees up to 8 m high in A. stenoloba ); the leaves have 9 or more pairs of lateral nerves (vs. 7); the pistillate inflorescences are terminal and axillary (vs. only terminal); the pistillate sepals are completely free from each other (vs. connate at the base) and their shape is ovate-lanceolate (vs. triangular); the pistillate bracts are cuneate at the base (vs. cordate at the base); the styles are glabrous (vs. puberulent) and almost 12 times longer than the ovary (vs. almost 5 times longer).

From the Mesoamerican species of Acalypha , A. amithii resembles A. ferdinandi Hoffm. (in Pax & Hoffmann 1924: 63) the most. Both species share the presence of simple trichomes in the vegetative organs and penninerved leaves. However, the new species differs from A. ferdinandi in the habit, being a suffruticose herb (vs. tree); the pistillate bracts have 7 teeth (vs. 13–15 teeth); the margin of the pistillate sepals is non-ciliate (vs. ciliate); the ovary surface is smooth and lacks glandular trichomes (vs. muricate surface with glandular trichomes). Finally, the distribution of these species is different, A. ferdinandi is found in the Atlantic slope, while A. amithii is distributed in the Pacific slope.

Figures

FIGURE 1. Acalypha amithii, a: Branch with terminal pistillate inflorescence and axillary staminate inflorescences; b: Close-up of the lower surface of the leaf, showing venation pattern; c: Close-up of the staminate inflorescence; d: Close-up of the pistillate inflorescence; e: Staminate flower; f: Immature bract of the pistillate flower; g: Pistillate flower.All drawn from K. Velasco G. 40441 (FCME) by María Teresa Jiménez Segura.