Tragia chiltepeca Urtecho ex Martínez-Gordillo & R. Torres, 2015

Martínez-Gordillo, Martha, Colín, Rafael Torres & Gernandt, David S., 2015, A new species of Tragia (Euphorbiaceae) from Oaxaca, Mexico, Phytotaxa 202 (2), pp. 161-164 : 162

Tragia chiltepeca Urtecho ex Martínez-Gordillo & R. Torres , sp. nov. ( Fig. 1 )

Species habitu erecto nunquam volubili a congeneribus diversa. Differt etiam inflorescentiis pedunculo 1.5–6.5 cm longo axe longiore et gemmis pyriformibus.

Type:— MEXICO. Oaxaca: Distr. Tuxtepec, Mpio. Acatlán, Cerro Buenos Aires, lado oeste de la Presa Temascal (Miguel Alemán), 6 March 1986, L. Cortés A. 193, R. Torres & P. Tenorio (holotype MEXU!, isotype FCME!)

Herbs 12–15 cm tall, erect, basally branched from herbaceous taproot, with simple and stinging trichomes. Leaves 1.4– 5.5 cm × 2.2–3 cm, ovate to ovate-lanceolate, apex acuminate, margin crenate-serrate, base deeply cordate, with 4–5 veins arising from the base, secondary veins 3–5(–8) on each side of primary vein, upper surface with scattered simple trichomes, lower surface with stinging hairs along veins; petiole 2.9–5.8 cm long; stipules 1–2 × 1.5–2 mm, lanceolate, ciliate. Inflorescences simple, axillary, 2.5–6.9(–9) cm long, peduncle (1.5–)3.3–5.5(–6.5) cm long, pubescent, with stinging and simple trichomes; floral buds pyriform; 1 pistillate flower proximally, 5–8 staminate flowers distally; bracts 0.5–1 mm long, lanceolate or subulate, margin entire, ciliate. Staminate flowers pedicellate, pedicels 0.8–1.75 mm long, erect, sepals 3, ovate-lanceolate, 0.8–1.2 mm long, ciliate; stamens 3, erect, 0.5–0.7 mm, filaments thickened, adnate only at base. Pistillate flowers pedicellate, pedicels 0.75–1.5(–2.0 in fruit) mm long, sepals 6, lanceolate, ca. 0.8 × ca. 1.5 mm, ovary 3-lobed, strigulose, styles 1.5–2 mm long, connate for ¾ of their length, forming a long projection from the ovary, stigmas 3, surface smooth. Fruit a 3-lobed capsule, sparsely hirsute, 2.5–4 mm long. Seeds 2–3 mm in length, ovoid, slightly apiculate, beige, mottled, ecarunculate.

Distribution and habitat:— Tragia chiltepeca is endemic to Oaxaca. It is known only from the Tuxtepec region, surrounding the Miguel Alemán Dam. It occurs in semi-deciduous tropical forest at an elevation of 60 m.

Additional material examined (paratypes):— MEXICO. Oaxaca: Tuxtepec, Chiltepec and vicinity, 2 November 1941, G. Martínez-Calderón 782 (MO). Tuxtepec, 30 July 1965, G. Martínez-Calderón 156 (MO).

Phenology:— Flowering and fruiting in March, July, and November.

Etymology:— The name of this species refers to Chiltepec, Oaxaca.

Discussion:— Tragia chiltepeca was first detected by R. Urtecho (1996) in an unpublished thesis, and possesses morphological features that are unique in the genus; it is an erect herb without flexuose or twining apical branches. Its pedunculate inflorescences are as long as its leaves, and it has pyriform floral buds that are conspicuously different from the globose buds in all other Mexican species of the genus. It is herbaceous like T. nepetifolia Cavanilles (1800: 37) , a variable species distributed in northern, central, and southern Mexico, but T. chiltepeca has ovate to ovate-lanceolate leaves, inflorescences with longer peduncles, and styles united for ¾ of their length.

Figures

FIGURE 1. Tragia chiltepeca. A. Plant habit. B. Inflorescence and pistillate flower. C. Staminate flower. D. Fruit, apical view. E. Mericarp after dehiscence, ventral view. F. Seed. G. Trichomes (A–G from Luis Cortés A. 193, R. Torres & P. Tenorio, MEXU).