Struthanthus ramiro-cruzii Martínez-Ambriz & Soriano-Benítez, 2017

Martínez-Ambriz, Emmanuel, Saldaña, Saddan Morales & Soriano-Benítez, Jacqueline V., 2017, Struthanthus ramiro-cruzii (Loranthaceae), a new species from Guerrero, Mexico, Phytotaxa 326 (4), pp. 269-273 : 270

Struthanthus ramiro-cruzii Martínez-Ambriz & Soriano-Benítez , sp. nov.

Diagnosis: Struthanthus deppeanus affinis, sed apiculato vel acuto apice, subcordata vel truncata basi, flore ad centrum sessile et stylo valde convoluto.

Type: MEXICO. Guerrero: Mochitlán: Cerro Tepila, 5 km al O de Coaxtlahuacán (♀), 2000 m, 26 July 1982 (fl), A. Núñez 875 (holotype: FCME; isotype: MEXU) .

Perennial hemiparasitic shrubs, pendulous, with sympodial branching; stems terete, green when young, sulcate, grayishbrown when old, with conspicuous reddish lenticels, glabrous, epicortical roots usually present. Leaves opposite to decussate; petiole 5–10 mm long, canaliculate; blades ovate to lanceolate, 3–5.5 × 2.4–4.7 cm, apex apiculate, sometimes acute, base usually subcordate, sometimes truncate, margins entire to repand, sometimes slightly undulate, venation pinnate, glabrous, coriaceous. Inflorescence a raceme of triads, indeterminate and axillary, usually 1 (2) per axil, 2.5–6.2 (10.5) cm long, glabrous, with 4–10 pairs of triads, opposite to alternate, central flower of the triad sessile; inflorescence peduncle 0.4–1.5 cm; triad peduncle 3–10 mm; pedicels of lateral flowers 2–4 mm; bracts and bracteoles caducous. Pistillate flowers, 3–4 × 1.5–2 mm, actinomorphic, hexamerous. Calyx green, reduced to a calyculus with the margin undulate to irregularly dentate, glabrous. Corolla greenish-yellow, 2.2–3 mm long, petals free, glabrous. Staminodes equal to the number of petals, adnate to the corolla, opposite the petals, conspicuous. Ovary inferior, 1.5–2 × 0.8–1.2 mm, glabrous. Style strongly convoluted, 1.8–2.5 mm long, stigma capitate. Staminate flowers, 5–6 × 3–4 mm, actinomorphic, hexamerous. Calyx green, reduced to a calyculus with the margin undulate to irregularly denticulate, glabrous. Corolla greenish-yellow, 3.7–4.3 mm long, petals free, glabrous. Stamens equal to the number of petals, adnate to the corolla, opposite the petals, inserted at two different heights, three ¾ up the petal and three ½ up, arranged alternately. Anthers versatile, 1.7–2.3 × 0.7–1 mm, with a connectival horn, dehiscence longitudinal. Ovary inferior, 0.8–1 × 0.5–0.8 mm, glabrous. Style slightly curved near the apex, 1–1.2 mm long, stigma undifferentiated. Berry ovoid, 4–6 × 3–4 mm, glabrous.

Distribution and Habitat: Struthanthus ramiro-cruzii ( Figure 1 ) is endemic to Guerrero, Mexico, where it is restricted to the physiographic province of the Southern Coastal Range ( Cervantes et al. 2008) in the Guerrerense region. It grows in oak and pine-oak forests, at elevations from 1860 to 2410 m. Flowering occurs from May to August, whereas fruiting takes place from September to November. The only known host of S. ramiro-cruzii is the genus Arbutus Linnaeus (1753:395) ( Ericaceae ).

Additional specimens examined: MEXICO: Guerrero. Atlixtac: 1.5 km al E de Alcozacan, camino Atzacoaloya- Hueycaltenango (♀), 1860 m, 5 November 1983 (fr.), F. G. Lorea 2716 (FCME). Leonardo Bravo: Leonardo Bravo, 3 km al SE, camino Chichihualco-Filo de Caballo (♀), 2340 m, 19 September 1997 (fr.), J. Calónico S. 4514 (FCME). Mochitlán: Cruz del Pastor, a 4 km de Coaxtlahuacán direcc. El Salado por camino de herradura (♂), 2030 m, 7 May 1983 (fl), A. Núñez 1134 (FCME). Zapotitlán Tablas: 11 km desv. a El Duraznal, camino Tlatlauquitepec-Tlacopa (♀), 2410 m, 20 August 1981 (fl.), S. Torres & A. Núñez 905 (FCME). Trayecto Tlatlauquitepec-Zapotitlán Tablas (♂), 2340 m, 1 July 1989 (fl.), E. Guízar N. 2068 (MEXU).

Etymology: The specific epithet honors Ramiro Cruz Durán in recognition of his continuous work on the description and knowledge of the flora of Guerrero, Mexico.

Discussion: Struthanthus ramiro-cruzii is similar to S. cansjerifolius (Oliver) Eichler (1868: 87) , S. deppeanus and S. quercicola (Schlechtendal & Chamisso) Blume (1830: 1731) . These species share similar inflorescence length, pedunculated triads, caducous floral bracts and bracteoles, and corolla color. They are contrasted in Table 1.

Figures

FIGURE 1. Struthanthus ramiro-cruzii. A) Habit, B) Pistillate triad, C) Pistillate flower, D) Staminate triad, E) Triad with fruits (A, B and C based on A. Núñez 875 (FCME); D based on A. Núñez 1134 (FCME); E based on F. G. Lorea 2716 (FCME); drawn by Ramiro Cruz Durán).