Asclepias sauronii M.G.Chávez & L.O.Alvarado, 2023

Chávez-Hernández, María Guadalupe, Álvarez-Ruiz, Julio Alejandro & Alvarado-Cárdenas, Leonardo Osvaldo, 2023, Two new Mexican species of Asclepias (Apocynaceae; Asclepiadoideae; Asclepiadeae), Phytotaxa 592 (3), pp. 255-266 : 256-261

Asclepias sauronii M.G.Chávez & L.O.Alvarado sp. nov.

Type: — MÉXICO. Coahuila: Arteaga, Sierra Zapalinamé , 2705 m, 25°28’01’’N 100°51’00’’W, 27 June 1990, G.S. Hinton et al. 20460 (Holotype: GBH!) .

Asclepias sauronii is morphologically similar to A. hypoleuca ( Gray 1882: 222) Woodson (1941: 206) , due to their similar sized flowers (more than 1 cm long), the stipitate gynostegium and sigmoid-shape corona hoods of the gynostegial corona, but differs from this taxon by its ovate-lanceolate to lanceolate leaves, its reddish or carmine petals and yellow hoods, its acute adaxial apex of the hood (vs. bilobed in A. hypoleuca ), and its exerted and curved horn without reaching the gynostegium (vs. horns included in A. hypoleuca ).

Perennial herb 30–100 cm tall. Stem single, cylindrical, unbranched, densely puberulent, internodes 13.7–15.1 cm long. Leaves opposite, 4–6 pairs on each stem, sessile to shortly petiolate, petiole when present ca. 4 mm long, lamina ovate-lanceolate to lanceolate, 11.6–13.9 cm long × 3.7–4.8 cm wide, base truncate to slightly cordate, apex acute, margin entire, pubescent adaxially, trichomes adpressed, more dense at the midvein, abaxially densely pubescent to tomentose, venation brochidodromous, 15–25 veins on each side of main vein, a pair of glandular multicellular trichomes (colleters) present in a stipular position. Inflorescences extra-axillary, 1–2 per node, umbelliform, the last produced sometimes appearing terminal, on densely pubescent peduncles (2.8)3.7–5.5(8.8) cm long, bracts linear to lanceolate, glabrous, 3.3–4.5 mm long, caducous; 20–32 flowers on pubescent pedicels 1.6–2.4 cm long. Calyx lobes lanceolate, reflexed, 4.5–4.9 mm long × 0.9–1.3 mm wide, green, abaxially puberulent. Corolla 1–1.8 cm diameter, lobes lanceolate to narrowly elliptic, reflexed, 0.93–1.3 cm long × 0.28–0.4 cm wide, reddish or carmine, glabrous. Gynostegium stipitate, with a white to yellow column 6–8 mm tall, corona composed of five yellow with a purple base, cucullate segments (hoods) opposite the filaments, ca. 2 mm tall in its adaxial side, apex acute, rested on the gynostegium, 7.2–8.6 mm tall in its abaxial side, acuminate, slightly curved, each hood with a digitate appendage (horn), curved, yellow, ca. 1 mm long, adnate to the dorsal surface of the hood and emerging from the hood’s sinus; anthers brown, ca. 2 mm long, with ovate white appendages inflexed over the apex of style head, style head pentagonal, 1.7–2 mm diameter, apex concave; pollinarium composed of a pair of pollinia 1.8–2 mm long, ovate-lanceolate, translator arms 0.5–0.6 mm long, oblanceolate, corpusculum 0.38–0.45 mm long, elliptic, black. Fruits fusiform follicles, 9.5– 10.5 cm long, densely puberulent, held erect on an erect stalk; seeds not observed. ( Fig. 1 ).

Phenology: —Flowering between May and July. Collected with fruits in August.

Distribution: — Asclepias sauronii is endemic to Mexico and distributed in the states of Coahuila and Nuevo León.

Habitat and ecology: —The species grows in oak-pine forest and disturbed areas derived thereof, range from 2115 to 2747 m a.s.l. ( Fig. 1 ). The flowers are visited by small bees of the genus Colletes (Colletidae) .

Etymology:— The name of the new species refers to the fictional character Sauron, the main antagonist of J. R. R. Tolkien’s “The Lord of the Rings”, due to the color of the plant with gray tones in the leaves and red tones in the flowers, as well as the presence of the elongated corona that resembles the helmet of Sauron in the Lord of the Rings movies.

Proposed conservation assessment:— Endangered (EN B1ab(iii)+B2ab(iii)) ( IUCN 2022). Asclepias sauronii has a minimum Area of Occupancy (AOO) of 24 km 2, and an estimated Extent of Occurrence (EOO) of 1,062.751 km 2. It is only known from two locations, one in Coahuila and another in Nuevo León, both outside the Mexican Protected Areas. Also, the species is restricted to the Quercus - Pinus forests of the north of Mexico, which is a highly vulnerable ecosystem due to erosion, wildfires, etc. ( Alanís-Rodríguez et al. 2015). More research is needed to know the population trends and the specific threats that could affect this species.

Notes:— This species is similar to A. hypoleuca , A. lemmonii Gray (1883: 85) and A. otarioides due to their similar sized (more than 1 cm long) flowers, the stipitate gynostegium and the very prominent marginal lobes (hoods) of the gynostegial corona ( Fig. 2 ).

The new species can be separated from morphological similar taxa based on the following differences: lamina ovate-lanceolate to lanceolate (vs. broadly oblong-ovate to oval in A. hypoleuca , and broadly oblong-ovate to ovate in A. lemmonii and A. otarioides ), reddish or carmine petals and yellow hoods (vs. reddish petals and hoods in A. hypoleuca , green or yellow petals and white hoods in A. lemmonii and pink, pinkish or pink-yellowish petals, and white to pink hoods in A. otarioides ), sigmoid-shape corona hoods (vs. usually tubular corona hoods in A. otarioides ), acute adaxial apex of the hood (vs. bilobed in the other species), exerted and curved horn (vs. horns, when present, included in A. hypoleuca , and laminar and erected horns in A. lemmonii ), and its shorter (ca. 2 mm long) and curved horns without reaching the gynostegium (vs. longer (ca. 4 mm long) and curved horns reaching and resting the gynostegium in A. otarioides ).

Besides the morphological features, the new species is also distinguished by its geographic distribution restricted to the states of Coahuila and Nuevo León (vs. Chihuahua to A. hypoleuca , Chihuahua, Durango, Jalisco, and Sonora to A. lemmonii and states of the north and center of Mexico to A. otarioides ).

Additional specimens examined:— MÉXICO. Nuevo León: Galeana, SE of El Potosí, G. B. Hinton 18758 (GBH).

Additional observation from Naturalista:— MÉXICO. Coahuila: Arteaga, Sierra de Zapalinamé, Arturoc 26998910 (Naturalista, https://www.naturalista.mx/observations/26998910), L. Jiménez 53088784 (Naturalista, https:// www.naturalista.mx/observations/53088784). Saltillo, Sierra de Zapalinamé, A. Huereca 48207926 (Naturalista, https://www.naturalista.mx/observations/48207926), Arturoc 3970732 (Naturalista, https://www.naturalista.mx/ observations/3970732), cesargzz 80694311 (https://www.naturalista.mx/observations/80694311).

Figures

FIGURE 1. Asclepias sauronii. A. Known distribution of A. sauronii and morphological related species in the region of study. B. Habit. C. Fruit. D. Leaves. E. Inflorescences. Photographies from Naturalista by Alejandro Huereca (B,E), Arturo Cruz (C), and Leticia Jiménez Hernández (D).

FIGURE 2. Comparison between flowers and types of Asclepias sauronii and morphological related species.1. A.sauronii 2. A. hypoleuca. 3. A. lemmonii. 4. A. otarioides. Photographs from Naturalista by Arturo Cruz (1a, 1b), ddoyle (2a), semiferalhiker (2b), José Jesús Sánchez Escalante (3a) Jason Ksepka (3b), and Leopoldo Hurtado (4a). Types of the morphological related species. A. sauronii (Hinton et al. 20460, GBH!) (1c). A. hypoleuca (C.G. Pringle s.n., P!) (2c). A. lemmonii (J.G. Lemmon 2814, GH!) (3c). A. otarioides (K.E. Roe 432, WIS!) (4c). Scale bar 1 cm.