Polianthes alboaustralis E.Solano & Ríos-Gómez, 2014

Solano, Eloy & Ríos-Gómez, Ramiro, 2014, Polianthes alboaustralis (Asparagaceae, Agavoideae), a new species from the State of Oaxaca, Mexico, Phytotaxa 174 (2), pp. 97-104 : 98-102

Polianthes alboaustralis E.Solano & Ríos-Gómez , sp. nov. ( Fig. 1 , 2 ).

This species is morphologically similar to P. nelsonii and P. palustris , but it differs from these by its longer leaves, longer sterile primary bract, and its much longer inflorescences (36–63 cm, 29–56 cm, and 94–160 cm, respectively), as well as its extrafloral nectaries that are usually present in the widest part of the tube, its broadly ovate lobes ( Table 1).

Type:― MEXICO. Oaxaca: Distrito Putla, municipio Putla Villa de Guerrero, 33 km al NE de Putla, carretera Putla-Tlaxiaco , 17° 11ʹ 12ʹʹ N, 97° 53ʹ 00ʹʹ W, 6 agosto 2009, 1945 m, E. Solano y R. Ríos, 2516 (holotipe, MEXU!, isotipes, CHAPA!, IEB!, UAMIZ!, FEZA!, OAX!)

Perennial herbaceous plant. Corm 1.5–3.6 × 1.0– 2.2 cm, cylindrical, with growthbuds and thickened contractile roots. Bulb 1.7–4.0(–6.0) × 1.3–3.5 cm, ovoid, and covered by the bases of dried leaves. Leaves 2–6 per rosette in fertile plants; alternate, 36–63 cm × 0.4–0.7 cm, linear, cartilaginous, apex acute, thickened, margin papillosetoothed, upper and lower surface with papillae, unevenly distributed over the veins. Inflorescence spike-like, 94–160 cm long, internodes decreasing in size towards the distal portion, with 3–7 floral nodes; first sterile bract 29–56 cm × 0.3–0.8 cm, linear, margin papillose-toothed, apex acute, thickened, base truncated, fertile portion 7–25 cm, first floral bracts 4–34 mm × 2–10 mm, lanceolate or ovoid, flowers at base with two bracteoles, 0.7–3.0 mm × 0.3–2.0 mm, ovoid, margin hyaline, entire, base truncated, apex acute or acuminate. Flowers sessile, geminate, white at anthesis, white-pink at senescence, succulent, aromatic; mouth of tube regular, diffuse to divaricate at anthesis; perigone tube 4–6 cm × 0.4–0.8 cm at the base of the lobes, curved almost in half and subsequently infundibular, with widening between the curvature of the tube and the base of the lobes, broadest part usually with extrafloral nectaries, internal and external lobes much shorter than the tube, extended, apex pink, purplish, or reddish, succulent, papillose on both sides, almost equal, 2–6 × 2.0– 3.7 mm, broadly ovate, margin hyaline; apex cucullate, obtuse to rounded, papillose. Stamens included, filaments white, filiform, 2–10 mm from their insertion into the perigon tube, inserted 3–6 cm above the apex of the ovary; anthers 5–10 × 1–2 mm, linear, yellow to green-yellowish, in anthesis surrounding the mouth of the tube. Style 3.9–4.5 cm, filiform, white, included at anthesis; stigma trilobed, papillose; ovary 4–10 × 1.5–3.0 mm, cylindrical. Fruit a loculicidal capsule, 1.6–2.3 × 1.0– 2.1 cm, globose, crowned by the remains of the dried perigone. Seeds 5–6 × 4–5 mm, ovate-depressed, flat, black, and opaque ( Figs. 1 and 2 ).

Distribution and habitat:― Polianthes alboaustralis is the only species of the genus with fragrant and white flowers, that is distributed south of the Trans-Mexican Volcanic Belt. It grows in restricted areas in the western part of the State of Oaxaca, in the districts of Tlaxiaco and Putla and most likely Juxtlahuaca, on the Sierra Madre del Sur ( Fig. 3), in Juniperus Linnaeus (1753: 1038) forests, montane cloud forests, and Quercus Linnaeus (1753: 994) and Pinus Linnaeus (1753:1000) forests, with Bidens Linnaeus (1753: 831) , Calochortus Pursh (1814: 240) , Cuphea Browne (1756: 216) , Desmodium Desvaux (1813: 122) , Dahlia Cavanilles (1791: 56) , Echeandia Ortega (1800: 135) , Mimosa Linnaeus (1753: 516) , Passiflora Linnaeus (1753: 955) , Penstemon Schmidel (1762: 2) , Salvia Linnaeus (1753: 23) , and Tagetes Linnaeus (1753: 887) . It grows in black or brown Leptosol soils with a texture that is sand loam, loam or clayey, and also in clayey chromic Luvisols. The elevation is 1945 to 2130 m.

Phenology: ― P. alboaustralis flowers from August to September and fruits from September to October.

Additional specimens examined (paratypes): ― MÉXICO. Oaxaca: Distrito Tlaxiaco, Mun. Santa María del Rosario, 3–5 km al NE de la desviación a Santa Catarina Tayata , [17° 22ʹ 10ʹʹN, 97° 36ʹ 01ʹʹW], 2322 m, 13 agosto 2009, E. Solano y R. Ríos 3162 (CHAPA!, IEB!, FEZA!, MEXU!, UAMIZ!) ; Mun. Heroica Ciudad de Tlaxiaco , 2 km después de Tlaxiaco, sobre la carretera 125 hacia Putla , [17° 13ʹ 32ʹʹN, 97° 43ʹ 10ʹʹW], 2037 m, 5 agosto 2008, E. Solano y R. Ríos 2512 (CHAPA!, IEB!, FEZA!, MEXU!, UAMIZ!) ; Mun. San Pedro Mártir Yucuxaco, Llano Grande, carretera 125 Yolomecatl-Tlaxiaco , [17° 25ʹ 29ʹʹN, 97° 35´47ʹʹW], 2130 m, 26 agosto 2008, E. Solano y R. Ríos 2511, 2610 (CHAPA!, IEB!, FEZA!, MEXU!, UAMIZ!) .

Etymology:―The specific epithet refers to the white color of the flowers and the southern geographical distribution of this species (albus = white, australis = southern).

Uses:―In the Tlaxiaco district, the inflorescences are used for ceremonial purposes in the adornment of altars.

Taxonomic relationships:―According to Solano & Feria (2007), species of the genus Polianthes with white and fragrant flowers are distributed along the Trans-Mexican Volcanic Belt biogeographic province and towards northern Mexico, mainly in the northwestern portion, and, less frequently, in the northeast, in the Sierra Madre Occidental and Sierra Madre Oriental biogeographic provinces. No species of the genus Polianthes with the above characteristics were previously known from the southern part of the Trans-Mexican Volcanic Belt province which, according to Morrone (2010), is a center of diversification, endemism, and biogeographic transition for many taxa. Polianthes alboaustralis is the first record with white and fragrant flowers that is distributed to the south of this biogeographic province, occurring the western part of the State of Oaxaca, in the districts of Tlaxiaco and Putla, and most likely Juxtlahuaca. The Trans-Mexican Volcanic Belt has functioned as a physical and climatic barrier for the dispersal of this species and other genera of plants. All Polianthes south of the chain are endemic to the area. One of them, Polianthes bicolor , has orange flowers with green perigone lobes, while P. oaxacana has flowers that are yellowish-pink; both species are endemic to the State of Oaxaca ( Solano & García-Mendoza 1998; García-Mendoza & Solano 2007). Polianthes alboaustralis grows sympatrically with P. bicolor , but they differ in their flowering time. The new species described here belongs to the subgenus Polianthes due to its spike-like inflorescences and white and fragrant flowers ( Solano 2000). Within this subgenus, P. alboaustralis has longest corms and bulbs and largest leaves and inflorescences; its extrafloral nectaries, which are located in the second third of the floral tube, are noteworthy. This type of nectary is described here for the first time for the genus.

IUCN conservation status: ―The conservation status is VU (Vulnerable) in accordance with the D2 criterium of the IUCN (2001) because Polianthes alboaustralis covers a surface area of less than 4 km 2. It is restricted to four localities in the western part of the State of Oaxaca, forming localized populations with few individuals in disturbed habitats that are near roads and rural or urban areas.

MER conservation status: ―The MER conservation status is T (Threatened). Polianthes alboaustralis covers a surface area of less than 5% of the Mexican territory (SEMARNAT 2002).

Figures

FIGURE 1. Polianthes alboaustralis. a) Contractile roots, corms with growth buds and bulb, b) complete plant, c) inflorescence, d) dissected flower, e) fruit, and f) seed. Illustration by Elvia Esparza.

FIGURE 2. Polianthes alboaustralis: A. Flower, B. Perigone with extrafloral nectary, C. Detail of the nectary. D. P. palustris. E, F. P. nelsonii: E. Flowers during anthesis, and F. Senescent flowers (Photos: Eloy Solano, A, B and C; Aarón Rodríguez, D, E and F).