Polianthes aarodriguezii Art.Castro, 2023

Castro-Castro, Arturo, González-Bernal, Marco Antonio & Aguilar, Edmi Itzel Rojas-, 2023, New insights on Polianthes montana (Asparagaceae, Agavoideae) and the description of P. aarodriguezii a new species, both from Sierra Madre Occidental, Mexico, Phytotaxa 583 (1), pp. 61-71 : 68-70

Polianthes aarodriguezii Art.Castro , sp. nov. Figure 3

Type:— MEXICO. Sinaloa: Cosalá and San Ignacio municipally border, 4.5 km al NE del poblado Guadalupe de Los Reyes , rumbo a La Escondida , 1340 m, 24.28202ºN, - 106.487650W, 17 September 2022 (fl, fr), A. Castro-Castro, M.A. González-Bernal, L. Martínez-Rubí & R. Rodríguez-Peña 4867 (holotype CIIDIR!, isotypes CIIDIR, IBUG!, IEB!, MEXU!, QMEX!, SLPM!, USON!, XAL!) .

Polianthes aarodriguezii is morphologically similar to P. alboaustralis , but it can be differentiated in having (1–)3–4 ensiform leaves (vs. 2–6 linear), inflorescence raceme (vs. spike), perigone without a nectary on the floral tube (vs. nectary located in the second third of the floral tube), and filaments 6.5–9.7 mm long (vs. 2–10 mm long); P. aarodriguezii is also similar to P. montana , due to the type and size of its inflorescence, but P. aarodriguezii perigone reaches 5–5.5 × 0.4–0.7 cm (vs. 2–2.8 × 0.3–0.5 cm), with diffuse to divergent lobes, 5.6–6.8 × 3.4–5 mm (vs. appressed to assurgent, 2.4–3 mm × 1.9–2.3 mm), and the filaments (6.5–9.7 mm vs. 5–5.4 cm), and the style (4.2–4.8 cm vs. 1.7–2 cm) are longer.

Perennial herb. Corm oblong (0.5–)1.2–1.9 × 1.1–1.5 cm, with growth buds and thickened contractile and fleshy roots, the roots horizontally oriented. Bulb oblong, 2.6–7.5 × 1.2–2.2 cm, covered by the persistent leaf bases. Leaves (1–) 3–4 in a basal rosette, with an additional one attached a few cm above the peduncle base, erect; alternate, ensiform, (10–)15–46.5 × 0.7–1.4 cm, chartaceous and soft, shiny when fresh, acute, glabrous, margin papillose-toothed, hyaline. Inflorescence racemose, (44–) 84–122 cm long, internodes decreasing in size towards the apex, with 3–7 floral nodes; scape bracts 2–7, primary sterile bract linear-lanceolate, 15–26 cm × 0.4–0.5 cm, apex acute, base truncate, margin papillose-toothed, primary floral bracts lanceolate to triangular, 0.6–1.8 × 0.2–0.3 cm, apex acute, base truncate, margin smooth, becoming scarious. Bracteoles deltoid, 0.3–5 × 0.1–0.2 mm, entire, acute, truncate. Pedicels 0.25–0.55 cm during anthesis, 0.53–0.68 cm in fruit, ascending. Flowers geminate, 5–5.5 × 0.4–0.7 cm, white concolor, succulent, scented, ascending; perigone tube 4.4–4.8 × 0.4–0.7 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. Lobes broadly ovate, external and internal similar, inner ones sometimes slightly thinner, 5.6–6.8 × 3.4–5 mm, imbricate, slightly cucullate, acute to obtuse, papillose, both diffuse to divergent. Stamens included, filaments white, filiform, 6.5–9.7 mm long from their insertion into the perigone tube, inserted 3–3.5 cm above the ovary apex; anthers linear, 6.2–7.5 × 1.3–1.8 mm, yellow, included on the upper portion of the mouth of the tube in anthesis. Ovary 5.3–7.5 × 3.2–3.5 mm; style filiform, 4.2–4.8 cm, white, included or exserted 2–3 mm from the perigone in mature flowers; stigma trilobed, lobes 1.5–1.6 mm long, papillose. Fruit a loculicidal capsule, 1–1.4 × 1–1.2 cm, globose, crowned by the remains of the perigone. Seeds ovatedepressed, 3–6 × 3–5 mm, flat, dark brown, opaque.

Etymology:—The specific epithet is a contraction name honoring Dr. Aarón Rodríguez Contreras from Instituto de Botánica, Universidad de Guadalajara, Jalisco, Mexico in recognition for his achievements in studying the floristic diversity of Mexico, and his dedicated work as a mentor of young botanists.

Distribution, habitat and phenology: — Polianthes aarodriguezii grows in the upper basin of the Elota River, in the east central part of Sinaloa, Mexico. The species is known from a population located just on the border of the states of Sinaloa and Durango states, and between the transition of the Madrean Tropical and Tropical ecoregions of the Sierra Madre Occidental, according to the proposal of González-Elizondo et al. (2012a). It inhabits open Pinus-Quercus forests, in association with Conostegia xalapensis (Bonpl.) D.Don ex DC. , Coreocarpus congregatus (S.F.Blake) E.B.Sm. , Cosmos linearifolius (Sch.Bip.) Hemsl. , Dahlia coccinea Cav. , Malaxis unifolia Michx. , Manfreda jaliscana Rose , Miconia saxicola Brandegee , Phaseolus spp. , Pinus luzmariae Pérez de la Rosa , Quercus magnoliifolia Née , Q. viminea Trel. , and Verbesina spp. The plants are found in areas with deep and acid soils at 1330–1355 m elevation. Polianthes aarodriguezii flower from late August to early October and fruit from September to late October.

Conservation status:— Polianthes aarodriguezii is represented by one collection in only one locality. Using GeoCAT ( Bachman et al. 2011) the extent of occurrence (EOO) is 0.001 km 2, and the size of the area of occupancy (AOO) is 4 km 2, employed cells of 2 × 2 km. Based on EOO and AOO area results, and following the IUCN (2019) criteria (extent of occurrence estimated to be less than 100 km 2 and known to exist at only a single location), a preliminary category of Critically Endangered is suggested (CR/B1a). One threat to the known population of the species is the development of the mining industry in the area ( Servicio Geológico Mexicano 2021).

Taxonomic relationships: — Morphologically, Polianthes aarodriguezii falls within Polianthes subgenus Polianthes . It has scented and geminate flowers at the nodes and the filaments inserted above the midportion of the perigone tube. Polianthes aarodriguezii shares morphological similarities with P. alboaustralis , but it can be differentiated in the number and shape of the leaves, inflorescence architecture, absence of a nectary in the perigone, and complementary there is also a partial distinction in inflorescence length, as well as the length of the filaments ( Table 2 ). In addition, the populations of both species are allopatric, more than 1100 km apart, and develop in different physiographic provinces ( Table 1 ). The new species may also be related to P. montana , due to the type and size of its inflorescence. However, species differ in the perigone size, the orientation and size of perigone lobes, and length of filaments and styles ( Table 2 ).

Finally, the discovery of Polianthes aarodriguezii represents the first record for the genus for the Sinaloa flora ( Villaseñor 2016, Vega et al. 2021, Pío-León et al. 2022) and one more endemism for the Sierra Madre Occidental biodiversity.

Figures

FIGURE 3. Polianthes aarodriguezii Art.Castro. A. Habit. B, D. Inflorescence. E–G. Perigone views. C. Corm. H. Capsules. Pictures: Arturo Castro-Castro.