Macroscepis sinalobolana L.O. Alvarado, Pío-León et M.G. Chávez, 2022

Alvarado-Cárdenas, Leonardo O., Pío-León, Juan F. & Chávez-Hernández, María G., 2022, Macroscepis sinalobolana (Apocynaceae, Asclepiadoideae, Gonolobeae) a new and endemic species to Sinaloa, México, Phytotaxa 564 (1), pp. 104-112 : 105-109

Macroscepis sinalobolana L.O. Alvarado, Pío-León et M.G. Chávez , sp. nov.

Type:— MÉXICO. Sinaloa: Elota, entrada a presa Aurelio Benassini “El Salto”, 24°07’58’’N 106°44’10’’W, 105 m, 23 August 2020, Pio León J. F. 112 (holotype CIIDIR! Isotypes FCME! MEXU!) .

Macroscepis sinalobolana is morphologically similar to M. diademata by their flowers are about 3 cm of diameter, brown to orange in colour, and the corona lobes apices are exerted from the corolla tube; the new species is distinguished from the later by its gynostegial corona that is bilobed at the union with the stipe of gynostegium (vs. trilobed at the union with the stipe in M. diademata ); the corona lobes apex are inflexed and slightly bilobed (vs. corona lobes apex erect and truncated in M. diademata ); and the fruit wing margins are irregularly crenate to slightly dentate (vs. margins entire to slightly lobulated in M. diademata ). Additionally, M. sinalobolana is endemic to Sinaloa, México, while M. diademata is found from central México to Nicaragua).

Herbaceous perennial vines. Latex white. Stems cylindrical, with mixed indumentum, glandular, yellow trichomes, ca. 0.1 mm long, eglandular yellow to brown trichomes, 3–4.5 mm long. Leaves petioles 1.2–2.6 cm long, with mixed indumentum, glandular, yellow trichomes, ca. 0.1 mm long, eglandular yellow to brown trichomes, 2.5–3.5 mm long; laminas 5.5–14 × 3–9.5 cm, elliptic, base bilobate, apex mucronate, abaxially and adaxially pubescent, with long, multiseptate, scattered and sub-appressed trichomes, and a few tiny erect glandular trichomes; secondary veins 5–6 on each side of midvein, more prominent in the abaxial side; (2)4–8 colleters at the base of the midvein on the adaxial side, conical, 0.7–1 mm long. Inflorescences umbelliform, 3–8 flowers; peduncles 1–1.6 cm long, with mixed indumentum, glandular, yellow trichomes, ca. 0.1 mm long, eglandular yellow to brown trichomes, 1.5–4 mm long; bracts linear to lanceolate, 6–13 mm × 1 mm, pubescent; pedicels 1.1–2 × 0.6 cm long, with mixed indumentum, glandular, yellow trichomes, ca. 0.1 mm long, eglandular yellow to brown trichomes, 3–4 mm long. Calyx green, lobes 14–15 × 7–9 mm, membranous, glabrous or glabrescent adaxially and abaxially, ovate to elliptic, apex acuminate, 1–2 colleters between each lobe, conical, ca. 1 mm long. Corolla rotate, 3.1–3.3 cm diameter, brown to orange, tube 7.3–7.5 × 10–12 mm, faucal annulus ca. 0.5 mm thick, green to brownish, corolla lobes ovate, 1.1–1.2 × 1.2–1.4 cm, orange, sometimes slightly reticulated, adaxial face strigosus with trichomes ca. 1 mm long, abaxial face velutinous with trichomes 1–3 mm long. Corona lobes fleshy, 3.7–4 mm long from attachment to stipe, laterally connate and forming a tube adnate to the corolla tube, slightly bilobed at the junction with the stipe, apices free, 1.5–2 × 3.7–4 × 1.2–1.5 mm, thickened, laterally concave, exerted and inflexed, slightly bilobed. Gynostegium stipitated, 5–6 mm long, with a plane to slightly convex stylar head, anthers 1.6 mm long, wings 1.5 × 1.6 mm. Pollinarium ca. 1.75 × 1.1 mm, corpuscle broadly elliptic, ca. 0.6 × 0.65 mm, brown; caudicle ca. 0.55 mm long; pollinia pseudoreniform, 1.15 × 0.7 mm, laterally excavated. Fruits 1 rarely 2 per flower, asymmetrically fusiform, 8.5–10.5 × 3–5 cm, glabrous to glabrescent, slightly verrucose, 5 complete and 2 incomplete wings, wigs 0.3–0.8 cm tall, margin irregularly crenate to slightly dentate. Seeds 150–200 per fruit, obovate, compressed, 7 × 5 mm, irregularly dentate distally, verrucose on both sides, more on the concave side, farinaceous on the convex side, margins 0.5 mm long, white coma 2.2–3.3 cm long. Figure 1 .

Phenology: —Flowering between August and September. Fruiting between October and December ( Figures 1 , 2 ).

Distribution and Habitat: — Macroscepis sinalobolana is found in the state of Sinaloa, in tropical dry forest, observed in areas with low to moderate anthropogenic impact, often associated with Lysiloma sp. Bentham (1844: 82) and Vachellia spp. Wight & Arnott (1834: 272), growing from 50 to 300 of elevation. ( Figure 3 ). Ants ( Formicidae ) were observed visiting the flowers and approached the faucal annulus and the corona lobes ( Figure 1H ).

Etymology: —The specific epithet refers to the name of the state of Sinaloa to which the species is restricted. Sinaloa comes from the Cahíta language, where Sina , which means “pitaya” (a columnar Cactaceae ), and Lobola, “rounded”. Thus, Sinalobola, which later derived to Sinaloa, means “round pitaya” ( CEDEMUN 1986).

Conservation Status: —Based on GeoCAT ( Bachman et al. 2011) M. sinalobolana has an EOO= 10,665 km 2 (qualifying for IUCN category: Vulnerable) and AOO= 52 km 2 (qualifying for IUCN category: Endangered) ( Figure 3 ). The individuals of this species grow in tropical dry forest and, based on the observations from the second author and Naturalista records, appear to tolerate some anthropogenic impact, growing on the fences of the houses or agricultural land associated with the remaining trees and shrubs.Additionally, this species is not frequent, but some of its populations have numerous individuals, and some of them showed several fruits (Naturalista, Sosar 70893741, Pío-León comm. pers.). Although individuals of this species have an apparent tolerance to disturbance, the probable decrease in habitat quality due to land use change in the region, may negatively affect populations; likewise, the species is restricted to one state of Mexico and in a reduced area with few populations (<5 localities from herbarium specimens, and 10 localities from Naturalista records), we recommend the inclusion of this species in the category of vulnerable (B1a, biii) ( IUCN 2019).

Additional specimens examined: — MÉXICO. Sinaloa: Culiacán de Rosales. Cercanías de Bebelama de San Lorenzo a 7 km al E de Tabalá, R. Vega 5766 (UAS); Sinaloa de Leyva. Cerro del puerto al oriente de Santa Fé, G. Bojórquez 386 (MEXU, UAS).

Additional observation from Naturalista examined:— MÉXICO. Sinaloa: San Ignacio. Agua Caliente de los Yuriar, J. Castro 10128264. Culiacán de Rosales. Culiacán, licepayan 60561687, 60561690. Elota. Elota, J. Pio 38771995, 44178284, 57867410; Miramar, La Cruz, laurareginaac 54811785. Mazatlán. Mazatlán, laurabrivera 78199290, P. Samperio 25358979, S. Escutia 25364245. San Ignacio. San Ignacio, S. Escutia 39475456, 9413850. Sinaloa de Leyva. sin localidad, Sosar 70893741.

Notes: — Macroscepis is a very poorly known genus in Gonolobinae because the collections are scarce, many of them are fruiting specimens, and due to the absence of an updated revision for the genus. This new species is a remarkable finding because it increases the morphological patterns of the flowers, such as the slightly reticulated corolla and the inflexed apex of the gynostegial corona, and distribution of the genus, attributes very important in the systematic of the group, as pointed out by Stevens (2009) and Morillo (2012, 2013). With this addition, there are five species of Macroscepis recorded in Mexico, and three of them are endemic ( M. sinalobolana , M. stevensii , and M. yucatanensis ).

Macroscepis sinalobolana is morphologically similar to M. diademata , and M. stevensii . They share sepals with a similar length (around 1 cm long) and corolla brownish to orange, densely pubescent ( Figure 2 , Stevens 2009, Morillo 2012), but we can recognize each of them by the following characters. The new species has a gynostegial corona that is bilobed at the union with the gynostegium ( Figure 2b ); the corona lobes are exerted and apically inflexed and slightly bilobed, and are in contact with each other; the fruit wigs have margins irregularly crenate to slightly dentate. Macroscepis diademata , on the other hand, has a gynostegial corona that is slightly trilobed at the union with the gynostegium ( Figure 2d ); its corona lobes are exerted and apically straight and truncated to slightly bilobed, and are apically in contact with each other ( Stevens 2009; Hernández-Barón et al. 2019 Figure 2d ); the fruit wigs have margins entire to slightly lobulated. In M. stevensii the corona lobes are included and apically truncated to slightly bilobed ( Morillo 2012). The lobes apically are not in contact with each other ( Figure 2e ). The fruits of this species are unknown.

Additionally to the morphological attributes, the geographic distribution of the new taxon is helpful in its delimitation within this species complex ( Figure 3 ). Macroscepis sinalobolana is restricted to Sinaloa state. This is the species with the northernmost distribution among the members of the genera. M. diademata is distributed from the center of México to Nicaragua, and M. stevensii is restricted to Chiapas, Mexico.

Figures

FIGURE 1. Macroscepis sinalobolana. A. Leaf. B. Lateral view of the flowers. C. Inflorescences. D. Section of the flower showed the gynostegium and the gynostegial corona. E. Pollinarium. F. Fruits. G. Seeds without coma. H. Ants (Formicidae) visiting the flowers. Abbreviations: GC: gynostegial corona, FA: faucal annulus, LE: pollinia laterally excavated. Photos: J. Pío-León

FIGURE 2. Comparison between Macroscepis sinalobolana and similar species.A. Macroscepis sinalobolana inflorescence. B. Section of the flower. C. Macroscepis diademata. D. Section of the flower. E. Macroscepis stevensii. Abbreviations: A: anther, CG: gynostegial corona, a: apex, i: insertion, SH: stylar head. Photos: J. Pío-León (A), L.O. Alvarado-Cárdenas (B–D), P.Aguilar (E).

FIGURE 3. Known distribution of Macroscepis sinalobolana and morphologically related species M. diademata and M. stevensii.