Magnolia chimalapana A.Vázquez, Padilla-Lepe & Rodr., 2024

Vázquez-García, J. Antonio, Padilla-Lepe, Jesús, Gallardo-Yobal, Sergio, Rodríguez-Pérez, Ciro, García-Escobar, Alan & Muñiz-Castro, Miguel Á., 2024, Three new Mesoamerican species of Magnolia (M. sect. Talauma, Magnoliaceae) from the Chimalapas-Uxpanapa region, Mexico, Phytotaxa 652 (1), pp. 10-32 : 13-18

Magnolia chimalapana A.Vázquez, Padilla-Lepe & Rodr. -Pérez, sp. nov. (Figs. 2,3)

Type:— MEXICO. Oaxaca: Mpio, Sta. María Chimalapa , 4.3 km al SE de Chalchijapa , camino al Río Verde , 17°01’3.4”N 94°38’31.8”W, 523 m, 19 May 2024 (fl. & fr.), J. Antonio Vázquez-García 10350 w/ Ciro Rodríguez-Pérez & Alberto Luis Pérez (IBUG!, MEXU!, XAL!).

Magnolia chimalapana has similar leaf shape and size of peduncular internodes to those of M. wendtii ( Figs 4 , 5 ) but differs from the latter in being taller (30.0–40.0 vs. 7.0 m) with longer, narrower petioles (4.0–6.6 × 0.1–0.2 vs. 2.5–4.0 × 0.4–0.5 cm), smaller leaf blades (12.3–17.0 × 5.8–8.4 vs. 16.0–44.0 × 13.0–14.0), fewer pairs of secondary veins (7–10 vs. 18–19), longer and narrower flower buds (5.0–6.0 × 1.1 vs. 4.0 × 1.7–2.0 cm) and fewer stamens (48–50 vs. 71) and fewer carpels (8–9 vs. 19–28).

Trees, 30–40 m tall, 30.0–98.0 cm dbh; bark, finely fissured, smooth, grey-brown, light brown bark gap, fragrant, cream-coloured sapwood; twig internodes 1.0–1.8 × 0.3–0.4 cm, lenticellate, internodes glabrous, nodes yellowish. Leaves 16.8–22.9 × 5.8–8.4 cm; petioles 2.8–8.0 × 0.1–0.2 cm, glabrous, canaliculate, green; stipular scars 2.4–7.6 cm long, along most of the petiole length; leaf blades 12.3–17.0 × 5.8–8.4 cm, glabrous, ovate elliptic-obovate, apex obtuse or rounded and base acute, sometimes asymmetrical, margin entire with slightly wavy edge, green; secondary veins 7–10 per side, slightly curved upwards, glabrous; peduncle 2.1 × 0.3 cm, glabrous, green, internodes 1.5 cm; longest peduncular internode of mature flowers 19.0–20.0 × 3.0– 3.8 mm. Flower buds 5.0–6.0 × 1.1 cm, narrowly ovoid, open flowers 5.0–6.0 cm diam., cream; sepals 3, 3.8 × 1.6 cm, lanceolate, glabrous, outer petals 6, 3.6–4.5 cm, glabrous, oblong, creamy white, fleshy; stamens 48–50, 1.1–1.3 × 0.2–0.3 cm, ribbed, a little curved, yellowish; gynoecium 1.8 × 1.1 cm, rhomboid, attenuate at the base rounded at the apex, glabrous; carpels 8–9, 1.5 × 0.5 cm decurrent by 1.1–1.2 cm. Fruits 5.5–6.5 × 2.5–3.0 cm, rhomboid to narrowly ellipsoid; seeds unknown.

Etymology:— Named for the Chimalapa region, an area of extremely high endemism and species diversity ( Wendt 1987, Arriaga et al. 2000), ferociously defended by the Zoque culture, the true owners of one of the last remnants of tropical rainforests of Mexico.

Distribution and ecology:— Confined to Santa María Chimalapa, Río Verde watershed, on deep soils of steep slopes with tropical rain forests ( Fig. 1 ), with Terminalia sp. , Calophyllum sp. , Dialium sp. , Tapirira sp. , Guarea grandifolia DC. , Symphonia sp. etc., 300– 525 m. It is absent form Arroyo Hamaca, a fully deforested area; the Chimas (Zoque culture) located there for agriculture and grazing. Only two trees were found south of Chalchijapa, Santa María Chimalapa, without any regeneration saplings.

Conservation status:— Assessed as critically endangered (CR) with EOO 25.2 km 2 and AOO 8 km 2. Additional to its narrow distribution and rarity (IUCN criteria and conditions B1a, B2a; IUCN 2022), this species is projected to decline in area and quality of habitat, B2b(iii), because of increasing deforestation due to introduction of crops and pasturelands. The number of mature individuals is <50, and there is an observed and projected decline in population size (C2(a)(i) and D).

Additional specimens examined:— MEXICO. Oaxaca: Santa María Chimalapa, SE de Chalchijapa, Camino al Río Verde , 17°01’3.4”N 94°38’31.8”W, 523 m, 6 Jun 2023 (sterile), Vázquez-García & Rodríguez-Pérez 10322 (IBUG) ; Mpio. Sta. María Chimalapa, 30 km al S. luego al SE de Esmeralda en brecha maderera al Río Verde y rumbo a Sta. María Chimalapa, en lomas entre Arroyo Hamaca y Río Verde, un poco al N del Río Verde , 17°00’N 94°42’W, 300 m, 20 Apr 1985, Wendt et al. 4783 (CHAPA, LSU, MO, TEX) .

Figures

FIGURE 1. Geographic distribution of Magnolia sect. Talauma in Chimalapas-Uxpanapa region, Oaxaca and Veracruz, Mexico.

FIGURE 4. Magnolia wendtii. A,B. Flower buds. C. Flower. D. Top row: inner petals; middle row: outer petals; bottom row: sepals. E. Stamens showing the long connective. F. Immature fruit with stamens hanging by their hooked connective. G. Gynoecium. H. Closed fruits. I. Fruit with detached carpels without seeds. Photographs by A. Arango.

FIGURE 5. A. Habit <10 m tall, near Río La Cueva, Uxpanapa.B. Flower bud. C. Flower at male phase. D. Developing gynoecium. E. Leaf veins. F. Teresa Cruz holding a flowering branch, SE of Francisco Villa Dos, Uxpanapa. Photographs: A. by A. Arango, B.–F. by C. Rodríguez-Pérez.