Magnolia uxpanapana A.Vázquez, Padilla-Lepe & Gallardo-Yobal, 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 : 21-27

Magnolia uxpanapana A.Vázquez, Padilla-Lepe & Gallardo-Yobal , sp. nov. ( Figs 8–13 )

Type:— MEXICO. Veracruz: Mpio. Minatitlán, lomas bajas, 2-4 km S of Uxpanapa (Pob. 12), al E del Río Oaxaca; 17°11’N 94°13’W, 120 m, suelos profundos, selva perturbada, 20 Oct 1983, Wendt 4237 (holotype: ENCB!; isotypes: LSU!, CHAPA!).

Magnolia uxpanapana has similar leaf length, number of secondary veins and fruit shape to those of M. perezfarrerae ( Fig. 8 ) but differs from the latter in being taller (25.0–35.0 vs. 8.0–20.0 m) with shorter petioles (3.2–5.0 × 0.2–0.3 vs. 8.0–12.7 × 0.8–0.9 cm), narrower leaf blades (8.0–9.5 vs. 9.5–14 cm), shorter longest peduncular internode of mature flowers (9.0–10.0 × 11.0–12.0 mm), ovoid, small flower buds (6.5 × 5.0 vs. 8.0–12.0 × 5.6–8.4 cm and broadly ovoid), more numerous stamens (192–216 vs.175), smaller fruits (6.0–8.0 × 4.5–5.5 vs. 8.0–12.0 × 5.6–8.4 cm), apical carpels falling separately (vs. irregular masses) and fewer (57–58 vs. 89–92) and smaller basal carpels (2.1–1.7 × 0.9–1.4 vs. 3.5–4.7 × 1.4–1.5 cm).

Evergreen trees, 25–35 m tall, 90 cm dbh with small buttresses; bark with numerous small and prominent warts with orange dots light brown or cream-coloured, the inside white with strong odour to hierba santa ( Piper auritum ); first branches after 6 m; twigs 0.4–0.5 × 1.4–2.5 cm, lenticellate, glabrous, green; stipules 0.3–0.4 × 3.3–3.5 cm, triangular, glabrous. Leaves 17.0–23.5 × 8.0-9.0 cm; petioles 3.2–5.4 × 0.2–0.3 cm, glabrous, adaxially grooved and abaxially slightly grooved, straight to slight curves, green; stipular scars 2.8–5.0 cm long, along most of the petiole length; leaf blades 14.5–20.5 × 8.0– 9.5 cm, glabrous, broadly elliptical, base acute, on the other side revolute, apex rounded, entire margin, slightly wavy, glossy, decurrent by 4.0 mm, green; secondary veins 8–9, curved, glabrous; longest peduncular internode 9.0–10.0 × 13.0–14.0 mm, glabrous, brown. Flower buds 6.5 × 5.0 cm, glabrous, ovoid; open flowers 14.0.0– 15.2 cm diam., white; sepals 3, 4.8 cm long, broadly obovate, glabrous; petals 6, 5.2 cm long; stamens 192– 216, 0.2 × 0.8 cm, glabrous, linear furrowed with the obtuse apex. Fruits broadly ovoid, 6.0–8.0 × 4.5–5.5 cm; carpels 57–58, 2.1–1.7 × 0.9–1.4 cm; detaching singly, each one Y or Y-shaped, recurved triangular to elongate, smooth on the ventral side with glossy bone-coloured warts, glabrous, carpels decurrent by 0.8–1.2 cm. brown. Seeds 9.0–12.0 × 7–11 cm, 2 per carpel, ovoid to triangular, sclerotesta orange-brown.

Etymology:— Named after the Uxpanapa region, an area of extremely high endemism and species diversity ( Wendt 1987, Arriaga et al. 2000) and non-renewable, quickly vanishing resources.

Distribution, ecology and ethnobotany: — Endemic to the Uxpanapa region, 80–150 m, on deep flat soils in perturbed tropical rainforest with Dialium sp. , Pouteria sapota and Poulsenia armata ( Fig. 1 ). Locally known as magnolia (Wendt et al. 4237).

Conservation status:— EOO 1,040.154 km 2 and AOO 20 km 2. However, according to the IUCN criteria C2(a)(i) and D, the species is assessed as CR. The Uxpanapa region lacks municipal, state, or federal protection ( Ochoa-Ochoa et al. 2009), and the forest as a result has been severely fragmented and forest cover reduced to about 20% of the total area ( Arriaga et al. 2000).

Additional specimens examined:— MEXICO. Veracruz: Mpio. Las Choapas , Rancho El Milagro, 5 km en línea recta al SW (202 grados) de la colonia Nueva Tabasqueña, 17°31’48”N 94°1’44”W, 115 m, Selva Alta perennifolia, 27 Apr 2002, Rincón G. 3043 (MEXU, XAL) ; Municipio Uxpanapa, km 6 camino Hnos. Cedillo-La Laguna , 17°15’44.09”N, 94°33’18.34”W, 140 m, 15 Jul 1974 (fl bud), Dorantes 3461 (MEXU, XAL) ; Mpio. Uxpanapa , 4 km al E de Campamento Hnos. Cedillo, camino a La Laguna, 17°15’26.64”N, 94°34’19.39”W, 105 m, 18 Mar 1974 (fl. bud and gynoecium), Dorantes 2607 (F, MO) ; Mpio. Uxpanapa , 18 km de Campamento Cedillo, al NE, camino a La Laguna, 17°15’50.35”N, 94°31’47.94”W, 18 Mar 1974, Ponce 218 (MEXU, XAL) .

Notes:— Magnolia chimalapana has leaf blades of similar size and shape to those of M. sinacacolinii (Figs 14,15), but it differs from the latter in being taller (30.0–40.0 vs. up to 25.0 m) with longer, narrower petioles (4.0–6.6 × 0.1–0.2 vs. 1.5–6.0 × 0.4–0.6 cm), fewer secondary veins (7–10 vs. 12–14), the longest peduncular internode longer and narrower (19.0–20.0 × 3–3.5 vs. 5.0–8.0 × 6.0–7.0 mm), flower buds longer (5.0–6.0 × 1.1 vs. 4.0 × 3.0– 3.5 cm) and narrowly ovoid (vs. broadly ellipsoid), lanceolate sepals (vs. broadly obovate), fewer stamens (48–50 vs. 71–112) and fewer carpels (8–9 vs. 20–28) ( Vázquez-García et al. 2012b). The most distinctive characteristic of M. chimalapana among all Mexican species of M. sect. Talauma is its few-carpellate fruits (8–9). It and M. wendtii are the rarest species of the Mexican M. sect. Talauma ( Aldaba-Núñez 2020) .

Magnolia heribertoi has similarly shaped fruit and texture of dorsal carpel walls to those of M. lacandonica ( Fig. 8 ), but it differs from the latter in its larger petioles (9.5–10.0 vs 6.0– 7.5 cm), shorter leaf blades (12.5–17.0 vs. 18.0– 30.0 cm), more pairs of secondary veins (12–14 vs. 10–11), shorter but wider longest peduncular internode 12.0–13.0 × 22.0–23.0 (vs. 15.0 × 15.0 mm), larger flower buds (5.5 × 6.8 vs. 3.5–4.5 × 3.0–3.5) that are broadly ellipsoid vs. ovoid, broadly ellipsoid sepals (vs. broadly obovate to subrotund), smaller fruits (5.8–8.3 × 5.5–8.2 vs. 11.5 × 9.5 cm), carpels detaching in multi-carpellate irregular masses (vs. unicarpellate, individually detaching), fewer carpels (36–46 vs. 61–70) and smaller basal carpels (4.2–4.3 × 1.1–1.2 vs. 4.5–4.6 × 1.4–1.5 cm) ( Vázquez-García et al. 2013c). The most distinctive characteristics of M. heribertoi are its spheroidal fruits ( Fig. 8 ) dehiscing apically carpels in multi-carpellate irregular masses, a common character with South American and the Caribbean species and in Mexico only observed in M. perezfarrerae (Vázquez et al. 2013b) .

Magnolia uxpanapana shares with M. decastroi obovate leaves, but it differs from the latter in being taller (25–35 vs. 12 m) with shorter petioles (3.5–5.0 vs. 6.5–7.5 cm), smaller leaf blades (14.5–20.5 × 8.0–9.5 vs. 27–28.5 × 10.0– 10.5 cm) and more carpels (57–58 vs. 30–40). A distinctive characteristic of this species are its attenuate, mostly obovate leaf blades, shared with M. decastroi ( Vázquez-García et al. 2013b) .

Unless immediate action is taken to protect these incredible Magnolia species, their precious ecosystems and the rights of the Zoque indigenous people and their livelihoods, these rainforests are condemned to become tropical pasturelands (Villalobos-L. 2001, Lira-Torres & Briones-Salas 2011, Doane 2012). In addition to these direct anthropogenic pressures, there are other serious threats to the southern Mexican tropical rainforests, such as climate change, with which biome shifts are predicted ( Baumbach et al. 2023). There are plans of for a megaproject of interoceanic trans-isthmic corridor that will trigger commercial and industrial development of the region with its attendant human population growth that will increase pressure on the ecosystems in the Isthmus of Tehuantepec ( Ceceña 2020).

This research increases the number M. sect. Talauma species in the Chimalapas-Uxpanapa region from one to four, making this region richer than Los Tuxtlas with only three. Currently, the total species number of M. sect. Talauma in Mexico is fifteen.

Figures

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

FIGURE 8. Differences between the species of Magnolia sect. Talauma with spheroid to sub-globose fruits at the same scale. A. M. perezfarrerae. B. M. lacandonica. C. M. uxpanapana. D. M. heribertoi. E. M. zoquepopoluca. F. M. yajlachhi. Photographs by A. Vázquez.

FIGURE 9. Magnolia uxpanapana. A. Leaves and flower bud. B. Flower bud. C. Developing gynoecium. D. Fruit near maturity with staminal scars on staminophore.A and B from Wendt et al. 4237, C from Dorantes 2607 (F) and D from Rincón-G. et al. 3043 (XAL). Photographs by A. Vázquez.

FIGURE 10. Magnolia uxpanapana. Herbarium specimen with leaves and flower, Rancho El Milagro, SW of Nueva Tabasqueña, Las Choapas, Veracruz, Rincón-G. et al. 3043 (MEXU). Photograph by A. Vázquez.

FIGURE 11. Magnolia uxpanapana. Type specimen with leaves, fruit axis, carpels, seeds and wood, Uxpanapa (poblado 12) E of Río Oaxaca, Wendt et al. 4237 (ENCB). Photographs by A. Vázquez.

FIGURE 12. Magnolia uxpanapana. A. Leaf blade attached to bract. B. Inner petal. C. Sepal and inner petal. D. Leaf. E. Tree in situ, General Valerio Trujano, Uxpanapa. Photographs by A. García

FIGURE 13. Magnolia uxpanapana, A. Tree in situ. B. Stem showing bark detail. Photographs by A. García.