Tabernaemontana riverae L.O. Alvarado & V. Saynes (2018:275–277)

Alvarado-Cárdenas, Leonardo O., Lozada-Pérez, Lucio, Cadena, Joselin, Hernández, Sofia Islas-, Martínez-González, C. Ramiro, Cortez, Ericka B., González- Martínez, César A. & González-Ramírez, Ixchel S., 2019, The triad of knowledge: Systematic, diversity and conservation status of the Mexican species of Tabernaemontana (Apocynaceae; Rauvolfioideae: tribe Tabernaemontaneae), Phytotaxa 388 (1), pp. 1-46 : 35-36

15. Tabernaemontana riverae L.O. Alvarado & V. Saynes (2018:275–277) . ( Fig. 2 , 3 ).

Type:— MEXICO. Veracruz: Municipio Hidalgotitlán, Campamento Hermanos Cedillo a 4 km hacia Río Alegre, 150 m, 21 March 1975, Juan & Avendano 15 (holotype XAL, isotype MEXU).

Trees or shrubs 1.5–6 m tall. Petioles 0.5–1.2 cm long; blades 5–19 × 1.8–4.5(8) cm, membranaceous, elliptic, ovate to obovate, base obtuse to acute, apex acuminate, margin entire, glabrous on both sides, to spreading pubescence abaxially. Inflorescence 2–4 flowers, peduncle 2–7 mm long; bracts 3.5–6.3 mm long, linear to linear-lanceolate, papyraceous; pedicels 4–8 mm long; sepals equal to subequal, 1.4–2.1 × 0.4–0.7 cm, elliptic-lanceolate, acute, glabrous, conspicuous venation; corolla infundibuliform, yellow to yellowish, lower tube (1.3–)1.5–2.2 × 0.3–0.5 cm, twisted around the anthers, staminal ridges present, upper tube 1.0–1.4 × 1.0– 1.5 cm, campanulate, suprastaminal corona of five wing-shaped lobes present, opposite the anthers, along the tube, limb lobes 1.5–1.8 × 1.4–1.6 cm, obliquely obovate; stamens inserted near of middle of the lower tube, anthers 4.8–5.2 mm long, included, yellow; pistil 1.2–1.5 cm long, nectary present. Follicles (2.7–)2.8–4.3 × 1.5–2 cm, obliquely ellipsoid, recurved, short apiculate, finely striate and with 2 lateral ridges, not lenticelate, brownish, glabrous; seeds 8.5–9 mm long.

Habitat and phenology: —Evergreen forest and secondary vegetation, with an altitudinal range of 130–300 m a.s.l. Flowering and fruiting from February to July.

Distribution: —Endemic to Mexico in the states of Oaxaca and Veracruz ( Fig. 6b ).

Conservation status: — Endangered ( EN). Tabernaemontana riverae is restricted to a few known localities in the states of Oaxaca and Veracruz ( Fig. 6b ). The area covered, according to its EOO of 2,023 km 2 and AOO of 40 km 2, is less than 1% of the area of Mexico ( Table 3) ; its populations are scarce, and grazing and building activities may significantly reduce the number of individuals in the future, mainly in Veracruz, which has significant deforestation rates ( Pérez et al. 2005). We suggest the category of endangered for this species.

Additional specimens examined:— MEXICO. Oaxaca: Mun. Matías Romero, 22 km al S de Esmeralda 9 km al S del Aserradero La Floresta, lomas al S del Río Verde , 290 m a.s.l., 26 Mar 1981, Wendt 3073 ( MEXU) ; Veracruz: Mun. Hidalgotitlán, Campamento Hermanos Cedillo a 4.5 km por la escuadra, 150 m a.s.l., 2 Apr 1975, Ortíz 80 ( MEXU) ; Km 8–12 del camino Plan de Arroyo-Álvaro Obregón, 140 m a.s.l., 18 Apr 1974, Dorantes 2872 ( XAL) ; Km 0–25 del Campamento Hermanos Cedillo, camino hacia Río Alegre , desviación al E, 22 Apr 1974, Dorantes 2951 ( XAL). Mun. Jesús Carranza, A 2 km N del poblado 2. Ejido F. J. Mina, 120 m a.s.l., Vázquez V-2378 ( MEXU) ; Mun Minatitlán, 6.6 km al Norte de la terracería La Laguna-Río Grande, sobre el camino nuevo a Ejido Belisario Domínguez , el cual sale de la terracería 14.7 km al E de la Laguna, 130 m a.s.l., 13 Jul 1980, Wendt 2554 ( MEXU) ; Zona Uxpanapa, a 13.7 km al E de La Laguna sobre terracería a Uxpanapa, luego 5–7 km al N, 130 m a.s.l., 29 Mar 1982, Lorence 3972 ( MEXU, XAL) ; 13.7 km al E de la Laguna, sobre terracería a Uxpanapa, luego 8 km al N sobre camino nuevo a Belisario Domínguez, 130 m a.s.l., 21 Mar 1981, Wendt 3018 ( MEXU) ; Mun. Uxpanapa, along road to Uxpanapa from Sarabia, 220 m a.s.l., 20 Feb 1987, Croat 65421 ( MEXU). Esfuerzo Nuevo, al E cerro Cordón Platanillo, 255 m, 03 May 1996, Rivera 92 ( MEXU) .

Common names and uses: —In Veracruz “cojón de burro”, “cojón de chivo”, and “lecherillo”.

Notes: — Tabernaemontana riverae is morphologically similar to T. eubracteata due to the foliose sepals, which are typically persistent with conspicuous venation, and infundibuliform corolla ( Fig. 2 ), but can be separated by its infundibuliform corolla with upper tube 1.0–1.4 × 1.0– 1.5 cm (vs. slightly infundibuliform with upper tube 0.3–0.65 × 0.6–0.8 cm), its sepals 1.4–2.1 cm long, elliptic-lanceolate (vs. sepals (0.5) 0.8–1.0 cm long, ovate to ovate-lanceolate) and its distribution below 300 m a.s.l. (vs. above 500 m a.s.l.).

Figures

FIGURE 2. Comparison of flowers of selected species of Tabernaemontana in Mexico. a T. alba. b T. arborea. c T. stenoptera. d T. venusta. e T. chamelensis. f T. citrifolia. g T. amygdalifolia. h T. hannae. i T. oaxacana. j T. donnell–smithii. k T. ochoterenae. l T. eubracteata. m T. riverae. n T. glabra. o T. tomentosa. p T. litoralis.

FIGURE 3. Comparison of fruits of selected species of Tabernaemontana in Mexico. a T. alba. b T. amygdalifolia. c T. arborea. d T. chamelensis. e T. citrifolia (open fruit). f T. donnell–smithii. e T. glabra. h T. eubracteata. i T. hannae. j T. litoralis. k T. mixtecana. l T. oaxacana. m T. ochoterenae. n T. riverae (open fruits). o T. tomentosa.

FIGURE 6. Distribution maps of Tabernaemontana species in Mexico. a T. alba and T. chamelensis. b T. amygdalifolia and T. riverae. c T. arborea, T. eubracteata, and T. oaxacana. d T. citrifolia and T. hannae. e T. donnell–smithii and T. ochoterenae. f T. glabra and T. venusta. g T. litoralis and T. mixtecana. h T. stenoptera and T. tomentosa.