Dioon mejiae Standley & Louis Otho Williams (1950: 37)

Hernández-Tapia, Jessica E., Jiménez-Ramírez, Jaime & Vovides, Andrew P., 2020, Taxonomic revision of the genus Dioon (Zamiaceae), Phytotaxa 442 (4), pp. 267-290 : 280-283

Dioon mejiae Standley & Louis Otho Williams (1950: 37) . Type:— HONDURAS. El Paraiso, cultivated in the garden of Dr. Isidoro Mejía, 750 m, 17/February/1949. Standley P. C 16756 (holotype: F!, isotype: EAP!).

= Dioon edule var. latipinnium Dyer (1884: 191) . Type:— MEXICO. Cultivated at Royal Botanic Gardens Kew from material collected in Mexico, Dyer without number.

= Dioon pectinatum Masters (1893:718) . Lectotype (designated by Stevenson & Sabato 1986): Icone, in Gard. Chron. 73(338):1893.

Plants 1–2 m or taller. Stems 30 cm wide. Cataphylls triangular-elongated acuminate, lanate, 15–18 cm long, 4–5 cm wide. Leaves 11–14 per crown, 1–2 m long, glabrescent, trichomes whitish brown. Leaflets 100–140 pairs, falcate, acute, flat-convex, not-imbricate, sometimes slightly imbricate, covering less than a third of the width of the leaflet, opposite to subopposite, margin entire, rarely with 1–3 prickles, veins 17, the apical leaflets 3.8–10.6 cm long, the intermediate ones 12.7–19.3 cm long, the basal ones 5–5.7 cm long, all of them (1.2) 1.3–1.6 cm wide, distance between articulations 0.1–0.4 cm, with glabrate pinnacanths; rachis straight to semicurved at the apex, subterete, glabrate; petioles semiterete, 1–8 cm long, 1.5–3 cm wide, lanate at the base. Male strobili cylindrical, 30–80 cm long, 8–10 cm wide, slightly stalked apparently sessile; microsporophylls cuneate, lanate, recurved and mucronate distally. Female strobili ovoid, 30–50 cm long, 20–30 cm wide, stalked; megasporophylls deltoid, flat, 5–7 cm long, 3–4 cm wide, lanate on the outer surface, the inner surface glabrate, rarely lanate. Seed globose to subglobose, 4–5 cm long, 3–4 cm wide, sarcotesta of cream color to yellow-whitish.

Distribution and habitat.—This is the only Dioon species that is distributed in Central America ( Honduras); however, plants in Nicaragua are cultivated. Even though it is likely that there are wild populations in the border with Honduras, further explorations are needed to confirm this. This is the only species of the Spinulosum clade that is found in tropical deciduous forest, in warm-humid to semi-dry regions. The altitudinal range is from 100– 500 m. According to the IUCN red list of species, it is considered within the Least Concern (LC) category.

Uses and common names.—It is used as an ornamental plant, the leaves are used in religious fests and in crowns for funerals, the female strobili are used as food, including the seeds which are used for making flours for tortillas. In the region it is known as palma teosinte and tiusinte ( Bonta et al. 2019; Bonta & Osborn 2007).

Taxonomic notes.—For the synonym D. edule var latipinnium , mentioned by Dyer, the type specimen is cultivated in the Royal Botanical Gardens, Kew, but the origin of the specimen remains uncertain, as the publication indicates vaguely that it belongs to the southern region of Mexico ( Standley & Williams 1950). It is characterized by the presence of pinnacanths, the entire leaflet margin and globose seeds. It is akin to D. rzedowskii for presenting ovoid-cylindrical seeds, even though D. rzedowskii is known for not presenting pinnacanths while D. mejiae does.

Specimens examined:— HONDURAS. Tegucigalpa , 800 m, without date, Molina A. 35148 ( MEXU) ; Tegucigalpa , 950 m, October/1973, Rees J. 1601 ( XAL) .— NICARAGUA. Chontales, 100 m, 3/October/1984, Stevenson W. D. 23377 ( MO) .

Dioon merolae De Luca, Sabato & Vázquez Torres (1981: 180) . Type:— MEXICO. Chiapas: Tonalá, 1200 m, 29/ May/1979, Vázquez Torres V–2301 (holotype: NAP, isotypes: NY!, XALU!).

Plants 3 m tall. Stems 25–40 cm diameter, normally erect to decumbent, rarely branched. Cataphylls triangular-caudate, densely lanate, 6–10 cm long, 2 cm wide. Leaves 12–25 per crown, 100–120 cm long, glabrescent, trichomes brown. Leaflets 90–120 pairs, linear-lanceolate, acuminate, keeled-recurved, oblique, strongly imbricate, along two thirds of the leaflet, subopposite, the margin entire or with 1–2 prickles, veins 12, the apical leaflets 0.5–7.4 cm long, the intermediate ones 5.8–13.5 cm long, the basal ones 1.3–5.5 cm long, all of them 0.58–1.2 cm wide, distance between articulations 0.1–0.6 cm, pinnacanths absent, glabrate; rachis twisted at the apex, semiterete, tomentose; petioles terete to subterete, 7.5–20 cm long, 0.5–2.2 cm wide, lanate at the base. Male strobili cylindrical, 30–40 cm long, 8–10 cm wide, peduncles short, appearing sessile; microsporophylls cuneate, tomentose, mucronate and recurved distally, 2.5 cm long. Female strobili ovoid, 45 cm long, 25 cm wide, slightly stalked, apparently sessile, megasporophylls trulate, flat, 10–12 cm long, 4–5 cm wide, lanate on the outer surface, the inner surface glabrate. Seeds ovoid, 3 cm long, 2 cm wide, sarcotesta yellow.

Distribution and habitat.—It is distributed in Oaxaca and Chiapas, in xeric shrubland, tropical deciduous forest, oak forest and pine-oak forest. It thrives in warm-humid climates, sometimes in temperate and arid climates, within 500– 800 m. The specimens of Veracruz are cultivated plants.

Uses and common names.—The plant is used as an ornamental, the leaves are used in religious fests ( Pérez-Farrera & Vovides 2006). In the region is known as espadaña, nimalari, maíz viejo, morrito, palma espinuda, or palmilla ( Bonta & Osborne 2007).

Taxonomic notes.—It is akin to Dioon califanoi and can be distinguished by its caudate apex of the cataphylls, the keeled and recurved leaflets and the trulate megasporophyll. The synonym Dioon dohenyi and Dioon edule var. merolae are in fact invalid names, as there is neither a publication nor type specimens supporting them.

Specimens examined:— MEXICO. Chiapas: Arriaga, 900 m, 9/July/1998, Farrera O. 1046 ( MEXU) ; Arriaga, 510 m, 23/May/2002, Meléndez E. 260 ( MEXU) ; Cintalapa, 700 m, 17/February/1982, Calzada J. & Elizondo J. 8548 ( MEXU) ; Cintalapa, 950 m, without date, Castillo J. 616 ( HEM) ; Cintalapa, 725 m, 9/July/1994, Pérez M. A. 70 ( MEXU) ; Cintalapa, 900 m, 28/May/1979, Vázquez et al. V-2302 ( ENCB) ; Jiquipilas, 560 m, 22/October/1993, Brigada T. Walters (25-1) FGT ( XAL) ; Jiquipilas, 600 m, without date, Farrera O. 562 ( HEM) ; Jiquipilas, 12/ October/1987, Palacios E. 286 ( MEXU) ; Jiquipilas, 650 m, 28/April/1994, Pérez M. A. 34 ( XAL) ; Jiquipilas, 600 m, without date, Pérez M. A. 478 ( HEM) ; Jiquipilas, 550 m, 20/March/1993, Vovides A. P. et al. AV-1239, AV-1240, AV-1241, AV-1242 ( XAL) ; La Concordia, 583 m, 4/March/2005, Carrillo-Reyes P. & Cabrera-Toledo D. 5158 ( XAL) ; La Concordia, 525 m, 15/May/1994, Pérez M. A. 31 ( XAL) ; Tonalá, 1300-1400 m, 18/December/1996, Guízar E. & Castañeda A. 3708 ( XAL) ; Tonalá, 960 m, 5/September/1995, Pérez M. A. 730 ( XAL) ; Tonalá, 900 m, without date, Pérez M. A. 900 ( HEM) ; Tuxtla Gutiérrez, 1000 m, 5/November/1983, Sabato et al. V-2303 ( ENCB) ; Villaflores, 955 m, 28/June/1994, Pérez M. A. 33 ( XAL) ; Villaflores, 1200 m, 38/ June /1994, Pérez M. A. 35 ( XAL) ; Villaflores, 850 m, 25/June/1994, Pérez M. A. 36 ( XAL) ; Villaflores, 1060 m, 28/October/1995, Pérez M. A. 780 ( MEXU, HEM) ; Villaflores, 900 m, 27/April/1995, Pérez M. A. 275 ( MEXU, HEM) ; Villaflores, 915 m, 27/April/1995, Vovides A. P. & Pérez M. AV-1262 ( XAL) . Oaxaca: Magdalena Tequisquitlán, 1097 m, 26/May/2004, Walters T. et al. TW 2004- 27 A ( SERO) ; Magdalena Tequesquitlán, 1705 m, 28/May/2004, Walters T. et al. TW-2004-29 B ( SERO) ; Nejapa de Madero , 1300 m, 12/February/2000, Avendaño S. & Vázquez A. 5175 a, 5175 b, 5175 x ( XAL) ; San Carlos Yautepec, 1000 m, 9/March/1996, Castillo J. & Amezcua F. 829 ( MEXU) ; San Carlos Yautepec, 866 m, 9/March/2006, Espinosa A. 327 ( MEXU, XAL) ; San Jerónimo Taviche, 1716 m, 16/January/2004, Salas-Morales 5159 ( SERO) ; San Juan Lajarcía, 1500 m, 14/February/2000, Salas-Morales 2683 ( SERO, MEXU) ; San Lorenzo Albarradas, 1700 m, 24/ March/1988, Martin G. J. GJM-M309 ( MEXU) ; San Miguel Tenango, 1150 m, 16/February/1995, Salas-Morales 808 ( XAL, SERO) ; San Pedro Huamelula, 736 m, 10/May/2009, Sánchez A. 2482 ( SERO, MEXU) ; Santa María Ecatepec, 884 m, 16/June/2010, Canek J. JCLC 767 ( MEXU) ; Santa María Ecatepec, 883 m, 16/May/2010, Canek J. JCLC766 ( MEXU) ; Santa María Ecatepec, 1340 m 14/March/2006, 1242 ( SERO, MEXU) ; Santa María Petapa, 810 m, 10/December/1995, Salas-Morales 1098 ( XAL) ; Santiago Lachiguiri, 1060 m, 1/April/1991, Campos A. ( MEXU) ; Santiago Lachiguiri, 1780 m, 23/February/1995, Torres E. & Salas S. AV-421 ( XAL) ; Santiago Lachiguiri, 1380 m, 2/March/2007, Velasco K. 1891 ( SERO) ; Santiago Lachiguiri, 1097 m, 25/May/2004, Walters T. et al. TW 2004-25 A ( SERO) ; Santo Domingo Tehuantepec, 1200 m, 7/November/1990, Torres R. 13855 ( MEXU) . Veracruz, Xalapa, 1270 m, 29/August/2007, Luna V. E. 1585, 1586 ( XAL) .

Dioon planifolium Salas-Morales, Chemnick, & Gregory (2016: 35) . Type:— MEXICO. Oaxaca: San Jorge Nuchita, 1600 m, 3/November/2001, Salas-Morales S. 4344 SS (holotype: MEXU!).

Plants 1–4 m tall. Stems 20–25 cm diameter. Cataphylls triangular-acuminate, lanate. Leaves 25–40 per crown, 90– 220× 13–24.2 cm, glabrescent, trichomes brown-whitish. Leaflets 91–144 pairs, linear-lanceolate, acuminate, flat, not imbricate, subopposite, sometime opposite, margin entire, sometimes with 1–2 prickles at the apical margin, veins 10–12, the apical leaflets 2–5 cm long, the intermediate 6–9.5 cm long, the basal ones 1–6.5 cm long, all of them 0.4–0.6 cm wide, distance between articulations 0.3–0.8 cm, without pinnacanths, glabrate; rachis straight, semiterete to subterete, glabrate to slightly pubescent along and at the insertion of leaflets to the rachis; petioles semiterete to subterete, 8–19 cm long, 0.8 cm wide, glabrate, becoming lanate at the base. Male strobili cylindrical, 30–39 cm long, 8–11.5 cm wide, peduncles short, appearing sessile, microsporophylls cuneate, tomentose, recurved mucronate distally, 2.7–4 cm long. Female strobili ovoid, 38.7–51 cm long, 19–20.5 cm wide, slightly stalked, apparently sessile, megasporophylls deltoid-acuminate, flat, 10.5–12.2 cm long, 2.6–3.1 cm wide, outer surface lanate, inner surface glabrate. Seeds ovoid to subglobose, 3.3–4.3 cm long, 2.6–3.1 cm wide, sarcotesta yellow.

Distribution and habitat.—It is found in xeric shrublands, tropical deciduous forests and oak forests in the state of Oaxaca, with an altitudinal range of 1400–1650 m. It thrives in warm-humid, semiarid and temperate climates.

Uses. It is used only as an ornamental plant.

Taxonomic notes.—It is distinguished mainly for presenting flat, not imbricate leaflets, acuminate apex of the cataphylls and deltoid-acuminate megasporophylls.

Specimens examined:— MEXICO. Oaxaca: San Jorge Nuchita , 2090 m, 8/February/2000, Avendaño S. & Vázquez A. 5171 a ( MEXU) ; San Jorge Nuchita , 1249 m, 9/January/2014, Salas-Morales ( SERO) ; San Jorge Nuchita , 1600 m, 9/February/2000, Salas-Morales 2687 ( SERO, FCME) .

Dioon purpusii Rose (1909: 260) . Type:— MEXICO. Oaxaca, Cañón Tomellín, 7/September/1906, MacDougal D. T. & Rose J. N. 11352 (holotype: US!, isotype: F!).

Plants 1.5–2 m tall. Stems short 25–40 cm diameter. Cataphylls triangular-acute, lanate, 6–12 cm long, 1.5–5 cm wide. Leaves 8–25 per crown, 80–160× 16 cm, glabrescent, trichomes brown. Leaflets 75–130 pairs, linear-lanceolate, acuminate, ascending, slightly imbricate, covering a third of the leaflet width, subopposite, rarely opposite, margin entire or with 2–3 prickles, rarely 1, veins 10, the apical leaflets 1.8–6.4 cm long, the intermediate 5.1–15.5 cm long, the basal ones 1.4–4 cm long, all of them 0.3–1.1 cm wide, distance between articulations 0.3–1 cm, with pinnacanths, glabrate; rachis straight or slightly twisted at the apex, semiterete, glabrate to tomentose at the insertion of the leaflets; petioles terete, 10.5–31 cm long, 0.5–2.1 cm wide, tomentose to lanate at the base. Male strobili cylindrical, 20–36 cm long, 7–13 cm wide, peduncles short, appearing sessile, 2–5 cm long, microsporophylls cuneate, tomentose, recurved mucronate distally, 2.7–2.8 cm long, 1.4–2 cm wide, sori with 4–6 sporangia. Female strobili ovoid, 44–52.5 cm long, 20–25 cm wide, peduncles short, appearing sessile; megasporophylls deltoid-acuminate, flat, recurved distally 10–18.5 cm long, 5–9.5 cm wide, lanate on the outer surface, the inner surface glabrate and sometimes the apex. Seeds subglobose, 3–4 cm long, 3 cm wide, sarcotesta yellow.

Distribution and habitat.—It is distributed in xeric shrublands, oak forests, tropical deciduous forests and the ecotone between these types of vegetation in the states of Oaxaca and Puebla. It thrives in warm-humid. semiarid and arid climates, within 900–1750 m.

Uses and common names.—It is used only as an ornamental plant. In the region, this species is called la-fanetejua, lan-zi-le, chamal and palma real (Bonta & Osborn 2007).

Taxonomic notes.—It resembles D. argenteum for presenting ascending leaflets, slightly imbricate, acute cataphylls and deltoid-acuminate megasporophylls. However, it can be distinguished for presenting pinnacanths, brown tomentum, 2–3 marginal prickles in the leaflets and longer leaflets compared to those in D. argenteum . The synonym Dioon edule var. purpusii is an invalid name, as there is neither publication nor type specimen to support it.

Specimens examined:— MEXICO. Oaxaca: Concepción Pápalo , 1589 m, 3/February/2000, Avendaño S. & Vázquez A. 5163, 5166 ( XAL) ; Concepción Pápalo , 1350 m, 4/February/2000, Avendaño S. & Vázquez A. 5167, 5168 ( XAL) ; Concepción Pápalo , 1589 m, 3/February/2000, Avendaño S. & Vázquez A. 5165 ( XAL, MEXU) ; Concepción Pápalo , 1598 m, 29/July/2007, Ayala M. 2553 ( MEXU) ; Concepción Pápalo , 1740 m, 14/February/2000, Salas-Morales 2682 ( SERO, MEXU) ; San Jerónimo Coatlán , 1450 m, 4/December/1990, Campos A. 3546 ( MEXU) ; San Juan Bautista Cuicatlán , 1520 m, 27/March/1980, Dávila P. & Ruíz P. F-865 ( MEXU) ; San Juan Bautista Cuicatlán , 27/March/1980, Dávila P. & Ruíz P. F-888 ( MEXU) ; San Juan Bautista Cuicatlán , 620 m, 19/September/2002, García R. 865 ( OAX) ; San Juan Bautista Cuicatlán , 1288 m, 8/July/2004, Juárez G. 453 ( MEXU) ; San Juan Bautista Cuicatlán , 1400 m, 18/September/1979, Rees J. 1688 ( XAL) ; San Juan Bautista Cuicatlán , 1230 m, 19/February/1993, Salas-Morales 1132 ( XAL) ; San Juan Bautista Cuicatlán , 1240 m, 14/February/2000, Salas-Morales 2688 ( OAX, SERO, MEXU) ; San Pedro Jaltepetongo , 1500 m, 11/June/2002, Medina R. 1072 ( MEXU) ; San Pedro Jaltepetongo , 1360 m, 3/December/1993, Torres 784 ( XAL), 133 ( SERO) ; San Pedro Jaltepetongo , 1360 m, 26/January/1994, Torres 1154 ( XAL) ; Santiago Chazumba , 1830 m, 5/February/1999 ( UAMIZ) ; Santiago Nacaltepec, 1000 m, Sep /2001, C. C. y V. S. s.n. ( MEXU) ; Santiago Nacaltepec , 1501 m, 29/October/2004, Cruz-Espinosa C. A. 1655 ( MEXU) ; Santiago Nacaltepec , 1380 m, 30/October/2004, Juárez G. 666 ( MEXU) ; Santiago Nacaltepec , 1320 m, 25/July/1993, Salinas T. 7342 ( MEXU) ; Santiago Nacaltepec , 900 m, 17/June/1979, Vázquez M. et al. V-2310 ( ENCB, MEXU) ; Santiago Nacaltepec , 900 m, 17/July/1979, Vázquez M. et al. V-23106 ( MEXU) ; Santo Domingo Tonaltepec , 900 m, 10/July/1981, Hernández & Estrada 117 ( UAMIZ) ; Teotitlán de Flores Magón , 1350 m, 14/October/1993, Brigada T. Walters (6-1), (6-2) ( XAL) ; Teotitlán de Flores Magón , 1500 m, 23/May/1978, Rzedowski 35670 ( ENCB) ; Villa de Tututepec de Melchor Ocampo , 41 m, 19/October/2000, Purpus C. A. 2705 ( XAL) . Puebla: Ajalpan , 2500 m, 11/ October/1970, Robert M. F. & Díaz J. M. s.n. ( ENCB) .

Dioon rzedowskii De Luca, Moretti, Sabato & Vázquez Torres (1980:225) . Type:— MEXICO. Oaxaca: Teotitlán de Flores Magón, 650 m, 22/May/1979, Vázquez Torres V–2300 (holotypes: XALU!, isotipos: ENCB!, NY!, K!, FI!, MEXU!).

Plants 5–7 m tall. Stems 25–40 cm diameter. Cataphylls triangular-elongated acuminate, densely lanate, 10–18 cm long, 2–5 cm wide. Leaves 10–20 per crown, 160–200 cm long, glabrescent, trichomes brown-whitish. Leaflets 60–80 pairs, falcate, acute, convex, not imbricate, rarely slightly imbricate, less than a third of the leaflet width, opposite, sometimes subopposite, margin entire (when juvenile, spinose with 1–16 prickles along the whole margin), veins 12, the apical leaflets 4.7–11 cm long, the intermediate ones 13.2–19.1 cm long, the basal ones 2.5–6 cm long, all of them 0.5–2.4 cm wide, distance between articulations 0.3–1.8 cm, without pinnacanths, tomentose to glabrate; rachis straight to semicurved at the apex, semiterete, tomentose at the insertion of leaflets, petioles semiterete, 20– 13 cm long, 2.8–3.1 cm wide, lanate at the base. Male strobili cylindrical, 30–35 cm long, 8–12.5 cm wide, peduncles short, appearing sessile, 4.5–5 cm long; microsporophylls cuneate, slightly lanate to tomentose, recurved mucronate distally, 3–5 cm long, 1.5–1.7 cm wide, sori with 3–5 sporangia. Female strobili ovoid to cylindrical, 60–75 cm long, 20–25 cm wide, elongated stalked; megasporophylls linear-trulate, flat, 11–15cm long, 1.7–3 cm wide, lanate at the outer surface, the inner surface glabrate. Seeds ovoid to cylindrical, 5–6 cm long, 3 cm wide, sarcotesta yellow.

Distribution and habitat.—It is one of the two species of the genus that is distributed in tropical rainforest in Oaxaca. It can be found in very humid regions, within the 400–1300 m. The specimens of Veracruz correspond to cultivated plants.

Uses and common names.—It is used only as an ornamental plant. The species is called Tush -kju ( Bonta & Osborne 2007).

Taxonomic notes.—It is akin to D. spinulosum and can be distinguished by its leaflets which are not reduced to pinnacanths, therefore the petiole is evident, the leaflets present prickles in juvenile states, and are lost when the plant matures. On the other hand, D. spinulosum presents pinnacanths and many prickles, even in old plants.

Specimens examined:— MEXICO. Oaxaca: San Bartolomé Ayautla , 450 m, 25/October/1993, Walters T. et al. (28) FGT ( XAL) ; San Bartolomé Ayautla , 416 m, 7/October/2005, Salas-Morales 5336 ( SERO) ; San Bartolomé Ayautla , 508 m, 7/October/2014, Salas-Morales 7527 ( SERO) . Veracruz: Xalapa , 1270 m, 29/August/2007, Luna V. E. 1589, 1590 ( XAL) .