Linum mexicanum Kunth (1823: 39)

González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, Phytotaxa 549 (2), pp. 141-184 : 158

Linum mexicanum Kunth (1823: 39) . ( Fig. 7b ).

Type:— MEXICO. Guanajuato, Santa Rosa, Humboldt & Bonpland s.n. (holotype P-Humb. (photo, F-035185, IEB!)) .

Mesynium mexicanum Rafinesque (1837: 33) .

Cathartolinum mexicanum Small (1907k: 79) .

Description: — Herbs, perennial, 50–120 cm in height, glabrous or almost glabrous, often with a voluminous root; stems erect, striate, branched to the middle part, sometimes from the base, glabrous. Leaves entire, often ciliate, basal leaves opposite or in whorls, distal leaves frequently alternate, often lanceolate or suboblong, varying from linearlanceolate to oval, 10.0–45.0 × 4.0–20.0 mm, sessile or subsessile, apex acute, 2 prominent lateral nerves near the base, coriaceous, glabrous, occasionally pubescent on the abaxial surface, stipular glands present at the base. Inflorescence a cymose panicle, pedicels 2.1–12.6(–15.0) mm long; bracts 1.9–4.6 mm long, margin entire, apex acute, stipular glands black at the base; sepals persistent, lanceolate to ovate, 2.0–3.5 × 1.2–2.0 mm, margin glandular-dentate, apex acute or cuspidate provided with hairs, 3-nerved, stipular glands absent; petals light yellow, obovate, 8.0–12.0 mm long, glabrous; stamens 5.0–8.0 mm long; anthers 0.7–1.0 mm long, light brown; staminodia present; styles fused up to half or near the apex, 4.0–7.0 mm long; stigmata capitate, light brown. Fruit ovoid to conical or subspherical, yellow with purple hues in the upper portion, 1.7–2.3 × 1.6–2.4(–3.0) mm, glabrous, pericarp thick, apex apiculate, dehiscent into 10 acute segments, septa ciliate; seeds elliptical to oblong, reddish-brown, 1.5 × 1.0 mm.

Distribution: —Endemic to Mexico, in Chiapas, Mexico City, State of Mexico, Guerrero, Jalisco, Michoacan, Oaxaca, Puebla, and Queretaro ( Fig. 5a ).

Habitat and ecology: —Oyamel fir forest, deciduous forest, crassi-rosette-leaved thorny shrublands, oak forests, pine-oak forests, thorny shrubland, thornless or sub-thornless small-leaved shrubland, palm-tree forests, pine forests, grasslands, low deciduous tropical forest, low thorny evergreen tropical forest, medium or low evergreen tropical forest. Elevation 2000–2700 m. Acrisol, Andosol, Cambisol, Phaeozem, Lithosol, Luvisol, Ranker, Regosol, Rendzina, Vertisol, and Xerosol soil types.

Phenology: —Flowering in May–September; fruiting in July–November.

Note: — Linum mexicanum is closely related to L. orizabae , with which it shares much of its natural distribution, thus leading to recurrent taxonomic identification issues; L. mexicanum can only be differentiated by the presence of fused styles to half or three-quarters of their length.

Conservation status: —According to the criterion B established by the IUCN (2019), L. mexicanum can be considered as VU (B2b(iii)), with an AOO of 64 km 2, which is added to the deterioration of its habitat as a consequence of its proximity to large nuclei of human population and an important loss of vegetation cover ( Rodríguez-Echeverry & Leiton 2021).Although its EOO is 225,655.320 km 2, its distribution is scattered. It is worth mentioning that Rzedowski & Calderón de Rzedowski (1992) indicated that this species is at risk of extinction.

Specimens examined: — MEXICO. Chiapas: Oxchuc, Terracería hacia 20 de Noviembre, 2050 m, 16°45’20”N, 92°20’58”W, 23 August 1995, H. Mejía E. & A. Luna G. 679 ( XAL!) ; San Andrés Larrainzar, Cloud Forest near the summit of Chuchil Ton , 2700 m, 3 August 1972, D.E. Breedlove 26756 ( CHAPA!) ; San Cristóbal de las Casas, Cerro San Cristóbal , 2195 m, 15 October 1965, D.E. Breedlove & P.H. Raven 13309 ( MEXU!) ; San Cristóbal de las Casas, Arroyo del Rancho Pellizzi , 20 July 1986, A. Méndez G. 9166 ( UAMIZ!) ; Totolapa, 6-8 km west of Teopisca , 2150 m, 16 August 1972, D.E. Breedlove 27054 ( CHAPA!) ; Zinacantán, Paraje Navenchauk , 2195 m, 30 July 1981, D.E. Breedlove 51847 ( MEXU!) ; Zinacantán, Paraje Patosil , 2100 m, 16°45’15”N, 92°44’29”W, 26 September 1994, A. Chame & M. de J. Gutiérrez 471 ( MEXU!) . Mexico City: Álvaro Obregón , La Angostura, 2480 m, 19°19’43.4”N, 99°14’11.1”W, 1 September 1941, E. Lyonnet 3436 ( MEXU!) . State of Mexico: Temascalcingo, 1.53 km de San José de los Reyes , 2714 m, 19°59’13”N, 100°06’33”W, 27 August 2014, D. Álvarez et al. 13634 ( MEXU!) . Guerrrero: General Heliodoro Castillo, Verde Rico , 2.3 km al N, Camino a la Cienega, 2050 m, 17°43’39”N, 99°53’39”W, 5 October 1998, R. Cruz-Durán 3066 ( MEXU!) . Jalisco: Ciudad Guzmán, Campamento de Atenquique en camino al cerro de la Media Luna, 2124 m, 18 September 2016, A. Castro et al. 4167 ( IBUG!) ; Tecalitlán , Rancho El Tigre, 2100 m, 12 August 1979, F. Gutiérrez L. 20 ( IBUG!) ; Tecalitlán , 17 km al E de Llanitos, 16 August 1990, J. Villa C. & J. Chávez L. 842 (IEB!, SLPM!) . Michoacan: Epitacio Huerta, Cerca de Polvillas , 2600 m, 2 August 1990, Rzedowski 49726 ( XAL!) ; Hidalgo, Cañada de la Trampa, San Lucas Huarirapeo , 2720 m, 1 October 2004, X. Madrigal S. 244 ( MEXU!) ; Morelia, Cerro La Máscara , 2300 m, 12 September 1991, C. Medina G. 2359 (IBUG!, XAL!) . Oaxaca: Ixtlán de Juárez, Suroeste del río de la Y, 2100 m, 17°19’5.9”N, 96°26’31.9”W, 24 September 2003, S. Figueroa B. & F.Y. Guzmán R. 801 (CHAP!, UAMIZ!) . Puebla: Cholula, Camino al Cerro El Campanario, 2580 m, 19°04’45”N, 98°31’00”W, 24 August 1987, T. Ubierna 299 ( MEXU!) . Queretaro: Pinal de Amoles , 3-4 km al NE de Pinal de Amoles, 2230 m, 24 September 1991, E. Carranza G. 3534 ( IEB!) ; Amealco , 2 km de Laguna de Servín, 2650 m, 22 August 1991, H. Díaz-Barriga et al. 6902 ( XAL!) .

Figures

FIGURE 5. Geographic distribution in the Mexican territory of:A. L. cruciata, L. lasiocarpum, L. lewisii, L. mexicanum, and L. tenellum; B. L. elongatum, L. neomexicanum, L. puberulum, L. rzedowskii, and L. schiedeanum; C. L. modestum, L. orizabae, L. pringlei, L. scabrellum, and L. vernale. Maps by Ma. Isabel Olivares.

FIGURE 7. A. Linum longipes; B. Linum mexicanum; C. Linum nelsonii; D. Linum neomexicanum. Photography by José Luis Colin.