Linum australe A. Heller (1898: 627)

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 : 147-149

Linum australe A. Heller (1898: 627) . ( Fig. 3b ).

Type:— UNITED STATES OF AMERICA. New Mexico: 4 mi E of Santa Fe, Heller & Heller 3724 (holotype NY!, isotypes F!, GH!, K!, KANU, KSC, MO!, MSC, NEB, US!) .

Cathartolinum australe Small (1907b: 81) .

Linum aristatum var. australe (A.Heller) Kearney & Peebles (1939: 485) .

Mesynium australe (A.Heller) W.A.Weber (1984: 3) .

Description:— Herbs, annual, 10–55 cm in height, puberulent in the basal part, glabrous or almost glabrous in the distal part; root thin; stems erect, striate, usually branched from the base, glaucous, puberulent. Leaves entire, sometimes slightly glandular-dentate, involute, alternate, linear, 4.0–20.0 × 0.5–2.0 mm, sessile, apex acute to acuminate, tip whitish, 1-nerved, coriaceous, glabrous, stipular glands present. Inflorescence a cymose panicle, pedicels 2.0–15.0 mm long, striate; bracts (3.9)4.0–6.0 mm long; margin scariose, glandular-dentate; sometimes with purple spots, apex acute, stipular glands present or sometimes absent; sepals deciduous, linear-lanceolate, 4.0–6.0 × (0.9)1.0– 1.5 mm, margin glandular-dentate, occasionally with reddish-purple spots, apex cuspidate-aristate, tip whitish, 1(–3)-nerved, stipular glands present or absent; petals light yellow to yellow-orange, oblanceolate or obovate, 6.0– 100 mm long, stamens 3.0–7.0 mm long; anthers 0.5–1.0(1.1) mm long, yellow; staminodia absent; styles fused to near the apex, 2.0–6.0 mm long, stigmata capitate. Fruit ovoid, yellow, 3.0–3.2 × 2.4–4.0 mm, glabrous, pericarp thick, apex obtuse, dehiscent into 5 segments; seeds elliptical, reddish-brown, 2.0–3.0 × 0.8–1.0 mm.

Distribution: — United States of America; in Mexico, in Baja California, Chihuahua, Coahuila, and Durango ( Fig. 2b ).

Habitat and ecology: —Oyamel fir forest, oak forests, oak-pine forests, thorny shrublands, and pine forests. Elevation 1500–2700 m. Montane soils, mainly Andosol, Cambisol, Phaeozem, Fluvisol, Lithosol, Regosol, Rendzina, Vertisol, Xerosol, and Yermosol.

Phenology: —Flowering and fruiting in August–September.

Note: — Linum australe is the only species within its distribution range that is glabrous beyond the base, with yellow flowers and fused styles almost to the apex. The stems and pedicels strongly striated to sulcate in the distal part are a distinctive character of the species. Its distribution in the northern part overlaps with the distribution of L. aristatum ; however, they can be differentiated, since the latter presents a much more branched habit, a glabrous stem, and an ellipsoid fruit with thin pericarp.

Conservation status: —According to the criteria established by the IUCN (2019) this species is EN (B2ac(iii)) with an EOO of 512,558.866 km 2 and AOO of 16 km 2, and <5 localities areknown. It stands out that this species has a wide distribution in the United States of America and that the evaluation presented here only considered Mexican specimens.

Specimens examined: — MEXICO. Baja California: Sierra San Pedro Mártir, canyon at base of Cerro Botella Azul , 2700 m, 19 July 1988, S. Boyd & A. Liston 2700 ( MEXU!) . Chihuahua: Road between Babicora and Yepomera , 2500 m, 8 April 1977, Bennett et al. 821 ( CHAPA!) . Coahuila: Acuña , 75 km al noroeste de Ciudad Acuña, 565 m, 29°34’56”N, 101°43’31”W, 29 May 2016, J. A. Encina et al. 5415 ( ANSM!) . Durango: Súchil , Hacienda El Mortero, 1970 m, 15 September 2001, N. Almaraz et al. 60 ( CIIDIR!) .

Figures

FIGURE 2. Geographic distribution in the Mexican territory of: A. H. micranthum, L. aristatum, L. berlandieri var. filifolium, L. longipes, and L. rupestre; B. L. australe, L. australe var. glandulosum, L. flagellare, L. nelsonii, and L. usitatissimum. Maps by Ma. Isabel Olivares.

FIGURE 3. A. Linum aristatum; B. Linum australe; C. Linum berlandieri var. filifolium; D. Linum cruciata. Photographs by José Luis Colin.