Astragalus zacatecanus (Rydb.) Barneby, Mem. N. Y. Bot. Gard.

Castillón, Eduardo Estrada, Quintanilla, José Ángel Villarreal, Delgado-Salinas, Alfonso & Rebman, Jon P., 2023, The genus Astragalus (Leguminosae: Papilionoideae: Galegeae) in Mexico, Phytotaxa 586 (1), pp. 1921-1935 : 1921-1935

102. Astragalus zacatecanus (Rydb.) Barneby, Mem. N. Y. Bot. Gard. 13: 165. 1964

Type:— MEXICO, Zacatecas, SW of Zacatecas, near Monte Escobedo, 1897, Rose 2638 (holotype: NY00006108 !; isotype: US 00001650 digital image!).

Atelophragma zacatecanum Rydb., Bull. Torrey Bot. Club 55: 157. 1928.

Perennial. Stems up to 100 cm long, ascendant, decumbent to erect, minute strigose, trichomes short, up to 0.5 mm long. Stipules 2–7 mm long, connate, triangular. Leaves 4–7.5 cm long, leaflets 9–17, 5–20 mm long, oblong to oblanceolate, apically obtuse or notched, adaxially scattered pubescent. Peduncles 7–13 cm long; the racemes (2.2–) 9–18 cm long, flowers 10–58. Flowers green yellowish, cream to ochroleucous; the calyx 4.5–7 × 2.5–2.8 mm, strigose, trichomes white and black mixed, the tube 2–3.1 mm long, campanulate, the teeth 2–4.2 mm long, subulate; the banner 6.4–9 × 3.5–4.6 mm, obovate, basally narrowed, recurved; the wings 6.8–9 × 1.5 mm, the claw 3–4 mm long, the blade 5.6–6 mm long, oblong, distally oblique, obovate, thence incurved; the keel 6.2–7 × 2.1 mm, the claw 2.8–3 mm long, the blade 4–4.4 mm long, apically oblique, almost obovate, incurved. Pod 13–23 × 5–7 mm, deflexed, stipitate (stipe 2.8–3.1 mm long) lanceolate, oblong to elliptic, dorsoventrally flattened, straight, acute at both ends, distally ending in a triangular beak, dorsally wide sulcate, the valves thin, papery, glabrate, septum incomplete; ovules 18–24; seeds 1.2–1.9 mm long, mitten shaped, brown to dark brown, opaque.

Distribution:— Registered in Durango (Súchil and Vicente Guerrero) and southern Zacatecas (Monte Escobedo, 22°18’N – 103°23’W), adjacent to northern Jalisco ( Fig. 28 ).

Habitat:— Clayey and sandy soils; oak forest; pine forest; 2630 m.

Comments:— Both known localities are separated at about 160 km and at least five Astragalus species occur in this range, but only two, A. jaliscensis and A. zacatecanus have ochroleucous flowers and stipitate pods. Astragalus jaliscensis can be distinguished by its leaves with more leaflets (19–29), fewer flowers per raceme (12–25), longer petals (banner 10–15 mm, wings 10–10.5 mm, the keel 8.5 mm) and a longer pod (20–38 mm).

Specimens examined:— DURANGO: 14August1984, Súchil. San Juan de Michis,rumbo al Cerro “Chihuahuilla”. F. Chávez 53 ( ANSM, MEXU, NY); 26 July 1990, SSW of Vicente Guerrero on road to Las Margaritas, on the Reserve de la Biosfera “La Michilia” on the mesic W slope of Sierra Urica on the old jeep road to Cerro de el Purgatorio, R. Spellenberg 10354, S. González E. ( MEXU, NY); 15 July 1982, 14 km al W de Garame de Abajo P. Tenorio L. 994, C. Romero de T. ( MEXU). JALISCO: 15 July 1982, Santiago Papasquiaro, Garame , 26 kms. al W de Santiago Papasquiaro, R. Hernández M. 7900 et al. (M. XU); ZACATECAS: 1898, Zacatecas, J. N. Rose 2638 ( NY).

Figures

FIGURE 28. Map showing the distribution of Astragalus wootonii var. wootonii, A. wootonii var. candollianus, and A. zacatecanus in Mexico.