Astragalus tijuanensis A. E. Estrada, Rebman, C. González & Villarreal

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

95. Astragalus tijuanensis A. E. Estrada, Rebman, C. González & Villarreal , Phytotaxa 577(1): 1–13

Type:— MEXICO. Baja California (Municipio Tijuana): Boulevard 200, at the surroundings south side of the city of Tijuana , Baja California, in a recent burned area, 32° 20’11.04” N, 116°57’44.593” W, alt. 171 m, 5 June 2022, C, González 104 (Holotype SD!; isotype MEXU!) .

Perennial with deep single buried root, without superficial crown of a woody taproot, 13 × 0.7 cm long. Stems three to several, up to 30 cm long, 3–7.5 mm diameter, erect, arising from the base, the lower part of the stems, 7–10 cm, gray color, with stipules and lower leaves persistent, without leaflets, the upper part of the stem geen, striate, densely strigulose, the trichomes 0.1–0.3 mm long, appressed, white. Stipules free or semi-amplexicaul, clasping ¼ to ½ of the stem´s circumference, 2–3 × 3–4 mm, persistent, almost always wider than longer, triangular to triangular-ovate, white to light brown, sparsely strigulose or glabrate, with only few trichomes on the edges. Leaves 4.5–8.5 cm long, petiole (3–)11–12(–17) mm long, leaflets (17)21–29(33) opposite, rarely some of them alternate, (2–)8–10 × 0.7–1 mm, linear to linear-oblong, glabrate and light-green adaxially, and dark-green and sparsely strigulose abaxially as stem pubescence, flattened or slightly concave, acute at both ends. Peduncles erect or incurved-ascending, 2–3 cm long, elongating with age (5–)7–11(–14) cm long, exceeding the length of the leaves, sparsely strigulose, trichomes white; the recemes 1.5–5 cm long, flowers 13–19. Flowers white with purple tones; the calyx (3.5–)3.9–4(–4.2) × 2.5–2.7 mm, campanulate, the tube 3.2–3.3 mm long, inequilaterous, green mixed with purple, sparsely strigulose, the trichomes white and purple mixed, occasionally sub-glabrous, the teeth 0.7–0.9 mm long, triangular to triangularsubulate; the banner sessile, 12.5–13 × 6.3–7 mm, obovate, elliptic obovate to obovate-rhombic, gradually attenuated at the base, apex noteche, the notch 0.4–0.5 mm deep; the wings 11.9–12.2 × 2–2.3 mm, the claw 5–5.2 mm long, the blade 6.8–7 mm long, straight, narrowly obliquely oblong-obovate, rounded to truncate at apex, basally auriculate; the keel 9.4–9.8 × 2.5–2.8 mm, the claw 4.8–5 mm long, the blade 4.6–5 mm long, half obovate, incurved, apex rounded, auriculate. Pod spreading or slightly ascending, sessile, (17–)19–20(–24) × 6–8 mm, incurved, semi-lunate in profile, at first subcylindrical to elliptic, sub-fleshy, and at maturity strongly compressed laterally or low convex at the lateral faces, somewhat plumpy (not inflated like a bladder), ventral suture concave, keeled, dorsal suture almost straight to low convex, base acute, apiculate and rigid at the apex, the beak 0.7–1 mm long, with the sub-persistent style, the valves coriaceous, stramineous, brown to light-brown, glabrous, noticeably transversely reticulate and wrinkled, unilocular, septum absent; dehiscence apical; seeds 1.9–2.2 mm long, mitten-shaped, black, opaque.

Distribution:— As far as we know, Astragalus tijuanensis is only known from the type locality, at the surroundings south side of the city of Tijuana, Baja California ( Fig. 26 ),

Habitat:— In a recent burned area, inhabiting arid shrublands, in open gravelly or clayish hillsides, low slopes or flats, on clayish substrate, associated to arid shurblands.

Comments:— In the area where A. tijuanensis develops, five other Astragalus species are distributed that can be easily distinguished by their particular morphological characters, A. brauntonii var. lativexillum (compact inflorescences, pod less than 1 cm long), A. acutirostris (triquetrous pod), A. didymocarpus (ovary with two ovules and inflated bladder-like pod), A. idrietorum (inflated, semi-transparent pod with 8–12 ovules) and A. palmeri (pod inflated, pubescent).

Figures

FIGURE 26. Map showing the distribution of Astragalus strigulosus, A. tephrodes, A. thurberi, A. tijuanensis, and A. tioides in Mexico.