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Vachellia bravoensis - leaves

Vachellia bravoensis - pods and leaves

Vachellia bravoensis - pods and leaves

Name

Vachellia bravoensis (Isely) Seigler & Ebinger, Phytologia 87:  146.  2005.
syn.  Acacia schaffneri (S. Watson) F. J. Hermann var.  bravoensis Isely, Sida 3:  383.  1969.

Synonymy and types

Basionym:  Acacia schaffneri (S. Watson) F. J. Herm. var. bravoensis Isely,  Sida 3: 383.  1969. - TYPE:  UNITED STATES.  TEXAS:  San Patricio Co., 7 miles S of Taft in clay loam soil, 29 Mar 1950, F. B. Jones 100 (holotype:  SMU).

Formal description

Shrub or small tree to 4 (6) m tall.  Bark grayish brown, shallowly furrowed.  Twigs dark purplish brown to dark brown, slightly flexuous, glabrous to very lightly pubescent with erect hairs.  Short shoots commonly present above the stipular spines, to 5 mm long, covered with acuminate stipules and old leaf bases.  Leaves alternate, commonly clustered on the short shoots, 5-20 mm long.  Stipular spines light to dark brown, usually becoming light gray with age, symmetrical, terete, straight, thin to stout, to 15(30) x 1.5 mm near the base, usually pubescent at least near the base.  Petiole adaxially grooved, 2-8 mm long, usually densely pubescent with erect to ascending hairs; petiolar gland solitary, located at or just below the lower pinna pair, sessile, circular, 0.2-1.1 mm across, doughnut-shaped, glabrous.  Rachis adaxially grooved, 0-18 mm long, pubescent, usually a sessile, circular gland 0.1-0.3 mm across, between the terminal and occasionally the other pinna pairs.  Pinnae 1 to 3(4) per leaf, 7-28 mm long, 2-8 mm between pinna pairs.  Petiolules 0.4-1.0 mm long.  Leaflets 10 to 24 pairs per pinna, opposite, 0.5-1.1 mm between leaflets, oblong, 2.0-4.2(5.0) x 0.6-1.1 mm, glabrous, lateral veins sometimes obvious, only one vein from the base, base oblique, margins ciliate, apex broadly acute to obtuse.  Inflorescence a densely flowered globose head, 8-11 mm across, solitary or in clusters of 2 to 5 on the short shoots.  Peduncles 7-24 x 0.3-0.9 mm, densely pubescent, and small, red, deciduous glands also present.  Involucre 4- to 5- lobed, located at the base of the globose head, lightly pubescent, persistent.  Floral bracts spatulate, 0.8-1.3 mm long, puberulent, deciduous.  Flowers sessile, yellow; calyx 5-lobed, 0.8-1.6 mm long, the lobes glabrous to puberulent; corolla 5-lobed, 2-3 mm long, the lobes glabrous to puberulent; stamen filaments 3.2-4.2 mm long; distinct ovary glabrous to densely pubescent, on a stipe to 0.2 mm long.  Legumes dark brown to black, straight to slightly curved, nearly terete, usually constricted between the seeds, linear, 70-160 x 6-9 mm, coriaceous, recticulately striate, densely pubescent with erect hairs, glandular with minute, red, deciduous glands, indehiscent; stipe to 10 mm long; apex acute to obtuse.  Seeds uniseriate, no pulp, light to dark brown, ovoid, slightly flattened, 6.0-9.1 x 5.0-6.5 mm, smooth; pleurogram oval, 3.1-5.0 mm across. Flowers in February to April. Chromosome number:  2n = 26 (Turner and Fearing 1960)

Distribution

Mostly disturbed sites between sea level and 1500 m elevation from southeastern Texas to Tamaulipas, Nuevo León, eastern Coahuila and northern San Luis Potosí, Mexico.

Additional info

Vachellia bravoensis is separated from V. schaffneri by the characteristics mentioned in the key, as well as the appearance of flowers before the leaves, smaller overall size, glabrous to only lightly pubescent twigs, and mostly glabrous petiolar glands.  Though the number of pinna pairs found on V. bravoensis leaves is usually 3 or fewer, occasionally primary leaves have 4 pinna pairs.  By far, however, the majority of the leaves have only 3 pinna pairs, whereas in V. schaffneri, the primary leaves mostly have 4 pairs of pinnae, with 5-6 common, and 7 rarely encountered.  Also, the more northerly distribution of V. bravoensis, being extremely common in southern Texas and northeastern Mexico, helps to separate the two species.  Though the two species are sympatric in a limited area of northeastern Mexico, only a few specimens were encountered that could not be assigned easily to a particular species; these were sterile individuals.  Like V. schaffneri, all specimens of this variety tested were strongly cyanogenic.

Isely (1969) resolved the status of this taxon when he described it as a variety of Vachellia schaffneri. Turner (1959), as well as many others, placed this material with V. tortuosa as the fruit of these two taxa are similar, being constricted around the seeds, relatively long and narrow, and pubescent. Vachellia bravoensis, however, is easily separated from V. tortuosa by the presence of a circular petiolar gland located between to just below the first pinna pair, the fewer pinna pairs (1-3 vs. 4-6), the obscure lenticels, and the straight twigs.

Britton and Shafer (1908) first described this taxon as Acacia subtortuosa, recognizing that it is distinct from V. tortuosa, and citing its occurrence in Texas and adjacent Mexico. Though clearly describing V. bravoensis, the specimens cited (Palmer 11 and 510, from near Durango, Mexico) are clearly V. schaffneri.

Flowering time

February-April.

Representative specimens

UNITED STATES:

Arizona:

Pinal Co.:

California:

San Diego Co.:

Texas:

Atascosa Co.:

Bee Co.:

Bexar Co.:

Blanco Co.:

Cameron Co.:

Dimmit Co.:

Duval Co:

Hidalgo Co.:

Jim Hogg Co.:

Jim Wells Co.:

Karnes Co.:

Kinney Co.:

Kleberg Co.:

La Salle Co.:

Maverick Co.:

McMullen Co.:

Medina Co.:

Nueces Co.:

Refugio Co.:

San Patricio Co.:

Starr Co.:

Uvalde Co.:

Victoria Co.:

Wharton Co.:

Webb Co.:

Zavala Co.:

MEXICO:

Coahuila:

Hidalgo:

Nuevo León:

San Luis Potosí:

Tamaulipas:

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