Vachellia zapatensis (Urban & Ekman) Seigler & Ebinger, Phytologia 87: 170. 2005.syn. Acacia zapatensis Urban & Ekman, Ark. Bot. 22a(8): 30. 1928.
Synonymy and types
Basionym: Acacia zapatensis Urb. & Ekman, Ark. Bot.. 22a(8): 30. 1928. - TYPE: CUBA. MATANZAS: Zapata Peninsula, in shrub forest towards Bahía de Cochinos, in open places on limestone, 31 Jan 1924, E. L. Ekman 18358 (holotype: B, destroyed; isotype: NY).
Shrub or small tree (height unknown). Bark unknown. Twigs gray to dark reddish-brown, not flexuous, puberulent. Short shoots commonly present above the stipular spines, to 2 mm long, enclosed by a few indurate, triangular bract, the short shoots covered with acuminate stipules and old leaf bases, sometime elongating into branches with scattered leaves. Leaves alternate, also commonly clustered on the short shoots, 1.5-10.5 mm long. Stipular spines light gray with a reddish-brown apex, symmetrical, terete, straight, subulate, to 4.5 x 1.1 mm near the base, sparsely puberulent. Petiole adaxially grooved, 1.5-4.3 mm long, puberulent; petiolar gland solitary, located just below the first pinna pair to medial on the petiole, sessile to subsessile, circular to elliptical, 0.6-0.8 mm across, apex flattened, glabrous. Rachis adaxially grooved, 0-8 mm long, sparsely puberulent, lacking a gland between the terminal pinna pair. Pinnae 1 or 2(3) pair per leaf, 11-20 mm long, 2-5 mm between pinna pairs. Petiolules 0.7-1.2 mm long. Leaflets 11 to 16 pairs per pinna, opposite, 0.9-1.2 mm between leaflets, linear to elliptic-linear, 3.5-4.8 x 0.7-1.0 mm, glabrous, lateral veins obvious, only one vein from the base, base oblique, margins sparsely ciliate, apex acute to obtuse. Inflorescence a densely flowered globose head, 5-8 mm across, in fascicles of 1 to 2 from the short shoots. Peduncles 11-20 x 0.3-0.5 mm, sparsely puberulent. Involucre 4- to 5-lobed, located near the middle of the peduncle, lightly puberulent, persistent. Floral bracts spatulate, 0.2-0.5 mm long, sparsely puberulent, more or less persistent. Flowers sessile, yellowish-orange; calyx 5-lobed, 0.9-1.1 mm long, glabrous or nearly so; corolla 5-lobed, 1.4-1.8 mm long, glabrous or nearly so; stamens 30 to 35, stamen filaments 3.5-4.5 mm long, their bases fused for about 0.5 mm; ovary sparsely pubescent with a few scattered hairs, on a stipe to 0.2 mm long. Legumes unknown. Seeds unknown. Flowers in January-February. Chromosome number unknown.
Known only from the type locality near Bahía de Cochinos, Zapata Peninsula, Matanzas Province, Cuba, where it occurs in open places on limestone in shrub forests.
Endemic to Cuba, and known only from the type collection, which lacks fruit and enlarged stipular spines on the short shoots of older growth, Vachellia zapatensis may be placed with confidence with the V. acuifera group. Its lustrous, coriaceous leaflets, leaves with few pinna pairs, and the elongated-clavate receptacle all indicate a relationship to that group. Vachellia zapatensis bears many similarities to both V. daemon and V. cucuyo. It may be distinguished from V. daemon, the only other member of the V. acuifera group having an involucre positioned near the middle of the peduncle, by its leaves with 1 to 3 pairs of pinnae (1 pair in V. daemon), stipular spines to 4.5 mm long (vs. 12-42 mm long), and petiole 1.5-4.3 mm long (vs. 0.6-1.5 mm long). Vachellia zapatensis is distinguished from V. cucuyo, the only other member of the V. acuifera species group having leaves with more than 1 pair of pinnae per leaf, by the distance between leaflet pairs on the pinnae (0.9-1.2 vs. 1.3-2.3 mm), the narrower leaflets (0.7-l.0 vs. 1.2-1.9 mm wide), and the involucre located near the middle of the peduncle (vs. 1-2 mm below the globose head).
In the original description, Urban (1928b) suggested that this species was most closely related to V. daemon. This conclusion seems reasonable, especially if greater emphasis is placed on what may be assumed to be the more invariant reproductive characteristic of involucre position than the probably more plastic vegetative characteristics of the number of pinna pairs per leaf. This determination must remain tentative. A more complete understanding of this species and its affinities to other taxa is dependent on the availability of better material. The only collection of this species was found to be weakly cyanogenic.