Acacia globulifera Saff

David S. Seigler & John E. Ebinger, 1995, Taxonomic Revision of the Ant-Acacias (Fabaceae, Mimosoideae, Acacia, Series Gummiferae) of the New World, Annals of the Missouri Botanical Garden 82, pp. 117-138 : 128-129

7. Acacia globulifera Saff ., J, Wash. Acad. Sei. 4: 360. 1914. Myrmecodendron globuliferum (Saff.) Britton & Rose , N. Amer. FI. 23: 93. 1928. TYPE: Mexico. Yucatan: at the port of Silam (Tzilam), N coast of Yucatan , Apr. 1895, G. F. Gaumer 1909 (holotype, F, fragment and photo, US; isotypes, GH, MO, NY, US) .

Acacia donnelliana Saff ., J. Wash. Acad. Sei. 4: 361. 1914. Myrmecodendron donnellianum (Saff.) Britton & Rose , N. Amer. FI. 23: 93. 1928. type: Honduras. Santa Barbara: San Pedro de Sula, Cortes , 600 ft., Mar. 1888, C. Thieme 5216 (holotype, US) .

Shrub or small tree usually less than 3 (rarely 10) m tall, young twigs brown to reddish brown, glabrous to lightly puberulent. Stipular spines (Fig. IB) usually dark brown to black (sometimes yellow to ivory), smooth, terete, glabrous to lightly puberulent, symmetrical, V-shaped with an angle of 40-120°, straight to reflexed near the apex, 25-60 mm long, 4-7 mm thick near the base. Leaves 60-250 mm long; pinnae 6-26 pairs per leaf, 30-65 mm long, 6-11 mm between pinna pairs, rachis grooved, glabrous to lightly puberulent, a small volcano-shaped gland present between each pinna pair; petiole grooved, glabrous to lightly puberulent, 8-18 mm long. Petiolar glands (Fig. 1 G) volcano-shaped, commonly laterally compressed, densely puberulent, usually lightly striate, apex nearly circular, 0.3-0.9 mm across, base 1-2 mm across, usually 2-5 glands scattered along the petiole. Leaflets 20-50 pairs per pinna, glabrous, linear, 4-6 mm long, 0.6-1.2 mm wide, lateral veins not obvious, only one vein from the base, apex mostly acute. Inflorescence a densely flowered globose head 4-7 mm across, in clusters of 4-8 in the axil of slightly reduced leaves, or in small clusters in the axil of small spines on lateral, usually leafless branches; peduncles glabrous to lightly puberulent, 6-25 mm long, 0.5-1.0 mm thick, nearly the same thickness throughout; involucre located on the lower 1/4 of the peduncle, glabrous to lightly puberulent, 4-lobed. Floral bracts peltate, apex circular, the stalk about 1 mm long. Flowers sessile; calyx 5-lobed, glabrous, 1-1.5 mm long; corolla 5-lobed, glabrous, pale yellow, 1.5-2.0 mm long. Legumes slightly curved, elliptical to nearly terete in cross section, 50-90 mm long, 9-12 mm wide, glabrous, not striate, black to dark brown, dehiscent along one suture, stipe less than 5 mm long, the apex narrowing to a terminal spinelike beak usually less than 10 mm long. Flowering January-April.

Distribution. In riparian and swamp successional stages as well as open, dry habitats, from sea level to about 1200 m, in southern Mexico (Campeche, Oaxaca, Yucatan), Belize, Guatemala, and Honduras.

Representative specimens. BELIZE. El Cayo: Vaca , Gentle 2275 ( AA, F, MICH, MO, NY) . GUATEMALA. Amatitlân: Laguna (Lake Amatitlan ) , 1200 m, Kellerman 5042 ( UC) . Guatemala: 20.5 mi. NE Guatemala City on hwy. 9 , Janzen 1565 ( F, GH, MEX, MICH, MO, US) . El Petén: in Mananche , Contreras 5480 ( F, MICH, US) . Zacapa: along Rio Teculutan , above Teculutan , 250-275 m, Steyermark 42146 ( F, NY) . HONDURAS. Cut over river valley lands, Yoro 2800 ft., Edwards P- 748 ( AA, F) ; 26 mi. SW of San Pedro Sula on hwy. 18 , Janzen 1608 ( F) ; 10.4 mi. SW of Santa Rosa on hwy. 18 , Janzen 1634 ( F, MICH, MO, UC, US) . MEXICO. Campeche: 48 mi. NE of Puerto Real (Isla Aguada) on hwy. 180 , Janzen 611 ( F, MICH, US) . Oaxaca: 11.3 mi. N of intersection of Mexico hwy. 185 and 190, on hwy. 185 , Janzen 1502 ( F, GH, MEX, MICH, MO, NY, UC, WIS) . Quintana Roo: en San Jose de la Montana, km 8 de la carreterra a Tomas Garrido , Cabrera et al. 4504 ( MEX) . Yucatán: Silám, Gaumer 655 ( F, GH, US) .

Acacia globulifera is easily distinguished from most ant-acacias by its spherical inflorescences, small leaflets that lack obvious secondary veins, and 2-5 narrow volcano-shaped petiolar glands. It is most closely related to A. chiapensis and has been occasionally combined with it ( Janzen, 1974). These two species differ, however, in petiolar glands, inflorescence clusters, and fruit characteristics (see discussion under A. chiapensis ). Acacia globulifera is commonly found in riparian or relatively dry sites from sea level to about 1200 m, which is the upper elevation limit of ant-acacias. It usually grows in open, fully insolated habitats, rarely exceeds 3 m in height, and is usually restricted to young successional habitats ( Janzen, 1974).

Beltian body production in Acacia globulifera is typical of that found in most ant-acacias that inhabit more open sites. These bodies, which are less than 0.8 mm long, usually are present on more than half of the leaflets of a developing leaf. The bodies are rarely seen, as they are usually “harvested” soon after development by obligate acacia- ants.

Acacia globulifera is similar to A. chiapensis in that many individuals of both species are cyanogenic; the cyanogenic glycoside of A. globulifera is ( R)- epiproacacipetalin, whereas that of A. chiapensis is ( S)- proacacipetalin. Of the specimens of A. globulifera tested, most gave a positive test for HCN. Of these specimens, however, nearly one- third required the addition of emulsin to give a positive test. This suggests that many individuals of this species either lack the enzyme capable of hydrolyzing the cyanoglycoside, or that the enzyme is inactivated by drying and storage ( Seigler & Ebinger, 1987).

Janzen (1974) suggested that Acacia globulifera may occasionally hybridize with a non-ant-acacia of the A. macracantha complex. During the present study no specimens were found that would indicate hybridization involving this species.