Acacia collinsii Safford, G. N.

3. Acacia collinsii Safford, Science N. S. 31: 677. 1910. Myrmecodendron collinsii (Saif.) Britton & Rose, N. Amer. FI. 23: 92. 1928. TYPE: Mexico. Chiapas: between Chicoasén and San Fernandino, 1005 ft., 13 Jan. 1907, G. N. Collins & C. B. Doyle 180 (holotype, US; photo, F). [Safford (1910) listed Guy N. Collins as the only collector, and cited 14 Jan. 1907 as the date collected; on the label of the herbarium specimen G. N. Collins and C. B. Doyle are listed as the collectors, and 13 Jan. 1907 is given as the date of collection.]

Acacia costaricensis Schenck, Repert. Spec. Nov. Regni Veg. 12: 361. 1913. Myrmecodendron costaricensis (Schenck) Britton & Rose, N. Amer. FI. 23: 93. 1928. TYPE: Costa Rica. Alajuela: Alajuela, 900 m, 1896, J. D. Smith 6488 (lectotype, designated here, US [B destroyed]; isotypes, BM, GH, K, MO).

Acacia yucatanensis Schenk, Repert. Spec. Nov. Regni Veg. 12: 361. 1913. TYPE: Mexico. Yucatan: 1895, G. F. Gaumer 353 (lectotype, designated here, US [B destroyed]; isotypes, BM, GH, F, MO).

Acacia panamensis Schenck, Repert. Spec. Nov. Regni Veg. 12: 362. 1913. TYPE: Panama. Aljahuela: Prof. Alex. Koch (holotype, B destroyed).

Acacia nelsonii Saff., J. Wash. Acad. Sei. 4: 363. 1914. TYPE: Mexico. Guerrero: Acapulco, sea level, 30 Apr. 1903 * E. W. Nelson 7024 (holotype, US; isotypes, GH, F).

Acacia penonomensis Saff., J. Wash. Acad. Sei. 4: 363. 1914. TYPE: Panama. Codé: Penonomé, 50-1000 ft., 23 Feb.-22 Mar. 1908, R. S. Williams 113 (holotype, NY; photo, F; fragment and photo, US; isotype, US).

Tree to 10 m tall; young twigs reddish brown to dark brown, glabrous. Stipular spines shiny, light reddish brown to dark brown, rarely ivory to yellowish, smooth, glabrous, terete in cross section, mostly symmetrical, V- to U-shaped with an angle of 50-180°, 20-50 mm long, 4-13 mm wide at the base, sometimes reflexed near the tip. Leaves 40-195 mm long; pinnae 3-15 pairs per leaf, 30-90 mm long, 7-17 mm between pinna pairs; rachis grooved, glabrous to lightly puberulent, rachis glands usually absent; petiole grooved, glabrous to lightly puberulent, 4-18 mm long. Petiolar glands 3-5 (rarely 2), dome-shaped to broadly volcano-shaped, usually near the base of the petiole, puberulent, striate, apex 0.3-0.8 mm across, base 1-2.5 mm across. Leaflets 11-29 pairs per pinna, glabrous, linear, 6-13 mm long, 1.3-3.1 mm wide, 2-3 veins from the base, lateral veins obvious, apex obtuse, margins usually not ciliate. Inflorescence of densely flowered cylindrical obtuse spikes, 15-35 mm long, 4-6 mm thick, commonly in short, leafy racemes with 1-3 (rarely 5) spikes per node; peduncles glabrous to lightly puberulent, 6-20 mm long, 0.8-1.8 mm thick, nearly the same thickness throughout; involucre located near the base to lower third of the peduncle, glabrous to lightly puberulent, 4-lobed, the lobes unequal. Floral bracts peltate, apex circular and usually puberulent, stalk 0.6-1.1 mm long. Flowers sessile; calyx 5-lobed, glabrous, 1-1.4 mm long; corolla 5-lobed, glabrous, yellowish, 1.1-1.5 mm long, slightly longer than the calyx. Legumes nearly straight, elliptical in cross section, 30-60 mm long, 7-13 mm wide, glabrous, not striate, dark brown to black, dehiscent along both sutures, not stalked, the apex acute with a short beak 1-6 mm long. Flowering January- August.

Distribution. In shrubby vegetation of pastures and on rocky ridges, in habitats ranging from moderately wet to very dry, at lower elevations (below 1000 m) along the west coast of Mexico from Guerrero east to the Yucatan Peninsula, south through the dry lowland of Central America to the lowlands of northern Colombia.

Representative specimens. BELIZE. Maskall, Gentle 1112 (GH, WIS). COLOMBIA. Bolivar: Municipio de Arenal, Forero G. & Jaramillo M. 496 (F). COSTA RICA. Alajuela: El Coyolar, 240 m, Standley 40026 (US). Guanacasle: vicinity of Cañas, Finca La Pacífica, Daubenmire 449 (F). Puntarenas: ca. 10 mi. NE of Palmar Sur on the Inter-American hwy., Janzen 1852 (US). San José: Villa Colon, Janzen 1862 (F, US). EL SALVADOR. La Union: 7.1 mi. W of El Amatillo, Janzen 1801 (F). GUATEMALA. Zacapa: Jones Bridge, 5.8 mi. NE of Rio Hondo on hwy. 9, Janzen 1797 (MEX). HONDURAS. Colon: 4.5 mi. NE of Trujillo on old road to Castilla, Saunders 1040 (F, MO). Comayagua: on slope down to Rio Selguapa, Comayagua valley, ca. 600 m, Burch 6033 (MEX, MO). Olancho: vicinity of Juticalpa, 380-480 m, Standley 17522 (F). Valle: 28.4 mi. SE of El Amatilla on Inter-American hwy., Janzen 1841 (F, MEX, US). MEXICO. Campeche: 0.8 mi. E of Campeche on hwy. 180, Janzen 428 (MEX, F). Chiapas: along hwy. 190, 13 mi. S of La Trinitaria, 3000 ft., Breedlove & Raven 8448 (F). Guerrero: Petatlán, Montes de Oca, Hinton 10333 (MO). Oaxaca: 11.4 mi. W of Tehuantepec, Janzen 1780 (F). Quintana Roo: 32 mi. N of jet. 307 & 186, N of Chetumal on hwy. 307, Seigler et al. 11595 (MEX, ILL). Yucatan: Chichén Itzá, Seigler et al. 11599 (EIU, ILL). NICARAGUA. Esteli: 1 mi. N Condega, Janzen 1810 (F). Rivas: Pena Blanco, Janzen 1830 (F, MEX). Zelaya: in vicinity of La Luz-Siuna, 150-200 m, Bunting & Licht 666 (US). PANAMA. Canal Zone: Victoria fill, near Miraflores Locks, Allen 1743 (US). Codé: roadside pasture 20 mi. S of Nata, Croat 9643 (MO).

Acacia collinsii has the most extensive geographical distribution of all New World ant-acacias and is the only ant-acacia that occurs in South America. It also has the widest ecological distribution, growing in dry to moderately wet pastures and fields and in open shrubby vegetation from sea level to 1000 m. It is a common component of early successional areas. This wide ecological and geographical distribution has resulted in a relatively broad morphological diversity, which is reflected in the extensive synonymy. Though morphologically diverse, it can easily be distinguished from all other ant-acacias by the following combination of characters: elongated cylindrical inflorescences, 3-5 petiolar glands that are broadly dome-shaped, absence of rachis glands, leaflets with obvious lateral veins, and relatively small stipular spines that are terete in cross section.

As is typical of most xerophytic ant-acacias, Beltian body production in Acacia collinsii is relatively extensive. In this species the nearly globose Beltian bodies are 0.4-0.8 mm long and usually are found on more than 50% of the leaflets of developing leaves. As most individuals of this species are inhabited by obligate acacia-ants, the Beltian bodies are generally “harvested” soon after development.

Cyanide tests of more than 400 specimens of Acacia collinsii indicate that this species is not cyanogenic. Herbarium material of this species was reported to be cyanogenic (Seigler et al., 1978), but reinvestigation of these same specimens failed to confirm activity (Seigler & Ebinger, 1987). Janzen (1981) did not report cyanogenesis for this species.

Acacia collinsii probably hybridizes with A. hindsii. These species are sympatric in parts of their ranges in Mexico and Central America, and occasionally occur at the same site. Acacia collinsii also hybridizes with the non-ant-acacia A. pennatula (Ebinger & Seigler, 1992).