Acacia ruddiae D. H. Janzen

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 : 132-133

12. Acacia ruddiae D. H. Janzen , Smithsonian Contr. Bot. 13: 34. 1974. type: Costa Rica. Limon: ferry landing, Moin River, Moin , 13 Feb. 1965, D. H. Janzen 828 (holotype, US ; isotypes, CAS, F, GH, MEXU, MICH, MO, NY, UC) .

Tree to 30 m tall; young twigs dark brown to dark reddish brown, glabrous to puberulent. Stipular spines dull, dark reddish brown to black, smooth, glabrous to lightly puberulent, nearly terete in cross section, symmetrical, broadly V-shaped with an angle of 70-180°, to 9.5 mm long, 4-9 mm wide, abruptly tapering to a narrow, sharp-pointed tip; many spines not enlarged, usually less than 8 mm long and to 0.4 mm wide. Leaves 130-400 mm long; pinnae 17-40 pairs per leaf, 30-55 mm long, 5-13 mm between pinna pairs; rachis grooved, densely puberulent; rachis glands glabrous, striate, cylindrical, commonly narrowing toward the base, to 1 mm long, one located at the node of each pinna pair, its apex 0.4-0.9 mm across; petiole grooved, densely puberulent, 6-25 mm long. Petiolar glands commonly absent, rarely 1 or 2 present, identical to the rachis glands. Leaflets 25-75 pairs per pinna, glabrous, ciliate along the margins, linear, 3.5-6.5 mm long, 0.6-1.1 mm wide, lateral veins not obvious, only one vein from the base, apex acute. Inflorescence a densely flowered globose head 6-7 mm across, in clusters of 1-8 in the axil of normal leaves; peduncles densely puberulent, 8-11 mm long, 0.5-0.7 mm thick, nearly the same thickness throughout; involucre located near the middle of the peduncle, puberulent, 5-lobed. Floral bracts peltate, apex circular, ciliate, stalk less than 0.8 mm long. Flowers sessile; calyx 5-lobed, glabrous, 0.7-1.0 mm long; corolla 5-lobed, glabrous, pale yellow, 1.3-1.6 mm long. Mature legumes not seen. Flowering July.

Distribution. Very wet rainforest, particularly in primary succession along rivers, at edge of swamps, and on landslide scars in the Caribbean lowlands, from Puerto Barrios area of Guatemala to northern Panama.

Representative specimens. COSTA RICA. Alajuela: 11 mi. N Florencia , Janzen 1883 ( F) , 1885 ( F) , 1886 ( F, MICH) . Heredia: Finca La Selva, the OTS Field Station on the Rio Puerto Viejo just E of its junction with the Rio Sarapiqui , 100 m, Hammel & Trainer 12918 ( MICH, MO) ; 16 mi. N of Vara Blanca on rd. from Heredia to Puerto Viejo , Janzen 819 ( F, GH, MICH, NY, US) . Limon: 1 km W of La Lola (on Limon- Siquirres railroad) , Janzen 1868 ( F, NY) , 1872 ( F) , 1874 ( F) , 1875 ( F) , 1877 ( F, NY, US) , 1881 ( F) . GUATEMALA. Izabal: 1.9 mi. W of Puerto Matias de Galvez (on rd. to Escobas) , Janzen 1582 ( F, GH, MEX, MICH, US) . HONDURAS. Atlántida: Lancetilla Valley, near Tela , 20-600 m, Standley 54627 ( F) . NICARAGUA. Zelaya: Municipio de Rama , Robleto 664 ( MO) . PANAMA. Bocas del Toro: Campamento forestal, Boca Chica , Correa A. et al. 3581 ( MO, NY) ; along Changuinola River, Changuinola Valley , Dunlap 462 ( F) .

Acacia ruddiae is probably most closely related to A. cookii and A. janzenii , which it resembles in having small globose inflorescences, large leaves with numerous small leaflets, and rachis glands between each pinna pair. However, both A. cookii and A. janzenii have asymmetrical stipular spines that usually curve around the stem, whereas A. ruddiae has symmetrical spines. Also, the rachis glands of A. ruddiae are urn-shaped, narrowing slightly toward the base, whereas in A. cookii and A. janzenii they are elongated to volcano-shaped.

Though Acacia ruddiae has a relatively extensive geographical range in the Caribbean lowlands from Guatemala to Panama, it has rarely been collected. The presence of this species in Costa Rica was discussed by Calvert & Calvert (1917) who mentioned a bull-horn acacia with swollen thorns and urn-shaped rachis glands that lacked Beltian bodies and obligate acacia-ants. Though referring to this species as Acacia campeachiana Miller (= A. cochliacantha ), there is little doubt that the taxon discussed is A. ruddiae .

This wet forest species is only marginally an ant-acacia. Janzen (1974) found that relatively few of the stipular spines were swollen, none were occupied by obligate acacia-ants, and Beltian bodies were not formed on the leaflets. During the present study, no indication of Beltian bodies was found on developing leaves; all of the mature leaves examined lacked the scar left by these bodies. However, a characteristic entrance hole made by ants was observed on two specimens (Correa A. et al. 3581 and Janzen 819). These probably represent chance encounters, as none of the other spines on the specimens had entrance holes.

Of the specimens of Acacia ruddiae examined, none tested positive for HCN production. Seigler & Ebinger (1987) obtained similar results, finding one individual that was weakly cyanogenic while the rest tested negative.