Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Identification
An obligate Cecropia ant.
Workers: scapes and tibiae lack erect hairs; mesonotum densly covered with setae of irregular lengths (median number of setae more than 20, but some with as few as 10, n=40); typically concolorous yellow-brown.
Queens: scapes and tibiae lack erect hairs; second gastral tergum with more than 20 setae, exclusive of posterior row; scape relatively long (median SI 0.61, range 0.59-0.67, n=19); HL 1.51-1.72mm (median 1.59, n=19); HW 1.20-1.39 (1.32, 19), SL 0.73-0.85 (0.80, 19), WL 2.70-3.15 (2.88, 16), CI 0.785-0.863 (0.820, 19).
In many parts of the Neotropics there are two locally sympatric forms in the alfari complex, one of which is less setose than the other. Longino (1989) treated them as two species, with the less setose species being alfari and the more setose species being ovaticeps. The distinction is often clear when members of the alfari complex are locally abundant. For example, in the Atlantic lowlands of Costa Rica, ovaticeps queens have a dense brush of setae on the abdomen, and are conspicuously distinct from alfari in the same area. However, in some areas the distinction is not as clear. In Monteverde, some colonies are identical to standard alfari s.s. from elsewhere in Costa Rica. Other colonies show a range of seta abundances, but are not as densely setose as the Atlantic lowland ovaticeps.
Range
Costa Rica south to Amazonian Brazil and Bolivia. In Costa Rica, clearly differentiated populations of ovaticeps occur throughout the Atlantic lowlands to about 500m elevation. Occasional specimens that are intermediate between ovaticeps and alfari occur in northwestern Costa Rica.
Natural History
See also general treatment of the Cecropia-Azteca association in Costa Rica.
Azteca ovaticeps, a close relative of A. alfari, is enigmatic. It shares behavioral features and size with alfari, but tends to occur in areas of frequent disturbance which are embedded in primary forest: river margins in Brazil and Peru, new roadcuts or new clearings in otherwise forested areas of Costa Rica and Venezuela (Longino 1989, Yu and Davidson 1997). In Costa Rica, ovaticeps will inhabit any of the myrmecophytic Cecropia species (Longino 1989, 1991b). At low elevations on the Atlantic slope, most mature trees of Cecropia insignis are inhabited by ovaticeps.
Mature colonies have a dispersed colony structure (Longino 1991a). There is no central carton nest. Brood and any alate sexuals are in branch tips. Older parts of the tree are gradually abandoned, and internal passages are not maintained among occupied branches. Workers are relatively timid and will not defend a mature tree (small saplings are more aggressively defended). When a tree is disturbed, workers usually remain in the branches. Only when a branch is broken open will workers rush out to attack. The foliage of trees occupied by ovaticeps hosts a diverse insect fauna, including foraging ants of other species.
The alfari group, containing alfari and ovaticeps, is a lineage that has colonized Cecropia trees independently of other obligate Cecropia ants (Ayala et al 1996).
Literature Cited
Ayala, F. J., J. K. Wetterer, J. T. Longino, and D. L. Hartl. 1996. Molecular phylogeny of Azteca ants (Hymenoptera: Formicidae) and the colonization of Cecropia trees. Molecular Phylogenetics and Evolution 5:423-428.
Longino, J. T. 1989. Taxonomy of the Cecropia-inhabiting ants in the Azteca alfari species group: evidence for two broadly sympatric species. Contributions in Science (Natural History Museum of Los Angeles County) 412:1-16.
Longino, J. T. 1991a. Azteca ants in Cecropia trees: taxonomy, colony structure, and behavior. Pages 271-288 in C. Huxley and D. Cutler, editors. Ant-plant interactions. Oxford University Press, Oxford, U.K.
Longino, J. T. 1991b. Taxonomy of the Cecropia-inhabiting Azteca ants. Journal of Natural History 25:1571-1602.
Yu, D. W., and D. W. Davidson. 1997. Experimental studies of species-specificity in Cecropia-ant symbioses. Ecological monographs 67:273-294.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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