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Pseudomyrmecine ants associated with specialized ant-plants


Phylogenetic analysis of representative groups of ants in the subfamily Pseudomyrmecinae indicates that specialized relationships with domatia-bearing plants have evolved independently at least 12 times within the subfamily (Ward, 1991). The plants involved in such associations include swollen-thorn acacias in Mexico and Central America; Neotropical trees in the genera Cordia, Myrcia, Tachigali and Triplaris; African species of Acacia, Barteria and Vitex; a Malagasy species of Mimosa; and an Australian tree in the genus Cupaniopsis. In most instances the plant provides some kind of intrinsically hollow, or easily excavated, cavity (domatium) in which the ants keep brood and scale insects (Coccoidea). The ants, in turn, protect the host plant from herbivores and (sometimes) from other competing plants. In the case of the interaction between Pseudomyrmex ants and swollen-thorn acacias, scale insects are absent from the domatia, but the ants receive nutritional rewards from extrafloral nectaries on the leaf petiole and from lipid-rich food bodies (Beltian bodies) produced at the leaf tips.

Pseudomyrmex ferrugineus workers on swollen-thorn Acacia Area at base of a swollen-thorn Acacia cleared free of competing plants by its resident ants

Table 1. The obligate plant-ants in the subfamily Pseudomyrmecinae (from Ward, 1991, 1993, 1999b). These are species which, as far as known, nest only in live plant domatia. Taxa identified only by a code number (e.g., Pseudomyrmex sp. PSW-35) represent undescribed species whose descriptions and new names will be found in Ward (1999b).

Genus/species group Species Distribution Plant(s) Notes
Ps. ferrugineus group ferrugineus Mexico to El Salvador and Honduras Acacia spp. (9 species) See Ward (1993) for full list of Acacia species
Ps. ferrugineus group flavicornis Guatemala to Costa Rica Acacia collinsii, A. cornigera, A. hindsii
Ps. ferrugineus group janzeni Mexico Acacia hindsii
Ps. ferrugineus group mixtecus Mexico Acacia collinsii, A. hindsii
Ps. ferrugineus group nigrocinctus Guatemala to Costa Rica Acacia collinsii, A. cornigera, A. hindsii
Ps. ferrugineus group particeps Costa Rica Acacia allenii
Ps. ferrugineus group peperi Mexico to Nicaragua Acacia spp. (6 species) See Ward (1993) for full list of Acacia species
Ps. ferrugineus group satanicus Panama Acacia melanoceras
Ps. ferrugineus group spinicola Honduras to Colombia Acacia allenii, A. collinsii, A. cornigera
Ps. ferrugineus group veneficus Mexico Acacia collinsii, A. hindsii
Ps. gracilis group hospitalis Peru Tachigali
Ps. gracilis group nigropilosus Mexico to Costa Rica Acacia collinsii, A. cornigera, A. hindsii Non-protective “parasite”
Ps. gracilis group reconditus Nicaragua Acacia collinsii
Ps. gracilis group simulans Panama Acacia collinsii
Ps. sericeus group cordiae Panama to Bolivia Cordia
Ps. sericeus group crudelis Peru Tachigali
Ps. sericeus group deminutus Brazil Tachigali
Ps. sericeus group eculeus Ecuador, Peru Tachigali
Ps. sericeus group ferox Colombia, Peru, Brazil Tachigali
Ps. sericeus group fortis Mexico to Colombia, Venezuela Triplaris (part) See discussion in Ward (1999b)
Ps. sericeus group longior Colombia to Brazil, Bolivia ?Platymiscium
Ps. sericeus group pictus Colombia, Peru, Brazil, Bolivia Tachigali, ?Platymiscium
Ps. sericeus group rubiginosus Colombia, Peru, Brazil Gustavia, Ocotea, Pleurothyrium, Tachigali, Triplaris,
Ps. sericeus group vinneni Colombia, Peru Venezuela, Brazil Tachigali
Ps. subtilissimus group subtilissimus Nicaragua, Costa Rica swollen-thorn Acacia
Ps. viduus group concolor Venezuela, Guyana, Brazil Tachigali
Ps. viduus group dendroicus Colombia to Brazil, Bolivia Triplaris
Ps. viduus group insuavis Colombia Tachigali
Ps. viduus group malignus Venezuela, Guianas, Brazil Tachigali
Ps. viduus group mordax Panama, Colombia, Venezuela, Triplaris
Ps. viduus group penetrator Venezuela, Guianas, Brazil Tachigali
Ps. viduus group tachigaliae western Brazil, Peru Tachigali
Ps. viduus group triplaridis Colombia to Brazil Triplaris
Ps. viduus group triplarinus Colombia to Brazil, Bolivia Triplaris
Ps. viduus group ultrix Ecuador Triplaris
Ps. viduus group viduus Mexico to Brazil, Bolivia Cordia, Coussapoa, Macrolobium, Ocotea, Pseudobombax, Pterocarpus, Sapium, Triplaris See discussion in Ward (1999b)
Pseudomyrmex perboscii Mexico to Brazil, Bolivia Albizia saman, Cordia, Pseudobombax
Myrcidris epicharis Brazil Myrcia sp.
Tetraponera aethiops west Africa Barteria
Tetraponera latifrons west Africa Barteria
Tetraponera nigra (part) India Acacia horrida, Stereospermum personatum Possibly an obligate plant-ant at the population (not species) level
Tetraponera penzigi east Africa Acacia, Stereospermum
Tetraponera tessmanni west Africa Vitex
Tetraponera tucurua Australia Cupaniopsis Additional details in Ward (2001)
Tetraponera binghami Malaysia Gigantochloa
Tetraponera sp. PSW-87 Madagascar Mimosa

For general reviews on the interactions between ants and domatia-bearing plants see Beattie (1985), Benson (1985), Davidson & McKey (1993), and Wheeler (1942).

Identification of pseudomyrmecine plant-ants

Identification keys are available for the Pseudomyrmex species inhabiting swollen-thorn acacias (Ward, 1993) and Triplaris and Tachigali plants (Ward, 1999b). Problematic specimens of Pseudomyrmex may be sent for identification to: Philip S. Ward, Department of Entomology, University of California, One Shields Ave., Davis, CA 95616, USA.

Literature Cited

  • Beattie, A. J. 1985. The evolutionary ecology of ant-plant mutualisms. New York: Cambridge University Press, 182 pp.
  • Benson, W. W. 1985. Amazon ant-plants. Pp. 239-266 in: Prance, G. T., Lovejoy, T. E. (eds.) Key environments. Amazonia. Oxford: Pergamon Press, xiv + 442 pp.
  • Davidson, D. W., McKey, D. 1993. The evolutionary ecology of symbiotic ant-plant relationships. J. Hym. Res. 2:13-83.
  • Ward, P. S. 1991. Phylogenetic analysis of pseudomyrmecine ants associated with domatia-bearing plants. Pp. 335-352 in: Huxley, C. R., Cutler, D. F. (eds.) Ant-plant interactions. Oxford: Oxford University Press, xviii + 601 pp.
  • Ward, P. S. 1993. Systematic studies on Pseudomyrmex acacia-ants (Hymenoptera: Formicidae: Pseudomyrmecinae). J. Hym. Res. 2:117-168.
  • Ward, P. S. 1999b. Systematics, biogeography and host plant associations of the Pseudomyrmex viduus group (Hymenoptera: Formicidae), Triplaris– and Tachigali-inhabiting ants. Zool. J. Linn. Soc. 126:451-540.
  • Ward, P. S.¬† 2001. Taxonomy, phylogeny and biogeography of the ant genus Tetraponera (Hymenoptera: Formicidae) in the Oriental and Australian regions. Invert. Taxon. 15:589-665.
  • Wheeler, W. M. 1942. Studies of Neotropical ant-plants and their ants. Bull. Mus. Comp. Zool. 90:1-262.

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