Abstract
The current state of ant systematics is reviewed. In recent years substantial progress has been made in identifying the major clades of ants and the relationships among them. Earlier inferences about ant phylogeny based on morphology have been refined and modified as a result of a recent influx of molecular (DNA sequence) data and new fossil discoveries. It is now apparent that much of the biological and taxonomic diversity of ants is contained within the “formicoid clade” which comprises 14 of the 20 extant subfamilies and about 90% of all species. Whether the remaining groups of extant ants (Leptanillinae and the poneroid subfamilies) represent a clade or a grade at the base of the ant tree remains unresolved. The fossil record for crown group ants extends back to 90–100 mya. Stem ants (sphecomyrmines, armaniines) were also present during this period. Molecular divergence date estimates that take into account the fossil record of both ants and other Hymenoptera suggest that crown group ants arose ~115–135 mya. Most of the extant ant subfamilies and genera are well defined morphologically and likely monophyletic, but there are some notable exceptions including the subfamily Cerapachyinae and several large and ambiguously delimited genera such as Pachycondyla. Several tribes in the large subfamilies Formicinae and Myrmicinae also represent artificial assemblages. Finally, while the species-level taxonomy of some ant genera is in a satisfactory state, taxonomic anarchy reigns in others, with numerous ill-defined species and many names of uncertain applicability. Progress in this area of ant systematics will require sustained individual efforts, expansion of job opportunities, enlistment of new technologies, and a deeper understanding of the nature of ant species and the differences between them.
References
Anderson, K.E., Gadau, J., Mott, B.M., Johnson, R.A., Altamirano, A., Strehl, C. & Fewell, J.H. (2006) Distribution and evolution of genetic caste determination in Pogonomyrmex seed-harvester ants. Ecology, 87, 2171–2184.
Archibald, S.B., Cover, S.P. & Moreau, C.S. (2006) Bulldog ants of the Eocene Okanagan Highlands and history of the subfamily (Hymenoptera: Formicidae: Myrmeciinae). Annals of the Entomological Society of America, 99, 487–523.
Baroni Urbani, C. & de Andrade, M.L. (2003) The ant genus Proceratium in the extant and fossil record (Hymenoptera: Formicidae). Museo Regionale di Scienze Naturali Monografie (Turin), 36, 1–492.
Baroni Urbani, C., Bolton, B. & Ward, P.S. (1992) The internal phylogeny of ants (Hymenoptera: Formicidae). Systematic Entomology, 17, 301–329.
Bergsten J. (2005) A review of long-branch attraction. Cladistics, 21, 163–193.
Bolton, B. (1974) A revision of the Palaeotropical arboreal ant genus Cataulacus F. Smith (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History). Entomology, 30, 1–105.
Bolton, B. (1976) The ant tribe Tetramoriini (Hymenoptera: Formicidae). Constituent genera, review of smaller genera and revision of Triglyphothrix Forel. Bulletin of the British Museum (Natural History). Entomology, 34, 281–379.
Bolton, B. (1977) The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Oriental and Indo-Australian regions, and in Australia. Bulletin of the British Museum (Natural History). Entomology, 36, 67–151.
Bolton, B. (1979) The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Malagasy region and in the New World. Bulletin of the British Museum (Natural History). Entomology, 38, 129–181.
Bolton, B. (1980) The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Ethiopian zoogeographical region. Bulletin of the British Museum (Natural History). Entomology, 40, 193–384.
Bolton, B. (1982) Afrotropical species of the myrmicine ant genera Cardiocondyla, Leptothorax, Melissotarsus, Messor and Cataulacus (Formicidae). Bulletin of the British Museum (Natural History). Entomology, 45, 307–370.
Bolton, B. (1990a) Abdominal characters and status of the cerapachyine ants (Hymenoptera, Formicidae). Journal of Natural History, 24, 53–68.
Bolton, B. (1990b) The higher classification of the ant subfamily Leptanillinae (Hymenoptera: Formicidae). Systematic Entomology, 15, 267–282.
Bolton, B. (1990c) Army ants reassessed: the phylogeny and classification of the doryline section (Hymenoptera, Formicidae). Journal of Natural History, 24, 1339–1364.
Bolton, B. (1994) Identification guide to the ant genera of the world. Harvard University Press, Cambridge, Massachusetts, 222 pp.
Bolton, B. (2000) The ant tribe Dacetini. Memoirs of the American Entomological Institute, 65, 1–1028.
Bolton, B. (2003) Synopsis and classification of Formicidae. Memoirs of the American Entomological Institute, 71, 1–370.
Bolton, B., Alpert, G., Ward, P.S. & Nasrecki, P. (2006) Bolton’s Catalogue of ants of the world. Harvard University Press, Cambridge, Massachusetts, CD-ROM.
Borgmeier, T. (1955) Die Wanderameisen der neotropischen Region. Studia Entomologica, 3, 1–720.
Brady, S.G. (2003) Evolution of the army ant syndrome: the origin and long-term evolutionary stasis of a complex of behavioral and reproductive adaptations. Proceedings of the National Academy of Sciences U. S. A., 100, 6575–6579.
Brady, S.G., Fisher, B.L., Schultz, T.R. & Ward, P.S. (2006) Evaluating alternative hypotheses for the early evolution and diversification of ants. Proceedings of the National Academy of Sciences U. S. A., 103, 18172–18177.
Brady, S.G. & Ward, P.S. (2005) Morphological phylogeny of army ants and other dorylomorphs (Hymenoptera: Formicidae). Systematic Entomology, 30, 593–618.
Brown, W.L., Jr. (1954) Remarks on the internal phylogeny and subfamily classification of the family Formicidae. Insectes Sociaux, 1, 21–31.
Brown, W.L., Jr. (1955) Ant taxonomy. In: Kessel, E.W. (Ed.) A century of progress in the natural sciences, 1853–1953. California Academy of Sciences, San Francisco, pp. 569–572.
Brown, W.L., Jr., Gotwald, W.H., Jr. & Lévieux, J. (1971) A new genus of ponerine ants from West Africa (Hymenoptera: Formicidae) with ecological notes. Psyche (Cambridge), 77, 259–275.
Buhs, J.B. (2000) Building on bedrock: William Steel Creighton and the reformation of ant systematics, 1925–1970. Journal of the History of Biology, 33, 27–70.
Carpenter, F.M. (1930) The fossil ants of North America. Bulletin of the Museum of Comparative Zoology, 70, 1–66.
Carpenter, F.M. (1992) Treatise on invertebrate paleontology. Part R. Arthropoda 4. Volume 4. Superclass Hexapoda. Geological Society of America, Boulder, pp. i–ii, 279–655.
Crozier, R.H., Jermiin, L.S. & Chiotis, M. (1997) Molecular evidence for a Jurassic origin of ants. Naturwissenschaften, 84, 22–23.
de Andrade, M.L. & Baroni Urbani, C. (1999) Diversity and adaptation in the ant genus Cephalotes, past and present. Stuttgarter Beiträge zur Naturkunde. Serie B (Geologie und Paläontologie), 271, 1–889.
de Queiroz, K. & Gauthier, J. (1990) Phylogeny as a central principle in taxonomy: phylogenetic definitions of taxon names. Systematic Zoology, 39, 307–322.
Dlussky, G.M. (1999) The first find of the Formicoidea (Hymenoptera) in the lower Cretaceous of the northern hemisphere. [In Russian.] Paleontologicheskii Zhurnal, 1999(3), 62–66.
Dlussky, G.M., Brothers, D.J. & Rasnitsyn, A.P. (2004) The first Late Cretaceous ants (Hymenoptera: Formicidae) from southern Africa, with comments on the origin of the Myrmicinae. Insect Systematics and Evolution, 35, 1–13.
Dlussky, G.M. & Rasnitsyn, A.P. (2003) Ants (Hymenoptera: Formicidae) of Formation Green River and some other Middle Eocene deposits of North America. Russian Entomological Journal, 11, 411–436.
Doyle, J.A. & Donoghue, M.J. (1993) Phylogenies and angiosperm diversification. Paleobiology, 19, 141–167.
Eguchi, K. (2001) A revision of the Bornean species of the ant genus Pheidole (Insecta: Hymenoptera: Formicidae: Myrmicinae). Tropics Monograph Series, 2, 1–154.
Emery, C. (1920) La distribuzione geografica attuale delle formiche. Tentativo di spiegarne la genesi col soccorso di ipotesi filogenetiche e paleogeografiche. Atti della Reale Accademia dei Lincei. Memorie. Classe di Scienze Fisiche, Matematiche e Naturali, (5)13, 357–450.
Engel, M.S. & Grimaldi, D.A. (2005) Primitive new ants in Cretaceous amber from Myanmar, New Jersey, and Canada (Hymenoptera: Formicidae). American Museum Novitates, 3485, 1–23.
Fournier, D., Estoup, A., Orivel, J., Foucaud, J., Jourdan, H., Le Breton, J. & Keller, L. (2005) Clonal reproduction by males and females in the little fire ant. Nature (London), 435, 1230–1234.
Grimaldi, D. & Agosti, D. (2000a) The oldest ants are Cretaceous, not Eocene: comment. Canadian Entomologist, 132, 691–693.
Grimaldi, D. & Agosti, D. (2000b) A formicine in New Jersey Cretaceous amber (Hymenoptera: Formicidae) and early evolution of the ants. Proceedings of the National Academy of Sciences U. S. A., 97, 13678–13683.
Grimaldi, D., Agosti, D. & Carpenter, J.M. (1997) New and rediscovered primitive ants (Hymenoptera: Formicidae) in Cretaceous amber from New Jersey, and their phylogenetic relationships. American Museum Novitates, 3208, 1–43.
Grimaldi, D. & Engel, M.S. (2005) Evolution of the insects. Cambridge University Press, Cambridge, xv + 755 pp.
Helms Cahan, S., Parker, J.D., Rissing, S.W., Johnson, R.A., Polony, T.S., Weiser, M.D. & Smith, D.R. (2002) Extreme genetic differences between queens and workers in hybridizing Pogonomyrmex harvester ants. Proceedings of the Royal Entomological Society of London. Series B, 269, 1871–1877.
Helms Cahan S. & Vinson S.B. (2003) Reproductive division of labor between hybrid and non hybrid offspring in a fire ant hybrid zone. Evolution, 57, 1562–1570.
Hölldobler, B. & Wilson, E.O. (1990) The ants. Harvard University Press, Cambridge, Massachusetts, xii + 732 pp.
Imai, H. T., Kihara, A., Kondoh, M., Kubota, M., Kuribayashi, S., Ogata, K., Onoyama, K., Taylor, R. W., Terayama, M., Tsukii, Y., Yoshimura, M. & Ugawa, Y. (2003) Ants of Japan. Gakken, Tokyo, 224 pp.
Krieger, M.J. & Ross, K.G. (2002). Identification of a major gene regulating complex social behavior. Science (Washington, D.C.), 295, 328–332.
Kugler, C. (1994) A revision of the ant genus Rogeria with description of the sting apparatus (Hymenoptera: Formicidae). Journal of Hymenoptera Research, 3, 17–89.
LaPolla, J.S. (2004) Acropyga (Hymenoptera: Formicidae) of the world. Contributions of the American Entomological Institute, 33(3), 1–130.
Lattke, J.E. (1995) Revision of the ant genus Gnamptogenys in the New World (Hymenoptera: Formicidae). Journal of Hymenoptera Research, 4, 137–193.
Lattke, J.E. (2004) A taxonomic revision and phylogenetic analysis of the ant genus Gnamptogenys Roger in Southeast Asia and Australasia (Hymenoptera: Formicidae: Ponerinae). University of California Publications in Entomology, 122, 1–266.
Lattke, J.E., Fernández, F. & Palacio, E.E. (2007). Identification of the species of Gnamptogenys Roger in the Americas. Memoirs of the American Entomological Institute, 80, 254–270.
Linnaeus, C. (1758) Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. L. Salvii, Holmiae [= Stockholm], 824 pp.
Longino, J.T. (2003) The Crematogaster (Hymenoptera, Formicidae, Myrmicinae) of Costa Rica. Zootaxa, 151, 1–150.
Magallón, S. (2004) Dating lineages: molecular and paleontological approaches to the temporal framework of clades. International Journal of Plant Science, 165(4 Suppl.), S7–S21.
Masuko, K. (1990) Behavior and ecology of the enigmatic ant Leptanilla japonica Baroni Urbani (Hymenoptera: Formicidae: Leptanillinae). Insectes Sociaux, 37, 31–57.
Moreau, C.S., Bell, C.D., Vila, R., Archibald, S.B. & Pierce. N.E. (2006) Phylogeny of the ants: diversification in the age of angiosperms. Science (Washington D. C.), 312, 101–104.
Morley, B.D.W. (1938) An outline of the phylogeny of the Formicidae. Bulletin de la Société Entomologique de France, 43, 190–194.
Ouellette, G.D., Fisher, B.L. & Girman, D.J. (2006) Molecular systematics of basal subfamilies of ants using 28S rRNA (Hymenoptera: Formicidae). Molecular Phylogenetics and Evolution, 40, 359–369.
Pearcy, M., Aron, S., Doums, C. & Keller, L. (2004) Conditional use of sex and parthenogenesis for worker and queen production in ants. Science (Washington D. C.), 306, 1780–1783.
Perrichot, V., Lacau, S., Néraudeau, D. & Nel, A. (2007) Fossil evidence for the early ant evolution. Naturwissenschaften, doi: 10.1007/s00114-007-0301-8.
Poinar, G., Jr., Archibald, B. & Brown, A. (1999) New amber deposit provides evidence of early Paleogene extinctions, paleoclimates, and past distributions. Canadian Entomologist, 131, 171–177.
Poinar, G., Baroni Urbani, C. & Brown, A. (2000) The oldest ants are Cretaceous, not Eocene: reply. Canadian Entomologist, 132, 695–696.
Sanderson M.J. (2003) r8s: inferring absolute rates of molecular evolution and divergence times in the absence of a molecular clock. Bioinformatics, 19, 301–302.
Saux, C., Fisher, B.L. & Spicer, G.S. (2004) Dracula ant phylogeny as inferred by nuclear 28S rDNA sequences and implications for ant systematics (Hymenoptera: Formicidae: Amblyoponinae). Molecular Phylogenetics and Evolution, 33, 457–468.
Seifert, B. (2007) Die Ameisen Mittel- und Nordeuropas. lutra Verlags- und Vertriebsgesellschaft, Tauer, 368 pp.
Schlick-Steiner, B.C., Steiner, F.M., Moder, K., Seifert, B., Sanetra, M, Dyreson, E., Stauffer, C. & Christian, E. (2006) A multidisciplinary approach reveals cryptic diversity in western Palearctic Tetramorium ants (Hymenoptera: Formicidae). Molecular Phylogenetics and Evolution, 40, 259–273.
Smith, M.A., Fisher, B.L. & Hebert, P.D.N. (2005) DNA barcoding for effective biodiversity assessment of a hyperdiverse arthropod group: the ants of Madagascar. Philosophical Transactions of the Royal Society of London. B. Biological Sciences, 360, 1825–1834.
Taylor, R.W. (1978) Nothomyrmecia macrops: a living-fossil ant rediscovered. Science (Washington D. C.), 201, 979–985.
Trager, J.C. (1984) A revision of the genus Paratrechina (Hymenoptera: Formicidae) of the continental United States. Sociobiology, 9, 49–162.
Ward, P.S. (1994) Adetomyrma, an enigmatic new ant genus from Madagascar (Hymenoptera: Formicidae), and its implications for ant phylogeny. Systematic Entomology, 19, 159–175.
Ward, P.S. (2007) Edward O. Wilson and his contributions to ant systematics. Memoirs of the American Entomological Institute, 80, 3–7.
Ward, P.S. & Brady, S.G. (2003) Phylogeny and biogeography of the ant subfamily Myrmeciinae (Hymenoptera: Formicidae). Invertebrate Systematics, 17, 361–386.
Ward, P.S. & Downie, D.A. (2005) The ant subfamily Pseudomyrmecinae (Hymenoptera: Formicidae): phylogeny and evolution of big-eyed arboreal ants. Systematic Entomology, 30, 310–335.
Watkins, J.F., II. (1976) The identification and distribution of New World army ants (Dorylinae: Formicidae). Baylor University Press, Waco, Texas, 102 pp.
Wheeler, W.M. (1920) The subfamilies of Formicidae, and other taxonomic notes. Psyche (Cambridge), 27, 46–55.
Wilson, E.O. (2003) Pheidole in the New World. A dominant, hyperdiverse ant genus. Harvard University Press, Cambridge, Massachusetts, [ix] + 794 pp.
Wilson, E.O., Carpenter, F.M. & Brown, W.L., Jr. (1967) The first Mesozoic ants, with the description of a new subfamily. Psyche (Cambridge), 74, 1–19.
Wilson, E.O. & Hölldobler, B. (2005) The rise of the ants: a phylogenetic and ecological explanation. Proceedings of the National Academy of Sciences U. S. A., 102, 7411–7414.