Tree of Life: Ants

Phil Ward, Brian Fisher, Sean Brady, Ted Schultz

---

The Ant AToL (Assembling the Tree of Life) Project

Collaborative Research on Ant Phylogeny: A Comprehensive Evolutionary Tree for the World's Premier Social Organisms

Supported by NSF grant EF-0431330

PIs
Philip S. Ward (University of California, Davis)
Seán G. Brady (Smithsonian Institution)
Brian L. Fisher (California Academy of Sciences)
Ted R. Schultz (Smithsonian Institution)

Introduction
Ants, aculeate wasps in the family Formicidae, are one of the great success stories in the history of terrestrial Metazoa. These eusocial organisms, numbering 12,500 described species and perhaps as many undescribed, monopolize 15-20% of the total animal biomass in many ecosystems, and thus serve as major conduits of energy and organic material. Ants are among the leading predators of invertebrates in most communities, and in the Neotropics they are the principal herbivores as well. Ants participate in symbioses with plant species in over 52 families, thousands of arthropod species, and as-yet-unknown numbers of fungi and microorganisms. As a group, ants display remarkable adaptive strategies and specializations—agriculture of fungi, seed harvesting, herding and "milking" of other invertebrates, communal nest weaving, cooperative hunting in packs, social parasitism, slave-making—which have fueled scientific and public curiosities alike. A clearer picture of how the major ant lineages evolved will shed light on the ecological and historical factors that have contributed to the dominance and behavioral diversity of ants.

The Ant AToL Project has three broad objectives: (1) to resolve relationships among the major lineages of ants; (2) to estimate divergence times of the principal clades; and (3) to use the resulting phylogenetic and temporal framework to better understand the evolution of key biological traits in ants. The project emphasizes the use of multiple, single-copy, protein-coding nuclear genes for phylogenetic inference. We are currently employing 12 nuclear genes, many developed specifically for use in ant phylogenetics, for the first time. Data are analyzed using model-based approaches (maximum likelihood and Bayesian methods), with careful evaluation of different models and partition schemes. Divergence times for major events in ant evolution are inferred by combining fossil information with molecular dating methods that do not assume clocklike evolutionary rates. Dating analyses also permit the testing of specific biogeographic hypotheses addressing ant distributions.

In addition to probing the “deep history” of the major ant lineages (Brady et al., 2006), we have also been investigating phylogenetic relationships within several large subgroups of ants. We recently completed a study of the ant subfamily Dolichoderinae (Ward et al., 2010), which demonstrated that diversification of crown-group dolichoderines postdates the K/T boundary and occurred later in Australia than other parts of the world. This study also revealed the striking sensitivity of phylogenetic estimates to data partitioning, outgroup composition and base frequency heterogeneity. Current work is focused on the evolutionary history of dorylomorphs and myrmicines, and a reevaluation of relationships among early branching lineages of poneroids and leptanillines.

Selected Publications from Research supported by the Ant AToL Project

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.; Larkin, L.; Danforth, B. N. 2009. Bees, ants, and stinging wasps (Aculeata). Pp. 264–269 in Hedges, S. B.; Kumar, S. (eds.) Timetree of life. New York: Oxford University Press.

Fisher, B. L. 2010. Biogeography. Pp. Pp. 18-37 in: Lach, L., Parr, C. L. & Abbott, K. (eds). Ant ecology. Oxford: Oxford University Press, xvii + 410 pp.

LaPolla, J. S.; Brady, S. G.; Shattuck, S.O. 2010. Phylogeny and taxonomy of the Prenolepis genus-group of ants (Hymenoptera: Formicidae). Systematic Entomology 35: 118-131.

Schultz, T. R.; Brady, S. G. 2008. Major evolutionary transitions in ant agriculture. Proceedings of the National Academy of Sciences U. S. A. 105:5435–5440.

Ward, P. S. 2006. Ants. Current Biology 16:152-155.

Ward, P. S. 2007. Phylogeny, classification, and species-level taxonomy of ants (Hymenoptera: Formicidae). Zootaxa 1668:549-563.

Ward, P. S. 2010. Taxonomy, phylogenetics and evolution. Pp. 3-17 in: Lach, L., Parr, C. L. & Abbott, K. (eds). Ant ecology. Oxford: Oxford University Press, xvii + 410 pp.

Ward, P. S.; Brady, S. G. 2009. Rediscovery of the ant genus Amyrmex Kusnezov (Hymenoptera: Formicidae) and its transfer from Dolichoderinae to Leptanilloidinae. Zootaxa 2063:46-54.

Ward, P. S.; Brady, S. G.; Fisher, B. L.; Schultz, T. R. 2010. Phylogeny and biogeography of dolichoderine ants: effects of data partitioning and relict taxa on historical inference. Systematic Biology 59:342-362.

Wernegreen, J.J., Kauppinen, S.N., Brady, S.G., & Ward, P.S. 2009. One nutritional symbiosis begat another: Phylogenetic evidence that the ant tribe Camponotini acquired Blochmannia by tending sap-feeding insects. BMC Evolutionary Biology 9:292.

Ward, P. S. 2011. Integrating molecular phylogenetic results into ant taxonomy.Myrmecological News 15:21-29.