Phylogeny of Fungus-farming Ants (Formicidae: Myrmicinae: Attini)
Ted R. Schultz, Department of Entomology, Smithsonian Institution, Washington, DC, DC 20013-7012 and Sean G. Brady, Department of Entomology and Laboratories of Analytical Biology, Smithsonian Institution, Suitland, MD 20746.
Understanding of the evolutionary history of the attine agricultural symbiosis requires well-resolved and well-supported phylogenies for all four symbionts. This study reconstructs the phylogeny of the attine fungus-farming ants using nucleotide sequences from five nuclear genes (EF 1-alpha F1, EF1-alpha F2, wingless, LwRh opsin, and 28S rDNA), totaling approximately 4.5kb of data, for 90 ant species.
The results indicate that the Attini are monophyletic; that some combination of Mycocepurus, Myrmicocrypta, and Apterostigma comprises the sister group of the remaining Attini; that Cyphomyrmex is quite derived within the Attini; that yeast-cultivating Cyphomyrmex species are derived within Cyphomyrmex; and that the “higher attines,” Trachymyrmex, Sericomyrmex, Acromyrmex, and Atta, constitute a “crown clade” within the Attini. Trachymyrmex appears to be paraphyletic both with respect to Sericomyrmex and with respect to (Acromyrmex + Atta).
These results are congruent with a scenario, previously proposed based on a comparison of preliminary phylogenies for the four attine symbionts, of four broad, phylogenetically correlated groups (some clades, some grades) of attine agriculture, including three forms of leucocoprineaceous agriculture (lower agriculture, yeast agriculture, and higher agriculture) and Apterostigma pterulaceous agriculture.
Index terms: Attini, Formicidae, phylogeny, molecular systematics, fungus-growing