Cladistic analysis of the fire ants of the Solenopsis saevissima species‐group (Hymenoptera: Formicidae)

Results are presented from a phylogenetic study of the fire ants comprising the Solenopsis saevissima species‐group (Hymenoptera: Formicidae). Six most‐parsimonious trees were identified following a cladistic analysis utilizing 18 taxa and 36 morphological characters derived from three castes and two developmental stages. A strict consensus tree recovered the following relationships: (S. daguerrei ((S. electra, S. pusilignis) (S. saevissima (S. pythia (S. interrupta, S. ‘undescribed species’, S. weyrauchi (S. richteri, S. invicta (S. megergates (S. quinquecuspis, S. macdonaghi)))))))). This phylogenetic hypothesis implies trends in fire ant evolution towards both polygyny (multiple egg‐laying queens per colony) and large major worker size. The phylogeny also provides a test of Emery's Rule, which is not supported in its strictest sense because the social parasite S. daguerrei is not the sister species to its host species. A modified version of Emery's Rule is supported, because the social parasite is the sister species to a larger clade containing its hosts, as well as nonhosts.