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

Abstract

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.