AmoimyrmexCristiano, Cardoso & Sandoval, gen. nov. (Hymenoptera: Formicidae): a new genus of leaf‐cutting ants revealed by multilocus molecular phylogenetic and morphological analyses

Leaf‐cutting ants (generaAcromyrmexandAtta) are the most important herbivores in the Neotropical region. Within the genusAcromyrmex, the species and subspeciesAcromyrmex striatus,Acromyrmex silvestriisubsp.silvestriiandAcromyrmex silvestriisubsp.bruchiare morphologically similar to one another but differ from the rest of their congeners. Recent studies have suggested thatAc. striatusbelongs to a currently undescribed leaf‐cutting ant genus. Herein, we propose a new phylogenetic hypothesis for leaf‐cutting ants based on five nuclear genes (wg, LW Rh, EF1αF1, EF1αF2 and Top1) and describe a new genus. We used colonies ofAc. striatus,Ac. silvestrii silvestriiandAc. silvestrii bruchicollected from Brazil, Argentina, Uruguay and Bolivia, covering most of their known distribution. We constructed a molecular phylogenetic hypothesis for these three taxa using sequences from the mtDNA COI gene. The retrieved phylogenetic tree reveals thatAc. striatus,Ac. silvestrii silvestriiandAc. silvestrii bruchiform a well‐supported clade (P.P. = 1). Through analyses of molecular phylogenetic and morphological data, we propose a new genus of leaf‐cutting ant,AmoimyrmexCristiano, Cardoso & Sandoval,gen. nov., redescribe the speciesAmoimyrmex striatus(Roger, 1863)comb. nov.andAmoimyrmex silvestrii(Emery, 1905)comb. nov., and elevateAc. silvestrii bruchito the level of species asAmoimyrmex bruchi(Forel, 1912)comb. nov. et stat. rev.. We also provide information on the geographic distribution ofAmoimyrmex, an illustrated identification key for its taxa and descriptions of all the known castes of each species, including diagnostic characteristics, high‐quality images and distribution maps. We believe that the results of this study contribute substantially to taxonomic knowledge of leaf‐cutting ants and reaffirm the complex evolutionary history of the group.