A phylogenetic analysis of the fungus‐growing ants (Hymenoptera: Formicidae: Attini) based on morphological characters of the larvae

Abstract

A phylogenetic hypothesis of the fungus‐growing ants (subfamily Myrmicinae, tribe Attini) is proposed, based on a cladistic analysis utilizing forty‐four morphological characters (109 states) of the prepupal worker larva. The fifty‐one attine species analysed include representatives of eleven of the twelve currently recognized attine genera, excluding only the monotypic workerless parasite Pseudoatta ; the non‐attines include two outgroups (species of the basal myrmicine genera Myrmica and Pogonomyrmex ), two myrmicine species presumed to be distantly related to the attines, and twelve species representing taxa that have been proposed by prior workers as possible sister groups of the Attini. There is strong character support for the monophyly of the Attini and for a sister‐group relationship of the Attini and the Neotropical Blepharidatta brasiliensis. The Attini are divided into two distinct lineages, an ‘apterostigmoid’ clade (containing Apterostigma and Mycocepurus) and an ‘attoid’ clade (containing all other attine genera except Myrmicocrypta). The attine genus Myrmicocrypta appears to be paraphyletic with respect to these two groups; the species M.buenzlii in particular retains many attine plesiomorphies. These results indicate that the fungus‐growing behaviour had a single evolutionary origin in the ants. They also indicate that mycelium cultivation is plesiomorphic and that yeast cultivation is derived within the Attini, overturning the long‐standing assumption that the yeast‐growing Cyphomyrmex species are the most primitive Attini. Behavioural and ecological investigations into the origin and evolution of the fungus‐growing behaviour might more profitably focus on species in the attine genus Myrmicocrypta , as well as those in the closely related non‐attine genera Blepharidatta and Wasmannia.