Molecular evidence for the origin of workerless social parasites in the ant genus pogonomyrmex

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Description/Abstract

Speciation of two social parasites from their respective hosts is tested using a molecular phylogeny. Alignment
of 711 DNA base pairs of mitochondrial cytochrome b gene was used to assess phylogenetic relationships of inquiline
species to their hosts and to other members of the genus.

We show that the inquiline social parasites of the North
American seed harvester ants are monophyletic, descending from one of the known hosts (Pogonomyrmex barbatus) in
the recent past and shifting hosts in a pattern similar to that observed in other Hymenopteran social parasites. In addition,
the host populations unexpectedly were found to be polyphyletic.

Populations of Pogonomyrmex rugosus from an area
east of the Chiricahua Mountains in Southern Arizona belong to a mitochondrial clade separate from the more western
clade of P. rugosus from the Sonoran and Chihuahuan Deserts. Evidence of mitochondrial DNA introgression between
P. rugosus and P. barbatus was also observed. We conclude that Emery’s rule does not strictly hold for this system, but
that the hosts and parasites are very closely related, supporting a loose definition of Emery’s rule.