Ph.D. Candidate University of California Davis, California
Ants of the genus Dorymyrmex Mayr 1866, the "pyramid ants" or "cone ants," are abundant in dry landscapes throughout the Americas and form an ideal system for studies of New World biogeography. In contrast to traditional latitudinal diversity theory, their distribution forms an "inverse" gradient concentrated in the deserts and grasslands north and south of the tropics, a pattern also seen in other taxa such as desert plants and ground-nesting bees. Additionally, in Dorymyrmex, this distribution is asymmetrical. All three major lineages occur south of Amazonia, but only one has undergone a northward radiation. Remarkably, this D. pyramicus clade of similar species now spans from Paraguay to New York, including Central America and most Caribbean islands. The timing of this radiation is particularly intriguing: Ultraconserved element (UCE) phylogenomics reveals that the pyramicus group reached North America millions of years before the Isthmus of Panama was complete. When did these ants cross the wet tropics? How did they traverse the Central American Seaway? In order to better understand the processes that created the modern distribution of Dorymyrmex, I increased my sampling twentyfold to densely cover the Neotropics. Extending previously published results, I completed targeted genome sequencing using UCEs, inferred Bayesian phylogenies, and performed dedicated biogeographic analyses. Here I examine the rapid radiation of the D. pyramicus clade, discuss paleoclimate regimes that may have aided dispersal, and draw comparisons to other Hymenopterans. Reconstructing the evolutionary history of Dorymyrmex is an important step towards understanding this abundant but understudied New World ant genus.
