First Phylogenomic Assessment of the Amphitropical New World Ant Genus Dorymyrmex (Hymenoptera: Formicidae), a Longstanding Taxonomic Puzzle

Abstract

Abstract Dorymyrmex Mayr 1866, the ‘pyramid ants’ or ‘cone ants’, are conspicuous inhabitants of arid landscapes across the Americas. Ranging from the Great Plains to Patagonia, they are concentrated north and south of the tropics in contrast to the latitudinal diversity gradient canon. Despite being frequently collected and ecologically important, Dorymyrmex ants exemplify the taxonomic neglect typical in the subfamily Dolichoderinae. The genus has never had the benefit of a global revision, and even the major lineages are still uncertain. This work characterizes the issues at hand and ushers 22 Dorymyrmex species into the world of modern-day phylogenomics: By targeting ultraconserved elements (UCEs) across the genome, I construct an alignment of 1,891 loci, infer phylogenies under maximum likelihood and Bayesian approaches, and estimate divergence dates. Three major clades of Dorymyrmex emerge with maximal support, corresponding to former genera: Dorymyrmex sensu stricto, Araucomyrmex Gallardo 1919, and Conomyrma Forel 1913. The pyramicus group (‘Conomyrma’) shows a recent, rapid radiation with minimal morphological differentiation, reaffirming the difficulty of species delimitation in this widespread clade. Finally, I observe a general south-to-north pattern of dispersal, likely by way of savanna ‘stepping stones’ across the tropics during cooler, drier periods. Intercontinental dispersal occurred after the hypothetical Caribbean landspan in the Miocene, but before the Pleistocene or the completion of the Panamanian isthmus, suggesting dispersal by flight. This corroborates patterns observed in other arid-adapted amphitropical New World taxa. Characterizing the major Dorymyrmex species groups is an important first step towards stable taxonomic definitions—which underpin active studies in behavior, chemical ecology, and physiology.