Evolution of the North American seed‐harvester ant genus Veromessor (Hymenoptera: Formicidae)

Veromessor Forel is a genus of seed‐harvesting ants endemic to arid and semi‐arid regions of western North America. Despite comprising only 10 described species, Veromessor exhibits striking ecological and morphological diversity, including variation in colony size, foraging strategies, mating phenology and colony founding modes. Two species have long served as models in behavioural and ecological research, yet their evolutionary relationships and trait diversification remain poorly understood. We reconstruct a comprehensive phylogeny of Veromessor using ultraconserved elements (UCEs), including multiple populations from all known species. The resulting phylogeny is well supported and robust across analyses, with maximal support for all inter‐species relationships except the placement of the V. chicoensis plus V. stoddardi pair. This uncertainty yields three alternative topologies, with support for each ranging from 30% to 93% of the maximum. Molecular species delimitation shows general agreement between genomic and morphological species boundaries. Analysis of trait evolution reveals that key ecological and morphological features in Veromessor have evolved rapidly and repeatedly in response to habitat, with a stronger correlation to ecological conditions than to phylogenetic ancestry. We also test whether colony founding polymorphism in V. pergandei and colour polymorphisms in V. andrei and V. julianus indicate incipient speciation but find little phylogenetic signal, except for subtle colour variation in V. julianus . Biogeographic models suggest considerable uncertainty about the ancestral range of Veromessor , but the Mojave Desert and California Floristic Province together emerge as likely. This study integrates phylogenomics with ecological and morphological data to illuminate the evolution of an ecologically important ant genus.