Author(s): Megan DuVal
Mentor(s): John Longino, Rodolfo Probst
Institution U of U
Army ants (Formicidae: Dorylinae) are top predators across most tropical and subtropical regions and serve as keystone species in many ecological communities. Their nomadic colonies and complex social hunting strategies make them particularly vulnerable to habitat fragmentation, underscoring the need for their conservation. However, outdated taxonomy – which has not been updated since the 1950s – limit conservation efforts, particularly for genera like Labidus, a widespread and ecologically important army ant genus in the Americas. Currently, Labidus taxonomy comprises seven species identified solely through morphological characters of either workers or males, with four of these species known primarily from workers, and three known only from males. Cryptic species likely exist within the four worker-based taxa, creating further taxonomic ambiguities. To refine Labidus taxonomy, I integrated detailed morphological analyses with cutting-edge phylogenetic and phylogenomic methods. I used ultraconserved elements (UCEs), genetic markers which span thousands of genomic regions and are known to accurately infer evolutionary relationships over extensive timescales. I constructed a robust phylogenetic tree for 31 Labidus specimens. I also used cytochrome c oxidase subunit I (COI) barcodes, a mitochondrial genetic marker popularized for use in species identification. I obtained 71 COI barcodes from the Barcode of Life Database (BOLD) and 62 new COI barcodes obtained via in-house Nanopore sequencing. I discovered that Labidus comprises at least 13 distinct species, and all previously recognized, broadly distributed species actually consist of multiple cryptic species with geographically restricted ranges. Notably, we resolved the taxonomic status of all three male-based species by associating them with corresponding workers. Moreover, we discovered that one long-standing Labidus species, initially classified over a century ago, actually belongs to a different army ant genus altogether. Geographic analyses further highlighted patterns of parallel and sympatric biogeography across several Labidus clades. By combining morphology, UCEs, and Nanopore sequencing, this study provides a comprehensive revision of Labidus taxonomy, advancing our understanding of its evolutionary history and supporting more targeted conservation strategies.