Integrating UCE phylogenomics with traditional taxonomy reveals a trove of new world syscia species (Formicidae: Dorylinae)

Authors: LONGINO, JOHN - University Of Utah; Branstetter, Michael

Submitted to: Insect Systematics and Diversity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2020
Publication Date: 3/5/2021
Citation: Longino, J.T., Branstetter, M.G. 2021. Integrating UCE phylogenomics with traditional taxonomy reveals a trove of new world syscia species (Formicidae: Dorylinae). Insect Systematics and Diversity. 5(2). Article ixab001. https://doi.org/10.1093/isd/ixab001.
DOI: https://doi.org/10.1093/isd/ixab001

Interpretive Summary: A trove of New World Syscia (Formicidae, Dorylinae): The genus Syscia is a relatively understudied group of Neotropical ants whose species-level taxonomy is challenging and neglected. Little is known about the biology of this group because they occur in leaf litter and are most often collected only when using specialized sampling techniques. As a consequence, few species have been described, and reliable resources for species identification have been lacking. Using genome-scale molecular data, mitochondrial barcodes, and many new specimen collections, the taxonomy of the Syscia of Central and South America was reviewed in an integrative manner. The molecular analyses revealed the existence of many new cryptic species, with 31 species formally described as new to science and given names and an additional 23 species treated as informal morphospecies only. An identification guide to all 57 named and unnamed species was created. The results present new insights into ant biodiversity in the Americas, provide new resources for identifying Syscia ants, and demonstrate the utility of integrating genomic data into species-level taxonomic study.

Technical Abstract: The ant genus Syscia is part of the cryptic ant fauna inhabiting leaf litter and rotten wood in the Asian and American tropics. It is a distinct clade within the Dorylinae, the subfamily from which army ants and driver ants arose. Prior to this work the genus was known from two Old World species and three New World species, each known from a single or very few collections. Extensive collecting in Middle America has revealed an unexpected diversity that is investigated here using integrative taxonomic methods. Species delimitation was based on an iterative process of establishing morphospecies, obtaining DNA sequence data for each geographically separate population of each morphospecies, and revising species boundaries. Sequencing of Ultra-Conserved Element (UCE) loci was used to infer phylogenetic relationships among 130 specimens, and these results were complemented with additional mitochondrial COI (DNA barcode) data. The resulting taxonomy expands the number of known species in the New World from 3 to 57. We describe and name 31 new species, and 23 species are assigned morphospecies codes pending improved specimen coverage. Queens may occur in fully alate or brachypterous forms, and there is a wide variety of intercaste females (possibly ergatoid reproductives). All species have a similar habitus and species identification based on morphology alone is very difficult due to continuous character variation and high similarity of phylogenetically distant species. An identification aid is provided in the form of a set of distribution maps and standard views, with species ordered by size.