A trove of New World Syscia (Formicidae, Dorylinae)

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 revealed an unforeseen diversity. 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. We increased the number of known species in the New World from 3 to 57, more fully characterizing the three previously described New World species and describing 31 new species. The remaining 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. 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.