(2nd Place) Delimiting species boundaries within the Nylanderia bourbonica (Hymenoptera: Formicidae: Formicinae) complex using an integrative approach

Nylanderia is a globetrotting ant genus known for its invasive potential, with at least sixteen species identified as having devastating effects. The taxonomy of this group has been hampered by the difficulty of distinguishing species based solely on worker morphology. The inability to differentiate between native and non-native species can have significant implications for the early detection, control, and management of invasive species. One specific species complex that has garnered significant interest in studying ant invasions is N. bourbonica. To better understand the diversity and evolution of this complex, a combination of phylogenetic and quantitative morphological data was used to clarify species boundaries. The phylogeny of Nylanderia was reconstructed using Ultra-Conserved Elements (UCEs) with comprehensive sampling from different biogeographic regions. Using molecular species delimitation methods bPTP and STACEY, four morphospecies were identified within the N. bourbonica complex, including N. bourbonica, N. vaga, and two undescribed species. Despite overlapping intraspecific variations, N. bourbonica and N. vaga were found to be independent, monophyletic species. Furthermore, a strongly supported clade of nine morphospecies resembling N. bourbonica (i.e., bourbonica-like species) was identified. To differentiate between N. bourbonica and bourbonica-like species, a 3D geometric morphometric analysis was conducted using high-resolution computed tomography (CT) scans. Principal component analysis and character loadings were calculated using 27 standard body measurements and five body indices and estimated the extent to which different characters contribute to species differentiation by comparing the shape and size of morphological features among specimens.