Widespread and ongoing invasion by the ant Technomyrmex brunneus Forel in eastern Asia as elucidated by molecular data

Ants are among the most pervasive and impactful invasive species. While some characteristics of invasive ants have been linked to establishment success and competitive dominance, these traits are not universal to all successful invaders and much crucial information on the biology of both well-known and lesser-known invasive ants remains lacking. In this study, we address this knowledge gap using a molecular approach to define the ongoing invasion by the white-footed ant, Technomyrmex brunneus, in eastern Asia. This species is native to eastern and south-eastern Asia but has become a problematic invader in Japan where significant expansions in range have been documented in recent decades. Its status in eastern Asia is complicated by taxonomic confusion and misidentifications, creating significant hurdles to threat assessment, management, and the establishment of fundamental information such as the delineation of the native and invasive range. We combine mitochondrial DNA sequences with genome-wide single-nucleotide polymorphisms to elucidate relationships between populations from Vietnam to Japan. Our data reveal very limited genetic differentiation among populations despite their broad geographic spread. This can most parsimoniously be explained as a recent and ongoing invasion, likely facilitated by human dispersal. The one exception to this pattern was strong genetic distinction between two regions in China indicated by mitochondrial DNA. We speculate that this may indicate a boundary between a native population and more recent wave of invasion. Finally, we present the results of climate niche modeling indicating that extensive additional areas remain suitable for this species, suggesting this invasion is far from complete.

Automated summary

This study uses a molecular approach to investigate the invasion of the white-footed ant in eastern Asia. The findings show that the geographic distribution of this ant species in eastern Asia is complex, with strong genetic differentiation observed in certain regions of China. Climate niche modeling suggests that there are still extensive suitable areas for the white-footed ant invasion, indicating that the invasion is not yet complete.