Microbial, genetic, and urban drivers of ant invasions

Invasive ants are among the most destructive invaders worldwide, causing ecological disruption, economic losses, and public health risks. While classic traits such as polygyny, colony budding, and supercoloniality are well-known contributors to their success, emerging research reveals a broader suite of mechanisms driving their invasiveness. This review synthesizes recent findings on the microbial, genetic, and behavioral factors that facilitate ant invasions. Microbial interactions play a crucial role; invasive ants often exhibit a loss of natural enemies, including microbial pathogens such as Wolbachia. However, Wolbachia has received growing attention for its potential mutualistic role in enhancing colony productivity and nutrient provisioning. The bridgehead effect, wherein invasive populations establish strategic hubs that facilitate secondary invasions, has been increasingly recognized as a key driver of global ant spread and may promote genetic intermixing among invasive lineages. Genetic mechanisms such as double clonality, sexually antagonistic selection, and tolerance to inbreeding help invasive ants maintain genetic diversity despite founding populations often consisting of relatively few individuals. Additionally, urban environments impose unique selective pressures that may lead to adaptations favoring success across all stages of the invasion process. This framework aligns with the Anthropogenically Induced Adaptation to Invade (AIAI) hypothesis and helps explain why many urban-adapted ants become globally invasive. As urbanization continues to expand, human-modified landscapes may inadvertently serve as breeding grounds for future invasive species. Understanding these multifaceted invasion dynamics provides critical insights for managing invasive ant populations and mitigating their widespread impacts.