Invasive ants have been continually expanding their range with an increased level of globalization. The yellow crazy ant (Anoplolepis gracilipes), listed among the 100 World’s Worst Invasive Alien Species, represents a major threat to local biodiversity and alters native ecosystems, especially in insular habitats. The current distribution of the yellow crazy ant spans across tropical and subtropical regions including East Asia, India, Islands in the Indian and Pacific Oceans, and North and South America. Despite being a globally distributed ant species, the population structure and invasion history of this ant remains ambiguous. To assess the global population structure, we conducted population genomic analysis using double digest restriction-site associated DNA sequencing (ddRAD-seq) and mitochondrial COI gene from 73 yellow crazy ant nests across 13 geographical regions. We found a genetic barrier at the tip of the Malay Peninsula which separated A. gracilipes into two major phylogenomic clades. The yellow crazy ant population is composed of complex genetic clusters in Mainland Southeast Asia. Our result indicated the yellow crazy ant in Southeast Asia may origin from three supercolonies. Using outlier approaches, we further pinpointed 12 genes located in genome regions under positive selection that is likely linked to genes involved in several signaling pathways and transposable elements. Our results provide the first population structure of yellow crazy ant at a global scale that constitutes a critical step forward to understand its species history and also to dissect mechanisms underlying rapid or local adaptation in this invasive ant.
.jpg "Chih-Chi Lee photo")