Ambrosia beetle invasions are structured by inbreeding, intraspecific hybridization, and bridgeheads

Abstract

When invasive populations establish in regions far from their origin, they may accumulate deleterious mutations that limit population viability and later expansion. Invasions stemming from such bridgehead populations may experience further sequential bottlenecks. However, deleterious mutations can be masked or eliminated when populations outbreed with other lineages. Here, we analyze global invasions of a species complex of persistently inbreeding ambrosia beetles, using genomic data (n = 247) from invasive populations in Africa, North America, and Australia, and from native populations in Asia. We mostly focus on one species of this complex (Euwallacea fornicatus), which poses a severe thre..