Genomic Structural Variation Rescues a Classic Biological Invader from a Population Bottleneck

Invasion genetics presents a classic paradox: how do species successfully establish and spread despite severe population bottlenecks? The brown treesnake (Boiga irregularis) in Guam represents a striking example of this phenomenon, having been introduced with only a handful of individuals. We show that the population endured an extreme bottleneck and high levels of inbreeding, with roughly half of the genome exhibiting runs of homozygosity, comparable to species of conservation concern. Despite this, we uncovered extensive diversity in the form of nearly 19,000 genomic structural variants, which affect almost eight times more of the genome than single-nucleotide variants and provide material for rescuing the population from inbreeding-driven declines. This diversity is not randomly distributed across chromosomes but rather is enriched in genes vital for immunity and olfaction, suggesting genomic diversity in key chromosomal regions can rescue populations from inbreeding. This work has implications for invasion biology and conservation genetics practitioners. TEASERGenomic structural variants rescue a textbook biological invader from a population bottleneck and inbreeding