Transposon-linked plasticity may contribute to drought tolerance in a pantropical invader, Mikania micrantha

Background and Aims Plant invasion poses severe threats to biodiversity, ecosystem stability, and human society. The prevailing “small-genome advantage” hypothesis—which attributes invasiveness to compact genomes that allow fast growth, high seed output, and short generation times—cannot explain why some aggressive invaders carry relatively large genomes. Here, we seek to explore why some large-genome plants are highly invasive. Methods Using the pantropical, large-genome invader Mikania micrantha as a model, we integrate controlled experiments, whole-genome resequencing, and transcriptomics to show that long-terminal-repeat retrotransposons (LTR-RTs)—the dominant repeats comprising 54.22% of its genome—may confer an advantage during rapid range expansion. Key Results Populations with larger genomes tended to exhibit stronger drought responsive activation of specific Ty1-copia and Ty3-gypsy retrotransposons. These elements may contribute to phenylpropanoid pathway activation, which indicates a potentially adaptive role of phenylpropanoids in drought response. Conclusions Genomic abundance is associated with environmental responsiveness, and LTR-RTs may function as eco-evolutionary catalysts that could allow large-genome plants to expand their ranges and become formidable invaders. Our findings uncover a previously overlooked benefit of large genomes and highlight transposon-driven plasticity as a candidate driver of invasion success worthy of further investigation.