Genomic and phenotypic signatures provide insights into the wide adaptation of a global plant invader
Résumé
Invasive alien species are a primary driver of biodiversity loss and species extinction. Smooth cordgrass (Spartina alterniflora) is one of the most aggressive invasive plants in coastal ecosystems around the world. However, genomic bases and evolutionary mechanisms underlying the invasion success of this species remained largely unknown. Here we assembled a chromosome-level reference genome and performed phenotypic and population genomic analysis between native US and introduced Chinese populations. Our phenotypic comparisons showed that introduced Chinese populations evolved competitive traits, such as early flowering time and greater plant biomass, during the secondary introductions along China’s coast. Population genomic and transcriptomic inferences revealed distinct evolutionary trajectories of the low- and high-latitude Chinese populations. In particular, genetic mixture among different source populations together with independent natural selection acting on distinct target genes might have resulted in high genome dynamics of the introduced Chinese populations. Our study provides novel phenotypic and genomic evidence of how smooth cordgrass rapidly adapts to variable environmental conditions in its introduced ranges. Moreover, candidate genes related to flowering time, fast growth and stress tolerance (i.e., salinity and submergence) provide valuable genetic resources for future improvement of the other cereal crops.
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