Local adaptation to climate facilitates a global invasion

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• Local adaptation can drive range expansion in invasive species.
• Mechanisms promoting destructive invasions, like cheatgrass (Bromus tectorum), are not fully understood.
• Cheatgrass causes severe ecological and economic impacts, particularly in western North America.

Purpose of the Study:

• To investigate the role of local adaptation in the destructive invasion of cheatgrass in North America.
• To identify the genetic and phenotypic basis of cheatgrass adaptation to novel environments.
• To understand how pre-adapted genotypes contribute to invasion success and dominance.

Main Methods:

• Sequencing of 307 cheatgrass genotypes.
• Controlled common garden experiments to assess phenotypic selection.
• Analysis of genomic ancestry and phenotypic clines in native and invaded ranges.

Main Results:

• Diverse cheatgrass lineages with pre-adapted genotypes colonized North America.
• Long-distance gene flow is common in the invaded North American range.
• Directional selection on flowering time was observed, reversing between warm and cold sites, maintaining adaptive clines.
• Genomic predictions identified highly adapted cheatgrass populations in the Great Basin, correlating with dominance.

Conclusions:

• Pre-adapted genotypes and local adaptation, driven by selection on traits like flowering time, facilitate cheatgrass invasion and dominance.
• Understanding these mechanisms is crucial for predicting and managing invasive species.
• Preventing new introductions is critical to curb further adaptation and spread of invasive cheatgrass.