Rapid Parallel Adaptation in Distinct Invasions of Ambrosia Artemisiifolia Is Driven by Large-Effect Structural...

Area of Science:

• Evolutionary Biology
• Genomics
• Ecology

Background:

• Invasive species offer insights into adaptation repeatability.
• Common ragweed (Ambrosia artemisiifolia) is a widespread invasive weed causing hay fever.
• Understanding adaptation requires studying genetic variation across native and introduced ranges.

Purpose of the Study:

• To investigate parallel adaptation in invasive common ragweed across North America, Europe, and Australia.
• To identify genomic signatures of adaptation and structural variations involved in range expansion.
• To assess the role of standing genetic variation in rapid adaptation.

Main Methods:

• Whole-genome sequencing of over 400 Ambrosia artemisiifolia samples.
• Inference of demographic histories for distinct invasion routes.
• Genomic scans for local climate adaptation and population divergence.
• Analysis of large haploblocks (structural variations) and their frequency.

Main Results:

• Genomic signatures of parallel adaptation were found between European and Australian invasions, despite different origins and population sizes.
• 37 large haploblocks, representing structural variation and standing genetic variation, were disproportionately associated with parallel adaptation.
• These haploblocks influence traits like plant size and flowering time, rapidly forming clines in invaded ranges.
• Some haploblocks showed extreme frequency divergence, indicating adaptation to different continental selection pressures.

Conclusions:

• Large-effect standing variants play a crucial role in the rapid adaptation of invasive species during range expansion.
• The pattern of adaptation is robust across diverse invasion histories.
• Structural variations within standing genetic variation are key drivers of rapid, repeatable adaptation in invasive populations.