Plant evolution tracked across 30 sites worldwide suggests rapid adaptation but clear limits

A coordinated five‑year experiment planted genetically diverse Arabidopsis populations at 30 sites and found repeatable genetic shifts indicating rapid adaptation at many locations, while some populations in the hottest sites showed random genetic changes and later went extinct.

Moisés Expósito-Alonso and a global consortium ran simultaneous field experiments at 30 locations from 2017 through 2022 to observe how Arabidopsis thaliana populations respond to differing climates. Each site contained 12 plots with genetically diverse populations left largely untended for five years, and researchers sampled plants annually to sequence whole genomes. An analysis of the first three years of genomic data was published March 26 in Science and focused on tempo and genetic targets of adaptation. The project aimed to identify how quickly evolution can proceed and where adaptation fails under extreme conditions. Key findings: - The study ran 360 distinct experiments (12 plots at each of 30 locations) spanning Western Europe, the Mediterranean, the Middle East and North America. - Researchers sequenced over 70,000 surviving plants from more than 2,500 pooled spatio-temporal samples to track genetic change. - In most locations the team observed repeatable changes in allele frequencies consistent with natural selection, often occurring within three to five years. - Similar climates showed similar genetic responses in 24 of the 30 locations; affected genes included those linked to heat stress sensing and to flowering time. - In the warmest experimental sites some plots displayed non-repeatable, stochastic genetic trajectories and these populations later went extinct. Summary: The results provide quantified evidence that rapid genetic adaptation can occur in a model plant across diverse climates, while extreme heat can reduce population sizes and push some populations past a point of decline. The researchers continue to analyze later generations, are planting seeds collected from the plots to extend the experiments, and plan further work that includes other plant species and efforts to observe year-to-year genetic change in natural populations. Detailed implications for other species are undetermined at this time.