FRANKFURT. The large-scale experiment began in autumn 2017 with 360 small plastic tubes containing a mixture of Arabidopsis thaliana seeds, an inconspicuous annual plant with small white flowers. The tubes were shipped to 30 locations across Western and Northern Europe, the Mediterranean region, and the United States. At each site, biologists from a global network sowed the seeds in twelve plots, each about a quarter of a square meter, establishing twelve Arabidopsis populations. These populations persisted into the following year thanks to their seeds.
For up to five years, researchers monitored plant growth and performance and collected tissue samples annually for genetic analysis. Their shared goal: to trace how plants evolve to adapt to highly diverse environments.
The network "Genomics of Rapid Evolution in Novel Environment" (GrENE-net) was launched in 2016 by Niek Scheepens, Professor of Plant Evolutionary Ecology at Goethe University Frankfurt, together with Dr. François Vasseur of the Centre d'Écologie Fonctionelle et Évolutive in Montpellier and Professor Moisés Expósito-Alonso of the University of California, Berkeley.
Plant samples from the first three years have now been genetically analyzed by the U.S. team. The result: in most climate zones, populations survived and adapted to their local environmental conditions. This became evident through millions of changes across their entire set of genes—the genome. Many of these genomic changes were statistically similar across all twelve populations at a given site. Moreover, sites with similar climates exhibited similar genetic changes, affecting genes related to traits such as drought tolerance or flowering time.
Scheepens explains: "Both findings show how climate exerts evolutionary selection pressure, favoring genes and gene variants that help the plant better adapt to its environment."
However, some thale cress populations – mostly at particularly hot and dry sites – went extinct after three years, leaving their plots barren. Genome analyses revealed that strong genetic fluctuations had preceded these extinctions, and the twelve populations did not evolve in the same direction. Scheepens notes: "In these populations, random changes apparently dominated due to the relatively small population size within each plot. Instead of successful adaptation, so-called 'genetic drift' prevailed."
Evolutionary ecologist Niek Scheepens concludes: "With this experiment, we can watch evolution unfold almost in real time. It demonstrates that evolutionary adaptation can occur very rapidly – provided sufficient genetic diversity is present. Rare plant species with small populations and low genetic diversity are therefore poorly equipped to cope with environmental changes, including climate change. Overall, our experiment is a compelling appeal to preserve biodiversity: diversity ensures survival."
Background information
GrENE-net project website: https://grene-net.org/
