Lagging adaptation to warming climate in Arabidopsis thaliana

Background/Question/Methods

Rapid climate change has already caused species range shifts and local extinctions and is predicted to have greater future impacts. As the suitable climate space for a species shifts poleward, populations previously well adapted to the historical climate in a particular region may experience strong selection to adapt to rapidly warming local temperatures.  In fact, rapid evolutionary response to climate change has already been observed in several natural systems.  However, if environmental change outpaces the rate of plant adaptation, populations and species may decline or disappear.  Although such adaptational lag has been predicted, it has not yet been directly observed in nature. 

Results/Conclusions

We tested for lagging adaptation to warming climate in banked seeds of the annual weed Arabidopsis thaliana in common garden experiments in four sites across the species’ native European range. Genotypes originating in climates similar to the site of planting had high relative fitness in each site, direct evidence for past adaptation to climate in this model species.  However, genotypes originating in climates historically warmer than the site of planting had higher relative fitness on average than native genotypes in every site, suggesting that local adaptive optima have shifted rapidly with recent climate warming across the species’ native range. The occurrence of adaptational lag over just a few decades in an annual species suggests that similar lags may be likely for other plant species conserved in ex situ seed banks.  If so, ex situ preservation of propagules from endangered populations may not be an effective strategy for future restoration of those populations.