Catch me if you can: Arabidopsis thaliana lags in adaptation to contemporary climate change

Anthropogenic climate change fosters unprecedented temperature challenges, with each year breaking a temperature record. Through evolution by natural selection, species and their populations have adapted to their previously local environments. However, as the average global land temperature has increased by ~2 C or more, natural selection on many species may not act fast enough with climate change, creating an adaptation lag. To understand potential adaptation lags to recent climate change, we conducted a meta-analysis on the largest set of single-species field transplantation experiments across climates with the broadly-distributed model plant, Arabidopsis thaliana, with a total of 1,600 germplasm and 42 field trials. We developed a Gaussian fitness model dependent on local environment and climate deviations to infer genotype-specific adaptation lag parameters. We estimate a mean thermal adaptation lag over 1.91 C, suggesting that local populations, on average, are better adapted when transplanted to locations cooler than their home climates. While a less than 2 C temperature mismatch appears small, its impact on fitness corresponds to a 14% cumulative burden over time, which compounds depending on the future climate emission scenario. Combining climate model projections under different scenarios, we found that by 2025, populations would have lost 30% demographic potential under a moderate emissions scenario. Our discovery of this adaptation lag shows that even this highly adaptable species has not kept pace with recent climate change.