Rate of evolution metrics are sensitive to environmental context

Rate of evolution metrics attempt to measure the speed of biological evolution by comparing the phenotypic traits of reference and evolved populations. However, phenotype is sensitive to environmental context, which could influence evolutionary rate estimates. We explicitly measure the effect of environmental sensitivity on evolutionary metrics and demonstrate the repercussions. We estimated evolutionary rates for 20 Raphanus raphanistrum half-sibling populations with different moisture selection histories (low and high rain regimes) grown in two different common garden environments (2015, 2016). We found that both the magnitude and direction of rate of evolution estimates changes dramatically depending on the common garden environment and the plant population’s selection history. For example, the rate of evolution for seedling emergence time was positive in the 2015 environment but negative in the 2016 environment, with differences in metrics exaggerated between years for plants from low rain selection histories. Our results suggest that evolution of evolution estimates should be interpreted with consideration of the environmental context – preferably multiple contexts – in which phenotypes are measured.