Background/Question/Methods
Forecasting how populations respond to global change is an ongoing challenge. Current approaches using population dynamic models ignore the potential for evolutionary adaptation. Evidence for eco-evolutionary dynamics suggests that such models might under or overestimate the impacts of climate change. Using a population genomics approach, we genotyped individual plants in a 5-year precipitation manipulation experiment in the sagebrush steppe to investigate short-term genetic changes. Focusing on the perennial bunchgrass, Pseudoroegneria spicata, we asked is there genetic variation under experimental precipitation gradients and are changes in genetic variation in response to experimental precipitation manipulations consistent with spatial patterns in genetic variation along natural elevation gradients. The precipitation experiment consists of three treatments of 1m2 quadrats consisting of: control, drought with 50% ambient precipitation, and irrigation with 150% ambient precipitation. Leaf tissues were collected from all treatments and at nearby sites along a natural elevation and precipitation gradient. DNA libraries were obtained from genotype-by-sequencing protocols and sequence data was used to identify variable nucleotides from de novo assembly. Genotype and allele frequencies were calculated across all loci to determine heterozygosity and genetic distance for genetic variation. Fst between experimental and elevation were determined to compare genetic differentiation between populations and across all loci.
Results/Conclusions
We found some evidence for genetic variation in response to the experimental and elevation precipitation gradients. Heterozygosity and genetic distance were similar across all experimental treatments, which was consistent with spatial patterns in genetic variation along natural precipitation gradients. However, elevation treatments had more genetic differentiation than experimental treatments, which suggests that there are more loci undergoing selection. Overall, this indicated that genetic variation is similar and consistent across experimental and elevation treatments but vary in genetic differentiation. Our study may provide a framework for population models to include adaptive responses to drought where current models may overestimate the mortality of drought-sensitive genotypes to future decreases in water availability.