Plant Evolutionary Response to Climate Change: Detecting Adaptation Across Experimental and Natural Precipitation Gradients

Global climate change is a real-time problem that presents threats to many species. Climate change can alter ecosystems and may lead to species extinction. Species can respond to climate change by moving to a better environment or adapting. Therefore, it is necessary to rely on several approaches and perspectives to anticipate ecological impacts of climate change. A common strategy uses models to understand how populations respond to different climate scenarios. Ecological models have helped us understand population persistence, but they often ignore how populations adapt to environmental stress. Adaptive evolution has been ignored because it was assumed that evolution was too slow to have any effect on ecology. Current research has shown that some populations are able to rapidly adapt to novel environments and this is essential for population persistence. We used a population genomics approach to understand how different precipitation regimes affect the perennial bunchgrass, Pseudoroegneria spicata, in the eastern Idaho sagebrush steppe. Our objective was to determine how genetic diversity changes under manipulated precipitation regimes and whether these changes were consistent with patterns of genetic diversity under natural precipitation regimes. The manipulated precipitation regimes consist of three precipitation treatments: control, drought with 50% ambient precipitation, and irrigation with 150% ambient precipitation. The natural precipitation regimes consist of two treatments: low elevation (drier than the experimental site) and high elevation (wetter). We collected plant tissue to isolate plant DNA and then used sequenced DNA for analyses. We used a hierarchical Bayesian model to estimate genotypes and allele frequencies across all loci. We found that there were low levels of genetic variation across all experimental precipitation treatments. When examining genetic differentiation, we found there was stronger differentiation in the natural precipitation regimes. Our study focuses on the short-term responses to climate to understand how environmental stress influences genetic diversity