Simplified depiction of the replicated common garden experiment (a) and graphical representation of testing the roles of phenological sensitivities to current climate (orange) and source climate (blue) (b). (a) Genotypes of Bromus tectorum were collected across western North America and, after a generation in the greenhouse, were planted in a replicated common garden experiment. In each common garden, we manipulated soil surface temperature using two different colored gravel coverings (black = warmer, white = cooler) and intraspecific densities, factorially. The common garden experiment was replicated in four locations across Idaho (ID) and Wyoming (WY), USA that varied in their regional climatic conditions. (b) Hypothetical illustration of flowering phenology being more sensitive to current climate (i.e., evidence for plasticity) than to source climate (i.e., evidence for local adaptation).