Rapid climate change has the potential to suppress plant population mean fitness below replacement such that persistence will depend on adaptation and range shifts. In the tallgrass prairie fragmentation limits dispersal which suggests adaptive evolution will be necessary for species persistence. To directly evaluate the role of ongoing evolution in maintaining a population as the climate changes, research is needed which measures a population’s additive genetic variance (VA) for fitness, as it represents a population’s immediate capacity to adapt to the environment in which it exists. Climate models predict Minnesota will experience warmer temperatures and infrequent precipitation, which could create drought conditions between rainfall. To gain an understanding of the adaptive capacity of the tallgrass prairie, in 2016 I imposed a drought treatment in the field on a pedigreed population of the annual prairie legume, Chamaecrista fasciculata. I deployed rain exclusion tents over the course of the growing season to reduce rainfall by 40 percent. For the control treatment seeds from the same pedigreed population received ambient rainfall. In addition to estimating fitness (number of seeds), I measured specific leaf area (SLA), plant biomass, and flower number to estimate the amount of genetic variation for traits associated with drought tolerance.
Results/Conclusions
Preliminary results show no significant difference in trait means for specific leaf area (p = 0.1311) and biomass (p = 0.2271) between treatments, indicating no phenotypic plasticity for these traits in response to reduced soil moisture. These results suggest that population persistence in a drier climate may depend on adaptive evolution of traits important to maintaining fitness under drought, rather than phenotypic plasticity. Estimates of heritability for these traits, and VA for fitness, which indicates adaptive capacity, are currently being estimated. This research will quantify adaptation in changing natural environments, an approach often called for in the literature, but rarely put into practice. My research will improve our understanding of the response of tallgrass prairies to climate change and will provide an evolutionary lens through which we can examine seed sourcing practices in restoration.