The range limits of a species are based on abiotic and biotic limits, genetic variation, and dispersal ability. Species that are well-adapted to current climates could struggle to persist or expand into more favorable climates given the rapid pace of climate change, which has already caused plant species to shift their distributions toward higher elevations and latitudes globally. In the southeastern U.S., average annual temperatures are predicted to rise whereas average annual precipitation will remain the same or increase. This will likely alter plant distribution patterns and disrupt evolutionary dynamics. Populations at the edge of a species distribution may be exposed to a greater range of climatic conditions than central populations, and so could tolerate increased environmental variation in novel geographic regions. However, edge populations also receive extensive gene flow from core populations, and typically have low genetic diversity and high rates of genetic drift. This can reduce fitness in a new environment by constraining the evolution of local adaptation. In addition to these genetic and climatic dynamics, a distributional shift may depend on biotic interactions. Spatial and phenological patterns of microbial communities will shift under climate change, and it is unclear if current microbial community members will migrate in pace with each other or with their associated plants. The majority of plant species associate with specific soil microbial communities, the effects of which depend on the environmental context. Plant-microbe interactions range from mutualistic, aiding the plant in nutrient acquisition and alleviating stressful environments, to antagonistic, consuming the plant or parasitically draining resources. If plant-soil microbe interactions are spatially structured, then a plant’s ability to expand may be affected by the existing distribution of soil communities, as well as the microbial response to rapid climate change. The spatial dynamics and local adaptation of plants, soil microbial communities, and plant-soil microbe interactions may impact the future fitness and composition of plant communities. To investigate these themes, we will use the native wildflower Elephantopus tomentosus (Asteraceae).
