From the ground up: Building predictions for how climate change will affect belowground mutualisms, floral traits, and bee behavior

Climate change affects species and their interactions, resulting in novel communities and modified ecosystem processes. Through shifts in phenology and distribution, climatic change can disrupt interactions, including those between mutualists. Mutualisms influence the structure and stability of communities and can link species to a common fate. However, research on climate change has focused on pairwise mutualisms, neglecting the higher-order interactions that can arise when species interact with multiple mutualists. We explore the effects of climate change on tripartite interactions involving belowground mutualists, namely soil bacteria and fungi, flowering plants, and pollinators. We outline how climate change is predicted to affect the phenology and distribution of these belowground mutualists, emphasizing the consequent effects on host plant floral traits, plant-pollinator interactions, and bee behavior. We find evidence that warming, advanced snowmelt, and drought are likely to cause phenological and distributional shifts in soil microbes, leading to diminished mutualistic interactions with plants and symbiont switching. Consequently, shifts in flowering phenology, smaller floral displays, and lower quality floral rewards are expected, increasing foraging time and energy demands for bees and altering their floral preferences. Such costs could translate into reduced fitness and novel selection pressures for bees and flowering plants in the short term. We highlight knowledge gaps and ways forward, urging studies on microbe dispersal and phenological cues, experiments that manipulate soil microbe-host plant interactions under simulated climate change conditions, and large-scale field studies across environmental gradients, all with the goal of understanding how climate change will affect soil microbe-plant-pollinator mutualisms.