Pollination in a fire‐prone world: Reduced solar radiation and warming alter plant–pollinator interactions

Abstract Climate change can disrupt ecosystem services such as pollination. Warming increases the frequency and scale of wildfires, leading to smoke‐induced reductions in incident solar radiation, which together may affect plants, pollinators and their interactions. To determine the emergent effects of these factors on pollination, we exposed experimental communities comprising a solitary bee species and three annual wildflower species to treatments representing combinations of warming and reduced solar radiation conditions. We measured floral traits, plant–pollinator interactions and reproduction. Slight warming did not affect floral traits or plant–pollinator interactions, whereas a higher level of warming combined with reduced solar radiation stressed both partners of the mutualism. Compared to ambient conditions, warming combined with reduced solar radiation significantly lowered floral abundance and caused a 91.5% reduction in nectar volume, likely by depressing primary productivity. This limitation of floral resources translated into less caloric intake for bees and lowered flower visitation rates, lengthened flower handling times and increased diet breadth. Slight increases in temperature above ambient allowed bees to produce 48.2% more offspring, likely by bringing bees closer to their thermal optimum, but the reduction in solar radiation negated this positive effect. Conversely, seeds produced under warming combined with reduced solar radiation had the highest germination success. Our results suggest that warming and reduced solar radiation have synergistic, negative effects on pollination through a range of mechanisms including changes in primary productivity and nectar production, and bee attraction and behaviour. The reduced strength of these plant–pollinator mutualisms raises concern for the future of biodiversity and pollination services in a warmer world with more frequent wildfires. Read the free Plain Language Summary for this article on the Journal blog.