The effects of climate change on floral anthocyanin polymorphisms

Pigmentation affords resistance to abiotic stressors, and thus can respond adaptively or plastically to drought and extreme temperatures associated with global change. Plants frequently display variability in flower coloration that is underlain by anthocyanin pigmentation. While anthocyanin polymorphisms impact plant-animal interactions, they also impact reproductive performance under abiotic stress. We used descriptions of population-level flower color from >1900 herbarium records representing 12 North American species spanning 124 years to test whether flower color responded to global change. Based on demonstrated abiotic associations with performance of anthocyanin color morphs, we predicted that pigmentation would increase in species experiencing precipitation declines, vapor pressure deficit (VPD; a metric of aridity) increases, and temperature declines. We found that the frequency of populations with pigmented morphs increased temporally in some taxa but displayed subtle declines in others. Pigmentation was negatively associated with temperature and positively associated with VPD across taxa. Species experiencing larger temperature increases over time became less pigmented, while those experiencing increases in aridity became more pigmented. Rapid change in anthocyanin-based color polymorphisms is thus linked with climatic change. Altered flower coloration spurred by abiotic change has the strong potential to impact plant-animal interactions and overall plant reproductive performance.